340 changes

[Newf]

Anyone know what changes were done to the 340 in 72' to bring the compression down to 8.5?? I am looking at getting a 72' 340 for my 340 Demon and was wondering what I would need to do to it to get it up to pre 72' power. Also did the cranks change from forged to cast?? Thanks for any tips in advance.

Cheers,

Joe

 

[70aarcuda]

the pistons pin height was lowered approximately .100

you will need to change pistons if you want the compression ratio back to the 71 and older engines...

dont know exactly what date they changed cranks..but it was late 72 and all 73 had cast cranks....

look at the balancer/damper on your 340......340 cast cranks had a balancer that says "for 340 cast cranks" on it..


at good set of pistons for the 340 is a KB 243.....just follow KB top ring requirements..

http://www.summitracing.com/parts/UEM-KB243-030/

 

[cudamark]

They went to the cast crank in Apr of '72.

 

[340sFastback]

'72 was the first year for the smaller intake valve. Although that does not make any difference unless you port the heads.

 

[70aarcuda]

if you are rebuilding the engine..and the heads...it would be easy to have the machine shop put 2.02 intake valves.

 

[Newf]

Thanks guys, will probably go with eddy heads anyways but keep the original if I buy it. He's actually asking a reasonable(IMO) $1300 CAD for the complete motor, and four speed tranny. That will make my Demon date correct but mine was an auto originally. The block stamp is 71' he said, but I'll know tonight when I look at the Damper.

Cheers