Speaking of reed blocks...any aftermarket options?

[STV_Keith]

Is anyone building aftermarket reed blocks? Any testing been done to find out what works and what doesn't? A CNC should be able to spit those things out pretty easy, if it's worth building one that makes a difference.

Are the 5 petal or 7 petal preferred? I know I had the 5-petal JSRE reeds in my other motor, but stock 260 reeds in my current one.

[The Big Al]

Their could be a after market 5 pedal (to replace the 7)

And it would be better and could very easy be priced competitive compared to the Factory mercury 5 pedal sport jets that now list for over 130.00 each!

<TABLE cellPadding=1 border=1><TBODY><TR><TD align=right bgColor=#ffffff>32</TD><TD align=left bgColor=#ffffff>840805T1</TD><TD align=left bgColor=#ffffff>--REED BLOCK ASSEMBLY (click here) (javascript:open_window())</TD><TD align=left bgColor=#ffffff> </TD><TD align=left bgColor=#ffffff> </TD><TD align=right bgColor=#ffffff>$137.15</TD><TD align=right bgColor=#00ccff>$117.04</TD></TR></TBODY></TABLE>

[1BadAction]

A CNC should be able to spit those things out pretty easy

you would be surprised how many setups it would take to get them right in a 3 axis mill. I can think of 8 off the top of my head...

best bet would be to have a custom aluminum extrusion made, that would cut the machine time by about 80% but the die fees for extrusions are expensive. 200 full sets and you MIGHT be able to match mercs prices. big advantage with billet ones - you could go bigger on the holes (more flow :D) and still have the durability to prevent cracking.

[STV_Keith]

I was thinking better material, just less of it. Finding the reeds to fit it would be the part that takes the looking. Also, my machinists all have at least 4-axis CNC's, so I don't think it would be a problem. Does that assembly price include the reeds or not?

And if they flowed better and made more power, I'd guess that the price could be higher than stock Merc.

[The Big Al]

http://img82.imageshack.us/img82/4158/reedcagesma140974210012db5.jpg (http://forums.screamandfly.com/forums/)

[MARINER RACING]

Those red ones are nice...BUT
the material needed to span the center hole(25 mil )has to be thick enough to not cave in on its self...there fore making the reed valve not lift as high as a valve that will span only 2 holes(20 mil)
according to all the people i have asked the best 7 peddle set up is a 260 reed block with a single stage independent valve
on a 5 peddle i like mine... in a 3 peddle 2-1-2 configuration:D

[Prof. O/B]

Interesting topic, but why would you want anything more than a good set of "Flowed" 7-petals. During a discussion with an Engineer at Boyesen a few months back, he pretty much confirmed my reasoning. If you can turn all the RPMs you need, or want to, why would you want a bigger reed. Because if you do go with a bigger reed, all you are really going to do is have a drop in air-speed, that drop is all the way from the bottom to the top RPM.

Now I'm not trying to step on anyone's toes, I think everyone should do exactly what they want to do. Don't want to argue with anybody, not asking anyone to violate a "Core" conviction. I also think everyone should experiment and think outside the "Box". If in fact, you "Know" you are right, then just disregard everything I've said. I don't want to quibble or justify my thoughts any further. Just one thing, can you see it on a Dyno, or on the tach, is the E.T. any better? And if ya did, was it after ya "tuned" the motor for the new "improved" reeds, and of course, discounted for any of the other modifications you made when you installed them. Or, did ya just really didn't do much of nothing on the ole obsolete 7-Petals? I'm familiar with the theory, "Big Reed - Big Flow" and how the big reeds are going to get the air easier..........so much easier.

However, don't confuse Quantity of flow, with Quality of flow. "Raw Flow Improvements" in a slobering-ass 2-stroke don't really mean "Jack Sheet". The flow improvements must be made with a complete commitment to flow velocity. What ever flow velocity I can achieve is too slow, I want twice that much. I will read, but post no further. You guys can work it out, but remember we are discussing, a "properly-flowed" set of 7-petals............The Humble Prof.

[STV_Keith]

I was thinking that perhaps being able to build a set of reed blocks for use with the 5 or 7 petal setups that could use a better material, could use less material to get in the way of the airflow. Just thoughts at this point. They sure don't look too hard to draw up and machine in a CNC.

But, I'm no engineer either. I'd just be taking a stock one, drawing it and cutting all the material I think I could get away with, off of it to not impede airflow. Start with 7075 or something stout, so you could make it as thin as possible and see what happens. Compare it with the same reeds on the same motor with two different reed blocks (stock, custom).

[The Big Al]

Prof.

Your not offending anyone. Your input like anyone is needed and food for thought.

One thing I would like to point out is RPM is not always good HP or torque.

Most who have changed to 5 pedal sport jet see and feel changes.

I feel those who don't, are over propped, and running only on RPM.

Same statement buy the guy from Boyesen, if the RPM is there why change?

Top RPM is not the only key.

Engines for the most part are no more than a mechanical air pumps.

Cool air and fuel in, hot air and used fuel out.
The better the engine can do this the more power it can make.

I my self have seen as little as 400 rpm form different reeds and read cages.(6100 to 6400) But have been able to increase pitch and gears changes to make use of new found power. Making use of that power, not just trying to turn the living **** out of it.

X amount of RPM is not the only factor, acceleration (IE HP)
And ability to pull more work (IE torque)

These two factors can be increased with gaining RPM.

And in some cases people over turn a engine not making use of these 2 factors.

AL

[The Big Al]

I was thinking that perhaps being able to build a set of reed blocks for use with the 5 or 7 petal setups that could use a better material, could use less material to get in the way of the airflow. Just thoughts at this point. They sure don't look too hard to draw up and machine in a CNC.

But, I'm no engineer either. I'd just be taking a stock one, drawing it and cutting all the material I think I could get away with, off of it to not impede airflow. Start with 7075 or something stout, so you could make it as thin as possible and see what happens. Compare it with the same reeds on the same motor with two different reed blocks (stock, custom).

I agree 100%, they can easly be improved. And the sport jet cages are not that strong, what you see that is black is not rubber, but a hard plastic with no metal frame and can break very easy.

[myron]

glad to see the PROF back

[Prof. O/B]

To "The Big Al",
I appreciate your comments and I'm glad you were not offended, I did however note that you were talking about repacing a set of "stock" 7-Petal cages, with no other changes. I have absolutley no reason to doubt your results. Under that scenario, you did in fact gave the motor some more air than would the stock cages, it leaned it down a little, and got exactly the results you spoke of. Of course you may could have also simply "pinched" the fuel pressure back a couple of Lbs. or so, and gotten the same fuel/air ratio you are now currently running, and achived the same results. I say that because the additional power didn't come out of "thin air", it obviously came from more efficient combustion, and more effiicent combustion came from somewhere, in this case your motor's leaner.

Of course that's just me, and I'm the type you mentioned that likes to turn the living ***** out of 'em. To me 6500 R's is a great place to be - right when you're "breaking-over" at the beginning of the pull, you know - the "bottom end". Ha! LOL...........Prof. O/B

[The Big Al]

To "The Big Al",
I appreciate your comments and I'm glad you were not offended, I did however note that you were talking about repacing a set of "stock" 7-Petal cages, with no other changes. I have absolutley no reason to doubt your results. Under that scenario, you did in fact gave the motor some more air than would the stock cages, it leaned it down a little, and got exactly the results you spoke of. Of course you may could have also simply "pinched" the fuel pressure back a couple of Lbs. or so, and gotten the same fuel/air ratio you are now currently running, and achived the same results. I say that because the additional power didn't come out of "thin air", it obviously came from more efficient combustion, and more effiicent combustion came from somewhere, in this case your motor's leaner.

Of course that's just me, and I'm the type you mentioned that likes to turn the living ***** out of 'em. To me 6500 R's is a great place to be - right when you're "breaking-over" at the beginning of the pull, you know - the "bottom end". Ha! LOL...........Prof. O/B

Well I have to bust that theory also.

See I have a Brucato PCU,with steam wheel and dual EGT's Dual Head temps.
And my engine was running at peak settings with lean or not.

My fuel adjustment with the reed change require more fuel.
So more fuel was needed with the air. And then the increase.

As a mater of fact the fuel air ratio was lean to start from setting of previous reeds. And EGT's climbed fast, scary fast.
New reeds needed +3 % more fuel.

[86vintage]

Curious with all that is being discussed if any one has 6 - 7 (14)pedal cages.

Just bought a 7 pedal Carburated front half for my 1995 2.5 Steel sleeve 200hp had the 5 pedal and the lower two reeds were all corroded with water damage so I gave myself a Christmas present!!http://forums.screamandfly.com/forums/images/icons/icon10.gif

Has any one done the swap and what can I expect for powerchanges. My stock 2.5 4 pedal EFI pulls hard from idle to 6500.
With the right prop and set - up (Have forged pinned piston coming)??

Thanks- James
86 vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[1BadAction]

New reeds needed +3 % more fuel.

VERY interesting... Al, did you likewise need to lean it out for some of the other reed setups?

Prof- OB nailed it on teh flow quality VS quantity. This is what separates the men from the boys when it comes to building a fast internal combustion engine. weather its a 2.5 merc, small block chevy, or a nitro burner out of an R/C car, Ive seen many times where the guy comes to the track with the biggest, baddest flowing setup and the car is average at best...

[Bruce Washburn]

I am sure that there are some designs that are better than others and reed thickness is also another item to test. I think all this has to be applied for the specific application that you are using. I would be willing to bet that on a 2.5 that you are planning to turn 6500 to 7000 that the five peddle front half will be a better choice than the 7. I am not sure at what point that the seven peddle would be a better choice but I would guess that it would be over 7500 RPM. Maybe some of the engine guru's on the board could tell us what they have found.
I have run the Chopper City blocks and they seem to work well at high RPM's. They do seem to go through reeds quicker than the stock reed blocks. I have also run a billet block that had seven individual runners that used bysens that also seemed to work well and the reeds lasted better than the stock seven peddle blocks. The sport jet reeds also seem to be a good choice and I think may work better with a little thicker reed.

[The Big Al]

VERY interesting... Al, did you likewise need to lean it out for some of the other reed setups?

Prof- OB nailed it on teh flow quality VS quantity. This is what separates the men from the boys when it comes to building a fast internal combustion engine. weather its a 2.5 merc, small block chevy, or a nitro burner out of an R/C car, Ive seen many times where the guy comes to the track with the biggest, baddest flowing setup and the car is average at best...
Never lean, always had to increase with more air.

Now, this is with a Brucato PCU tuned to the Money.
So I can see any change.

Not a Factory Unit that is on the rich side.
<table class="tborder" id="post806566" align="center" border="0" cellpadding="6" cellspacing="1" width="100%"><tbody><tr><td class="thead">http://forums.screamandfly.com/forums/imagesSF/statusicon/post_old.gif 01-01-2006, 04:58 PM <!-- / status icon and date -->
</td> </tr> <tr> <td class="alt2" style="padding: 0px;"> <!-- user info --> <table border="0" cellpadding="0" cellspacing="6" width="100%"> <tbody><tr> <td class="alt2">http://forums.screamandfly.com/forums/image.php?u=6412&dateline=1140558330 (http://forums.screamandfly.com/forums/member.php?u=6412)</td> <td nowrap="nowrap"> http://www.screamandfly.com/images/platinum_member_star.gifThe Big Al (http://forums.screamandfly.com/forums/member.php?u=6412) <!-- BEGIN TEMPLATE: postbit_onlinestatus --> http://forums.screamandfly.com/forums/imagesSF/statusicon/user_online.gif <!-- END TEMPLATE: postbit_onlinestatus --> <script type="text/javascript"> vbmenu_register("postmenu_806566", true); </script>
Platinum Team Member
</td> <td width="100%"> </td> <td nowrap="nowrap" valign="top"> Join Date: Oct 2003
Location: LAKE NORMAN, NC
Posts: 6,211
<!-- BEGIN TEMPLATE: im_aim --> http://forums.screamandfly.com/forums/imagesSF/misc/im_aim.gif (http://forums.screamandfly.com/forums/showthread.php?t=94712&page=2&highlight=reeds#) <!-- END TEMPLATE: im_aim -->

</td> </tr> </tbody></table> <!-- / user info --> </td> </tr> <tr> <td class="alt1" id="td_post_806566"> <!-- message, attachments, sig --> <!-- icon and title --> http://forums.screamandfly.com/forums/images/icons/icon14.gif Ok Test of 4 pedal! And Man! It's a differant game!
<hr style="color: rgb(114, 165, 216);" size="1"> <!-- / icon and title --> <!-- message --> This test is for Horizontal 5 pedal std front half black fishing engines! And the sport jet 4 pedal reeds that can replace them.


I will say, out of the 5 pedal sets, the SST are the fastest by 2 hundred rpm, but, they make the engine act funny, when you let off the throttle the engine act loose, midrange is never the same, idle is erratic. Stock reeds are very consistent, my Boyesen 2 stage seem to be the best very good idol, very strong midrange, cutback throttle engine comes down very predictable.

Bullet 20xd, 200 EFI, 1 inch spacer, Aeromotive regulator, 38 psi, SVS, Brucato ECU, 200 x CURV, MOD VP tuner, bucket out, heads CC to 35 cc, compression 138 all ci.
Sportmaster, 1.87, 27p Tempest Plus

1.stk steel reeds good idol, fair midrange, max rpm 5900
2.SST 5 pedal reeds erratic idol, strong midrange, 6400 rpm
Engine is also erratic when throttle is cut back
3. Boyesen 2 stage Boyesen 5 pedal (5 years old)
Good idol, Strong Midrange, 6200 rpm

Note, the 6400 rpm is the best my engine has pulled loaded so for.


Now 1-1-06 4 pedal day!!! Temp 58-61 degrees
boat the same, prop the same, fuel the same.

1st, had a little problem yesterday, have plastic spacer, have been changing reeds, looks like the spacer can not take a lot of changes without distortion. When engine got warm the reed cages came apart. So be carefull installing the 4 pedal cages.
The "rubber cages' are not rubber, they are very thin pot metal frames that or plastic formed, it's not rubber. It's Plastic! The metal you see is all the metal there is, the rest is plastic formed.

Now with test.

Only 2 reeds to try, did not try stock steel.
Have Boysene 2 stage and Steve's new style carbon fiber.

Absolute no differance! NONE! Between the 2!
Now, I have seen the Boysene decay, as a matter of fact the reeds I recieved were used. They had bad spots, so I mailed them to Boysene they did make them good.

Idal quality!!! Second to none!!! Absolute great!

Midrange! You feel it and it's smooth!

Top end!!!!!

6500 rpm, Engine made waist of my prop.

Very best yet!!!!!

Also, with my Adjustable ECU before with the other reeds (5 pedal)I ran the engine a little on the lean adjustment with the program in my unit.
No more!! Engine wanted +3%
So we know the engine was getting more air, so the more power!

If I adjusted back to old setting EGT's would got up fast, scary fast!

So, if you want bolt on performance! And you have standard 5 pedal reed cages, get them out! Change them to 4 pedal it's a no brainer!

We need to thank Steve on this site for giving me all the reeds to test. It's been fun, and it's been work. But I like it.

Al
</td></tr></tbody></table>

[jtb]

Curious with all that is being discussed if any one has 6 - 7 (14)pedal cages.

Just bought a 7 pedal Carburated front half for my 1995 2.5 Steel sleeve 200hp had the 5 pedal and the lower two reeds were all corroded with water damage so I gave myself a Christmas present!!http://forums.screamandfly.com/forums/images/icons/icon10.gif

Has any one done the swap and what can I expect for powerchanges. My stock 2.5 4 pedal EFI pulls hard from idle to 6500.
With the right prop and set - up (Have forged pinned piston coming)??

Thanks- James
86 vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif I have changed from a 4 then to a 5 now am running a 7 pedle front half and love it. i run a heavy set up and it seems to pull a lot harder.
Just my .02

[Hottrucks]

I talked to a good friend of mine you may have heard of if you have a dirt bike his name is Scott Tasinari also known as V force reeds.
This guy is top notch in the reed vavle biz I ask him his thoughts on making up some hot rod parts for me he said the R&D to make up a set was way out of my price range I said what about idf I could get some people together to buy them ??? He told me the market was so small that it wasn't worth it....... whan I brought up the name Boseen he knew exactlly who I was talking about .....

My thoughts are I would like to see someone else producing these things so it forces more R&D aqnd better pricing...

Jeff

[Prof. O/B]

VERY interesting... Al, did you likewise need to lean it out for some of the other reed setups?

Prof- OB nailed it on teh flow quality VS quantity. This is what separates the men from the boys when it comes to building a fast internal combustion engine. weather its a 2.5 merc, small block chevy, or a nitro burner out of an R/C car, Ive seen many times where the guy comes to the track with the biggest, baddest flowing setup and the car is average at best...

Badaction, In the words of Bush 41, let's create a "Kinder, gentler Nation". When Big AL tells me something, I believe him. But we moved from the initial discussion of a "properly flowed 7-petal" reed cage to the larger 5-Petal reed cage. Of course he's going to get more flow, but that does not mean he wouldn't have gotten as much flow with a superior air speed with a set of "flowed 7-petals". Now we have made some minor changes like a Brocato system with a controllable ECU. Hey I'm ole, I'm getting so confused, I can't keep-up!!! My head hurts! I thought we were talking about reed cages.

But Al, straighten me out here, and I ain't being a smart ass. Your EGTS are reading max, which would indicate the unburnt fuel is flaming down on your EGT probes, if it wasn't, the engine would be "Burnt-up". So you added 3% more fuel, which makes an over-rich engine, even richer and it runs faster?? We need to investigate this phenomena, because that 11,000 RPM Modified engine I built last year doesn't quite respond that way. Am I missing something? Do I need to add fuel and maybe go to 11,400. Now don't get mad Big Al, if you were standing right in front of me, you would know I'm just playing with ya, LOL.........Prof. O/B

P.S. I still believe ya, cause ya ain't got no reason to tell me otherwise

[jerry]

Jerry Would Like To See Jay Smith And Prof Ob Wrestling In Thongs !!!

[86vintage]

Merry Christmas lets all Have agreat New Year!!

Just watch out for those revinue hungry cops!!

DUI is a $10-25,000.00 oversight - call a Cab
I will - bein the fine drinkin Irishman that I am!!
Have Fun!!
James
86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[The Big Al]

Prof, OB

When it comes to the High rpm engine I am no help to you.
And that can be a very different animal.

MY changes have only been between the 5 pedal stock reeds for a fishing motor to the 4 pedals.

I am in the works of changing mine to the bigger 5 pedal sport jets.

I am only dealing with 6500 rpm engine.

Now If I had been reading flame I would have increased temp with the richer mix of +3% Now we are talking about temps in the 1200 to 1220 range And this is a long hard run, not a short blast.

I try to keep my engine in the 1180 to 1200 range.

Fact is, engine ran faster, pulled harder, accelerated better with every reed change that would flow more air.

I am a firm believer that air and fuel in is power out!

And what you calling air speed is actual air velocity.

Velocity can be increased with small ports being maxed out, and their is a power loss with to much port area not creating air velocity causing the engine to work to pull air in.

I feel even the best worked 7 or 5 pedal reeds would not cause this on the high rpm engines. Just to small a area for the amount of CFM needed to perform. The current RPM of 10k to 11k is not a result of better reeds but better block porting and timing. And any reed that can fill the rotating chamber faster and hold it will be a better combination.

The 5 pedal sport jet reed is only working the area better that is available, not increasing the actual block arrangement. Just making the air intake area more effective. And making this area more efficient and sealing better will increase HP and torque. Maybe not rpm, because that configuration is already maxed by the port arrangement in the engine.

Al

[86vintage]

When Al stated needed to go 3% richer, was due to the engine pulling more air so he made the mixture richer by 3% to keep the EGT (Exhaust temperature) temp in the right heat range.
James 86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[Prof. O/B]

Prof, OB

When it comes to the High rpm engine I am no help to you.
And that can be a very different animal.

MY changes have only been between the 5 pedal stock reeds for a fishing motor to the 4 pedals.

I am in the works of changing mine to the bigger 5 pedal sport jets.

I am only dealing with 6500 rpm engine.

Now If I had been reading flame I would have increased temp with the richer mix of +3% Now we are talking about temps in the 1200 to 1220 range And this is a long hard run, not a short blast.

I try to keep my engine in the 1180 to 1200 range.

Fact is, engine ran faster, pulled harder, accelerated better with every reed change that would flow more air.

I am a firm believer that air and fuel in is power out!

And what you calling air speed is actual air velocity.

Velocity can be increased with small ports being maxed out, and their is a power loss with to much port area not creating air velocity causing the engine to work to pull air in.

I feel even the best worked 7 or 5 pedal reeds would not cause this on the high rpm engines. Just to small a area for the amount of CFM needed to perform. The current RPM of 10k to 11k is not a result of better reeds but better block porting and timing. And any reed that can fill the rotating chamber faster and hold it will be a better combination.

The 5 pedal sport jet reed is only working the area better that is available, not increasing the actual block arrangement. Just making the air intake area more effective. And making this area more efficient and sealing better will increase HP and torque. Maybe not rpm, because that configuration is already maxed by the port arrangement in the engine.

Al


God knows I love ya Big Al, you too damn honest for me not to!! You are like an ole Brown Paper Bag, what ya see is what ya get. I like that. You know I actually agree with ya on several points.
(1) More Air Flow has the capacity to make more power
(2) Yes, better porting results in greater HP
(3) Air Speed (Air Velocity as I think you called it) will not make as much difference in a stock engine as it would in a modified one.
(4) Obviously your engine being is "held-back" by the existing porting to achieve only the advertised H.P. One way to "retain" H.P. at a certain level is to simply "hide the ports". By that I mean if you restrict the bottom windows of the ports, you're only going to get so much to go through them, regardless of what reed you use. By simply introducing more available air at reed opening, you can effectively increase "Primary Compression" (crankcase compression) which will force more charge through the ports. Resulting in a higher level of performance

Having said that, I have a little different perspective than you do, in that some of the issues with motors that have large unrestrictive ports are: Because you have bigger ports, they are not only harder to fill, but you must fill them fast. If you don't, there would be an insufficient fuel charge available at intake port opening. At high RPM, the duration of "physical" charge time is less; say a 11,000 RPM motor physically has only 59% of time to fill the combustion chamber as would a motor at 6,500 RPM. That of course, is not quite true as we do advance the intake port timing to augment charging, but I think you get my point.

But it doesn't stop there. We must at the same time try to retain a homengenous fuel mix. By that I mean, we must try to minimize the fuel particulate size in the charge stream. If we do not, the fuel simply falls out of suspension, i.e., into "streamers" and "droplets" in the large ports. Because of the weight of the fuel, it has a greater affinity for itself than it does for the air in which it is suspended. While shear RPM has the ability to "beat the fuel" back into suspension, at low RPM the engine performance will suffer mightily from the aforementioned large fuel particle size.

When I posted my original post it was done in the parameters of a Racing engine. Since I haven't dealt with a stock engine in over 25 years, I think you can see that I would not think in the terms of a stock engine. I must think within two parameters: (1) have enough air delivery to support the RPM I wish to achieve and, (2) do it at a fast of air speed as possible through the engine. And, be assured, I have means to increase the air flow through the reed cages other than just "flowing the reeds". My original post was to "tempt" people into supporting their position in regards to reed cages. Because I feel our purpose of being here is for an "idea" exchange, to which ends I have suceeded. I might also add Big Al, you have supported your position admirably and have gained my respect. You let me know how the large 5-petal blocks work-out, and as always, I will trust your findings. Merry Christmas, you ole Brown Paper Bag, LOL..........Prof. O/B

[The Big Al]

Prof. o/b

Youi have brought something to mind.
I feel improvement with a spacer plate. Were some will sware in front of God the all mighty they do not.

Could the slow air speed (Velosity) be a reason I do feel this improvement?

And thanks for the complements. You will find I am a little bit more than a part changer. I have to know and figure things out.

[Prof. O/B]

Big Al, you may as well have handed me a "Loaded Gun" to blow my brains out with. I thought we were friends? Regardless of what I say. you know I'm gonna catch hell. And by the way, a "Parts Changer" would be the last words I would use to describe you. When you say a "Spacer Plate" there are several instances of use, one could be:

A Plate to space out a Laser-style EFI which would simply allow more air to be available to the reeds. It would do this by allowing the air a greater distance to turn and re-enter the reeds. By making more air available it would be a Win, Win, in any circumstance.

Another circumstance would be the 1" spacer plate on for instance a "Horned" Drag motor. Merc put these on to improve bottom-end, which it does in accordance to the Helmholtz Theory. For improved bottom-end it is advantageous to have a larger Plenum box. There is more air in a larger plenum box, so the motor at low speeds can draw more air easily from box. However, on top-end two things occurr. As the air rushes into the horn, and begains to build dynamic pressure, there would be less pressure in front of the reeds with a larger box. This would be obvious, since basically the same amount of air is entering into the horn. If the box is larger, there would be less pressure. You would of course note that the Plate in no way changes the relationship of the outlet of the horn (where it ajoins the box itself) in respect to the reeds, because it is behind the reed plate. So there would be no advantages in "straightening-out" the flow from the outlet of the horn to reeds. This is however a mute point anyway, as this is not a segregated runner system, merely a pressure box. But, being behind the reed plate, it increases the distance from which the engine must draw air from the box. You then become subject to the "Column Effect". An example could be a water hose, a 50' hose flows "X" amount of water. If you add another 50' of hose to that hose and it will no longer flows "X" because of the weight of the column itself. The longer column the more difficult to draw air as the engine falls below atmospheric pressure (at the event of the reed opening).

Another use of Spacers could be a Carb spacer, in theory it provides a better (straighter) shot from the carb to valve, or reed. In automotive use, what it really does most is increase the size of the plenum area, again making the air more readily available, and to a greater extent, minimizes negative pulses in the plenum. It also allows a greater "fall" distance of a fuel/air mix which can by simple gravity increase the speed. In a practical sense, when a mid to high-rise manifold is used, where sufficient height and volume are already available, the spacers can actually have a negative effect by increasing the column length. Even when viewing the 4-stroke motor you must bear in mind this is on a "vertical" plane. The effects on a "horizional" plane could result in increased column length, a greater propensity for fuel fall-out and the minimizing of the "suction" effect as the engine falls below atmosphere. This would be because you are drawing on a larger area between the reed and the carb, thereby decreasing the velocity of the charge movement.

Another aspect of spacing is intake "phasing". A 2-stroke engine is subject basically to three "phases". One phase, would be the exhaust phase, when the exhaust port cracks, there is a given distance from the the port itself to the outlet of what we could only hope to be a expansion chamber. Ha! Since we do not have a expansion chamber, more emphasis should be placed on the actual outlet of the block itself. Everyone cries "Snake Oil" when we talk about tuners, which is because we do not have tuners but merely "diffusers". However, even a someone as humble as myself must validate that there is a little something to even a diffuser. That would be it must have some appropriate length to retain some back-pressure back at the exhaust port(s), while at the same time permit sufficient exhaust gas to exit the block. It may be of note, in this situation, length in and of itself is not the only determining factor, but also "area" of the outlet. Of course, area is determined once again by the outlet size of the block itself, and the matching of related components further down the tract. You might say, area determines amount of flow, length determines the resistance of flow.

Another phase is when the intake ports open, the rush of the charge not only sends the charge into the chamber, but sends a "negative" pulse back-up the intake tract to reeds. Now, finially let's get to your point. The "intake" phase: The intake phase occurrs as the reeds close, a negative pulse will rush back to the spill lips of the inlet. It doesn't work with a Horn motor as the waves are so scrambled, timing is not possible (in a plenum box about 3 cylinders are all you can tune). However, it is advantageous to "time" this pulse correctly if you are dealing with say one or two cylinders on an inlet tract (not a plenum box). Since it is a negative pulse, when it changes directions, it can come back with a positive pulse to the reeds. The distance from this reed to the horn lip in this case is the criteria for timing. However, even in this scenario the distance is determined by where you wish the positive pulse to take place (the RPM). If you put a spacer plate on the a scenario as described above, the longer distance will dictate the pulse will arrive at the reed at a lower RPM, therefore increased charging at that RPM; if you shorten the tract described the more favorable pulse will arrive at a greater RPM.............Prof. O/B

[The Big Al]

So, Promax, Laser type EFI like I have with the pairs of intake ports 2X3=6 is why I am feeling this great increase in torque were as Horn motors only benifit 3 or so cyc.

Very good read.

[Hottrucks]

Ummmmm what did he say??????

all I can remember is ( and I'm probably wrong) is a long tune pipe for high rpm power short for bottom end???? ( exhaust side) I think I got this from my dirt bike days ( that is when dirt bikes where dangerous and sex was safe???)

[Prof. O/B]

So, Promax, Laser type EFI like I have with the pairs of intake ports 2X3=6 is why I am feeling this great increase in torque were as Horn motors only benifit 3 or so cyc.

Very good read.

Big AL, I presume you are adding the spacer between the EFI unit and intake manifold; (1) an obvious benefit would be allowing more air to enter between the EFI and the manifold itself, that would be a win. (2) You would also be increasing the distance between the reeds and the air-inlet (where thay are radiused (where the injectors are mounted). I think increasing that distance would be a good thing. In my previous post I said that the "phase" of Intake pulse is primarily determined by the distance from the reed to air-inlet radius (or lips). If you desire to create more bottom-end then you time the return pulse to occurr where you want to peak the torque.

A very good example would be the old Hilburn style intake horns that were used in the 60's. you probably remember them, they had one per cylinder, they were a round horn that had the radiused lips on them and an injector mounted at the base where the horns attached attached. When the guys wanted Top-end they used a shorter horn, and of course a longer horn for bottom end. They had various lengths avaliable to tune to your specific applications.

The length of the these horns were determined by the intake phasing. When the intake valve (in our case the reeds) opens the charge entered the combustion chamber but, sent an accoustical wave back up the horn. This accoustical wave, would be a negative wave (below atmospheric pressure). That's a good thing, being below the positive pressure of atmosphere took advantage of this and rushed back down the horn with a force greater than amosphere (a little supercharging effect). Timing: It would become obvious that when the wave should return would be a function of the length of the horn. If you needed more power at the bottom you would want a longer horn, because both engine speed and pulse times would be low. If you wanted more in the middle, you would use the intermediate length horn, because the horn being physically shorter, would allow the allow the pulses to arrive quicker at the valve to match the increased RPM. You can extrapalote that out to see a even shorter horn yet would be required for an engine to operate at more elevated RPM. What is all about is, timing the return pulse to maximize cylinder charging at the RPM you desire. The greater the charge the greater the torque in a specific RPM range. Note I say range, not a specific RPM, while you may target a specific RPM, it will enhace performance in the range around that RPM. When you start changing the inlet length you are merely balancing that range "up" and "down" the RPM scale.

If you were to look at the distance from the reeds of your engine to the radiused intake inlets Vs. the distance from the reeds of a carbed engine to the front of the carb inlet, you would find you are running a pretty short intake tract. Would lengthing this tract to a more appropriate length at the RPM you are turning be a plus, I'm sure it would be. I would say it would probably present you with a more friendly torque curve. It probably could stand even more. I say that, because when you compare it to the intact length of a say 245 Hi-Perf. carbed motor, the increased intact tract length does not appear to have any adverse effect on RPMs of that engine.

I would not compare your intake box to a true plenum box in a traditional sense. The reason I say this is, when the air enters from the backside traveling forward, the inertia of the air wishes to pressure on the front side of the box, the direct opposite of what would be the case of an "Horned" motor. When one looks at flow, you kinda gotta to look at air as any other medium, be it water, or even mud. All have weight and the same flow principles apply. Your primary concern then would be to achieve good air flow. It is difficult for air to turn 180 degrees to present itself to the reeds. One of the greatest restrictions in your case would be the distance you are allowing it to do so. That's a tight turn. The tighter the turn, the greater the flow loss. By increasing the distance in which the air has to make the turn (spacing-out the front-side cover) would appear to be a great benefit.

One of reasons you are experiencing a good improvement with your large petal reeds may be from the location of the injector itself. It definitely is a restriction to flow. As in your case, the effect of having the larger petals on each side of the injector maybe definitely be benefical.

The configuration of the 3X2 arrangement you mentioned would be superior in taking advantages of intake tuning than it would be for the horned motor. In the horned motor these pulses are to scrambled to to be of any benefit.

Question for you (1) are you running the progressive-style linkage that open the butterflies and, have you played any with changing that? (2) Since you have changed the reeds have you tinkered with the TPI? and, (3) Are you running stock heads, I presume they are "O" ringed?........Prof. O/B :)