Charlie,



Cam WAS degreed, and reportedly installed "straight up". But, that would seem irrelevant, since isn't intake closing point in relation to crank TDC (ABDC) what needs to be determined for accurate calculation of DCR? Also, as measurement only relates to intake cycle, and cam specs. stated in crank degrees (?), turning ratios shouldn't apply. Will definitely need to put on my thinking cap for this one.



BTW: Rereading instructions for finding TDC reminds me that I usually forget to maintain thumb pressure on piston (to take up bearing clearance). As a result, will have to repeat piston-to-deck measurements made earlier

6 VOLTS/POS. GRD. NW INDIANA

Brain fart! You're right. For some reason, I was picturing the degree wheel on the cam. Ignore my previous post.


Lawrenceville, GA

Dan, the specs Isky is quoting for the E4 will be found .020" tappet movement. 260 crankshaft degrees from .020" tappet lift on the opening side  to .020" lift on the closing side. Intake closing should be close to 60 ABDC when the indicator reads .020" on the closing side.

This should be true for all E-4's, not just yours.

Most cam grinders quote advertised duration and opening/closing events @ .020" tappet lift.

Schneider and Clay Smith use lower lift numbers which means that a 280 degree cam from either of them will have less seat to seat timing than say an Isky or a Comp Cam will.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

Dan, I just went on Wallace Racing's website to figure your DCR and things look favorable.

The E4 shows an intake closing of 84 degrees at .016" lash. 3.820 bore, 3.47 stroke, 6.200 rod, 10.1:1 static compression, guessed at 500 ft elevation.

http://www.wallaceracing.com/dynamic-cr.php

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

Thanks John,



Now I'm thoroughly confused. The DCR calculator program doesn't specify which measurement height/cam specs. to use.

So you are saying then, that actual Isky cams specs. (vs. advertised specs. of the same E4 model) measure consistently from one to another? AND, the 84 degree spec. you listed is what you got when YOU measured one? If your measuring height is the same one as the cam spec. determination method the DCR calculator was designed to use, then THAT DCR is plenty low/safe for most pump gas with my current chamber CCs.

6 VOLTS/POS. GRD. NW INDIANA

Charlie,



I think YOU are right after all. Cam spec. sheet diagram/#s look to be degrees of CAMSHAFT rotation. Likely should double those #s to find ABDC crank position.

6 VOLTS/POS. GRD. NW INDIANA

Cerebral flatulence must be catching. If you stare at that circular cam spec. diagram long enough, it's like the pinwheel they use to hypnotize people. (was led astray since the "two revolutions" caption at the bottom in such ultra-small print).

6 VOLTS/POS. GRD. NW INDIANA

John,

Checked E4 specs. in my shortblock (#1 cyl.). Will repeat measurements to verify, but though finding precise crank degrees at .020" lifter rise difficult, it appears that specs. are very close to advertised. If anything, duration on both lobes measures 7 degrees short. Opening points are right on the nose (as expected with cam installed straight-up), but shorter closing would demonstrate a bit of built-in advance (unbalanced overlap). Disregarding heat expansion, it's hard to fathom how 51 degrees ABDC (.020" lifter rise) intake closing could end up being 84 degrees at .016" lash?

P.S. Total cam lift also comes up shorter than advertised (.244") Should be .283".

6 VOLTS/POS. GRD. NW INDIANA

Dan, do you have the 1.54 rockers?  Although it wouldn't make THAT much difference, total should only be roughly 6%.

   (.283 x 94% = .266)

Frank/Rebop

Bristol, In ( by Elkhart) 

Dan, when you use Isky's specs you are looking at the cam lobe only. In that case the tappet gets down to .020" off the base circle at 60 degrees ABDC. They call this intake closing but it is at the TAPPET.

The DCR programs use VALVE EVENTS with rocker arms and valve lash. This is what the running engine actually sees. In this case your intake closing is actually 83 degrees ABDC.

As far as .244" lobe lift, either your indicator was not properly zeroed or it was not firmly attached. I would not be surprised if the actual lobe lift was a few 1/1000's less than advertised .283". That's another gimmick that cam grinders do to make their life easier but costs us a small amount of lift.

Basically, when they grind a cam they leave a few 1/1000's clearance between the lobe master and the follower to make sure the base circle has no runout. But if the master has .283" lift and they leave .003" clearance your cam will have .280" lift.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico