Compression reading of 260

GalMR2
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Compression reading of 260

Postby GalMR2 » Mon Jun 10, 2024 2:46 pm

I may have achieved too much of a good thing. My 4A-GE build includes 12-1 forged pistons and a 1mm head gasket. I did check the valve clearance and checked out OK. I didn't cc the heads unfortunately so I can't do the calculation that I should have done.

I have the engine on a run-stand and it seems to run well on the factory ECU but that will be replaced.

So the question is; is a 260-compression test to be expected with this setup. I do want to run on pump gas.

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jondee86
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Re: Compression reading of 260

Postby jondee86 » Mon Jun 10, 2024 3:29 pm

Check your cam timing. Intake valves are probably closing too early.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

GalMR2
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Joined: Wed Jan 19, 2022 6:58 am

Re: Compression reading of 260

Postby GalMR2 » Tue Jun 11, 2024 3:30 am

That's a good point, thanks. once I have completed adjusting the valve lash I will degree the cams.

Is there a maximum compression reading that I should stay under for pump gas. The head gasket I used is on the thin end of what's available so I do have a thickness increase if necessary.

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jondee86
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Re: Compression reading of 260

Postby jondee86 » Tue Jun 11, 2024 3:09 pm

I'd suggest seeing if you can get the cranking pressure under 200psi... around 185-190psi
should work with 93 pump gas. There are a lot of variables involved, and some engines will
run fine at pressures over 200psi. But high pressures push the engine closer to detonation
so best to start low and work your way up :) Head gasket will be OK if you can get the
cranking pressure down by setting the cam timing.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.