How Much to Mill Heads? 73 Heads on 71 Block?

I have a spreadsheet I built and probably shared here at some point that calculates all that information. What I don't know is the CC change when milling heads. I'm making assumptions that will be close enough at this point.

I'm OK with it being slightly better and not the best it can be. I want it reliable and sturdy, not a max effort engine. Been there, done that, had to repair it too many times. I broke rocker arm shafts, snapped input shafts on T400s, broke sprags on T400s and lived with less than satisfactory power brakes.

This motor will have a little lope, a little rumble, run on the cheap stuff and be as reliable as I can make a 51 year old car. I'm of the age I want to enjoy it more than I want to race it. As long as it break the tires loose and pass a Camry, I'll be happy.

 

I measure 11.1 to 1 comp. ratio, its awesome

 

Hopefully the Camry doesn't get cha.

 

Sad but true, most all the newer 4 and V6s make as much hp as our Buick V8s, not the torque tho

 

im following you. i want to do the same. cheap fuel decent mpg but have a little more guts. let me know what this cost you to get those heads done. are you going to port them as well?

 

Probably not much if at all. Likely put more money in the valve job, back-cutting and shaving them so I can run steel shim head gaskets.

 

I’d be Leary of running steel shim head gaskets from the standpoint of water leaks, I’d run FelPro blues

 

i want to shave mine and port match them basically. i prob wont even do a valve job since they have no issues unless the machine shop says it needs it.

 

That's why I'm having everything milled flat, in hopes of using steel head gaskets.

 

Greg, If you use the steel shim gasket spray both sides with this:

 

I had planned to.

So, is the consensus that steel shim head gaskets are a bad idea for longevity and reliablity?

 

I think they are fine if you mill the heads and deck the block to ensure they are flat. You have to retorque after initial break in. Break the bolts loose and torque as new in three stages. My experience with 215, 300/340 and v6's with under 10.5 compression, you will gain close to a half point of compression with .020 steel compared to the composite .040 gaskets. Cometic multilayer gaskets are probably the best for high compression.

 

I'd do it, you already have lots going for you if you true up both the head and deck sealing surface. The only reason I'd think of going away from the steel shim and upgrading to a composite gasket would be if you were going to crank the static compression ratio up over 11:1.

Might even be worth asking the shop if they prefer a particular surface finish for the shim gaskets.

The above + the copper spray and you should be good to go.

Devon

 

I've always used steel shim gaskets. I've used them dry, as GM suggests, and sprayed with copper coat.
No adverse effects running 10-1 to 11-1 compression.
I've even run them without resurfacing block. Heads, yes.
Just slide a long straight stone on block surface to eliminate any small nicks or upsets.

 

The massive gears in transmissions now is to compensate for the lack of torque in smaller engines. Our cars with an overdrive is pretty nice. I'm putting an M23Z (2.98 first gear) Muncie in my 71 GS with 3.08 gears. I was skipping gears with the factory M21.

 

I have about 3000 miles on my rebuild. No issues with steel shim gaskets. The machine shop used copper spray when assembling. I also had 020 shaved off, and a valve job, i did about 4 or 5 hours of porting. Machinist said my efforts were worth while. I really concentrated on the valve bowls.

 

You'll be fine. I ran them on my last 350 w/o milling the block (was an orig. "SP" although not orig. to the car). Block was out maybe .002" IIRC. I wouldn't have done it if it was out any more & next time I'll mill/square it.

 

Is that .020 off the heads? Do you know what CC yours heads were afterward?

 

Yes .020 off heads. I have no idea on the cc. I wish I had paid better attention. They are 70 heads and were supposed to be 58 cc chambers stock. Some of the guys on here guessed my compression to be around 9:01 to 9.5 :01. Runs good on pump gas with my 284-88h cam