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[DavidB]

I replaced a set of Andrews 26g cams with a set of Andrews 37g cams in a 95 ci motor.
With the stock heads ,.030 cometics, and flat top pistons the motor was cranking 185 psi. With 95lbs of torque.
Wth the 37G cams the cranking pressure is down to 165 lbs. The bike runs better now at 80mph  but I wont my bottom end torque back.
Im thinking of trying a set of the SE HMR Heads with the Bath Tub Chamber to raise the compression ratio and staying with the flat top pistons.
I was hoping some has tried this combo and could let me know how it works.
Thanks,
    Dave

[skyhook]

Are you talking about mcr heads, what used to be called performance heads?  They work ok, but not as well as having your stock heads ported by a pro.  Also the mcr heads usually have 78cc chambers and this will make your compression too high for 37 cams.  You will want 81cc with zero deck height and  .030"  head gaskets.  You'd come out way cheaper just to have your stock heads milled to 81cc and maybe street ported with 1.9" intake valves.  We built my wife's '07 dyna with stock 96", street port heads, and 37 cams.  We used the .030 gaskets, but had a miscommunication with the head porter.  He thought we were going to use .040 gaskets and the compression ended up at 9.9.  The motor runs good, but it was a bear to get the pinging tuned out.  That's why I recommend staying around 9.7 with 37 cams.  Hope this helps and good luck to you!

[DavidB]

Are you talking about mcr heads, what used to be called performance heads?  They work ok, but not as well as having your stock heads ported by a pro.  Also the mcr heads usually have 78cc chambers and this will make your compression too high for 37 cams.  You will want 81cc with zero deck height and  .030"  head gaskets.  You'd come out way cheaper just to have your stock heads milled to 81cc and maybe street ported with 1.9" intake valves.  We built my wife's '07 dyna with stock 96", street port heads, and 37 cams.  We used the .030 gaskets, but had a miscommunication with the head porter.  He thought we were going to use .040 gaskets and the compression ended up at 9.9.  The motor runs good, but it was a bear to get the pinging tuned out.  That's why I recommend staying around 9.7 with 37 cams.  Hope this hepls and good luck to you!

I have 2004 stock heads on the bike now. I dont know the size of the combustion chamber. Are there different sizes for stock heads.
Your right MCR was what I was looking at. I dont know where the other name came from I typed in.

[rednectum]

I have 2004 stock heads on the bike now. I dont know the size of the combustion chamber. Are there different sizes for stock heads.
Your right MCR was what I was looking at. I dont know where the other name came from I typed in.

what skyhook said! and yes, there are different sizes for stock heads------every head is different. CC the heads off any bike and you will get different measure. example, factory says heads are 85 cc. you may get 87 on one and 91 on the other! but following skyhooks advice, your head guy will correct this.

oh, if you are gonna be riding in high ambient temps, or getting poor gas, i like to keep the tw37 motor at 9.4-9.6, they start wanting to ping at 9.8. keep in mind this is on the gulf coast.