.030 or .036 head gasket?

[adayrider]

Fed ex delivered my .036 this morning I ordered from FM ans wouldn't you know it they sent me .030 

[Ohio HD]

If you're sure that the pistons are no more than zero (not above the cylinder at all) use the 0.030" gasket. 0.006" one way or the other won't make or break the motor.

[rigidthumper]

It's a sign!

[FXDBI]

Lift @ TDC needs to be considered when doing all your math has well.  Bob

[rigidthumper]

552 has .183"  TDC lift on the exhaust lobe, so he should have .270" ish to be safe.

[Txwezl]

Fed ex delivered my .036 this morning I ordered from FM ans wouldn't you know it they sent me .030 

Denniskirk has the .036

[adayrider]

Fed ex delivered my .036 this morning I ordered from FM ans wouldn't you know it they sent me .030 

Denniskirk has the .036

I can't/couldn't find them. They do have 4.205 bore .036 but not 4.25 .036. Maybe I'm missing them?
I think I'm going with .040 now because I can't find .036 without special order. I had cylinders decked .008 and .011 so that puts me right where I would have been if I just bolted them on with .030   According to BB calc I'm still at 10.97-1
Mr. Rick Ward took time out of his day to call me because he seen this and took shot that it was me posting. He explained to me how it works and I could use the .030 but .036 would be best for what I was doing and .040 wouldn't hurt. So since nobody can source a .036 without special order I think I'm going with .040. I'm just a backyard hack and don't have all the top shelf dial indicators, micrometers special tools to be that precise. And even though I like to think and ride it like a race bike, it's still my riding and touring bike and I'll never miss the 1 lb or 1 hp I'll get from the extra squeeze. And I always have the .030 on the shelf if needed. LOL

Thanks for everyone's input and help.

[kd]

If Cometic has a gasket pattern and they don't list what you want but have the dimensional materials to stack or build a gasket they will do it at the cost of the same gasket they list.  No extra fee.  You may call that special order but when I spoke to them there was no extra time to build and ship the gasket.  It's a great service from a great gasket supplier.  Did you give them a call?

[No Cents]

  give Cometic gaskets a call as kd stated. 
Give them your bore dimensions and desired thickness of the head gaskets you want and they should be able to help you out.
(800)752-9850

[yobtaf103]

What size is the base gasket, seen no mention ?

Apparently the 0.014' base crushes to 0.013" in reality

[kd]

What size is the base gasket, seen no mention ?

Apparently the 0.014' base crushes to 0.013" in reality

I tested a .020 Cometic base gasket.  It was .020 crushed (no change) and with a light smear of aviation cement between 2 gaskets you could not even measure the added sealer because it squeezed out under pressure.  I needed to stack a .003 linen paper gasket to the .020 base gasket to achieve 0 deck. They couldn't come up with that dimension material to make them for me.   Cometic told me this is what I would find and I should have listened to them and saved my time and trouble. I guess I just needed to know.    FWIW, they sealed perfect and still live dry.

[Nutoy]

I did a 107 tc and the piston out of the hole .002 and a .030 gasket and after 5000 miles and some carbon build up on the pistons and pistons would hit the head when motor was cold. swapped the .030 gaskets with a .035 and no more problems.

[adayrider]

I did a 107 tc and the piston out of the hole .002 and a .030 gasket and after 5000 miles and some carbon build up on the pistons and pistons would hit the head when motor was cold. swapped the .030 gaskets with a .035 and no more problems.

So what happens in the extra .005? In other words if carbon build up causes contact in 5000 or 10,000 or even 50,000 miles with a .030, why doesn't it build up even more in 6000 or 15,000 or 60,000 and hit then? Or does it? I know there are bikes out there that have 100,000 miles and more and never been apart. Factory gasket is what,.042 or something? Why don't their motors build up and eventually make contact?

[Ohio HD]

I did a 107 tc and the piston out of the hole .002 and a .030 gasket and after 5000 miles and some carbon build up on the pistons and pistons would hit the head when motor was cold. swapped the .030 gaskets with a .035 and no more problems.

So what happens in the extra .005? In other words if carbon build up causes contact in 5000 or 10,000 or even 50,000 miles with a .030, why doesn't it build up even more in 6000 or 15,000 or 60,000 and hit then? Or does it? I know there are bikes out there that have 100,000 miles and more and never been apart. Factory gasket is what,.042 or something? Why don't their motors build up and eventually make contact?

Most OEM TC gaskets are about 0.045" when crushed. Most OEM TC motors the piston is down the hole 0.010" to 0.013" ish.

Most motors that see much carbon build up in the squish area (irregardless of squish) is due to poor tuning / oil burning. The smaller squish is to help prevent detonation with higher dynamic cylinder pressures and advanced ignition timing. 

[Mag19]

With a high level of success, Sheffer Performance of Evansville Indiana targets a net squish of .030 when ever heads are removed. This is normally done via zero decking and using a .030 MLS head gasket. The .030 squish is employed on his 124/128 M8 builds as well other cubic inch configurations and including Twin cams.

"Net" squish examples:
Deck height of .000 use a .030 thou head gasket
Deck height of .010 out of the hole use a .040 thou head gasket
Deck height of .003 in the hole use a .027 thou head gasket

His in-house tuning research and data compilation has shown .030 to work well to balance optimum power and rideability with mitigation of spark knock (ping).

Based on these findings, adjusting static compression ratio with head gasket thickness is of poor design.
Achieve desired static CR via net combustion chamber volume incorporating head and piston volumes with a gasket thickness based on a targeted net squish.

Avoid assumption.
Always check deck height.
As a minimum, use a true straight edge and a good feeler gauge set.
Front cylinder often differs from the rear.
Check with the pistons installed that will be used in the build. Or, at least measure the compression height of the new pistons (stated and actual can differ) and compare to the compression height of the old pistons using math factoring in the deck height before disassembly. Variances in cylinder height (block height) and rod length do happen.

Above all else, don't shortchange your build with a mediocre tune. Do the research and vetting process to get a professional and competent tune. Travel the distance if necessary. Too often guys travel the short local path which ends up being the heartache highway of an expensive incompetent tune. Max power Dyno graphs are only a small part of the story. Wide open tuning is the easy part. In the tuning arena, what separates the men from the boys is the knowledge, process and implementation of tuning procedures that are applied to all of the part throttle areas.

Cheers

While checking deck height does he omit the base gasket and then do the math for the proper base gasket? Thanks

[Barrett]

What size is the base gasket, seen no mention ?

Apparently the 0.014' base crushes to 0.013" in reality

I tested a .020 Cometic base gasket.  It was .020 crushed (no change) and with a light smear of aviation cement between 2 gaskets you could not even measure the added sealer because it squeezed out under pressure.  I needed to stack a .003 linen paper gasket to the .020 base gasket to achieve 0 deck. They couldn't come up with that dimension material to make them for me.   Cometic told me this is what I would find and I should have listened to them and saved my time and trouble. I guess I just needed to know.    FWIW, they sealed perfect and still live dry.

Are the Cometic base gaskets a true .020? My S&S base gaskets are .018 and I'm .002 out of the hole. (T/C)
I went with a .040HG.

[kd]

What size is the base gasket, seen no mention ?

Apparently the 0.014' base crushes to 0.013" in reality

I tested a .020 Cometic base gasket.  It was .020 crushed (no change) and with a light smear of aviation cement between 2 gaskets you could not even measure the added sealer because it squeezed out under pressure.  I needed to stack a .003 linen paper gasket to the .020 base gasket to achieve 0 deck. They couldn't come up with that dimension material to make them for me.   Cometic told me this is what I would find and I should have listened to them and saved my time and trouble. I guess I just needed to know.    FWIW, they sealed perfect and still live dry.

Are the Cometic base gaskets a true .020? My S&S base gaskets are .018 and I'm .002 out of the hole. (T/C)
I went with a .040HG.

The .020 Cometics I used on my 4.060 bore were exactly.020 when I torqued and dummied it up to confirm before assembly.  I was .003 out of the hole on both cylinders and added .003 linen paper to the .020 gasket with a light film of aviation cement to make it 0 deck (.023 gasket width).  The aviation cement squeezed out when torqued and sealed well at o deck and is still dry.  I guess the answer is, in my experience, yes they are a true .020.