Mallory HEI

[boatcarpenter]

Just installed new dizzy a Mallory 85 series HEI wires are installed correct and am in ballpark with timing.Had son roll it over while checking with timing light.It is backfiring through carb question is retard or to advanced?I know just rolling it over while checking timing is only a ballpark thing and it also flooded out and killed battery so that just added to the challenge.Will post some pics when I get her running,new dizzy to the door from Summit under $200 thought this would be the way to go since points conversion with a new coil would be around $150.Only problem going to have to switch air breather this things huge.

[boatcarpenter]

Update was to far advanced,got her running but was and is still acting very flooded.Pulled plugs to regap they were Autolite 126 plugs and were gapped at .028 which is very small I would think with electronic ignition so regapped at .038.they are very fuel fouled so wire brushed them and put em back in.Had rebuilt carb last weekend but may have blown econimizer valve due to backfiring. Was looking at Autolites website and looking at there recomended plugs and was trying to look into getting the plugs for a 75-76 302 which is electronic ignition but they went to 14mm instead of 18mm.So backtracked to 72,73,74 which they used a different plug with extended insulator and gapped .035.
Can anyone recommend a different plug for this application ?As to backfiring was thinking it was in advance mechanism of new distibutor so switched out the gold springs in dizzy to the stronger black ones which are supposed to advance from 1000 to 4000 rpm also vacuum advance is supposed to be adjustable as well with the Mallory there instructions are very vague.Truck had original points dizzy with twin vacuum hoses running to advance capped off the one at switch in back of engine but was thinking of running a T fitting and running this to new dizzy will this work?I is supposed to supply vacuum at deceleration to stop backfiring I would assume.Any thoughts would be appreciated.

[My427stang]

That HEI should fire any plug, including old moldies, thats a stout ignition.

Check your firing order again carefully for a crossed wire, and double check your initial timing with the vac unhooked, after you are 100% certain the firing order is correct.

As far as the vacuum advance, just run the line that used to go to the front most port on the vacuum canister to the new canister and plug the other line.

However, what you are seeing now is 100% certainly not due to the vacuum advance, and 99% certainly not the plugs. Sounds like a typical crossed wire or retarded timing problem.

I bet if you get those two things verified and dialed in, the old plugs will clean right up

[boatcarpenter]

You were absolutely right crossed my wires Of course they may have been that way on original dizzy as well was carefull to only install on the HEI as I was removing from original but they are a whole different beast I do think I will switch out these plugs to the plug used on 72-74 302's Motorcraft BF42C any regap recomendations?Or possibly NGK WR5 GP love my NGK's on my 94 TBird 4.6

[My427stang]

.035 is plenty, more gap doesnt do much, and just works the cap and rotor a little harder.

[heep70]

I have never had any good luck with Autolites. I laways use Motorcraft or NGK.

[My427stang]

A plug is a plug in my book, just dont use AC Delco, they'll run, but it's sorta creepy