I'm not looking for exact figures best guess will work, I have mad science ideas twirling around in my head but how much of a compression bump would you expect to get from changing the stock head gasket from .045 to the thiner .03 in a 114 M8? I can't find anything on the subject... I was thinking maybe it would be worth a .25 point or close to it bump up in compression?

Any idea or best guess?

 

Big Boyz used to have a compression calculator on their site. Looks like it doesn't exist anymore. You could probably find a generic calculator and plug in some numbers. You would need to know your cylinder head volume and deck height to get an accurate number.

Edit: Here is one. https://thedynoguy.com/compression-calculator

Using a 117" with 4.5" stroke the HG thickness change yields about .33 increase

Zach

 

I debated on running the 30 thousand thinner head gasket with my 103 twin cam. The stock compression on the 103 was set at 9.6 give or take. The thinner head gasket would set it at close to 9.9 if I remember right. The advice I got was not worth it unless you have the heads off for something else. So I had the heads done to make it worth it. The biggest benefit is the tighter squish. With the 114 compression is estimated at 10.5 so the not worth it recommendation is even more in affect I think. Do you have a blown head gasket?

 

And if you are still planning on going with the 22xE you will be very pleased with your upgrade with that pipe. I am guessing you won’t crave a compression bump.

 

Well here is what got my brain juices flowing, after moving down here to Louisiana where it’s real flat, the weather is much nicer and gas quality is much better for cheaper than Washington. I got smoked real bad by a Street Glide ST by a rider that’s much bigger and wider that me on a heavier bike. I figured there was a 200lbs difference between the two of us and I just couldn’t real him in, after a gas station chat up he told me how he set his set up.

So I was pretty set on the 22XE or the XD, after digging around looking a cams all over again the 508 stick has more duration so I was looking to cheat it up a little bit in the meantime to help it on the bottom end with the 114, I’m also considering a bigbore kit in the future and they eat duration like candy so I was figuring it wouldn’t hurt when that time came along either.

This is what planted the seed in my pea brain and I wanted a general idea from a reliable sounding board.

 

I tend to agree with Durham. The juice probably isn't worth the squeeze unless other things are being done at the same time. Head work, big bore, etc. If the cam you are selecting needs the bump in compression to get it to the ideal comp range, then maybe. To be honest there are so many good cams that work well within stock compression, a HG change shouldn't be needed.

So what was the bagger set-up that whooped you?

Zach

 

There will always be a machine that is quicker and faster.

 

BigBoyz calculator is still on their website.
http://www.bigboyzheadporting.com/TwinCamComp.htm

 

It will take you from 10.5:1 to 10.81. That is if all of the other parameters are as they should be, such as 0 deck and standard head chamber size. Any way you look at it, it is good for a .3 of a point increase in compression.

 

Found a M8 compression calc that includes a drop down with many of the popular M8 cams. Should have known that site would have one. It's a good reference for people planning builds.

https://harleytechtalk.com/tools/vtwin_comp.html

Zach