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Shaved Head/block

Don Dada

By Don Dada,
in Engines & Forced Induction

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  • 2 weeks later...
winstonusmc Enthusiast

winstonusmc

Posted
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The only tru way is to pull the head off and measure it. You could do a compression test. If the numbers are higher than factory specs, it is shaved. But I know with my shaved head, it pings a little in a low gear and high load, like going up a long hill at 2000 rpm. Is your ECU tuned? If so post up your tune if you know how and I can see if it has been adjusted for higher compression. Of course whoever built your engine could have put a thicker head gasket on to counter the shaved head.

My question is why do you want to know? Are you wanting to shave it again?

T04GTR Grand Master

T04GTR

Posted
Posted

on a rb26, on the underside of the head at the front there is a foil sticker. all virgin heads have them. if its gone then you know its been done. also the factory finnish is very fine. not cause like most machine shops do it.

you would have to get 2 side by side and see.

Don Dada Mentor

Don Dada

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Posted
The only tru way is to pull the head off and measure it. You could do a compression test. If the numbers are higher than factory specs, it is shaved. But I know with my shaved head, it pings a little in a low gear and high load, like going up a long hill at 2000 rpm. Is your ECU tuned? If so post up your tune if you know how and I can see if it has been adjusted for higher compression. Of course whoever built your engine could have put a thicker head gasket on to counter the shaved head.

My question is why do you want to know? Are you wanting to shave it again?

You hit he nail on the head!

It does ping on a hot day pulling off in first with the ac on and if i dont give it enough throttle,and comp did come up a little high, with 175 being the highest so all this lead me to believe it was shaved......also using 95oct on the stock ecu.

I guess compression hasn't raised by that much though because Nissan says it suppose to be 170 from factory, so surely 175 shouldn't make much difference.

I got the engine from the importers so god alone knows what the japs did, but i am thinking about putting in some forged pistons, freshen it up a bit and use a metal hg and i know the head has to be perfectly flat to use this so a wanted to know if it can be shaved again if the need be.

I dont have much knowledge in this area and i am not in Aus, and from my experience the builders here are not 100% trust worthy either and i cannot take their word for it, so when u say pull off the head and measure it....what exactly am i measuring???

Basically i just want to know if the head is within tolerance so i need to know if it has been shaved already,if so how much has it been shaved, and can it be safely shaved again

Also, only aftermarket gaskets are metal right??? so i must know if its a stock or aftermarket head gasket in there right now?

Thanks

winstonusmc Enthusiast

winstonusmc

Posted
Posted

You have the option of putting a larger head gasket in to drop the compression back to where it should be. I have a .4 mil shaved head and it raised the compression to 190 across all cylinders. Of course, the rings seem to be in great shape so I would guess .2mil over stock head gasket should get you to a better comp ratio.

Checking a head when you pull it off for warpage should let you know if any more material needs to be removed. If you are OK, then the thicker head gasket should get you back to normal compression. When you pull the head, check the gasket to see if its already a thicker one. If so, you may need to go thicker.

I also have chipped my ECU to almost eliminate the pinging. It pulls the low rpm timing down 5 degrees or so but retains the origional timing at higher rpm. seems to work pretty good so far. If you want the Bin, let me know. I will remove all the injector and MAF scaling to work with a stock engine.

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