66cc, picking a starter engine

[Rusty_S85]

On average there used to be 2mm from piston crown to the deck but now it's closer to 1mm and that can vari from engine to engine,The Jake diamond head is around 7cc and the copy(clone)is simmular but protrudes into the bore and takes up some of the 1mm space yeilding a real tight squish clearence!

Interesting. Might be a downgrade as Ive seen conflicting reports on the slant head. Ive heard some claim they are around 5.5cc.

 

[Street Ryderz]

Interesting. Might be a downgrade as Ive seen conflicting reports on the slant head. Ive heard some claim they are around 5.5cc.

The stock slant head is 6cc!Gary has cc'd them and posted the results a few times in the past on here!and his method is sound!

 

[Rusty_S85]

The stock slant head is 6cc!Gary has cc'd them and posted the results a few times in the past on here!and his method is sound!

Well then the stock slant head being at 6cc is going to provide higher compression than a 7cc high compression head. Unless the stock slant head doesn't have as big of a quench band. I'm not really a fan of the look of the slant head but I guess what I could do instead of going with the Jake diamond head I could pick up from CR Machine one of their "Competition Center Fire Heads" which comes in 5.0 or 5.5cc.

 

[Street Ryderz]

Well then the stock slant head being at 6cc is going to provide higher compression than a 7cc high compression head. Unless the stock slant head doesn't have as big of a quench band. I'm not really a fan of the look of the slant head but I guess what I could do instead of going with the Jake diamond head I could pick up from CR Machine one of their "Competition Center Fire Heads" which comes in 5.0 or 5.5cc.

There are lots of ways to keep the comp the same and use the larger chambered heads because the aid in cooling big time and dont warp! The most commen way is to deck the jug some and then if needed the head can also be altered and with much more meat to play with compared to stock it's pretty easy!A 5-5.5 cc head is going to run real hot real quick and not well suited for street use for what you want to do even Fred would recomend the 7.cc head!

 

[Rusty_S85]

There are lots of ways to keep the comp the same and use the larger chambered heads because the aid in cooling big time and dont warp! The most commen way is to deck the jug some and then if needed the head can also be altered and with much more meat to play with compared to stock it's pretty easy!A 5-5.5 cc head is going to run real hot real quick and not well suited for street use for what you want to do even Fred would recomend the 7.cc head!

Well with that in mind then it looks like the Jake Diamond head would be better for me even with the 7cc chamber. I just hate to lose compression if I don't have to. I would have to see what kind of deck clearance the engine has off the bat and see if one can shave the jug down to move the piston up closer to the head to bring compression back up. If possible I would go this route as the Jake head has some real beefy cooling fins which should help drastically in the Texas heat we have during summer.

 

[Street Ryderz]

Well with that in mind then it looks like the Jake Diamond head would be better for me even with the 7cc chamber. I just hate to lose compression if I don't have to. I would have to see what kind of deck clearance the engine has off the bat and see if one can shave the jug down to move the piston up closer to the head to bring compression back up. If possible I would go this route as the Jake head has some real beefy cooling fins which should help drastically in the Texas heat we have during summer.

Yes most certainly will!

 

[Rusty_S85]

I do want to run a aftermarket CDI to back the timing down some. I know that will make the engine run a bit cooler as well.

 

[Street Ryderz]

I do want to run a aftermarket CDI to back the timing down some. I know that will make the engine run a bit cooler as well.

Yea somewhat they keep the engine from beating it's self to death and smooth it out in the topend more than anything!Again the earlier engines were timed from 23-25 degrees btdc so when running at high rpm they shook badly from fighting the early ignition now adays there are much lower about 7 degrees on average witch seems to work well!

 

[Rusty_S85]

So a aftermarket CDI really wouldn't be needed then? Hate to throw on a performance CDI to back the timing down if its not really needed. Could spend the money in other areas for performance.

 

[Street Ryderz]

So a aftermarket CDI really wouldn't be needed then? Hate to throw on a performance CDI to back the timing down if its not really needed. Could spend the money in other areas for performance.

The point was that not so much for heat control but to put the timming closer to where it should be in the high rpm so as not to be hard on the bearings,cylinder treatment(chrome)witch is very thin and help to get some life out of the engine!