.030 or .036 head gasket?

[adayrider]

What should the piston to head clearance be?
I bought a 128" 11 to 1 kit from FM, I put pistons and cylinders on and measured. Sent heads and cylinders out, cut cylinders for 0 deck (-.008 on front and -.011 on rear)  and he ported heads and cut .002 from heads to get 88 cc. Kit comes with .030 gasket but guy that did the heads said to use a .036 or .038 gasket to get at least .035 between piston and head.

I'm no motorhead so what do the experts say? If I known this I would have less cut from cylinders. Either way I don't want contact.

Edit - 2019 SGS

[Ohio HD]

If the pistons are at 0.000" deck now, they 0.035" to 0.038" is fine for a street motor. 

[adayrider]

If the pistons are at 0.000" deck now, they 0.035" to 0.038" is fine for a street motor.

That is exactly what he said. .036 it is then and an extra $50
Thanks for the help and reply.

[Mag19]

My builder likes it to be 0 checked with old gasket. When assembled use .30 gasket.

[Ohio HD]

You don't need to put the head on to check. Just use a zeroed dial indicator. A lot more accurate than clay or soldier. Saves time as well.


[attach=0]

[Mag19]

Did fabricate that piece?

[Ohio HD]

No, bought it from Zippers.

[Mag19]

Nice, thanks. I already have the dial indicator so I may use the stand from summit for checking mine. Getting back to OP's original question. Do you check with gasket as well as rings on piston and what value are you going for on an 11:1 compression application

[Ohio HD]

I don't install the rings until I'm ready to assemble for good. I make a shim from 0.020" thick plastic shim stock and wrap the ring lands on the piston to stabilize it. Measure directly over the pin, both sides. The measure was 0.035", no base gasket. So I used an 0.031" base gasket and a 0.040" head gasket, gives me 0.036" squish.

Squish is more directed at motor / head style / design and intended use, not compression. That motor in the picture is 11.3:1.

 

[Mag19]

Yes squish is over my head at this point. I did ask the builder that's porting and cc'ing my SE heads for my build about squish and he replied with squish isn't even a thing. He decks the heads for clearance and sends them to me with recommendations of decking the pistons/cylinders to 0 and using a .030 base gasket. Not sure what the head gasket is. Thanks for the info on tour process

[adayrider]

I don't install the rings until I'm ready to assemble for good. I make a shim from 0.020" thick plastic shim stock and wrap the ring lands on the piston to stabilize it. Measure directly over the pin, both sides. The measure was 0.035", no base gasket. So I used an 0.031" base gasket and a 0.040" head gasket, gives me 0.036" squish.

Squish is more directed at motor / head style / design and intended use, not compression. That motor in the picture is 11.3:1.

Does this mean if you have 0 deck with base gasket  and .036 head gasket you still get .036 squish?

[Ohio HD]

Does this mean if you have 0 deck with base gasket  and .036 head gasket you still get .036 squish?

yes

[Herko]

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

[Mag19]

I think that that is the best advice I've seen someone put out there yet. Really nice clear concise explanation there. Thanks for that.

Cheers to you

[adayrider]

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

Well this contradicts what has been posted doesn't it? If I use .030 head gaskets that is .030 between piston and head.
I'm no machinist, motor head, mechanic or head porter, could someone tell me which head gasket I should use. I have both .030 and .036

[PoorUB]

Well this contradicts what has been posted doesn't it? If I use .030 head gaskets that is .030 between piston and head.
I'm no machinist, motor head, mechanic or head porter, could someone tell me which head gasket I should use. I have both .030 and .036

I would use the .030", BUT, use what ever the guy that is helping you build the engine recommends. He might have a reason to use the .036" that we are unaware of.


Fuel Moto kit? Call them and ask!

[adayrider]

Well this contradicts what has been posted doesn't it? If I use .030 head gaskets that is .030 between piston and head.
I'm no machinist, motor head, mechanic or head porter, could someone tell me which head gasket I should use. I have both .030 and .036

I would use the .030", BUT, use what ever the guy that is helping you build the engine recommends. He might have a reason to use the .036" that we are unaware of.


Fuel Moto kit? Call them and ask!

I did ask and and I shared the answer in first post. Now I'm looking for other opinions and an understanding of why. You can't hang a guy wanting to learn can you.

[skunk]

I've always shot for .030 in my builds and have not had any issues. Street motors, mostly in street baggers rode hard, twisted tight. My opinion only, YMMV

[PoorUB]

I did ask and and I shared the answer in first post. Now I'm looking for other opinions and an understanding of why. You can't hang a guy wanting to learn can you.

I'm confused! Did you send the cylinders and heads back to Fuel Moto to get cut? Your post says you sent them out, but not to who. You stated where you bought the kit, but not who cut the cylinders and heads.

Do what Fuel Moto said to do. They have a fairly good idea what is going on!

[adayrider]

I did ask and and I shared the answer in first post. Now I'm looking for other opinions and an understanding of why. You can't hang a guy wanting to learn can you.

I'm confused! Did you send the cylinders and heads back to Fuel Moto to get cut? Your post says you sent them out, but not to who. You stated where you bought the kit, but not who cut the cylinders and heads.

Do what Fuel Moto said to do. They have a fairly good idea what is going on!

I wasn't going to get in to all this so I'll make it short. I didn't buy from FM. I went their porting guy and bought through them do to lets say lack of communications. And the fact FM didn't seem to care about details such as 0 deck. I'm not bad mouthing anybody though, to each their own. I'd rather not go into any of that.

So after buying some parts I reached out to my preferred tuner and he recommend a different cam the RS 552 instead od wood 408.. So I decided to go with the RS 552 cam and send my heads, cylinders and intake out to be ported, new valves, springs, and cylinders cut for 0 deck. I told porting guy what cam I was using and all. So in the end the parts are done, I pay the man and he ships them and emails me saying it was going to be tight and he prefers .035-.038 piston to head clearance and I should use a .036 HG

I don't have a problem using the .036 except it will lower compression. I was just wanting to know why .036 clearance all of sudden when I have always thought .030 was optimal for squish. The 552 is 550 lift vs the 408 at 520 but the concern seemed to be piston to head not valve.

[PoorUB]

Well, there you go, your preferred tuner that helped you build the combination recommends a .036". I would go with his opinion, especially if he is tuning it too.

You have enough faith in him to change cams and so on, trust his head gasket recommendation.

That is one thing bad about coming here, you will get many differing opinions. None of them wrong, but with the combination you are running your tuner most likely has the best opinion.

[adayrider]

Well, there you go, your preferred tuner that helped you build the combination recommends a .036". I would go with his opinion, especially if he is tuning it too.

You have enough faith in him to change cams and so on, trust his head gasket recommendation.

That is one thing bad about coming here, you will get many differing opinions. None of them wrong, but with the combination you are running your tuner most likely has the best opinion.

Tuner is not the one that recommended it, it was the porter. Your right about the bad part. LOL
I was worried about piston hitting the head with .030 but I don't feel that is the case now.

[PoorUB]

The piston will never hit the head with a .030" or even a thinner head gasket. The problem arises a few miles down the rod when carbon starts to build up on top of the piston and in the combustion chamber. Thinner head gaskets and the carbon starts hitting the head or the piston sooner.

Most here will recommend a .030" head gasket, but I would still run what the guys, who ever they are, recommend. .030" or .036" or .006" difference probably will not make much difference. Most guys ask about the stock head gaskets which I believe are .045"

[yobtaf103]

What size is the base gasket, seen no mention ?

[adayrider]

What size is the base gasket, seen no mention ?

Same as factory .014