[cheifyoda]

i have a 454 with small street strip cam , timing gears, tunnel ram. holley 450's , pro comp dist, pro comp coil, a complete rebuild. when first started it ran great . now somewhere down the line i blew an intake gasket and was backfiring . i replaced the gasket. now at idle it runs good but backfires and sputters down the road. i found the vac advance blown i now changed the dist to a oem points type and set timing at 18 runs ok but under light acceleration still coughs and backfires in the exhaust now . this is not my first rodeo with a bigblock ive raced many years and built many good runners. im not an expert by no means , but ive done alot of timing. checking valves. checking for vac leaks. now time to pass it on to you guys. maybe a fresh thought would help. i did install the cam straight up lining up the marks. maybe i should have run it at 4deg:hammer::hammer:

 

[r66ss]

the cam straight up lining up the marks. maybe i should have run it at 4deg



what did the cam manufacture what it installed at? Is there any degrees ground into cam ?

 

[speedy55]

im not familiar with your 4150 carbs but backfires will kill the power valves in the carbs. If it is backfiring when you give it gas it could be a lean condition.

 

[cheifyoda]

they are new 4160 series carbs 9776 pn and the backfire is in the exhaust not thru carbs and cam is to be set straight up :goodnight:

 

[old school 55]

points style Ignition?

so you switched back to point style ignition? have you replaced the condenser and checked the points? they could be fouled or mis-gapped or the condenser could be shorting? I'd check there first.

 

[cheifyoda]

yea im going to check them again its i new oem dist ive had in the shop awhile ill go through it all tomorrow