Shaving heads?

[tbi92rs]

OK, Im reusing my stock E7's for now. Ive heard of "shaving" the heads to bump compression ratio. How much should I shave them (exact tenths)?

Im running the lunati 51014 cam with .500/.510 lift, 218/226 duration and 112 LSA......I do NOT want pistons and valves to become newfound friends, so to speak. They are stock replacement TRW forged pistons BTW.

Ill also be spraying a 100-150 wet NX shot too, keep in mind.

I plan on taking them to the machine shop in about 2 weeks or so......so how much is recommended? I already run 93 octane for the bottle, so thats no issue.

Thanks guys!

 

[86bluecobra]

i don't think they shave heads in tenths i think you only shave thousands off. like 20 thou

 

[dastang2]

it won't help much, and if they take too much off, you will need to shim the pedistal rockers to get the math correct. not worth it unless they are uneven. if you wan more compression get some 289 heads with 58cc

 

[tbi92rs]

Yeah, you do it in thousanths...my bad.

I heard shaving 30 thousandths raises the compression ratio by 1 or 1.5.....so if stock is say 9:3, then shaving 15 thousandths would put me at 10:1....thus giving me more HP because of raised CR.

So, again, anyone know how much I sohuld shave? I have the pedestal mount rocker shims already if needed.

 

[Topdowncruise]

I read that shaving .040 will gain you about .5 CR.max. to about 9.5.

 

[tbi92rs]

hmmm......ive heard its worth it since more ocmpression means more HP...but I dont want piston to valve clearance issues with my cam

 

[dastang2]

how much power are you looking to get, i'd say 10 hp or so is what you will get. they are stock heads, not worth it considering all the work and money to get them shaved.

 

[hamonkeiser]

I had Thumper shave 30 thousands off of mine for a little more compression. It'll bump you to about 9.8. You can safely go to 40 thousands but I wouldn't recommend pushing it any further.

 

[thumper460]

yep... .040 will do it with out intake manifold interface issues... and the valve will be fine!! ruff figure is 1cc for .005 off, ORrrrr..... .040 off = 8cc=62cc ( E7s) to 54CC , which is what the 289 heads carry!! and the HP gain will be felt!! IF you pull that 112 ICL up 2 or 4 degrees you will build MORE power!!
Just me............................

Thumper

 

[rd]

I ran through the math on D80E heads, and figured out that with 70 cc chambers to start, shaving .030 got me from 8.5 or so to 9.0 to 1. I went .025 the first time just to make sure it could be assembled w/o manifold issues. Works fine. Starting with late heads with smaller chambers does better. It was a pain to calculate the area of the chamber....