engine trouble

[calb42]

i need to help id this engine I think its a 400 Pontiac I told him but that I would try to find out cant get to any numbers, has 6x heads only other one is GM11 at back of drivers side. also it is popping back through carb like crosswired whats the firing order on it ? has edelbrock manifold and carb. and elec dist .runs fine no smoke good oil pressure but sounds like popcorn popping also starts fine but after running a short while starter drags thanks for any ideas guys

 

[melsg5]

to ID the engine you need the letter code on the engine block pad in front of the passenger side cylinder head.
the firing order is 18436572 usually cast on the intake manifold