rechambered my head

[headache]

ok guys i had been reading the stickys on head design and decided to try the hemi style head. i was running stock angle head with .018" milled off the deck and had 150psi compression. So i cut this head with 50% squish area on 11 degree angle and ended up with 165psi compression. I was hoping for around 175-180 but this will work for now. I've got .040" squish clearance. This design really helped out down on low-end power and smoothed out the powerband some. This motor was really doggy down low with the porting and dg pipe, now it rips! i just bought an fmf header and can't wait to put it on i know its gonna have more power everwhere, but i only ride woods/harescrambles so i need big smooth power down low.

 

[Blaaster]

Changing from the DG is going to need a jetting change.

Bung a reed spacer block between the reeds and the jug, advance the ignition 3 to 4 degs, and hang on.

Plug chop the jet change.

 

[Awk08]

good to see you're trying your hand at modifying a head.
165 psi. is all you need.
anything more will most likely require at least a mix of 100+ octane race fuel, or even straight race fuel, to deter detonation.
stick with the 165 psi. on 93 octane pump fuel !

 

[headache]

I went ahead and mixed up some 110 octane and 93 just to be safe for now. I'm only running a 260 main with this pipe will prob need at least a 290 or 300 with the fmf.

 

[best]

Amazing what the 50% hemi 0.040" squish can do isn't it?
The toroidal chamber (bathtub shape) is even better for low end but gives up some top end.

Steve

 

[Blaaster]

Changing from the DG is going to need a jetting change.

Bung a reed spacer block between the reeds and the jug, advance the ignition 3 to 4 degs, and hang on.

Plug chop the jet change.

Oops can I take the advance mod back.

I put my fingers into action before I put my brain into gear.

A timing advance may cause detonation with a re chambered head.

Sorry.

 

[headache]

I've got the timing advanced, ill prob just keep mixing in a little race fuel to keep detonation away.

 

[headache]

gonna try and post a pic again. it won't show up on my computer

 

[Blaaster]

I run 98 octane from the pump and as a precaution moved back to stock timing.