Cam and timing set install question
When I was putting my cam/piston combo together, many on the forum advised to stay below 8 DCR. I will be running a XE 262 in a 340, so I dropped the compression height down from the original 340 high comp pistons so I could run on pump gas with my J 202's.
For iron heads that is close to correct, the limiting factor being detonation with iron open chamber heads.
However, I recently fell on some data from David Vizard that teaches a rule of 128. He says every engine has exactly one LSA with which it will make the most power and torque; it goes like this;
128 (less cubic inches per cylinder/valve diameter x .91) = the correct LSA.
For a 2.02 valved 340 this comes to 109*
Since your 262 is a 110Lsa you are close enough to in the ballpark.
But I'll tell ya, if you went to a 108 on the same cam, your Compression cycle would increase by two degrees, as would your Power degrees. This would increase your CCP, and your Extraction, increasing fuel-economy AND your overlap would increase by 4 degrees, increasing your power throughout the rpm band, assuming headers are used....... with no other changes.
However your CCP might be a tad high, so you Would then retard that 108 cam to in at 106, drop the pressure back to what it is now, and gain a maybe 50 rpm at the top.
Now as to your current combo, the Forum was right.
To get a Dcr of 8.00 in your combo requires an Scr of ~9.5, depending on the Ica. Assuming 4* advanced you are spot on, and your CCP should come in at about 161psi. This is a lil tight with open chamber non-quench heads, so watch for detonation.
This combo should make good bottom-end torque, a strong midrange, and for a 340, awesome fuel-economy. This is gonna be so much fun......
