440 problems

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440superduster

440superduster

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The 440 in my duster backfires through the left side exhust of the motor only. This didnt start occuring till I changed the cam to a MP 509 lift.
The car has 906 heads Herb Mclandles headers eldbrock torqer II intake 850 holley double pumper 6 pack pistons decked block . The cam is installed 4 deeg advanced.
 
You could either have one of the plug wires on wrong, or you have lost a lobe on the cam during break in.
 
Backfires how? Up the intake, out the exh pipe? What was and how did the cam break in process go? Steady, or is it intermittant?
 
You're sure on the #5 and 7 wires? It will pop and sputter but run if those are reversed. Are you sure the headers are sealing? I know it sounds stupid... but I've had a few people tell me the engine was broke and it was simple gaskets. A rich idle that lets oxygen into the header pipe thru a bad leak can make the un-burnt fuel pop in the hot exh.
 
Is this on acceleration or deceleration? Backfire through the exhaust sounds like it could be unburned fuel. Maybe check your timing, drive it after a change and see if the problem goes away. The cylinders fill at different points now with the new cam, might need to adjust a little to get it right. Also, maybe check your plugs to see what they look like.

Simple stuff first.
 
I am gonna say it sounds like one I had doing the same thing and ended up bein a lobe on the cam.For some reason it went flat on break-in.And I have heard 509 do it pretty often.Dont know for sure.
 
If ya haven't allready pull your left bank valve cover and rotate the engine, by hand, to make sure that all the valves are going up and down, this is a quick and dirty to make sure ya didn't wipe a lobe. Also when rotating the engine check that the valves are all closing and that one of the exhausts isn't hanging up, this can occur when you only change to a higher lift cam and there is carbon build up on the valve stems. When a valve hangs up you end up bending pushrods, check them also.

Terry
 
added more timing and fuel seems like problem got a little better . also swaped out ballast resitor small problem now and again but will know when I drive it this weekend.
 
440superduster said:
added more timing and fuel seems like problem got a little better . also swaped out ballast resitor small problem now and again but will know when I drive it this weekend.
Click to expand...

Nice work. I think you would know it if you wiped a cam lobe, there would likely be much worse symptoms than backfiring through the exhaust.

Obviously, swapping the cam changes the entire dynamic of the engine, it stands to reason you would need to fine-tune the timing and mixture.
 
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