Compatability question: 2.4 heads and 81mm barrels
 

hi all,

is it possible to use 2.4 heads with 81mm barrels?

building a 2.1 litre motor (81mm bore and 66mm stroke) and some nicely ported 2.4 heads with 2.7 valves have become available.

if not, what are the best heads to start with if big ports/valves are desired?

Hi Ryan,

all heads from 1970-1977 will work . Valve sizes are all the same as well. My preference are 1970-1974 heads.

You still have the piston diameter issue; you'd need one of the Supertec kits to take the diameter of the head down to accomodate the smaller piston (81mm vs. 84mm). Also, using Mahle 81mm pistons will have issues due to the valve angle of the early design. If you use JEs, make sure to get the valves cut at the later valve angle.

thanks guys.

Oops, forgot that they are 2.0 liter based!
Here is a pic of the supertec cylinders that you would need for the heads and he has matched pistons as well.

http://forums.pelicanparts.com/uploa...1244075981.jpg

just so i'm clear: can the supertec shim kit be used with stock 2.0 biral cylinders- or will i need the supertec barrels shown also?

the plan was to use JE 10.5:1 pistons (spec'd with the 'later' valve angles)

from what i can gather, the 2.0 heads have a flat sealing surface around the combustion chamber, whereas the 2.4 2.7 heads have a recess. it appears that the shim kit fills in the recess and thus re-creates the flat sealing surface. is my understanding correct?

thanks again for the help.

here are the shims (for future reference)

http://forums.pelicanparts.com/uploa...1244079129.jpg

The cylinders above would be the ones you would need to run the 2.2-2.7 heads. Have you already purchased the pistons?

edit, the shims would be placed between the cylinder and the head. You would then need the Birals decked in order to use the 2.2-2.7 heads. I'll verify.

aaron,

thanks for your help. i haven't purchased the pistons or the barrels yet. the plan is to use 81mm JE's and rebored/honed Biral barrels.

i did some searching and found some other threads where Henry mentions the shims. however, they seemed to indicate that the shims allow 'regular' 2.0 barrels to be used with 'regular' 2.4 2.7 heads so now I'm a bit confused. I've sent Henry an email also.

Looks like you do not need to machine the cylinders. The spacer slips over the lip on the birals.
Birals will work for your application.

great news - thanks again for your help.