FL1970442

Good morning, I have a 70 442 with an original 455. Fresh rebuild 0 miles.
It has an Accel HEI ignition.
Questions: 1. Which plugs and gap?
2. What should I set the timing at with an HEI.
3.Do you recommend going with a petronix iginition sysytem?
Thanks

svnt442

If you have an original Olds HEI (not an aftermarket one) then set the base timing to 20° @ 1100 RPM to start. Your issue with this is the pointer from 1970 only goes to 16° so you will either need a dial back light or you will have to add a mark on the balancer at the 10° point so you will be able to read it.
Easy to do. Just put the timing mark at 10° and make a mark at 0°.
As far as the plugs go I'd use the ones for the 70 and gap them to .045. Don't use the ones for HEI because they are designed for gaps of .060 - .080 and you don't need that much gap.

Blk71SX

R45S gapped @ .045 should serve you well.

FL1970442

Thanks for the info! So will having the accel ignition make a difference in what I should set the timiong at?

svnt442

Well it's going to depend on the amount of mechanical advance built into the distributor. The factory only had 14° built into the HEI so you're going to have to do some reading on the distributor you have. If it has 24° then you had better start off with 10° initial and go from there.

MX442

Distributors vary so much from application to application that you can not rely on setting just any initial. Make sure that all-in mechanical advance is not over 34 degrees to start with. Add or subtract 2 degrees at a time until your engine is happy. It's the big end that matters most.