Shaved heads and head gasket thickness.

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Retroboy

Retroboy

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Hello all. I've come across some "J".heads from a 1970's C/Gas car. They've been shaved enough to consider them closed chamber heads now. I have KB pistons with small domes that protude a bee's dick above the deck. With a second hand FelPro head gasket and some plasticine on the piston I can turn it over but there's only a cigarette paper thickness clearance. Felpro suggest their gaskets are .039" thick.
What gaskets have others used with severely shaved heads? Who makes a thicker head gasket? Can you help me with a part number?
Cheers
 
The felpro 8553 are are pretty thick i believe they are around .054 before they are compressed they seal very well too. And btw rock auto had them on sale for pretty cheap last time I looked . You can buy custom cometic gaskets up to like .120 thick but they are very expensive they are like 215 each!
 
I went back and looked at some old post my new 8335 gasket was .056 uncompressed and a used one was .051 after it was compressed

20190214_140216-1.jpg
 
When you say secondhand Felpro gasket, are you talking about the 1008 performance gasket? Can you post some pics of your chambers? Is the thin clearance on the flat part of the piston away from the dome and what compression ratio are you targeting and what fuel are you going to be running this on?
 
If I need information like this I like looking at Summit's website. I bet their search criteria will list thickness as a choice. It's easier to choose what you need because of how they are listed.
 
If you haven't done so already. I would cc the heads and make all your measurements and see where you are before deciding on a gasket thickness.
 
The blue Felpro composite gaskets that I have used are usually 0.039-0.041" thick, compressed. Cometic make gaskets in various thicknesses. If you are going to keep the rpm under 7000 & using steel rods, then 0.025" gap is enough.
 
Thanks for your thoughts. Car runs on methanol so fuel isn't an issue. Gaskets shown are copper from a few years ago but photo shows pistons
Gasket I used last night to check ckearances is a used FP8553

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Minimum clearance for piston to valve I would consider to be .100" and .120 is better. "HOW" you'll get "THERE" with an off the shelf gasket beats me.
 
RustyRatRod said:
Minimum clearance for piston to valve I would consider to be .100" and .120 is better. "HOW" you'll get "THERE" with an off the shelf gasket beats me.
Click to expand...

Not piston to valve that's potentially the problem, more the piston crown to head clearance that is of interest.
 
Retroboy said:
Not piston to valve that's potentially the problem, more the piston crown to head clearance that is of interest.
Click to expand...
I misunderstood then. My bad. I was thinking valve clearance. I would think .020" as a minimum with steel rods and .035 and up for aluminum rods.
 
Can we get a good picture of the complete chamber side of the head? I'd love to see a closed chamber small block head. lol
 
Retroboy said:
Hello all. I've come across some "J".heads from a 1970's C/Gas car. They've been shaved enough to consider them closed chamber heads now. I have KB pistons with small domes that protude a bee's dick above the deck. With a second hand FelPro head gasket and some plasticine on the piston I can turn it over but there's only a cigarette paper thickness clearance. Felpro suggest their gaskets are .039" thick.
What gaskets have others used with severely shaved heads? Who makes a thicker head gasket? Can you help me with a part number?
Cheers
Click to expand...

Felpro SD521 . They dont know.. but I bought them and measured and used them...they are .054 compressed.
That'll give you a little bush cushion between pumps.
 
RustyRatRod said:
Probably close to whatever the 302 heads are. Chamber looks similar "now".
Click to expand...
Its been a long while but iirc I think my 302s cced at around 60. My 360 heads were milled .030 and came out around 63cc average.
 
dartfreak75 said:
Its been a long while but iirc I think my 302s cced at around 60. My 360 heads were milled .030 and came out around 63cc average.
Click to expand...
That's about right I am sure. I think they are actually advertised as 58cc, but they always cc bigger.
 
Retroboy said:
Hello all. I've come across some "J".heads from a 1970's C/Gas car. They've been shaved enough to consider them closed chamber heads now. I have KB pistons with small domes that protude a bee's dick above the deck. With a second hand FelPro head gasket and some plasticine on the piston I can turn it over but there's only a cigarette paper thickness clearance. Felpro suggest their gaskets are .039" thick.
What gaskets have others used with severely shaved heads? Who makes a thicker head gasket? Can you help me with a part number?
Cheers
Click to expand...
Why wouldn't you just machine 2 bee's dicks off the pistons?
That would solve all of your issues and allow you to use a cheap (and easy to find) off the shelf gasket.
BTW, you sure have big bees where you live.....
 
Well I was just thinking last night about talking to my best mate Jim about getting him to take a bit off the top with his mill.
I actually measured the piston above the deck yesterday with my dial indicator at .063" Yep us Aussie's have some killer wild life.
 
dartfreak75 said:
The felpro 8553 are are pretty thick i believe they are around .054 before they are compressed they seal very well too. And btw rock auto had them on sale for pretty cheap last time I looked . You can buy custom cometic gaskets up to like .120 thick but they are very expensive they are like 215 each!
Click to expand...

Something key to know and state.. is what cid engine and what fasteners did you use?
318/273 use less torque on the heads and fasteners can play a part in heat cycled clamping force. So less torque, less clamp, less clamp, less crush...
The same gasket used on a 360 crushed @.046 ,stock heat cycled bolts.
There's 10 lbs diff between 318 &340/360LA and even more for magnums, 114 or something near. So in order to give useful advice we need to add a description tag to our contributions of what and where and how
CID? Fastener?
 
RustyRatRod said:
Something key to know and state.. is what cid engine and what fasteners did you use?
318/273 use less torque on the heads and fasteners can play a part in heat cycled clamping force. So less torque, less clamp, less clamp, less crush...
The same gasket used on a 360 crushed @.046 ,stock heat cycled bolts.
There's 10 lbs diff between 318 &340/360LA and even more for magnums, 114 or something near. So in order to give useful advice we need to add a description tag to our contributions of what and where and how
CID? Fastener?
Click to expand...
:rolleyes:
 
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