Back again with overheating problems

[bubba22349]

You could probally use 10 or 10.5 to 1 and advanced the cam to 4 degrees at that alt.

 

[Lazy JW]

My CR is 9.0:1 after milling and decking. The cylinder compression avg is 110 psi. The timing at idle is 14 BTDC and vacuum gauge reads 10 hg at idle.......

Yup. More compression and more (advanced) cam timing would bring that idle vacuum up a bit, it should really be able to pull 14" or so. Give it as much ignition timing as it will stand.
Joe

 

[mustangsilly]

It wouldn't be practical to raise the compression. I've already milled the head .075 and gone with the thinnest gasket I can find. I used a '69 head with 62 cc chambers and brought it down to 52cc. I also don't want to run into a problem of not finding high enough octane gas. So I'm going to have to leave it at 9.5:1. I can try advancing the timing more, but it's set a 14 BTDC now. Should I just keep going until it starts "pinging?"

 

[bubba22349]

It wouldn't be practical to raise the compression. I've already milled the head .075 and gone with the thinnest gasket I can find. I used a '69 head with 62 cc chambers and brought it down to 52cc.

I understand that may not be practical at this point. But years ago Ford as well as others built special engine packages (small chamber heads etc.) for the Denver area's (thin air) with about 1 point higher compression! Some Drag racer's still build a special higher compression engine for competition use at the Denver races and or use a more boast with a supercharger different pulleys to spin the blower faster.

I also don't want to run into a problem of not finding high enough octane gas. So I'm going to have to leave it at 9.5:1.

Really doubt you could have a problem at 10.5. They also had special bends on fuel for that area to help that too.

I can try advancing the timing more, but it's set a 14 BTDC now. Should I just keep going until it starts "pinging?"

Yes go for it! Try adding more initial advance it until it pings and than back off about 2 degrees or if the starter is kicking back it’s too much lead. Do you know what your total advance is? You may need to work on distributor centrifugal advance some and also the vacuum can be moded to give even more total advance too. Though I won’t do it for most customer car's (common sense) on my personal cars since its mostly flat ground at close to sea level here. I would go a bit farther and used to set it so there was a very slight ping pulling a little grade (i.e. like climbing a Freeway on ramp) in high gear if I floored it. You would need to know when it's too much though.