Recently found combustion gases in my radiator so that means I blew a head gasket (probably )

I have a 350 with the Chevrolet Performance Composition Head Gaskets 10105117 that have a .028" compressed thickness, this is on an 880 crate engine block that's never been machined so I'm assuming the deck clearance is .025 meaning the engine has a .053" quench, seems a little high to me, to my understanding it should be around .040" for good detonation resistance, at least that's the general concensus on high performance engines pushing compression ratios above 9.8:1 from what I've seen. My motor however is 9.1:1 and I haven't had issues with detonation turning this thing at high RPM until one of the cam lobes went flat, which I am replacing with a mild roller cam (SUM-8800). The FEL-PRO 501 SD gasket I bought are a .041" compressed thickness and that would make the quench area .066" which is horrible in theory however this is not a high RPM screamer, it's a daily driver and I just don't want to have to do head gaskets again until I can park it and put aluminum heads on it, that's why I went with the 501 SD's, I don't even care that my compression ratio would drop to 8.9:1 by going to .041" gaskets. I don't wanna buy the 1094's and risk them not sealing correctly on my block because it's not a mirror finish and having a giant leak somewhere even though they would put my quench right at .040", it's the same reason why I'm not going with the 10105117 gaskets, because I'm pretty sure they require a mirror like finish to seal correctly which I don't think I'm getting with a carbide scraper.

My pistons are 12361371's which have a 13cc dish and valve reliefs, doesn''t that negate the effect of quench anyways???

I'm losing a lot of sleep over this because this is my daily driver and I need it back on the road and running reliably for the time being until I can move and park it. Will I be able to run the 501 SD gaskets without getting crazy detonation and being able to run on 87 octane with a full timing sweep? (32-34 degrees total) Or is there some other option I can do to help my quench height, I wanted to run the 10105117's originally since I know those will work with my application but I don't think they'll seal well against the block if it's not absolutely perfect.

I did my dynamic compression calculation with the new cam I have and it sits right at around 7.9:1 DCR and 8.86:1 SCR (using go fast math calculator, summits calculator shows 8.91 static)

Am I taking a severe misstep here with going to these head gaskets? The difference is only .013" but I know that CAN be A LOT in the engine world

 

Can't help you with the specifics but I can tell you I ran 1094's with my block, which I cleaned the deck with ~1000 grit sandpaper and wd 40. Maybe I spent 5-10 minutes per side? The used alu corvette heads I put on got the same treatment. No decking the block or milling the heads. Not saying you should rush the cleaning but the gasket doesn't need mirror like finish, actually afaik they prefer something to grip. Haven''t got a single problem. Probably luck

 

I'm not opposed to trying that, I wanna get the heads resurfaced while they are at the shop. I would rather have a thicker head gasket that seals well than a thin one that leaks, my luck is usually pretty bad.

With a fel-pro 1094 my static compression will be 9.3:1 with a DCR of 8.36:1

 

Anything running 87 octane is a throwaway regular traffic motor so don't sweat it and put back whatever was there.

 

I just got the gm 10105117's in the mail which is what was in there originally, according to scoggin dickey these will work just fine and .053 is nothing to worry about on a street motor with pump gas.

 

The "quench" isn't affected by the dish. If you look at the piston crown, you will see a ring of material that goes around the crown. The quench area is away from the valves, so even with 13cc dish piston, you still want to maintain the 0.040" quench.

The only way to know is to measure how much in, or out, or even with, the block deck that material "ring" is relative to the block deck at TDC. If the piston crown is down in the hole (say 0.008"), then subtract that from 0.040" and use that compressed thickness gasket (in this example, 0.032"). If the piston crown is out of the hole (again using 0.008" as an example), then add that to 0.040" and use that compressed thickness gasket (in this example, 0.048"). In SBCs, the pistons are typically down in the hole - but you need to check.

As stated, though, with 13cc dished pistons, you probably aren't going to notice much difference.

 

I'm going to use 113 aluminum heads that I found for REALLY cheap, they're getting milled at the machine shop right now. Same castings as the zz4 head which used a .051 head gasket, I'm gonna either use the 10105117s or the fel pro 1010s, not sure on what exactly I should go with yet. should boost my compression a considerable amount to 9.8:1 at least