What's Your Experience/Advice for Ignition Timing with High Swirl Heads?

Hi George,

I'm not quite there yet. I have Edelbrock heads on a short deck aluminum Ford block, a 401 Clevor. We should have it on the dyno in about three months. I will share our findings once done.

Mike

Hey Mike, thanks. Looking forward to reading about the results.

The heads look like they've been massaged. I'd be curious to learn how much CFM was gained via the valve job (assume 3 angle style). I'd also be curious to learn what the ID of the intake pocket throat is. It sets the upper rpm limit, i.e. sonic choke. Stock 2V is 1.65" (42 mm), good for 6647 rpm.

When you plot the 4V flow & Edelbrock flow on the same graph, the Edelbrock flow curve is steeper ... very cool.

-G

George, I've got A3 heads on my 377 Cleveland, I'm not sure how comparable they are to the others you mentioned...

In any event, I've got my MSD distributor set at 16 degrees initial, 32 degrees total, the advance is all in at 2900 RPM.  I've got the black (18 degree?) travel limiting bushing installed in the distributor.

Seems to run well.
Hope this helps...

I have A3 heads as well. I never thought to measure the diameter of the pockets though. Sorry.

I don't see with my set up any of this tendency some of the dyno tests show that the engine is happier with a total advance of 32-33°. Mine still like 36° total and 14-15° initial.

The determining factor for me is going to be how much the pump fuel can take. So far pump Premium is still ok and I am not feeling engine knock anywhere. Not yet anyway BUT when I put this engine together with stock stroke I didn't trust flat top pistons and used CJ dished pistons with the quench chamber heads.

If I check my notes I believe that I remember the calculated static cr at 9.8 or so?

Hi George,

Stock flow numbers are from Edlebrock.

Edelbrock #61625 Performer RPM head - Intake runner volume = 190 cc

Camshaft (Comp Cams): Hydraulic roller camshaft (custom grind)

Valve Lift (Int/Exh): .612”/.607”     Duration (@ .050): 230’/236’      LSA: 112’

             Stock                   Ported

.100”          58/54                     79/59

.200”          120/105                166/106

.300”               180/138                229/140

.400”            227/151                275/171

.500”          260/161                297/188

.600”           265/165                299/197

.650”                                              311

.700”                                              314

.750”                                              319

With several assumption made, the engine builder's dyno computer program estimated peak flywheel hp = 518 @ 5900 rpm and peak flywheel Torque = 545 @ 4100 rpm. The torque is above 485 from 2500 rpm to 5400 rpm. It will be interesting to see how close the numbers are to the dyno results.

Mike

Hi George,

About ten years ago, Scott Cook suggested"Set up for mechanical advance. 18-20° initial at Idle. Total 28° all in by  3200rpm."  That was for a 390 cu in Cleveland with 10.0:1 CR and Scott's heads and intake manifold.

18-20° initial would make hot starts difficult unless the ignition system had a 10° retard during starting.  (Hmmm...Pantera Electronics EIS ?   )

John