My spare cylinder head is at the machine shop getting ported and polished in preparation for my stage 2 build. The machinist convinced me to shave down the head a few thousands of an inch or gain a higher compression ratio. This is good also, but I think the head needed it anyway because I dont want the HG to blow and it had some nasty grooves in it. Any info on how much of a good/bad idea that was?

My DOHC swapped Neon was like that.

I had it milled .030 which should have netted a 10.3ish CR.

EDIT: I just searched the info I used on Neons.org, ended up finding something better:

milling .060 = one compression point, .030, half a point, .015 = 1/4 point
So that would be like from 9.6 to 1........... milled .015 around 9.8 to 1 or just a little bit over, between 9.8 and 9.9 to 1 compression going by the cylinder bore size.

-Eddy Fierro

You'll be okay, if there were some heavy gouges in the mating surface it was probably a good idea to get this done. Just keep an eye on things when you get ready to set the timing on the motor. Rule of thumb would be to find TDC and remark your cam gears, they shouldn't be off by much but you'll want to take this into account.

Ok cool thanks guys. I was thinking if the cam gears are off too far that it bothers me I could just get adjustable cam gears. Ill probably post up what he milled when I get it back.

I just picked up the head and it looks awesome. Although he told me he only milled it about 8-10 thousandths.

looks purdy, although I'm surprised that the intake ports look more polished than the exhaust. I was always told that you want things slightly rougher in the intake to prevent fuel from sticking to the walls and puddling. Whereas the exhaust should be polished to prevent carbom buildup.

I could be wrong.

Im not sure. All I know is this guy has a top fuel dragster and is pretty much he best machinist in my city. Everyone who does any kind of work brings it to him, so I trust his decisions. It goes on this weekend and Ill let you know the results.

Originally posted by 740 turbo brick
Im not sure. All I know is this guy has a top fuel dragster and is pretty much he best machinist in my city. Everyone who does any kind of work brings it to him, so I trust his decisions. It goes on this weekend and Ill let you know the results.

would this guy have a shop in the Canton area.
What machine shop would recommend for me, I'm from alliance.

Not sure, his name is Carl West. He has a shop up here in Ashtabula. I would ask around to see where to take stuff up by you. I just asked around and everyone said he was the best in town so I took it to him.

What you will find with .008-.010" is about a 1/2 tooth off on the cam gears. That is about 2* on my Fidanza cam gears.

I had my head shaved .080 and block .011 with wiseco 10.5:1 and love it. Getting 225 across the board with 1500 miles on fresh rebuild. However, I also went to OBX adjustable cam gears, which makes timing EASY

Originally posted by LLs420a
I had my head shaved .080 and block .011 with wiseco 10.5:1 and love it.

I don't think you did. You might want to check those numbers......

Originally posted by bullettdsm

Originally posted by LLs420a I had my head shaved .080 and block .011 with wiseco 10.5:1 and love it.

I don't think you did. You might want to check those numbers......

So he is at like 12.0 compression?

Lol. Its a high comp all motor build. Had the shaving and honing done by Benny Cranes in Abilene, TX. Guy has been doing it for over 25 years and told me that he could take 8 thousandths off the head and 11 thousandths off the block VERY MOST. He also mentioned before I left that I had no room for error in timing or I would introduce the pistons the the valves.

so you had 0.008 taken off, not 0.080.

0.080 is eighty thousandths and not likely that you had that removed.

Originally posted by CODE4
so you had 0.008 taken off, not 0.080. 0.080 is eighty thousandths and not likely that you had that removed.

Ah, makes sense now :)

Classic power of ten error :) And the valves?

Originally posted by VX100
Classic power of ten error :) And the valves?

.091 removed = valves, meet Mr Piston, lol.

Though Mr Cranes is pretty close with his assessment. I took .020 off my head with a slight block shave at 10.5 comp. I do know of a Neon guy who did .030 with 10.5 comp, but IMO that's dicey. I wouldn't do that unless I clayed the engine. I did .020 on my 12.5 comp (on Crower 3's) and over revved in the water box. I slightly contacted.

I see. Yes, my mistake for being off on the numbers. But that IS what I had taken off and the car is still running like a champ :)

How high can you get away with in terms of milling the head on a 420a n/a motor to get a higher compression ratio, and what ratio it can be at and still use 91 and 93 octane and not crunch valves.