back fire thru mufflers

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terry

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so I have a 360/380 crate motor with msd distributor and 6al box I notice that around 2000 rpm the motor miss/surge and if I bring the rpm up in third gear then let off I will get a backfire out of the exhaust. timing to advanced or retarded ? it start very good and does not diesel at all.
 
Could be too rich, but surging is a lean indication.
Could be sucking air into the exhaust somewhere.
Think about it like this (somehow you have unburned fuel and air getting into the exhaust system.)
Enough even that it detonates in there.
 
terry said:
so I have a 360/380 crate motor with msd distributor and 6al box I notice that around 2000 rpm the motor miss/surge and if I bring the rpm up in third gear then let off I will get a backfire out of the exhaust. timing to advanced or retarded ? it start very good and does not diesel at all.
Click to expand...

I have a crate also! Different one, but I think I have the same cam.

What is your initial timing ?
 
I have tried different setting anywhere from 13 to 20 degrees just to experiment. but I have to start over again with advancing the dis. until it pulls the motor down when I start it then move it back a bit till it starts easy then try the total advance which is usually around 34-36
 
Start by putting light on #1. If at idle the timing bounces around, the bushing in the dizzy shaft is worn, replace. I'm not a fan of MSD. To double check, turn curb idle up to 2000 rpm, if timing bounces, replace bushing in dizzy. A good place to start, good luck.
 
terry said:
I have tried different setting anywhere from 13 to 20 degrees just to experiment. but I have to start over again with advancing the dis. until it pulls the motor down when I start it then move it back a bit till it starts easy then try the total advance which is usually around 34-36
Click to expand...


You're on the right track.
You probably know to reset your mechanical.
Like TrailBeast said, are you rich?
What do your plugs look like?
Is your transition slot square?

If your motor is like mine, you have to get it square and idle up with secondary air.
 
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