Here's the chart:



If you look at it, you can see the following theoretical changes in hp as CR is raised.

• 8-9:1 2.0%
• 9-10:1 1.7%
• 10-11:1 1.5%
• 11-12:1 1.3%
• 12-13:1 1.2%
• 13-14:1 1.0%

This assumes no detonation and no other changes. These gains are less than people think. I can't verify them, but they are from David Vizard who is a real guru. YMMV.

Rich

 

Why does this diagram always have the original compression ratio values reversed in every book and magazine I've seen it in?

 

My thoughts on this, i would be pissed if i ask for 11.1 & got 10.2, but thats just me, now on the compression increases, you will normally see a nice power increase jumping from less then 8.0-8.5.1 to around 9.5 -10.1 then you would going from 9.0-9.5.1 to 10.-10.5.1, as for going from stock 10.5.1 to 10.2.1, you won't notice anything, just remember that the cam plays one of the biggest rolls in selecting a compession ratio, you mainly calculate by the Dur. @ 50 & LSA to figure out the best compression ratio for that cam, just like you would if you were to pick a cam/head package, the best overall investment would be a GOOD "quench" when selecting a piston/head combo, then the cam/head combo, then best compression ratio for the cam selected, if any of this makes sence lol.

Of coarse it needs to be built off of the whole entire combo & intended use, but if you don't want to live with 10.2.1 because you feel the cam would like 11.1 better, then you need to discuss this with your machinest, IF you have the piston/valve clearance, you can always mill the heads .030" or .040", this will get you very close to 11.1 like you want.

 

Bad editing? You can see where it took me two tries to get it right myself ;-)

Rich

 

As of this moment, I don't know how much power this motor is going to make. If it gets inside the range that I am looking for, then I won't be too dissatisfied. My main complaint would be that the guy seemed to have a predetermined idea on how the motor was going to be built and I had to fight like hell to get him to change it. And then there's those times when he'd just do whatever, like the CR. I also have a $400 single roller timing chain, woohoo!!!

 

The Cam specs are:

Max Lift .576/.571
.006 Tappet Lift 280/288
Duration @ .050 230/236
Lobe Lift .3610/.3580
LSA 113

I do have the 1.6 RR installed and I don't think these #s reflect that change. The final pushrod length is 6.950... If someone has desktop dyno and can run the numbers, that would be cool!!!