350 chevy overhaul

[CLAYAROBINSON]

Have never worked on marine engines. Did rebuild a few car engines in my 20's
My understanding is that they are different then a car engines.

Looks like engine was overhauled not to long ago.
As I am doing a complete restore of boat thought I would teardown engine.
This would also give me a break from the fiberglassing ever now and then

Have removed all the bolts and other parts (i.e. cam, crank, pistons, etc.....).
Crank has minor circular scratches on the bearing surfaces. Is this crank the same as a reqular car crank? Can I have a speed shop overhaul the crank?

Also need input on cam. Would like to put a performance cam in. Do they have performance marine cams or do I use a performance auto cam?

Can someone recommend a good book on rebuilding this engine. Any pionters would be greatfully accepted.

Thanks,

Clay

P.S. Check out my restore thread if you like.
http://forums.iboats.com/showthread.php?t=424690

 

[Bt Doctur]

Re: 350 chevy overhaul

aside from the cam and brass core plugs its just a normal 5.7 . good machine shop can recondition everything.You may want to read this concerning exaust reversion if you decide on a radical cam .http://www.michel-christen.com/ExhaustElbows.pdf

 

[Gary H NC]

Re: 350 chevy overhaul

I would stick with using a good GM truck cam.

 

[zbnutcase]

Re: 350 chevy overhaul

Yes the crank is the same as automotive, as is most internal parts. If you want more performance, keep the stock marine cam and upgrade the heads and intake. Keep compression at 9.5 or less. No need for a high volume oil pump, because of the sustained high speed marine engines run at. A good book on rebuilding is "How to rebuild your small block Chevy" by David Vizard, most speed shops carry it.

 

[ussoldier_1984]

Re: 350 chevy overhaul

If you want to know exactly what components are in your engine for replacement look up the casting numbers on the crankshaft, block, rods, and cam, you can do a google search chevy casting numbers. usually you can tell by the casting number what each component was used for, either truck or car or whatever.

 

[coheej]

Re: 350 chevy overhaul

Competition Cams has 2 or 3 cam grinds that they list for marine use.

I installed one in a 350 and have not heard any negative comments back from the owner.

 

[Bluestream]

Re: 350 chevy overhaul

Many marine engines have forged crankshafts, Most auto engines have cast cranks, Obviously the cast cranks are not as durable and may stretch when used in a high performance engine.

 

[CLAYAROBINSON]

Re: 350 chevy overhaul

Thanks guys, good input.

Interested in checking out performance exhaust systems. Does anyone have suggistions on this to send me in the correct direction.

Clay

 

[LAC_STS]

Re: 350 chevy overhaul

From what I've read the only true performance exhaust is a dry stack or dry whatever exhaust. Basically you need to but a 2-3K set of double walled marine headers and run them as a thru hull exhaust and then you run different lines to direct the water over board.

The headers are expensive but I did see someone on here that said he made some himself out of SS. They have to be double walled though.

You can also go to a regular wet thru hull exhaust but I don't think you will see any performance from it. It will just make it sound loud.

If I could get the headers cheaper or could make them I would do it. I might try one day to male some or see if a pro welder guy I know will help me out. Chepest ones I saw for a 350 were about $1800 and you still have to route everything thru hull if your not set up that way already. So add hose, fittings, flappers, etc on the bill there too.

 

[wire2]

Re: 350 chevy overhaul

Thanks guys, good input.

Interested in checking out performance exhaust systems. Does anyone have suggistions on this to send me in the correct direction.

Clay

While you can get a cheap set of car headers for a SBC for $150, hold on to your eyebrows when pricing performance marine exhaust. $2k is not unusual.

 

[gbeltran]

Re: 350 chevy overhaul

Many marine engines have forged crankshafts, Most auto engines have cast cranks, Obviously the cast cranks are not as durable and may stretch when used in a high performance engine.

I dont know about that. More likely to break, never seen anything cast stretch, but I'd be willing to bet there is a cast crank in the 350 he has now.

 

[Aloysius]

Re: 350 chevy overhaul

Definitely has cast crank. Bone stock bottom end. We're assuming it's a standard rotation engine.

 

[Fishermark]

Re: 350 chevy overhaul

A good book on rebuilding is "How to rebuild your small block Chevy" by David Vizard, most speed shops carry it.

That is a fine book.

A better book for marine engines is Dennis Moore's book Small-Block Chevy Marine Performance. I believe it is out of print, but your local library may have a copy - or check ebay, etc.

 

[CLAYAROBINSON]

Re: 350 chevy overhaul

2k+ for exhaust is not in buget
My local library does have Small-Block Chevy Marine Performance book and will be checking it out

Thanks

Clay

 

[CLAYAROBINSON]

Re: 350 chevy overhaul

yes the crank is the same as automotive, as is most internal parts. If you want more performance, keep the stock marine cam and upgrade the heads and intake. Keep compression at 9.5 or less. No need for a high volume oil pump, because of the sustained high speed marine engines run at. A good book on rebuilding is "how to rebuild your small block chevy" by david vizard, most speed shops carry it.

zbnutcase
Does anyone know why 9.5 compresion or less?

 

[Bondo]

Re: 350 chevy overhaul

Does anyone know why 9.5 compresion or less?

Ayuh,... Because Av-gas is Expen$ive... You won't be able to feed it the Octane it'll Need....

 

[CLAYAROBINSON]

Re: 350 chevy overhaul

Thanks bondo

20+ years ago when I worked on cars I remember something about over 10:1 required high octang. Anything under could run on standered Premimum gas. Did I remember incorrectly or was that wrong from the get-go?

What is AV-gas?
Is that what we called racing fuel O-so-long-ago?

 

[gbeltran]

Re: 350 chevy overhaul

Av gas is aviation fuel.

 

[mkast]

Re: 350 chevy overhaul

100LL
The most commonly used aviation fuel is dyed blue for easy visual identification. 100LL, spoken as "100 low lead", contains a small amount of tetra-ethyl lead (TEL), a lead compound that reduces gasoline's tendency to spontaneously explode (detonation or "knock") under high loads, high temperatures and high pressures. Sustained detonation causes catastrophic engine failure.

TEL, is known as an anti-knock compound. TEL's effect on detonation resistance is known as the "octane rating," derived from comparing performance of the gasoline under test to mixtures of iso-octane and normal heptane in a special test engine. If the product tests like 90% iso-octane and 10% normal heptane, it receives a "90 octane" rating. As higher levels of anti-detonation capability were required, the curve was extended beyond 100% iso-octane and called "performance rating." Example: a 118 octane rated gasoline is more detonation resistant than an 87 octane rated gasoline.

Historically, many post WW2 developed, low powered 4 and 6 cylinder piston aircraft engines were designed to use leaded fuels and a suitable unleaded replacement fuel has not yet been developed and certified for most of these engines?although some were designed for 91/96 octane AVGAS (long since discontinued) and many Continental and Lycoming light airplane engines designed for 80/87 continued in production. Engines designed for 80/87 can use AVGAS 100 or 100LL with special precautions to prevent lead buildup and lead fouling of the spark plugs.

Some of the lower powered (100-to-150-horsepower or 75-to-110 kW) aviation engines that were developed in the late 1990s are designed to run unleaded fuel, but use 100LL if unleaded fuel is not available. An example being Rotax 912.

Numerous current (2010) certificated reciprocating-engine aircraft require high-octane (leaded) fuels.

As of Jan 2010, 100LL has a TEL content of 1.2 to 2 grams TEL[6] per US gallon (0.3?0.5 g/l) and is the most commonly available and used aviation gasoline. One gram of TEL contains only 3/5 of a gram of lead.