383 Stroker marine build

[inspectorlance]

Well is about time to replace the tired sbc 307 in my 25' bayliner Saratoga. This thing is only rated at 200 hp,and barely gets the job done. A strong head wind can stop me from getting on plane. not kidding. I have a nice 383 stroker sitting in my garage left over from my past drinking and driving days. I had to keep the engine that helped get me in trouble in past years.

Im looking for a good build profile for the 383 motor. I think the cam will be the most important choice. It has to be able to idle smooth at 700 rpm for getting in and out of the marina. I also want as much torque as possible.
Currently the motor has 5.7 rods, performer rpm manifold, 10-1 comp and 202 heads ported and match.

The marine manifolds will also really restrict the exhaust. Anyone got cam recomendations or tips for max torque.This boat also is about 7k pounds.
I guess Im looking for a good combo to copy. I plan on getting the motor ready , and drop it in when winter hits.
Lance

[PROGRESSIVEAUTO]

Lance, I ran the Perf. RPM camshaft, Aluminum Perf. rpm heads, and intake in a Seebold Eagle about 5 years ago. This combination was awesome, for marine use. However, I must strongly suggest that you run inconel exhaust valves. This is a MUST in any marine application due to steady RPM, thus causing the valves to heat up, fatigue to occur, and eventually breaking off into the cylinders. I went through 2 blocks due to this. I used FARIA as my valvetrain supplier. I can get you the ph.# if you wish, or simply do a search. This Combo had a decent idle, and powerband came in at 2500rpm to 6500.
I ran a 750 Holley as well.

[inspectorlance]

great tip on the valves, Ill take your advice. I doubt I will be turning 6500 with this beast, but would be nice to see 5500 with a cruiser prop. I would like to see 45 mph out of it for top end and maybe cruise at high 30's. right now I cruise at 19 mph, and top out at about 28 with some barnicals on the bottom. I got 1200 hard hours on this wimpy 307. I figure this 307 is working so hard to barley keep the boat on partial plane that the 383 will likley get better GPH due to being able to run a bigger prop, and stay on plane with less throtle. At this time the bow only drops if I have it floored, So I know Im not really up on top at 19 mph with this boat.
Lance

[PROGRESSIVEAUTO]

I spun a 26 mirage plus with the old 24' Seebold Eagle at 5400. It would run 72-73mph give or take with the combination in which I gave you above. I sent you a p.m.

[dynobo]

Inspector, the 10:1 compression is probably a little higher than I would run in a marine application unless you have very tight quench chambers and aluminum heads. You said 2.02 heads so I'm assuming stock iron heads. Any engine I build under 5000 rpm or .500 lift cam gets the 062/906 casting vortec heads. They can be beat but not in the range that you are trying to run. They make gobs of torque below 4500 rpm and with a "milder" camshaft (210@ .050 or less /intake) they will idle forever at 700 rpm. I like the split duration of the Extreme Energy Comp Cams and with a 110 LSA, IT MAKES REAL GOOD POWER in the mid range as well. If you do decide to go with the vortecs, just bolt them on and go. They are not very responsive to 2.02 intakes or any extensive porting.

[inspectorlance]

Dynobo, tell me about the vortec heads 062/906 ? What kind of power will I be making with the combo you described?
Thanks
Lance

[dynobo]

The vortecs were the L31 truck option heads for the 1995/6-2001 350 truck engines. The early castings were the 906 and the later were the 062 casting. You will here some people claim they are different but, I have flowed dozens of sets of them over the past 10 years and the numbers are near mirror images of one another. The 305 also was a vortec during those same years but the chambers were about 55 cc's vs. 61 and the intake valve was smaller. Your horsepower will be in the 350-370 range (small cam) but the torque will be in the 500 foot range. In a boat I will swap torque for hp anyday. The car version of the vortec was the LT1 package offered in cop cars and the 94-96 model Impala SS but the truck heads flow a little better and the LT1 was a reverse flow coolant head so It won't easily work on your 383. Also just as a 411, unless you had your 383 internally balanced you will have to find a flywheel from an older 400 sbc or buy and aftermarket ext. balance wheel for the 383/400.

[inspectorlance]

Time to get on this project. need to have the criuser ready for summer, and the ladys :)

Can I easily install fuel injection on the motor. Could I just get a throtle body injection system off of a 350 or 454 chevy an slap it on ? Is it that simple ?? If so what years or models should I rob it off of ??

Thanks
Lance

[dynobo]

What type set up are you running. I would recommend spending a little dough and run the holley projection. Much easier to install and also easily tuned. You could probably run the "stock" set up but you would probably need a donor vehicle with most everything installed. Also, if you have anything for a CAM the stock will more than likely have to be reprogrammed.

[inspectorlance]

The motor currently is a farley average 383. 010 4 bolt block 202 chevy heads that have been professionally ported, preformer rpm manifold. 10-1 Keith black pistons, 5.7 rods, Holly 750 carb. Thats about it. I have had it sitting in my garage for the last 10 years. It was orignall built by a local drag racer that is well known. This thing would spin 12" wide tires with a possi through 2 gears. I'd have to baby it off the line , just to get traction.

Im looking for info for a strong reliable boat motor rebuild that will idle nice, and have max torque. I'll look into the Holly projection.

Thanks for the info.

Lance

[The Big Al]

I'm not here to get in pissing match.
But here are some facts.
Their was never a Vortex design GM head with smaller than 64cc chambers.
The truck heads were heaver and had thicker deck casting.

305 casting were 1.84 or 1.75 valves and were very light casting and had a bad history of cracking. (not a durable choice)

GM part number for flex plate external balance engine 14in is 471578
and uses GM Harmonic balancer 6272225 *(this is a must)

Also take the advise on the valves it is correct. No mater what the RPM THE VALVES WILL BE UNDER GREAT STRESS WITH HEAT!

The performance heads that came on the LT1 aluminum or steel were 1.94 valves with 64cc chambers. The reverse cooling was used mostly for the introduction of the aluminum head. And you will not see a problem using them. But I do not recommend this with the added RPM stress and weight of the exhaust manifolds for marine application.

GM makes a very cost effect new head assembly, but you can find a great replacement with DART or some other manufactures.
Herbert Performance or Jegs.
GM part number for the Vortex Bowtie head advantage to this head is no heat transfer crossover and a thicker deck surface.
66cc chambers 2.00 int 1.55 ext. Screw in studs are guide plates will be needed. 185cc intake chamber 25534421 //215cc 25534431 (not recommended)

Also GM performance site has a great DYNO example link to what changes to expect with the HT383

This is guide not exact, but surprisingly close!!!!
CLICK BELOW!

http://www.gmperformanceparts.com/EngineShowcase/engine_dyno.jsp?eng=383

AL

[dynobo]

Inspector, what cam shaft are you running now? You may be able to just find a Marine application cam and not have to modify anything else. Assuming your springs are not too stout. The Pro Jection system will give you excellent mid-range torque.

Big Al, the LT-1 was a 58cc aluminum reverse flow head. It had the same valves sizes as the vortecs but, doesn't flow as well. I just got thru porting a set for a guy with a swamp buggy. The 305 version of the Vortec is nearly 10cc's smaller than the L31 350. GMlists the Vortec at 64cc but, I have built more sets than I care to remember and have found very few that were 64cc. Most are in the 61-62 cc range. The LT-1 would be difficult to use unless he had the entire motor or unless he was wanting to do some plumbing work. All the cooling system is different.

[moparbarn]

10:1 is going to be a bit much with the cam/ rpm you want. i would recommend thicker head gaskets or maybe dished piston. possibly a D shaped dish to keep your quench area effective. with that heavy a boat, 3,000 to 4,500 rpm will probably detonate, and you may never hear it in a boat like you would in a car. be careful with your spark advance and total advance.

AIRWALK

[Riverman]

be careful with your spark advance and total advance.AIRWALK26 degrees total maximum!!

There is a version of GM distributors that work really well in a marine engine as is - I don't know what they are called, but they are the ones used after the HEI was discontinued. They are meant to be used with an ECM, but the internal module has a "limp home" mode in it that is perfectly curved for marine use. They advance 20 degrees by 1500 RPM with no moving parts. Just dial in 6 degrees initial and you're good to go!

You have to do the standard marine mods though - provide a screened vent underneath, and seal off the cap. :)

[dynobo]

Marine 4 strokes run much cooler (140-160) than auto engines. Depending on the heads used, the 10:1 pistons probably only yield low 9's or high 8's in actual compression. If the heads are in fact the early small chamber (64) then they may actually be close to 10:1. Most 10:1 motors are usually much lower. Give the casting # and I can give you an idea of what they are.

Riverman, why do you run your total timing so low. 10 degrees retarded will probably knock 75 horsepower and 100 lb/ft torque off the output of the engine. I always recommend using a mid-70's truck HEI because it has the slower advance curve built in. I usually run stock 350's at 36-38*'s and 383/400's at 33-36*s total.:confused:

[Riverman]

Not on a heavy boat with a 19" diameter prop you don't. That is way too much advance. You are in car country with that much advance.

[The Big Al]

Inspector, what cam shaft are you running now? You may be able to just find a Marine application cam and not have to modify anything else. Assuming your springs are not too stout. The Pro Jection system will give you excellent mid-range torque.

Big Al, the LT-1 was a 58cc aluminum reverse flow head. It had the same valves sizes as the vortecs but, doesn't flow as well. I just got thru porting a set for a guy with a swamp buggy. The 305 version of the Vortec is nearly 10cc's smaller than the L31 350. GMlists the Vortec at 64cc but, I have built more sets than I care to remember and have found very few that were 64cc. Most are in the 61-62 cc range. The LT-1 would be difficult to use unless he had the entire motor or unless he was wanting to do some plumbing work. All the cooling system is different.

Well the pissing match has started.
I don't believe you want to go were you are going with this.

LT1-350
<TABLE cellSpacing=0 cellPadding=0 width=660 align=center bgColor=#ffffff border=1><TBODY><TR class=wbg-blacktext vAlign=top align=left><TD class=wbg-blacktext vAlign=top align=left>88958692</TD><TD class=wbg-blacktext vAlign=top align=left>SBC Cast Iron High Performance (For leaded fuel)
This cast iron cylinder head is the same as P/N 12480092 except it has a softer exhaust seat for uses with leaded racing fuel only. This cylinder head (casting P/N 3991492) was originally installed on special high-performance small-blocks such as the 302ci Z-28 and 350ci LT-1. It is popularly known as the “fuel injection” head because it shares many features with previous high-performance Corvette heads. This head has straight spark plugs, 3/8” screw-in studs, pushrod guideplates, and heat riser passages. The 64cc combustion chambers are machined for 2.02” intake valves and 1.60” exhausts. Seats are not heat-treated.
</TD></TR></TBODY></TABLE>

L31 head ( I posted this just in case your confused on what the L31 is)
See the L31 is a Vortec head!
<TABLE class=wbg-blacktext cellSpacing=0 cellPadding=0 width=660 align=center border=0><TBODY><TR class=wbg-blacktexttitlebold-14px vAlign=top align=left><TD class=wbg-blacktexttitlebold-14px vAlign=top align=middle colSpan=2>P/N 12558060 L31 350 Vortec Cylinder Heads (See options below.)</TD></TR><TR class=wbg-blacktext vAlign=top align=left><TD class=wbg-blacktext vAlign=top align=middle>http://www.gilbertchevy.com/Cylinder_Heads/images/vortec2.jpg
http://www.gilbertchevy.com/Cylinder_Heads/images/vortec3.jpg</TD><TD class=wbg-blacktext vAlign=top align=middle>http://www.gilbertchevy.com/Cylinder_Heads/images/12558060large1.jpg</TD></TR><TR class=wbg-blacktext-12pxB vAlign=top align=left><TD class=wbg-blacktext-12pxB vAlign=top align=left colSpan=2>Small block Vortec heads, the head with huge performance gains that everyone is talking about.</TD></TR><TR class=wbg-blacktext vAlign=top align=left><TD class=wbg-blacktext vAlign=top align=left colSpan=2> This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. The intake and exhaust port are very similar to Corvette 350 LT1 heads. America’s favorite high performance cast iron small block cylinder head offers big power and bigger value. The Vortec cylinder head's fast burn combustion chamber and high velocity ports combine to produce big horsepower out of the box. The Vortec head can be mildly ported for additional performance and can be milled up to .040” for increased compression ratio. This head includes 1.94” intake valves and 1.50” exhaust valves, springs and retainers, and pressed-in 3/8” studs. This head with compatible valves flows more air than bow tie head P/N 10134392, but the casting may not be as durable. It is a 20 to 40 horsepower bolt on increase over earlier cast iron small block heads. The water passages are the same as the original 1955 small block design. The eight-holt intake bolt pattern is totally different than the early model V8 12-bolt design. The Vortec head REQUIRES a Vortec style intake manifold due to its improved manifold mounting flange and gasket design and raised intake ports. It is not recommended that the heads be modified to accept early design intake manifolds (They will never match up right.). Use new manifold P/N 12366573, 12496820, 12496821, 12496822, or any others that we have listed below for correct matching to the Vortec head. Vortec heads fit all small block engines produced 1955 to present, excluding LT1/LT4 reverse coolant flow engines and current LS1 style “GEN 3” engines.
Technical Note: The valves seats in these heads can be machined to 2.02” intake and 1.60” exhaust. The rocker arm studs can be pinned or drilled and tapped 3/8”. These heads require the use of self-aligning rocker arms. (Casting P/N 10239906 or 12558062) (65 ft./lbs. head bolt torque)
Please Note: The casting number myth debunked:
The myth is that there is a difference in the head performance produced by these two castings.
This myth was started by some Magazines that didn't do their homework before publishing their articles.
This is the truth the whole truth and nothing but the truth.
10239906 casting has one large single hump.
12558062 casting has 3 small humps.
If either of these two castings have not been altered by GM and the part number changed from 12558060 or altered by someone else (previous owner, etc.), the heads produced by either casting will be identical except for the external cosmetic difference. Both castings are used to make the 12558060 Vortec heads which are the true unaltered Vortec heads.
Heads from both castings come out of their cast IDENTICAL except for the minor cosmetic external differences!!!!!!!! </TD></TR></TBODY></TABLE>

[BarryStrawn]

I guess Al hasn't heard of the 1990's version of the LT1.

[dynobo]

Yea, I respect Al and he has lots of vital information, but everything I have posted is not from factory manuals or print, it is hands on. I have flow bench tested most every Chevy head since the 1955 265 version. Al stated earlier about the reverse flow LT-1. The 1969/70 LT-1 model #041 CASTING was NOT, I repeat NOT A REVERSE FLOW HEAD. The later Corvette ALUMINUM LT-1 was a reverse flow and had 58cc combustion chambers. I'm not trying to embark on a pissing contest I'm just trying to help a fellow board member with his engine. Like wise the numbers AL posts are blueprint specs and very few items that are mass produced are spot on. Try weighing 8 production GM connecting rods.
Al, I will get the cast # off the 305 Vortec tomorrow and post them. I don't just make up specs.and post them. I don't solicit business on S and F so I really have nothing to gain by knowingly deceiving anyone. The numbers I post are not numbers I got off the internet somewhere, they are numbers that I use to make a living with day in and day out. I certainly am no GURU on anything but I did sleep with small block Chevy engines for about 20 years so I do know a little about them.;)

[inspectorlance]

Great info guys. I'll get #'s off of my stuff in the next few days, and then go from there.

Lance

[Jet Boater]

If I may jump into this, I have a 19' fiberglass boat with a berkeley jet drive and a 350 engine. I got the boat last summer from a lady, only to find out the block was cracked. I plan to get another 350 block and stroke it. I see several stroker kits, but I don't know what cam to get. From what I have researched with jets horsepower is the main idea, not torque. I am interested in as many rpm's as I can get out of her, without sacrifising my low end for starting. I want to go with aluminum heads to cut down on weight. What do you guys recommend for cams and heads? Thanks!

[inspectorlance]

If you want to go fast in a jet you will need big block power.
The formula for HP is; torque x rpm devided by 5252.
You want torque ! On a dyno sheet torque and hp will allways cross at 5252 rpm.

[Jet Boater]

Ok that makes sense, thanks. My boat isn't a true speed boat. It's a custom built fiberglass that's pretty sleek, but not a speed demon. I think a big block would be overkill, anything the stroker would put out would be plenty for it. So if I want to stay with the small block and make a stroker can I get any stroker kit and get the marine seals and gaskets? Pro Comp has several hi performance aluminum heads, can I use those to make a good reliable 383 for a boat? Thanks