More V8 Help Needed--Down on Power

[Li'l Toy]

Sorry, guys--back to the well again with my dinosaur. I am down on power--max of maybe 5500 with a prop that usually pegs the limiter at 6800. I don't think I am down 4 cylinders-had that before, this is a little stronger than that. That, plus spark on all 8, makes me think it is not a power pack.

Been through all 8 carbs, though I did not do a full cleaning. Was really working on floats then for a flooding problem.

Spark on all 8, though 3 looked weak. Abundance of caution, replaced all 8 coils, wires and plugs. No change.

I will pull the carbs again and make sure all passages are clean. The throttle lever looks OK, but I didn't really look at the butterflies with the carbs out to be sure they were opening fully. I will make sure, but I doubt that's it.

Fuel pressure is good, and if it was a pump problem I would think it would be strong on the first push with full bowls, then peter out.

My only other thought, on my limited knowledge, is reeds.

Any other thoughts?

Thanks.

[rapidcraft22]

i hade week spark on my 3.6 before it turned out to be a bad ground on cdi box it might be worth a look

[Smoking Joe]

Hey Pat you are starting to give the V8's a bad name..... I am sure you will have it sorted soon, good luck and I'm watching, I need to learn all I can about these monsters.:cool:

[Instigator]

Compression? Pat, check the couplers between upper/lower banks of carbs. Twice, I've had one that was opening the carbs shut off but while running the damn thing would allow one bank to vibrate closed! Talk about a bitch to find....
On weak spark, the loopers are very sensitive to cranking speed to get good readings. Have failed many components due to this. A lot of times you can easily fix this. If the starter bendix has been regularly oiled, the residual oil can run down past the dust cover and get to the armature. The electric motor brushes contact the commutator bars on top of the armature. The oil builds up and due to heat, turns to gunk which causes the brushes to arc and reducing cranking power/speed. About 99% of the time I am successful at disassembling/cleaning/reassembling w/no new pats. Normally a 50% improvement in cranking speed.
Next on my list would be power pack. One of the work bench motors on my Sonic had me chasing my tale for a long while. Would pass all tests on the hose but would just decide to shut off in use. Got to where it would not restart. P.pack cured it.
Let me know if I can help my friend.
G

[flabum1017]

Check your shift cable adjustment, make sure it's not too tight in the full throttle forward position, if it's too tight, it can activate the shift switch and kill a few cylinders.

[Li'l Toy]

To answer a few--forgot to say, but compression is good all the way around. 144 to 150. And the problem was the same with the old fuel pump as the new.

Gary--Would a power pack go bad but not on all 4 it controls? I am pretty sure I am not losing 4 cylinders. I will look at the link for the butterflies--never thought of that. My cranking speed is slow, but my spark tester is a Mark 1 human eyeball--how fat/bright is the spark. And I basically replaced everything downstream of the packs wih no change.

Fla--shift switch disabled long ago. Almost never shift this motor running.

Joe--I know, I know--combination of old motor and very amateur mechanic. I love the uniqueness (is that a word?) of this motor and boat, but my frustration level is getting high. I did solve two problems on my last outing. Intermittent complete engine failure is my ignition/kill switch wire grounding somewhere. Had to disconnect the wire going into the packs while hanging off the stern in Boca Grande pass, but then it started. And my most recent overheat is most likely a bad sensor; motor ran (at 5500) for 45 minutes with the horn going off after I got it restarted. Fortunately, since I had disconnected the ignition/kill wires, I could turn off the ignitin switch and kill the horn.

Rapid--checked the grounds last time I had a bad box, but I will recheck.

[rapidcraft22]

I also hade the stator was arcing under the flywheel that was a hard one to find

[flabum1017]

Is the timer base moving all the way to the wot stop? sometimes when the stator melts, it will drip into the timer base and not let it move........

[Instigator]

Is the timer base moving all the way to the wot stop? sometimes when the stator melts, it will drip into the timer base and not let it move........

Good thing to look at at. One of the the 250's I bought for the Sonic did that but it wouldn't go beyond idle. Have seen this one several motors but with no timing advance it's almost catastrophic in performance. You get nothing.

Pat, in my experience, power packs have no rime or reason. Just did one for a friend/neighbor that made no sense. All the magnets came loose in the flywheel and evidently shocked the entire ignition system in doing so. Took out the timer base too which is one of the first I've replaced in yrs. It wouldn't run at all.
Are you running a electric fuel pump? I'm currently strugling with VRO pumps on the motors on the Sonic and they are also making no sense with what they are doing.

[Li'l Toy]

Electric

[jerry1865]

sorry to hear bout the trouble, i too run the big 4.0 and luv it. ive had a power pack drop one cyl at a time, ive also had them go fine until the hit operating temp and then drop a combination.
only suggestion i can give is that the last time i chased that particular rat my only solution wound up being to replace all thee components at once and that fixed it....that was after replacing them repeatedly one at a time.

[Li'l Toy]

It will be a few weeks before I can get time to work on it, but I will play with each idea here.

[velocityct]

I have an 88 OMC sea drive that I have had the entire ignition system replace, it had spark on one side saturday so thinking it was the stater that was replaced yesterday and now there is no spark at all.. I am stuck an need help, what should I check at this point??

[Li'l Toy]

OK--got back to it. Ran it at WOT, shut off the key and pulled the plugs. Every one was clean, dry, and good looking. So it is hitting on all 8, just about 1500 R's short. I am wondering if a power pack has just decided to only go so far.

I have a brand new power pack I ended up stuck with that is rev limited at 6000. On my next weekend, I intend to swap it out for my older power pack, see if I go from 5200 to 6000. If that does no good, then swap for the new pack with the same idea. If the 6000 pack gets me to 6, then I have found the problem, and I will pick up a proper 6700 pack. If not, don't know what is next.

I did check, the spark is advancing with the throttle. I will put a timing light on it to be sure it hasn't gotten way out of adjustment

[baja200merk]

Sounds like your making head way, Hope you can get it sorted out. Let me know if I can help some how.

[kimswang]

Try a timing light on each spark plug wire. The power packs sometimes sends out signal to spark twice on one round on one or more coils. Took me a while to solve that one too.....

[JrCRXHF]

Mine has always been low on power i am running about 135-140psi on all

I had the little screw come lose that hooks the top and bottom carbs togather that took out piston number 8 last year so those have lock tight on them now. I had the bad ground on a CDI once this year and that took me down to 4. my CDI number on the packs are 113-3072 they check out fine but i just really think that i should have more speed then 60mph out of a 24x7 hull with a pad. So threads like this are good for me to learn about the old V8 Bugs.

[speedfreak3.6]

Have you checked the black plastic roller on the timing throttle pickup? they wear flat spots and won't go wot. Also, do you have a fuel filter/water seperator? Mine gave me fits. Went with inline filter, now runs much better. Good luck.

[Li'l Toy]

Do have a water separator. I didn't specifically look at the roller,but I did pull the air box, push the pedal all the way down, and see that all 8 butterflies were wide open.

Trying the spare power pack tomorrow--if it works, try to get in a 6700 rpm pack befor Sebring.

[Instigator]

I did pull the air box, push the pedal all the way down, and see that all 8 butterflies were wide open.
Open the butterflies at the p.head while trying to close the lower two banks at the same time. I think I posted this before but I had one pass the test you just did but while running one butterfly would vibrate closed.

[Scmarineperformance]

in all this did you look at the reeds with a inspection camera and check the flywheel magnets for any being loose? also what is your fuel pressure?

[Instigator]

check the flywheel magnets for any being loose? also what is your fuel pressure?
Great tip. I just did two 225's on a neighbors boat and both flywheels had all the magnets loose and moving. They bought a spar p.head and it also had loose magnets.
I also had one on one of my hot rod motors that the reluctor ring on the bottom of the flywheel come loose and spun out of time.

[Li'l Toy]

Gary--I didn't do the "try to close them" test, but I did check to see of lower was loose compared to upper. Actually, basically I did do it by making sure the connection was tight

SC - Magnets are not loose--checked. No inspection camera, I thought about reeds but woudn't I see sneezing at idle and the like? If the pack doesn't do it, I will check them. But with all 8 plugs clean and dry, it sems like it is running well, just 1600 rmp short of where it should.

I will check the timing today if the power pack doesn't do the trick--I have to rebuild a timing light, will hold off until I try the pack.

Fuel pressure is regulated at 4.5, problem existed with my old Holley red and my new Carter

[Scmarineperformance]

yes and no on most motors yes you will notice coughing but a v8 is different ive seen multiple reeds failed on a v8 that was running very well at ideal do you know what kind of reeds you have metal or fiber? they can come with both. 4.5 pounds of fuel pressure is not nearly enough for a v8 the two vro pumps when working in tandem can produce 14-16 psi at high end and you should be running the same pressure. holley reds are known to not supply anywhere near enough pressure for an 8 they have a mx pressure of only 8 or 9 psi i forget instigator might know. its been awhile for me and cars also you say you have perfect compression but how is your piston to liner skirt sealing area? i have seen many v8 liners scored down there with scored skirts but with great compression ring areas on the pistons and excellent liner conditions toward the combustion area showing great compression on a test but bad performance when running.

[VELOCITOY]

...I always thought/have been told, that anything over 5LBs will blow the needles off the seats.?. I am watching this thread and am going to slowly increase my pressure, after going through the "PunchList" I'm making now...

...Appreciate the knowledge..Thanx..

[Scmarineperformance]

thanks for the reminder velocitoy, to do the fuel system correctly you do need an adjustable fuel pressure regulator that regulates about 4-5 pounds at ideal to about 14-16 at wide open throttle in a dynamic manner over 5 pounds at static on the seats could cause needle to seat leak through

[mrtlbeez]

I used a Holley red pump on my V-8 without any problems. It worked very well.

[Scmarineperformance]

not saying they wont run the motors, there just not the best and the flow dynamics and pressure on them do not meet the required demand of a v8 it produces much less flow and pressure then the original twin vro pump set up bottom line you may not make the running hours with a red that other set ups will make on a v8

[baja200merk]

PSI means nothing, volume is what you need to make them run. they will run at .001 psi if you have enough volume to keep the carbs full. 14-16psi will blow the needles off the seats and make it run like total asss.

[Riverratt]

Holley red works just fine on my V8

[powerabout]

years ago had a 235 that when it got hot a faulty timer base retarded the ignition
pull the cowl and get the timing light on it quick as in about 30 seconds the air cooled it enough and off it would go again

[Scmarineperformance]

baja200merk since your the expert here tell me what does a stock v8 run in pressure net out of both pumps at wot?

[Li'l Toy]

SC--I have fought the pressure issue as long as I have owned this motor. If you let a Holley Red sit at its stock pressure (about 7.5) you have to set the floats down about an 1/8" or you blow the needles off the seats--thanks to Monty for that help. I have to tell you I have never seen anything on these forums about 14-16 lbs. Unless you are flowing right through the bowls to feed the hungry dinosaur, your needles and seats are going to fail at that pressure and you will at minimum be running rich. Whole idea of a carb is for the venturi to draw the fuel from the bowl, not blow it in.

My Holley red had plenty of flow for WOT for this motor. If it didn't, I would have burned a top piston as it leaned out. I am just tired of the reds failing. Carter is supposed to have even more flow. But, either way, my problem was the same with both.

[Li'l Toy]

I think I have it identified. Put in the pack that is limitted to 6000 yesteday. I didn't see 6, but I did see 5800, which is way better that with the old pack. So I hope to get a new 6700 pack this week and have it together for Sebring.

[Scmarineperformance]

i was just saying they have the capability to run 14-16 with the two pumps yes at wot a race v8 bassically suspends the needles i have the factory 2nd effort test data sheets thats where i get my info from most of the output is 4-7 psi while running. and free flow to restricted flow psi means alot it is a direct relationship to achieve the gph of resticted flow the is a certain psi need to achieve the same outcome as free flow gph and a red flows even less free flow then the twin vro set up i was just giving advice from my v8 expeirence on reds ive seen them lean out motors but some work great for many hours
glad to hear you found your problem ive been seeing many packs fail recently too

[baja200merk]

Monty rigs 430+hp 8000+rpm V8s with holleys they use a lot more fuel then stock V8s with no issues.

[VELOCITOY]

...ttt...takin notes...

[jerry1865]

im not in ya'lls league but i came up with a very different solution to the fuel isssue on a 4.0 johny. had the same trouble...couldnt feed it on top without blowing needles off the seats at idle. lowereing the float levels didnt cure mine.
so i made my own pressure regulator and set it to open at 4.5 psi in a return line, plumbed the incoming lines ( all 3 tanks) with 1/2 inch line, and the problem just went away like majic.
almost forgot... blocked off the internal relief on my holly red. i find that it works a whole lot better now.
my regulator hasnt failed by even half psi in the several years since.

[ar300johnson]

When I had my Monty V-8 with big bore carbs, I had to run a $250.00 high volume, low pressure Aeromotive fuel pump. Both the blue and red Holley would limit RPM to just over 6000. With the Aeromotive, the motor would turn 65-6600 RPM. I also had power pac problems. Just an old motor that took a lot of tinkering to keep it running great. I miss the power and sound, but I love the hassle free operation of my 250 HO Etec. Now if Dave Bush can find another 75-100 HP in the Etec, everthing will be great.

[Instigator]

holley reds are known to not supply anywhere near enough pressure for an 8 they have a mx pressure of only 8 or 9 psi i forget instigator might know.
Reds are rated at 5 psi @ 67 gph. I've run them on hot rod 6's w/no regulator and no issues and I've also had them puke fuel out the vents w/o regulators on em. I'm sure it had to do w/where the floats were set at but the ones that puked were just rebuilt/set by me so go figure. I've also had pretty good luck w/just trimming the relief spring in the pumps themselves. On carbs I set everything at 4 - 6 PSI (normally w/an inline regulator) and have had no known issues.
As far as volume, if you use the yard stick of 10 HP's @ WFO = 1 GPH then a 300 HP V-8 should be at 30 GPH. Even a hot rodded version at 430/440 would only be @ 44 GPH so well bellow the 67 rating.
That's also on paper only and I ain't Monty ;)
If you look at the tiny fuel inlets on those carbs it's amazing they flow enough fuel to get on plane.
Also on volume, having the rated supply at the pump is way different than having it at the motor. I learned this when studying bilge pump flow rating for my old Sonic. Boat U.S. did a test of pumps ratings Vs reality. W/no outlet hose I don't think any of them hit their mark. When they installed the standard, ribbed flex hose they lost something drastic like 40% of their flow! By going to smooth hose they only lost around 20% but still a huge #. Spent twice on a bilge pump than what I had planned acrrordingly.

Pat, I've checked the coupler screws and still had the butterflies vibrate closed.

[baja200merk]

I think he does up the size of the lines and routes them differently with some kind of return setup. He also installs the bigger crossflow needle and seats (cant remember the PN). I spoke to him recently since I was looking at one of his older 400+hp v8s and he said its set up for a holley pump. :thumbsup:

[Instigator]

I think he does up the size of the lines and routes them differently
I know he does but I mean where the fuel line actually attaches to the carburetor. It is TINY and don't know how to change that.
Can't be but an 1/8"m I.D. :eek:

[VELOCITOY]

...When you guys say change the float level by 1/8".. Is the final level of the float 1/8" INSIDE or OUTSIDE the edge of the housing.?. I am confused... Thanx

[Li'l Toy]

I know he does but I mean where the fuel line actually attaches to the carburetor. It is TINY and don't know how to change that.
Can't be but an 1/8"m I.D. :eek:

Yah--but there are 8 of them!

[Li'l Toy]

...When you guys say change the float level by 1/8".. Is the final level of the float 1/8" INSIDE or OUTSIDE the edge of the housing.?. I am confused... Thanx

I can never get this right w/o looking at a float bowl. I believe it is 1/8 down into the bowl, where stock is even. I think you would say 1/8" inside the housing. Basically, look at the direction the float floats up to close off the needle. Set it so that it does that with the level in the bowl lower.

Does that help at all?

[Li'l Toy]

Jerry--

Trying to understand what you did. Your pressure regulator is essentially a pressure relief valve set in a return line? So if pressure goes up over 4.5, it opens and feeds fuel into the return? Nifty idea. I guess your pump can put out more than 4.5, and if the pressure drops as the volume requirement of the dinosaur increases, the valve just closes and lets the pump put its full output to the carbs?

[baja200merk]

I know he does but I mean where the fuel line actually attaches to the carburetor. It is TINY and don't know how to change that.
Can't be but an 1/8"m I.D. :eek:
5psi must be enough to keep em fueled unless he screws 3/8ths 90* npt barbs into the plastic :D

http://www.screamandfly.com/attachment.php?attachmentid=256270&d=1337818643

[VELOCITOY]

..Thanx LT.. THAT was the answer I was looking for to understand if I did it correctly..lol..

...I too, have been fighting the fuel delivery problems and have been slowly punch-listing them away...you guys have no idea how much you've helped..

...A HUGE intermittent problem I just solved, was a choke circuit that would blow fuel into the choke ports, when it isn't supposed to, at any time it felt like it...a frikkin nitemare...

...I am ordering 2 5-port fuel logs..mine has 1 5-port unit..I will have a feed port for each cylinder, I will use the "extra" 2 fuel ports as a balance/common exit return line, and regulate it from the return side, as talked about earlier...

...I would love to tell my kid "I think I got it figured out..." ...and not be "lying"...lol..

[powerabout]

Jerry--

Trying to understand what you did. Your pressure regulator is essentially a pressure relief valve set in a return line? So if pressure goes up over 4.5, it opens and feeds fuel into the return? Nifty idea. I guess your pump can put out more than 4.5, and if the pressure drops as the volume requirement of the dinosaur increases, the valve just closes and lets the pump put its full output to the carbs?
Thats exactly how OMC recommends to do their race engines

[jerry1865]

pat...you got it, exactly. was told by holly that the biggest difference between red and blue was the relief spring. now that relief is blocked solid and the spring went into a new anti-siphen valve in the return line...no worries with the system at all. can put-put as long as i need to and not even worry about the seats letting go, and then when i nail it ...it screams.

powerabout...really appreciate the tip, but thought i had something original....lol

[jerry1865]

got he idea for the anti-siphen valve because ive hade to make check valves from scratch to spec. even down to the half psi cracking presssure. ...

being a machinist/welder comes in handy.

[rockman69]

I think he does up the size of the lines and routes them differently with some kind of return setup. He also installs the bigger crossflow needle and seats (cant remember the PN) :thumbsup:

I believe its 396520, I run those too


I know he does but I mean where the fuel line actually attaches to the carburetor. It is TINY and don't know how to change that.
Can't be but an 1/8"m I.D. :eek:

Drill out the 90* nipple from both ends, I believe we used a 1/8" (.125") drill bit, maybe the next size up....