572 Motor 13.5 compression ,MSD crank trigger set at 32 degrees ,MSD 7 ignition,MSD digital retard box.

I occasionally get a backfire at start up thru the carb with the retard set at taking out 15 degrees. Should I set back to 10 or forward to 20 to try and eliminate this problem?
thanks mike

Spin engine with IGN off--when spinning flip IGN "ON"
That is how every race car needs to be wired--No retard needed

I agree with crabman. I used to use the start retard and it did the same thing. The backfiring was brutal on the ring gear and starter.

I tried one of those start retard boxes and decided it wasn't worth using. I just happen to have one for sale come to think of it!

I agree, for a race car set it up so you have a starter button and an ignition switch. Spin the engine a little bit to build oil pressure then flip the ignition switch and fire it off.

Or get serious and switch over to EFI. Then you can program in the start retard function as well as high speed retard and anything else you want.....

I had a start retard box with a locked distributor and it backfired a couples of times and hurt the carb. I got tired of worrying about it and removed it. I then I unlocked the distributor and put in the right springs to bring up the advance in a hurry. No problems since and it runs just as fast!
MJ

I tried using start retard, just made it harder to crank. Put in a MSD adjustable rotor, phased it to the cap and it was easier to crank over.

Same here, locked at 34 and never an issue either hot or cold.........

I have the digital retard box in there for Nitrous use. Just One of the functions is start retard. I will give it a try without any retard and see what it does.
Thanks Mike

If you're using the pickup in the distributor, you need an adjustable rotor for sure. Most of the backfires with start retard comes from the phase lighting up the wrong cylinder. Most racy stuff only needs 30-35 degrees, The relationship between pickup, and rotor is more for something like a stock motor that could see timing in the 40+ range. I guy at MSD told me years ago that for every thousand distributors they sell, one winds up on a race motor. He said they phase them for higher timing, because most racers lock them, and use crank triggers. no problem till you retard the timing a ton, like a start retard, or nitrous. Hence the adjustable rotor. Phase it up, and you can pull 20 on start with no backfire.

I agree. Electronic start retard bad.

Good idea. Just make sure to put the ignition on a separate circuit from the starter so you can get the engine cranking before you turn on the ignition.

Ignition dead while cranking (doorbell switch) was how 6 volt Chevies with 12:1 CR engines ran on the street 60 years ago.

I just had the same issue with the starter saver. less then 30 starts since installed. poping thru the exhaust and carb, !!

How much timing are you pulling out?

I have a 10 degree retard that I use off and on. Car rarely has a sputter as I pump the throttle while the starters spinning on first cold start. Engine runs funny until it hits 1,300. I still spin the starter before turning on the ignition. 7's need to see a crank signal before they start the engine. I have a 7 in my street car that has a small delay before starting because it's wired with the key switch. No retard on that one. I tried it and it starts better with no retard. 16V through a 12V Napa starter really helps.

If you're using an msd distributor, run your timing around 30, and using the internal pickup you're always about 10-12 degrees out of phase without an adjustable rotor.

Think about it, 45 degrees between poles on the cap. So 23.5 is the center where it's a crap shoot on which pole fires. Already 10 behind, now pull 20 on the start, and now you're closer to the wrong pole. Presto, bang, pop, spin backwards and strip your starter ring. 25 at the crank is 12.5 at the cap, plus 5 for the factory, add slop and you're at the wrong pole. Add to that the resistance increase of the correct cylinder is at pressure making it harder for the current to pass. The wrong cylinder is much lower pressure so the current path is easier, which adds to the problem.

When you're adjusting your timing with the distributor, the phase is locked no matter what you do. The relationship between the rotor, and the pickup are fixed at the factory, and you can't change it without an adjustable rotor. locking the advance out doesn't change this either. They had to decide where most of the product would be used.

Start retard is your friend. Phase it correctly, and 16:1 starts like a honda mower.

make sure your phasing is correct. I use a cap with a hole in it to to see where the metal electrode on the rotor is when it's firing. set the distributor so the the leading edge of the rotor is what is lined up with the electrode on the cap. This is a real issue when using a small diameter cap like a stock mopar.

The MSD spark retards only after enough cranks to pick up the signal from the crank trigger or distributor.

Seems like someone could make a box that would once started began keying of the magnet that is 90 degrees before TDC and effectively advance the timing rather than retard it.

The class I run does not allow fuel injection but down the road I plan to get a Megasquirt box to run the ignition and do data logging. Problem solved.

I do not think I have a problem with rotor phasing.
With a Cranktrigger rotor phasing is done by moving the distributor. Using a adjustable rotor is not necessary.I also use a old MSD distributor that uses a Chev cap. Terminals are further apart on these caps.
Problem is I have my rotor phasing set for nitrous use. I currently pull 18 of timing out using Nitrous. MSD suggests phasing the rotor midway between this number. So I have the rotor phase to be lined up at 8 pulled out. This will allow the rotor to be close enough to fire without backfire at full retard as well as without any timing pulled out. Using a timing light and open cap I can see that it is pretty close. I have no backfire on a Nitrous pass or without using it. Pulling 15 degrees on a start retard should be very close to what it is using nitrous where it should be more of a problem than at start up.
Going to try backing it down to 10 or no retard at all.
Thanks for all of the reply's
Mike