Don Terrill’s Speed-Talk

TBART1970 wrote:

David Vizard wrote:OK Let's get back to those Edelbrock heads on this 565 incher. Take a look at the intake flow of the heads I ported for the GM 572 project posted else where.

The Performer heads are the thick blue line and the DV ported AFR's the thin line. At first sight it looks like the AFR's flow curve just disappears of the top of the chart into space but the reality is I drew these charts on a .700 lift scale before I realized I needed at least 0.800 to show where the AFR topped out. At about 800 the curve leveled out here - the flow was 404 cfm. Max flow was 409 at 900 lift.

As you can seefrom the gragh the Edelbrock Performer, almost tracked the AFR's over much of the lift. But in many respects the true difference as seen by the engine can be much more than we are perceiving here. Sure those big high lift flow numbers are an obvious asset to the breathing capability of the cylinder but that, contrary to what may seem logic, has minimal to do with affecting the poptimal LCA. To see how the cylinder is far more affected by the low lift flow the valves have we need to look at a graph of the flow per sq inch of the CD.
That is what we will do tomorrow.
DV

548 cu inch
4.600 bore 4.125 stroke

David Vizard wrote: BBC LCA formula:- LCA = 133.5 –((cylinder displacement in CI/intake valve diameter) x 0.91)

Cylinder displacement is of course for one cylinder.

Guys - notice I took the advice to put in the extra brackets into the formula to make clearer the order in which to do the calcs.
Should have done that first time around!!

DV

raynorshine wrote:

David Vizard wrote: BBC LCA formula:- LCA = 133.5 –((cylinder displacement in CI/intake valve diameter) x 0.91)

Cylinder displacement is of course for one cylinder.

Guys - notice I took the advice to put in the extra brackets into the formula to make clearer the order in which to do the calcs.
Should have done that first time around!!

DV

David, does this formula work for SBC's? or is there another formula?

digger wrote:What about hemi ?

cstraub wrote:With the oiling issues this thing has the dyno sheet is a mute point.

TBART1970 wrote:Different intake on the dyno, dyno distributor, standard volume Moroso pump and standard shaft. Other than the valve adjustment, nothing was really wrong on the dyno. Oil filter from dyno runs was cut open and there was not much in there, not until I put it in the car did the problems start.

cstraub wrote:This things does not need cams thrown at it ......it needs the issues that it has fixed. The oil contamination being the number 1. It seems that the distributor gear issue has been addressed.

Newold1 wrote:I agree, this engine had some mechanical issues that probably affected time for adjustments and fine tuning but it achieved a result that was maybe just a little short of the OP's original expectation. The OP came on here asking for a little advise on camming, not asking for a pick a part of the entire build. Obviously per Mr. Vizard's concise and proven methods somethings could have been improved with ideal parts and rework but this OP is not looking for that at this point and he is just trying to get back to the dyno with some cam change and optimize what he has. Let's not over critique or analyse this situation here. I think all of us should just convey the idea to all new members here on Speedtalk that they should use and listen to good knowlgeable peers here and that the time to collect information and discuss choices and expectations is before they start choosing and buying parts and building their engines!!

I'll say it again " plan your work and then work your plan!"