engine popping and back firing?

[jrkracing54]

steel head limited engine is popping and back firing when it starts to get warm. Carb is off of my 604 crate and had been using 100 octane fuel. Now running 114. Could the carb be that lean? Any help would be great. Trying to race it tomorrow.

[dualdj1]

octane in itself shouldn't effect lean/rich much. Now if you switched from gas to alcohol, or are running an oxy enriched fuel, then you mixture may be off.

how long has it been acting up? Only since you switched carb? is it a new engine? backfiring is *usually* timing/msd related.

[jrkracing54]

I think I may have the wrong header gaskets on it. I think it is sucking air through there. I had the "D" shape gaskets on it and they are bowtie heads.

[zeke23z]

Toss the gaskets use 100 percent silicone

[rubbinsracin]

we have never had trouble with header gaskets, but we have always had the right size so that very well could be the problem. our engine builder recommended that we start using high temp silicone instead of the regular gasket. anyone else ever done this?

[dualdj1]

have used both high temp red or gaskets with no probs. That could do it. if you change out and it's still happening though, check your timing/msd box.

[zeke23z]

I use 100 percent silicone,not the automotive type the 100 percent i feel last longer

[vms]

cracked header, when it gets warm is swells the crack. Had it happen to me. Also like you said the gasket was bad and it was sucking air.. Def say exhaust gasket

[jrkracing54]

Still doing it. Only does it below 2000 rpm. I'm now thinking too much fuel pressure. It is right at 8 pounds of pressure. I have ruled out that it might be electrical because it only does it when it has ran for a minute or so and only below 2000 rpm. Any thoughts? I don't have a pressure regulator on the engine currently and don't think I could get one before tonight. John 1*

[dualdj1]

8 lbs isn't too much. we usually run about 9. Find a spare MSD box to try if you haven't already. They do wierd things like that sometimes. That's the only way you can truly rule it out.

[leadorfollow]

8 lb should be fine but you may want to check your floats and needles to make sure nothing is stuck or the secondaries to make sure it's not stuck open a little. Does it clear out on the track or only backfire at idle under 2000? We fought a problem on our car it ended up being the coil. The car would start and run fine but once it got warm the coil would get warm itself and cause issues.

[jrkracing54]

Found the problem. It was a bad connection from the distributor to the MSD box. I checked it several times too. Oh well you live and you learn. Thanks to everyone for all the help it was appreciated. John 1*