Does anyone know what the compression is on a 1995 C1500 Vin Code K, LO5, 5.7 liter, TBI motor with stock swirl port heads?

I've heard 8.5:1 - 9.3:1. I'm not sure if the combustion chamber is 65cc or 76cc. But I plan to install some L98 with 58cc and don't want to end up at 11.0:1 and have to run 100+ octane.

http://render2.snapfish.com/render2/.../of=50,590,323

 

I think this is it.

8.75:1

http://paceperformance.com/index.asp...D&ProdID=17686

 

Good find, that was the wrong engine for my GVW but the right one was in the same spot. According to Pace the trucks up 7500 GVW compression is 9.25:1 and over 7500 lbs is 8.75.

So you got me right where I needed to be to find the info. Thanks alot!

 

Yeah I remeber the HD trucks having lower compression.

 

HD trucks had 9.3:1 and the 305s did too and LD 350 had 8.3:1.
www.cfm-tech.com can confirm this information.

Engine-Cid-L
HP
Compression
Camshaft .050" I/E - Lift I/E - LSA
Injector Size lb/hr

L03-305-5.0L
170
9.3:1
179/194 - .350"/.385" - 109 cam
40 lb fuel injectors

L05-350-5.7L
210 hp
8.3:1
194/202 - .385"/.403" - 112 cam
55 lb fuel injectors

 

Wow! Those numbers suck, no wander these trucks are such dogs.

I'm really confused now, I've seen that at CFM before and forgot about it. Pace Performance is an authorised GM parts dealer and they say the LT's had 9.25 and the HD's had 8.75 and Chiltons and Haynes both confirm those numbers. I don't know who to believe.

I do know that 305's have always had smaller combustion chambers ever since the 70's so it would make sence that the compression would be higher in the LO3.

But what the !&$k, who's right?

 

Well, the stock 350 pistons in my truck look to be about 8cc dish pistons. So, 8cc with a 76cc combustion chamber = 8.3:1 on a 350. Like I said, I personally have some stock 350 pistons at my shop so, what I say is the truck. They have a dish design with 4 deep valve reliefs built in. Most say that the TBI heads are 76cc. I guess I need to cc my heads and pistons and finally lay this one to right once and for all. Anyone want to donate to the cause.....lol.


I calculated it up...here you go with the numbers I have:
Cylinder Head Volume 76 (cc) Cylinder Head Vol (cubic in.) 04.636
Piston Head Volume 8 (cc) Piston Head Vol (cubic in.) 00.488
Gasket Thickness .039 (in.) Swept Volume (cubic in.) 43.731
Gasket Bore 4.166 (in.) T.D.C. Volume (cubic in.) 05.970
Cylinder Bore Diameter 4.000 (in.) Gasket Volume (cubic in.) 00.532
Deck Clearance .025 (in.)
Stroke 3.480 (in.)
STATIC COMPRESSION RATIO 08.325
Deck Clearance is .025 stock for a 350
As long as the heads are 76cc, then my numbers are correct.

 

I always thought the HD trucks had lower compression to avoid detonation on high loads?

What where the 350s in the HD rated at then? Probably the same?

 

The swirl port heads are 64cc combustion and 185cc intake runner. These links have data and pics. When you see the pic its obvious how small the combustion chamber is.

http://www.sallee-chevrolet.com/Disc...3390/2930.html

http://www.customclassictrucks.com/t...l_block_chevy/

http://www.jegs.com/webapp/wcs/store...6326_-1_753961

 

I've always heard the HD had more compression to build more torque to pull more stuff with.

On that Sallee page, one said he cc'ed his at 67-68. Jegs said 65.3cc so....who knows. Like I said, I guess I need to cc my pistons and heads to get a truely honest answer.