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Discussion Starter #1
Ok guys I just built my first performance build for a 64 c10 that I'm working on. Everything has gone oddly well until now. I started the engine on the stand and it runs great, starts very easily, revs super fast and is pretty impressive. I figured I would do a cranking compression test just to see what I get. The online calculator I used during the build said I should get 161psi for cranking pressure.
Here's the kicker, I got between 195 and 205 psi on the 3 cylinders I could easily get to. The headers were blocking the others. This engine isn't even broken in yet. I was planning on running premium gas anyway, but now I'm not sure it'll be safe.

What do you guys think? Is the calculator wrong? Will I be fine on premium? Is there somewhere I screwed up?

Engine specs are as follows:

  • 4 bolt main 350 block out of a 77 c10
  • Eagle rotating assembly internally balanced with 3.75in stroke (stroker)
  • 12cc dished hyper pistons
  • 65cc chamber AFR 195 aluminum heads
  • Comp cams XR288HR (hydraulic roller) installed 2 degrees advanced for Intake closing 69 degrees abdc. (I degreed it)
  • pistons .021 in the hole with .015 thickness head gasket = .036in Quench
  • 10.3 static compression, 7.99 dynamic compression, 161 cranking pressure (according to summit calculator and wallace racing calculator)
  • Edelbrock rpm air gap intake manifold
 

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it runs great, starts very easily, revs super fast and is pretty impressive.


Your done get it installed.
 

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it runs great, starts very easily, revs super fast and is pretty impressive.


Your done get it installed.
This. I don't understand the question.
 

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Discussion Starter #6
It runs great on the stand with zero load on the engine. I'm afraid that I'll install it and it'll ping under any kind of a load, or worse, detonate at high RPM's when I can't tell its pinging and blow it all to hell.

From the little research I've done, it seems like people are all over the place regarding cranking pressure. I've read that "180 is the highest you want to go", or "200 is the max limit for pump gas", or "I ran 230 on my street car no problem". WTF!?

The truck still has a lot of work left to go before I put the engine in it, so I just wanted to see what people thought before I get to that point. Since the engine is still on the stand, I could easily put in thicker head gaskets or retard the cam timing which, SHOULD lower my cranking pressures.

Anyways, any thoughts, ideas or links to good articles are appreciated.
 

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Have you tried running the numbers with a thicker head gasket? I'd do that and see how much a difference it makes.
 

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, I could easily put in thicker head gaskets or retard the cam timing which, SHOULD lower my cranking pressures.

Anyways, any thoughts, ideas or links to good articles are appreciated.
If you factored in a correct quench during the build, then installing a thicker gasket might throw your quench out the window and INVITE detonation issues.
 

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Discussion Starter #9
Have you tried running the numbers with a thicker head gasket? I'd do that and see how much a difference it makes.
The calculator says my compression would drop to 9.7 using a stock .041 thickness head gasket. It also says my cranking pressure would drop to 148psi. But, I feel that I can't trust those numbers anymore because I'm supposed to have 161psi right now.
 

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Discussion Starter #10
If you factored in a correct quench during the build, then installing a thicker gasket might throw your quench out the window and INVITE detonation issues.
Your right about that. My current quench is .036, which is ideal, according to my research.
 

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You state pistons .021 in the hole. That's pretty specific...I'll assume that's actual measure and not numbers. Block decked? Calcs done before or after, if decked?
 

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Discussion Starter #12
The block was decked for flatness. I checked the piston depth at 4 corners afterwards and got .021. Stock is supposed to be .025.
 
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