just got my engine running today new heads
problem is at 3500 rpm the engine backfires through
the exaust. if i disconect the vacume advance its hard to
start but dosent backfire what do you think also excesive gasses out the
tailpipe

 

The timing is probably way off. It would help (a lot) if you posted some detail about your setup. Is it a go-kart, motorcycle, F1 car, top fueler, or what?

Rich

 

1981 z28 327 240 246 dur cam with 512 lift
.240 dome top pistons edelbrock heads ,intake and carb
msd ignition heddman heddars

 

Whats the timing set to?
what dist you running? Is it still vac advanced?

Sounds like timing is off or maybe a valve too tight.

Did you build it? the timing chain isn't off a tooth or anything?

 

Yeah,m the cam timing could be all futzed up as well. Or a crossed plug wire or something like that.

Rich

 

ok here is what happend
3 weeks ago i brock a valve spring dropped #4 exaust valve
busted the head cracked piston
replaced the piston bought new heads
reasembeld top end the cam cranck timming has not changed
has anyone run into the guide plates binding on the pushrods
oh ya someone brock into my shop and stoal my distributor
and oil pan so i have replaced both yes it a vacumb advance dis

 

Well if they stole your distributor then I would guess the timing is way off on the new one. Just my $.02 though, I am far from an expert.

 

have a few ideas on the problem the dis is out of a 79 camaro with a 305
my dis was a 81 z28 350 posibly the mecanical advane coming in to soon
and the fuel in the car is regular compression to high for that roughly abou 12-1 going to try better fuel and and removing the mechanical advance and see what happens anything else i could try?

 

Yeah timing is off and reg gas will not work on a 12:1 motor especially a carbed one with hei distributer.you will have a tough time tuning the car with that distributer,I would ditch it and run a msd probillet with no vacuume advance.