Folks,
Im piecing together a Frankenmotor as a side project here and i have a question that the mighty Google-fu cant sort.
This engine is using a stock HD jug that measures 3.875 and they are bored 010 over to 3.885
Measured deck and both front and rear need 0.022 removed to zero it with my oddball 3.885" Wiseco piston with a 3cc dome.
I want to use a 030 HG so i have a supercool squish of 030
The heads are stock HD SE 110 head with the cavernous 95cc CC
What head gasket do I use? Ideally I would want a 3.885" x 0.030 but Cometic only lists 3.875" in different thicknesses. If i use a 3.875 then i literally have zero squish for 0.010 and then 0.030 squish on both sides of the CC.
If i use a 4" bore twincam 0.030 application then i have more ugly numbers with 0.115" of cylinder deck by 0.030 thickness just sitting there being a fire ring.
Can anyone sort me out here? Am i totally twisted off in the wrong direction?
Thanks for any help you can give me.
Maybe I missed it, but what is the stroke?
The 3.875 will be fine. The thickness is my concern. Until we know the stroke of the crankshaft and cams you plan on using we can not help!
No problem. Its 4.625 stroke with a S&S600 cam.
All these numbers should put me right at 10.1-10.2:1 compression. Pretty much dead center for that cam.
The head gasket is the least of the problems. Your skirts will be uncovering the gauge point, popping out, at BDC and this motor will suffer a very short life IMHO
Sorry Don, I should have also mentioned, it's a Fatvo.
But my issues are with the head gasket which is TC
Cometic 3.875" bore MLS head gaskets for Twin Cams are larger than 3.875". I think they measure about 3.940" I.D., don't have one or I'd measure. I'd call Cometic and ask them.
Thank you sir! That is the information I was looking for.
Last set of 95 ci cometics I measured were 3.905 on the ID. Right at your 0.030 over. If you want to go bigger you can get 98/107 headgaskets which will accommodate up to a 3.937 bore. Sorry don't know the ID for that one.. IIRC it only slightly larger than the bore.
If you are running stock HD TC cylinders you still have the same issue with the stroke being too long for the cylinder. Stroke is stroke.
Max, the 98"/107" MLS I do know, they run 3.955". Wasn't sure at all about the 95"/103" gaskets.
It's a Fatvo the block deck height is different than the twin cam block deck height. He bought the bottom end fro me I had it set up with the 103 pistons worked fine
Yeah it mocks up 100% and no issues. The only concern was the head gasket bore.
Thanks guys, I appreciate everything.
Mock up and life are not the same. If the gauge point is uncovered at bdc the piston loses its stability
Quote from: HD Street Performance on February 04, 2019, 02:36:24 PM
Mock up and life are not the same. If the gauge point is uncovered at bdc the piston loses its stability
Ok as I stated earlier I sold him the lower end I ran it with the 103 pistons for3 years so I know it works
Yeah Don, it's a Sputhe FATVO / FATSO block. Designed for this exact application.
No worries man! I won't build a grenade!
When we did a 95" bored. .010 over iirc we used the cometic .030 3.875 std gasket. It worked and is still working fine. I think this is the info you wanted... I have the actual measurements of the gasket somewhere but it was more than enough.
Quote from: 838 on February 04, 2019, 07:08:26 PM
When we did a 95" bored. .010 over iirc we used the cometic .030 3.875 std gasket. It worked and is still working fine. I think this is the info you wanted... I have the actual measurements of the gasket somewhere but it was more than enough.
https://www.hdforums.com/forum/touring-models/1243130-030-head-gasket-for-3-875-005-bore.html
Quote from: donk_316 on February 04, 2019, 03:29:44 PM
Yeah Don, it's a Sputhe FATVO / FATSO block. Designed for this exact application.
No worries man! I won't build a grenade!
So is how much of the piston sticking out of the cylinder that you are OK with? A 4 5/8 stroke is a full 1/4 inch more than a 4 3/8 stroke..