I'm in the planning stages of my near future build up. I'm not sure what static CR I should go for though. I'll be doing a bored over 350....maybe a 400 if I can get one cheap. I'l planning on a big cam....right now the leading contender (subject to change of course) is a 234/244 5xx/5xx 114LSA grind. I want the Max CR I can use 87 octane with, with a cam that big and polished iron heads. I'll prolly use 93 octane anyway just to be safe, but I don't want my engine to knock itself to pieces if I'm broke and gotta use 87 for awhile. Opinions? What CR should I make it?

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
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[This message has been edited by Jester (edited October 19, 2000).]

 

Honestly, with that LSA and duration, I'd say no more than 9.5:1 to be able to use 87 octane safetly. JMHO Ask Damon for his CR scenario Excel spreedsheet (if you don't have it already) so you can mix and match components to reach the desired CR.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

 

i'd have to agree, 9.5 is about as high as you would really want to go. as usual it all varies on parts though. long rod engines can run higher compression with less problem, aluminum heads allow higher compression with less problem, higher duration cams same, small cc chamber heads also allow more compression than same ratio with larger cc heads. either way overall 9.5 with standard parts is about all your going to want to run.

 

2 votes for 9.5:1......any more?

 

Sounds like about the limit to me. And you better be ready to play with advance curves.

 

The advantages between 9.5 & 10.5 are not that great, and certainly not worth the money you'll need for higher octane.
You also have to throw in anbient temperatures also. If your borberline on the ping, and it gets to be 90 plus degrees...need I say more.

Make my vote 9.5 CR, since fuel nowa days SUCKS !!!!

Ron C. Terry
Running 9.6 CR w/Aluminum Heads.



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'82 Trans Am
'81 Camaro Z-28
'94 Vette LT1 Coupe

 

I'll throw another vote for 9.5:1. But I think you cam is a bit long for that compression ratio. Longer duration cams like more compression cause there is a tendency to bleed of pressure. Even though it has a 114 LSA, its duration is still long enough to have a fair amount of overlap. That cam likes something in the 10.5:1 (+/- .5)

I think you need a slightly shorter duration cam for 9.5:1.

 

LOL...the cam stays, give or take a bit. the smallest I'm even considering is 224/234 with a 112 LS. The CR is what I'll change as needs be to match...