Cometic .030 head gasket
Thread Starter
|
Cruiser
Joined: Oct 2009
Posts: 132
Likes: 7
From: South Carolina
Cometic .030 head gasket
I'm in the middle of a top end rebuild...here is my info.
2010 Road Glide
S&S 106 Kit
TW-555 cams
Fuel moto level b heads
Thunderheader 2:1 exhaust.
Should I use the Cometic .030 head gasket or the ones in the S&S kit?
If the cometic .030, does anyone know the correct p/n?
2010 Road Glide
S&S 106 Kit
TW-555 cams
Fuel moto level b heads
Thunderheader 2:1 exhaust.
Should I use the Cometic .030 head gasket or the ones in the S&S kit?
If the cometic .030, does anyone know the correct p/n?
Road Warrior
Joined: Jun 2009
Posts: 1,943
Likes: 3
From: NYC
hard to answer til you measure your valve to piston clearance (the clay method) . Since the .030 gasket is .015 thinner than the stock gasket. If you have flat tops you will be close. Forged high compression pistons could be a problem. If you don't have the clearence and want to use thinner gaskets, you will have to make the valve grooves on the pistons deeper. There is a max that you can cut into the groove.
Seasoned HDF Member
Joined: Dec 2005
Posts: 5,462
Likes: 619
You should measure the deck height of the new set up.
Put the new pistons and cylinders on with the old base o-rings.
Bring the piston to top dead center.
Put a straight edge over the cylinder directly over the wrist pin.
Then measure the gap with a feeler gauge.
Ideally the gap measured here plus the thickness of the head gasket should equal between .030 and .035.
HTH
Zach
Road Warrior
Joined: Jun 2009
Posts: 1,943
Likes: 3
From: NYC
I agree with this.
You should measure the deck height of the new set up.
Put the new pistons and cylinders on with the old base o-rings.
Bring the piston to top dead center.
Put a straight edge over the cylinder directly over the wrist pin.
Then measure the gap with a feeler gauge.
Ideally the gap measured here plus the thickness of the head gasket should equal between .030 and .035.
HTH
Zach
You should measure the deck height of the new set up.
Put the new pistons and cylinders on with the old base o-rings.
Bring the piston to top dead center.
Put a straight edge over the cylinder directly over the wrist pin.
Then measure the gap with a feeler gauge.
Ideally the gap measured here plus the thickness of the head gasket should equal between .030 and .035.
HTH
Zach
not being a PIA, but can you provide a reference for this. I'm goingt o start a 103 build and the only references to taking measurements involve the clay method for piston to valve clearance , in another reference side gaps between the pistons and the cylinder walls, and in another reference ring end gaps.
My problem with checking deck height using the method posted is the influence of the uncompressed base cylinder o rings, so you would basically have to use a torque plate before taking the measurements. Also thing the results can be influenced by piston type.....the measurements for flat tops could be one thing...but SE forged high compression pistons would be something else since they have raised platforms of almost 1/23nd of an inch.
Zach just gave you directions for checking squish. Running a squish of somewhere around .035 is why you're running a thinner head gasket.
Seasoned HDF Member
Joined: Dec 2005
Posts: 5,462
Likes: 619
not being a PIA, but can you provide a reference for this. I'm goingt o start a 103 build and the only references to taking measurements involve the clay method for piston to valve clearance , in another reference side gaps between the pistons and the cylinder walls, and in another reference ring end gaps.
My problem with checking deck height using the method posted is the influence of the uncompressed base cylinder o rings, so you would basically have to use a torque plate before taking the measurements. Also thing the results can be influenced by piston type.....the measurements for flat tops could be one thing...but SE forged high compression pistons would be something else since they have raised platforms of almost 1/23nd of an inch.
My problem with checking deck height using the method posted is the influence of the uncompressed base cylinder o rings, so you would basically have to use a torque plate before taking the measurements. Also thing the results can be influenced by piston type.....the measurements for flat tops could be one thing...but SE forged high compression pistons would be something else since they have raised platforms of almost 1/23nd of an inch.
Yes, measuring deck height on a domed piston is different than a flat top. The procedure I described above was for a flat top. When measuring a dome, I would measure on the flat portion of the piston as close to the dome as possible. Be sure the piston isn't rocking in the cylinder. You can do this without piston rings to make it a little easier. Just make sure the piston is square in the cylinder.
Measuring deck height and claying for piston to valve clearance are different. I'm not suggesting that verifying deck height will ensure adequate piston to valve clearance. Both should be checked. If all components were purchased as a package from FM, I doubt p to v clearance is an issue as long as all components in the kit are used.
Zach
Zach
Trending Topics
Cruiser
Joined: Jul 2009
Posts: 213
Likes: 3
You can check it without the o ring, the o ring only acts as as seal, the cylinder sits tight on the case once the cylinder is tourqued. If there was clearance due to the o ring the cylinder would move around like crazy and cause all kinds of problems. The only thing the o ring does is keep the oil from leaking out from the cylinder base
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Seasoned HDF Member
Joined: Dec 2005
Posts: 5,462
Likes: 619
You can check it without the o ring, the o ring only acts as as seal, the cylinder sits tight on the case once the cylinder is tourqued. If there was clearance due to the o ring the cylinder would move around like crazy and cause all kinds of problems. The only thing the o ring does is keep the oil from leaking out from the cylinder base
Zach
Thread Starter
|
Cruiser
Joined: Oct 2009
Posts: 132
Likes: 7
From: South Carolina
Zach,
So w/out the head gasket installed and the piston at TDC I should get a feeler gauge readout of 0 to 0.005. If my piston while at TDC is greater than zero then I can assume that a .030 head gasket would cause piston to valve clearance problems?
So w/out the head gasket installed and the piston at TDC I should get a feeler gauge readout of 0 to 0.005. If my piston while at TDC is greater than zero then I can assume that a .030 head gasket would cause piston to valve clearance problems?