Head volume for 67 Greenhead stock and 101 flat dome piston

[Tom Foley]

Hi , looking for known head volumes for running 60% both engines in monos Flat top on the 101 piston .. THX

 

[dwilfong]

Tom it depends on the EX timing as this will change the CR also the clearance you run this will also change the the CR.

What kind of boat? mono hydro?

If you want to be on the safe side same cc as the eng size including .02 for the plug.

The cc on my 1.01 is the same as stock .92cc but no flat and a 3 deg squash angle set at .008 clearance.

With a 190 ex timing gives a 9.4 CR.

Hope this helps.

David

 

[Joe Warren]

stk head? 3/4 ball end mill. Go to the stk plug dept. will measure approx .700 bowl dia cause you cannot get it .750 all the way in. .012 .014 squish I have been as low as .008. HANG ON when you pull the trigger.

 

[Jack ODonnell]

Tom it depends on the EX timing as this will change the CR also the clearance you run this will also change the the CR.

What kind of boat? mono hydro?

If you want to be on the safe side same cc as the eng size including .02 for the plug.

The cc on my 1.01 is the same as stock .92cc but no flat and a 3 deg squash angle set at .008 clearance.

With a 190 ex timing gives a 9.4 CR.

Hope this helps.

David

David is that 190 timing the full width of the exhaust port. J.O'Donnell

 

[dwilfong]

Tom it depends on the EX timing as this will change the CR also the clearance you run this will also change the the CR.

What kind of boat? mono hydro?

If you want to be on the safe side same cc as the eng size including .02 for the plug.

The cc on my 1.01 is the same as stock .92cc but no flat and a 3 deg squash angle set at .008 clearance.

With a 190 ex timing gives a 9.4 CR.

Hope this helps.

David

David is that 190 timing the full width of the exhaust port. J.O'Donnell

There is a slight arch to the top of a CMB 1.01 P/L . this is measured at the top of the arch. there is a .030 difference at the widest point of the port making the the timing 183 at the widest point.

 

[Tom Foley]

At .008 on a 101 you will be hitting the head button , mine are imprinting the piston with a shiny spot from the button at .011- .012 " on the VAC 91's ! . That will kill pistons quick !

David , timing is stock on the .67 and on the 1.01 on this sleeve .

 

[dwilfong]

Tom make it the same as the eng cc's then and squeeze it as much as you can and fell comfortable with.

Take the flat band out and put a 3 deg angle on the squash. It will only be at .008 at the edge and will tapper to .020 when it goes in to the chamber.

It will seat its self. will only just lick the chamber at the very edge if at all.

With out the flat it won't have a flat spot to slap on the piston.

make the band .260 wide if you can.

If you think about it the average squash will be .014 on the band.

Get some liner shims from Steve and jack the sleeve .015 this will bring the timing up to run the smaller chamber.

Will also uncover more transfer port at BDC.

I run at .011 on the VAC 1.05 eng build and it just licks the piston at the edge at first with the tapper band.

The one piece crank dose flex more with both bearing at one end. Kinda like a teeter toter