HEI center plate question
 

Had some extra time to tinker in my garage lately.
And while cleaning up some old parts I stumbled
into some old HEI parts. In relation to the size and
shape of the center cam which is more preferable.
The two I have are the 364 which is flatter or narrower
and gives 24 degree of advance using 139 weights.
Also have a 396 which is noticeably wider and gives
23 degrees of advance with same weights.
My HEI is a DUI and it’s center cam closely resembles
The 396 factory price. Just wondering if the rate
Of advance do to shape plays a factor and which
Is more preferable. This would be using original
Heavy HEI springs and weights.

Just had some extra time and was pondering
Why they are shaped so different.

This may help ya.

This was info derived by Jim Hand.
Please note that these pages loaded in reverse order.

thanks
 

thanks Steve

Welcome, but first and foremost thank Jim!

Note that his findings where durived on a 455 so on a 400 with about 9.5 comp depending on your overall gearing you may make good use of a faster curve since the cylinder pressure rise may be slower.

What publication is that? Not from the Jim Hand book is it?

No, it's not from Jim's, it's from a issue of Pontiac enthusiasts mag.

Rocky Rotella wrote a good article years ago in HPP, " A weighty Issue"
Maybe Rocky will chime in with a link.....

I'm trying to read the above posted photos. I think I can but it's tough. Thanks for posting that steve25.

Sorry, I would scan the pages if I could, but what I can do that may help is photo each page into 2 overlapping sections for ya.

I will post that up tomorrow.

Another option to limit advance is to heat and bend the advance weight tails inward.

https://www.tapatalk.com/groups/raci...less-t765.html

Advance
 

Really my question on how advance curve and rate is on
Take off. Which would be better a fatter plate or a skinnier
Plate. Would and auto car like a faster curve on take off.
Also due to 3:08 gearing would a slower curve be optimal.
I am just thinking aloud here.

68 Firebird, I adjust the rate of advance by changing the springs. It is a process of trial and error. I own a Sun Distributor machine so, it is fairly easy to run tests.