[DeTomaso] FW: MSD vs HEI

[JDeRyke at aol.com]

In a message dated 5/13/10 8:47:26 AM, pmenyhart at msn.com writes:

> Has anybody experience with a HEI distributor?
> 
HEI ignitions need to be extensively modified if you use them on 
performance V-8s- the spark energy drops off above 4500 rpms since GM designed them 
for mild street car use. Presumably the conversion companies are doing this.   
And the big cap- with or without the integral coil- makes for Pantera 
firewall clearance problems, exactly like big-cap Ford ignitions. Finally, 
there's apparently a hard-wired advance built into the modules; I found to my 
surprise when checking advance on a distributor machine, at 2215 rpm I had 18 
degrees and at 2220 I suddenly had 30, and nothing was mechanically sticking. 
Since most GM modules are interchangeable, they all likely have a slightly 
different amount so this is something to look out for. I've had two HEIs that 
spontaneously blew their internal modules, just like an MSD. But like the 
Ford TFI, they've been around since the mid-'70s and lots of parts etc are 
available anywhere. I don't see much advantage over a Ford TFI, personally. 
FWIW, the whole 351-C/ZF package can easily be slid backwards up to 3/4" on 
the motormounts, by interchanging the lower mount halves and bending a 
shallow 'S' in the ZF mount ears, than adding extra shims. Doing this makes 
plenty of clearance for any big-cap ignition, and it's reversible. Good luck- J 
Deryke