Looking for a reccomended thickness / brand of head gasket to use for a smog 440 build. I previously used the gaskets that come in a standard felpro 440 full gasket kit. This is a 78 block with stock pistons etc. I was using 516 closed chamber heads. Now im going to put on 906 open chambers... Am i going to be loosing much power/ compression with this swap?

you will loose a lot of comp. using the 906s but if you have to, use the steel shim head gaskets from summitt racing, i think mr. gasket makes them and they are the thinnest you can get at .018 to.020 thick.

I really don't want to but i believe i have a cracked head. I'm going to be ripping it apart shortly. And instead of spending 1k for heads, i have a set of fresh 906's sitting here. Do you think its going to be a big noticeable loss of power going from the 516's to 906's and i should just spend the money on aluminums?

I did a block test which you put a blue coolant in the system and run the engine. then use a tool like a turkey baster and suck the vapors off the top of the rad. It showed exhaust gases in system. Im going to pull the plugs and see if any are suspect. Engine RUNS FANTASTIC, just over heats quickly. 210-215

How do you know you dont have a head gasket issue instead of a cracked head? Just curious.

UPDATE.... this is getting interesting..
Pulled the plugs,they all looked about the same. Weird... Saw a little bit of oil on the valley pan..Pulled the intake. Look through the intake ports down at the valves. 6 of the 8 valves had fuel puddled in the seat. Wow..this might explain why when the car sits after running its a pain to start... Ah why i got the carb off let me just throw a different carb on. I replaced the holley with an eddy 600.

I run the car in the drive way... 5 minutes.. monitoring tempatures..10 minutes watching the coolant cycle ,15-20 minutes car is still at 170 highest at idle.

Wow...lets not get to excited..hop in the car go for a cruize,some stop and go but mainly 60mph roads, a good 30 min drive with some wide open passes . Car never got over 180. I idled it when i got back in the driveway for another ten minutes and it got to 185 but never higher and thats sitting after the beat down. I shut it down, and let it sit for 10 minutes. Did a relight and it lit right up instantly. Never would of done that before. Im going to keep my fingers crossed and the next HOT day try it out and see what happens...

Do an oil change right away.
If there was fuel puddled up, it could be in the oil now too. You don't want that.

That is good but we still have the exhaust gas in the coolant puzzle piece.

Where does it fit?

Remember me saying I didn't think it was a crack or gasket issue?
Yes fuel and timing has everything to do with temps. I know you said you were waiting on a timing light. You need about 15-20 degrees intial timing with 35 total all in by 3000 rpm.

Glad to hear the good news, but I still think you may need a shroud someday.