Increase Static Compresion ratio
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From: Venezuela
Increase Static Compresion ratio
Hi there I'm needing increase the Static compresión ratio of my EFI 300, I know there are several guys who alrerady did but I need to know How much do I need to shave ?
The astock compression ratio is 8.5:1 isn't it? I would like at least 9.0:1 since here we have 91 and 95 octane fuel, there won't be knocking problems
Any comments will be appreciated.
The astock compression ratio is 8.5:1 isn't it? I would like at least 9.0:1 since here we have 91 and 95 octane fuel, there won't be knocking problems
Any comments will be appreciated.
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From: Venezuela
Well I'm thinking:
If all stock engines have same parts, shaving the head will increased the Compresion Ratio same for all engines, isn't it?
I mean; shaving .020" to the head of several stock engines will increase the CR barelly same
I assume also there are a lot of guys who has done head sahving and all the calculations, maybe one of those can point to me in the right way...
If all stock engines have same parts, shaving the head will increased the Compresion Ratio same for all engines, isn't it?
I mean; shaving .020" to the head of several stock engines will increase the CR barelly same
I assume also there are a lot of guys who has done head sahving and all the calculations, maybe one of those can point to me in the right way...
Postmaster
Joined: Mar 2005
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From: Earth
Why do you need to raise your CR? Did you change cams?
Static compression is questionable at best in determining if an engine will knock. You need to look at dynamic compression. There are calculators out there that include rod length and intake closing.
You really do need a machinist to tell you how much you can safely mill from a head. They generally recommend as little as possible to true it. Milling a head is not the best way to get more compression. Maybe you can mill 8cc out of the chambers, maybe you can't.
Static compression is questionable at best in determining if an engine will knock. You need to look at dynamic compression. There are calculators out there that include rod length and intake closing.
You really do need a machinist to tell you how much you can safely mill from a head. They generally recommend as little as possible to true it. Milling a head is not the best way to get more compression. Maybe you can mill 8cc out of the chambers, maybe you can't.
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From: Venezuela
Yes It has a Crane 503901 + V8 injectors, exhaust and pressure regulator.
It is giving very nice power and performance but is having low economy, around 12 to 13 MPG. Beffore timming the Camsahft it was giving just 10 MPG.
Recently the head suffer some damage at one valve seat the I had to remove for some machining and I was considering the option to increase a little bit the Compresión. I know the best way is shave also the engine block but I don't want to dissasembly, at least not now
Thats why I was looking for a simple number to shave the head
It is giving very nice power and performance but is having low economy, around 12 to 13 MPG. Beffore timming the Camsahft it was giving just 10 MPG.
Recently the head suffer some damage at one valve seat the I had to remove for some machining and I was considering the option to increase a little bit the Compresión. I know the best way is shave also the engine block but I don't want to dissasembly, at least not now
Thats why I was looking for a simple number to shave the head
Lead Driver
Joined: Dec 2000
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From: South central, Minnesota
It's been a while since I played with an EFI 300. But I seem to recall the stock compression was either 8.8:1 or 9.0:1. The combustion chambers were right around 68cc. They also had some rather large dishes in the pistons.
I personally don't like to remove any more material then needed to true up the surface of the head. I prefer to go with different pistons.
But if you want to mill the head then take it to a machinist, have them CC it ( unless you have the equipment to do it yourself ) , mill it and then cc again to confirm it's where it needs to be to reach the compression you are shooting for.
I personally don't like to remove any more material then needed to true up the surface of the head. I prefer to go with different pistons.
But if you want to mill the head then take it to a machinist, have them CC it ( unless you have the equipment to do it yourself ) , mill it and then cc again to confirm it's where it needs to be to reach the compression you are shooting for.
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