Compression ratio 5.7l

[carlos515]

What would be the safest compression ratio for a 355cid with factory roller cam. 1995 . 0F786416 Block is 0 decked . No i did not do a stroker 383 . Too much cost and work to the block. Next boat I will do it though
Thanks,
Carlos

 

[Scott06]

What would be the safest compression ratio for a 355cid with factory roller cam. 1995 . 0F786416 Block is 0 decked . No i did not do a stroker 383 . Too much cost and work to the block. Next boat I will do it though
Thanks,
Carlos

Depends on gas you want to use , octane Piston profile may play a role if you have a quench build. But generally 9.5 or so if you want to use pump gas. A touch higher if you have quench pistons.

 

[achris]

What would be the safest compression ratio for a 355cid with factory roller cam. 1995 . 0F786416 Block is 0 decked . No i did not do a stroker 383 . Too much cost and work to the block. Next boat I will do it though
Thanks,
Carlos

Wow, how to answer this?

What do you mean by 'safest compression ratio'? Do you mean static compression or dynamic? What octane fuel? Are you advancing or retarding the cam timing? What ignition timing curve are you running? What will be the maximum ignition timing? What will be the maximum RPM?

I know it sounds a lot, but your question is the same as 'how long is a piece of string'?

If all you have done is opened the bore up a bit, and are running factory cam, with no retard or advance, and standard factory ignition system, factory head gaskets, etc. Then running 89 you should be fine.

BTW, with that serial number, your engine is 1996, not 95.

Chris......

 

[Scott Danforth]

Swap to vortec heads and you can go higher

 

[Scott Danforth]

'how long is a piece of string'?

50 feet

 

[achris]

50 feet

 

[carlos515]

My block was decked I have flat top 4 valve relief .030 over size pistons. compression height 1.548 with +6.90 cc piston head volume. The engine is stock build OEM otherwise. I would be using 91 octane from the marina. I have been playing with Summits compression calculator. Hence the question on safe compression .
I like the idea of vortec heads but I got the impression that they are 64cc. That would put me to 10.2 compression.
9.5 is what I will try for.
The block is a 96 but it came with 217 heads.

Thanks,
Carlos

 

[Scott06]

My block was decked I have flat top 4 valve relief .030 over size pistons. compression height 1.548 with +6.90 cc piston head volume. The engine is stock build OEM otherwise. I would be using 91 octane from the marina. I have been playing with Summits compression calculator. Hence the question on safe compression .
I like the idea of vortec heads but I got the impression that they are 64cc. That would put me to 10.2 compression.
9.5 is what I will try for.
The block is a 96 but it came with 217 heads.

Thanks,
Carlos

If you get 9.5 and run 91 with factory ignition advance you will be fine from a detonation standpoint. I would think the flat top is better than the factory dished piston for detonation potential .

 

[carlos515]

Thanks all,
Carlos

 

[Scott Danforth]

My block was decked I have flat top 4 valve relief .030 over size pistons. compression height 1.548 with +6.90 cc piston head volume. The engine is stock build OEM otherwise. I would be using 91 octane from the marina. I have been playing with Summits compression calculator. Hence the question on safe compression .
I like the idea of vortec heads but I got the impression that they are 64cc. That would put me to 10.2 compression.
9.5 is what I will try for.
The block is a 96 but it came with 217 heads.

Thanks,
Carlos

you sure the block is a 96. all 96 motors were assembled as vortec

 

[carlos515]

The serial number is F786416. It was in a 1996 Baja originally .
This is the fire slotted block.

Carlos

 

[Scott06]

The serial number is F786416. It was in a 1996 Baja originally .
This is the fire slotted block.

Carlos

If its in a 1996 boat it is possible it is a 95 engine. My 91 sea ray had a 1990 vintage engine and by serial number one of the last alfa gen ones built , 91 was transition year to gen 2. Really depends on boat builders inventory of engines.
my 2004 boat had an original engine showing a june 2003 build date

 

[Scott Danforth]

Boat builder buy motors in advance and the motor can sit in the warehouse for years before being installed in a boat. For example, Volvo was selling 8.1 liter motors as late as 2014 and these ceased to be made by GM in late 2008.

My 2002 SeaRay was a left over 2001 hull with a 1999 casting date on the 5.0

 

[carlos515]

Makes sense , The heads were 1995 tbi ....217 casting.
Question...I was offered a set of late model truck heads with 3/8 exhaust valves. Not sure of the casting numbers yet. The valves are 1.94 and 1.50. Would staying with the mid sized valves produce more mid range power? Since a boat only revs at 4600 to 4800 .

 

[Scott06]

Makes sense , The heads were 1995 tbi ....217 casting.
Question...I was offered a set of late model truck heads with 3/8 exhaust valves. Not sure of the casting numbers yet. The valves are 1.94 and 1.50. Would staying with the mid sized valves produce more mid range power? Since a boat only revs at 4600 to 4800 .

If they are 96 and up vortec heads yes you can pick up 35 or so hp, but will need a vortec intake as well. What do you mean by 3/8 exhaust valves ? As you mention exhaust valves are 1.50” …

 

[carlos515]

I was referring to the stem size.

 

[Scott Danforth]

I would swap to vortec heads myself

 

[Bondo]

I would swap to vortec heads myself

Ayuh,.... So would I,...... You'd be ok at 10.2, so long as ya don't get into a lean condition,.....

 

[Scott Danforth]

Stock GM flat-top pistons with 4 valve reliefs in stock deck height block and vortec heads is 9.4:1. With block decked .010 CR is under 9.5:1.

 

[carlos515]

Thanks,
I found a Summit Vortec head at 67cc.