I have no clue about quench and what size head gasket to use with my setup. The setup is a 355 TPI which 180 cc runner heads and they are 64cc chambers. Im using a cast 10:1 piston. Ive been told Im going to have alot of detonation with that combo or have to run premium or greater all the time. Ive also been told to keep quench on the tight side. The head gaskets I do have are .0525. I think that is it or maybe I have a zero in the wrong place. Will these head gaskets work to keep detonation down or will I need to go thicker or thinner? Let me know your opinions on this. I dont want to mess this up the first time. It's my first rebuild and this is one of the only things Im not exactly clear about with engines. Thanks guys.

 

Thinner, try for .032" or thinner compressed thickness, this will tighten up the quench area.

 

That may be what the thickness of you gaskets are NOW, but what's the compressed thickness?

 

Also, what is your deck height? Do you have enough clearance for you valves to pistons with a thinner head gasket. There lots of variables involved with making the quench area smaller/tighter.

 

.041" compressed thickness is about standard on aftermarket gaskets.

 

Did I ask you? Is it your gasket?

I understand that, but obviously HE/SHE doesn't.

And it is quite possible to have a head gasket that's .0525" thick.

In order to accurately answer the question, you have to know for sure.

 

10:1 is doable with optimum quench. You want your quench to come out at 0.040 .. To do that you'll need to know your deck hieght.. Get a dial caliper or some other way to accurately measure piston depth at TDC... most undecked blocks will come out around 0.025.. but you have to measure to be sure. Stock type rebuilder pistons actually increase the deck heigth to lower compression and compensate for being bored. No way to know for sure without measuring. Friend of mine just increased his compression from 9.3:1 to 10:1. And used a tighter 0.015 steel shim gasket to get the quench from 0.065 to 0.040... No more detonation!! He had bad knock counts at 9.3:1.. now he barely has any.

Anyway, the important thing is to measure the deck height and use that to calculate gasket thickness. You can buy gaskets of all different kinds of thickness'.. And like somebody else mentioned, make sure your valves will not hit the pistons if you use a thinner gasket.

 

No one asked you either, don't get your panties in a bunch
If he is measuring his gasket with a micrometer or calipers before installing, then he will get about that reading on a gasket that compresses to .041" installed

 

If you cannot correctly measure your piston height, favor on the tight side in regards to quench. If you are using cast pistons, I would guess that the piston is .020-.025 in the hole. Use GM 10105117 head gaskets. The have a compressed height of .028.
This will tighten the quench and the engine will not be as octane sensitive.

For what it's worth, the ideal quench is .040.

www.geocities.com\dzperf

 

Wow...I didnt expect these many answers when I woke up this morning! Thanks guys. Well we had measured them with digital calipers. Im pretty sure that is what they are called. I can have my dad measure the deck height tonight to give you guys more of an accurate description of how thin they will be/or need to be. I got the gaskets in a whole rebuild kit off ebay so Im not sure of exact numbers and all like the compressed thickness of them.

Morley you said that after my gaskets are compressed, I will have a reading of about .041. Is this ideal then for having no detonation? This is the absolute next step in putting my engine together so I would hope not to have to buy or wait for more gaskets to arrive. Hopefully they'll be good.

 

I asked HIM what the compressed thickness was. So yea, you're right. Nobody did ask me, since I was the one that asked the question. It was meant as a joke. You need to calm down.

SanitariumTour0,

If you're this concerned, and want to find out the TRUE compressed thickness of the gasket which YOU have, then call the gasket company and find out. Don't trust some SPE at a website.

 

OK well my dad says that the deck clearance is .050 roughly. Good or bad?

 

bad, way too much. Also, for those with knowledge, What if you have aluminum heads? Thin head gaskets, could make it easier for blown head gaskets? Yes or no what is you opinion-Jeff

 

Not if they are made of the proper material, also if it is a concern you get the heads/block O-ringed, best way to foil the head gasket daemons.

 

ok so you say it is bad and way too much then what do I do to get the number down and what are the best deck clearance numbers?

 

.050 piston deck height seems off base. The proper way to check is with a dial indicator. You are faced with a couple options:
1. Buy new pistons and have the block zero decked. $$$$
2. Tear the block down and have it zero decked.
3. Just use the GM 10105117 head gaskets.
I've built several engines using these gaskets without fail.

 

ok....well i might just buy the new gaskets then since you say they will work. Can I buy them at any local auto parts store? My dad and I already spent a few weeks putting together the bottom end with what little time we can work on it so taking it back apart is not an option. And even with the deck clearance as high as it is, those gaskets will still be fine right?

 

Any GM dealer can get the gaskets. I would try Chevy first.

 

Read this it will help you understnd everything you ever need to know about quench. Also Dynamic compression is also explained to help determine what grade of fuel you need to run your engine. Download the calculator:

Thanks Pat Kelly for this awesome program

http://members.uia.net/pkelley2/DynamicCR.html