head shaving

[brian]

i'm NOT reffering to myself!

i've come in to a '75 head from a blown motor.
i'm looking to rebuild it and while i'm there, i'd like to shave it alittle for a compression gain.

what would be a starting number to think about removing?
i'm not looking to go over board, just help things out.

it will be gone over to check for cracks and the like first.

 

[IDave]

20/1000s would be a good start. If the machinist f/us and nicks it afterward like mine did, he may end up taking off another 15. Like mine did.

 

[brian]

and is 35/1000 too much?

 

[folsom50]

and is 35/1000 too much?

I had mine decked .020" when it was rebuilt. I looked in my manuals and all I could find was max specs for warpage. You'll need to talk to your machinists to find out how much can be removed, or maybe somebody else in here knows the limits.

 

[60wag]

I think Mark Whatley routinely takes off 0.100" I had 0.050" taken off mine during the rebuild. Its nice but I can't how much of the improvement was the shave or the rest of the overhaul. It does ping a bit on 85 octane. I'm at 5400 ft. 87 octane is usally ok but sometimes I need 91 to quiet the knock.

 

[IDave]

35/1000s along with the head rebuild and valve seats brought the compression up to 168 on all of the cylinders. Standard for the F engine is 150. Thing is, my rings are still quite worn so I burn oil to beat the band. I like the extra compression, but it is of limited value, and the fact that so much came off limits the life of that F head. Who knows how much more can be shaven in the future if need be? I have heard that 50/1000s is pushing the limit realistically. Now, I have another head sitting waiting for later, so I don't feel too worried, but I would rather have limited the shaving to 15-20 thousandths.

 

[T Y L E R]

Shaved head ... I think I'm giving Eron the bird here , half juiced at an outdoor cafe .

50/1000's I think .. ;p

TY

 

[brian]

i have good reason to believe that this head was never touched, so i'll have all the meat to start with.
it's looking like i'm thinking 20ish/1000 to start with, depending what it looks like when i get it. this head was next to free with no motor to go with it, so i'm free to play

 

[toddslater]

You should be very safe at .020. Hasn't someone on board done the math on these yet ? If you have time...cause I'm up to my ass in projects right now, I can dig out the head specs and see what your bumpin the compression to based on a given HG thickness and how much your shaving off. Two things you obviously want to avoid: 1) I'd definitley keep it under 10:1 and 2) if you get too dramatic you will change you valve/rocker angles and need to make either custom rocker pedastal shims or custom length push rods (shims obviously easier) to correct those angles.