i have a problem i have a freshly built 305 in a 86 iroc and my problem is that gas blows back out of the top of my carb when i try to start it.i do not know that much about the motor b/c i did not put it together.i have checked the timing,and the compression and they are all perfect but still my problem persist if anyone has any ideas please tell me your help will be greatly appreciated

 

You may have more luck in the 3rd gen tech forum, so I'll move this there for ya.

 

does it start?

doesn't sound like it, sounds like the dist is in 180 out, or really far off

 

What brand carb? If Holley, did you get the flotes set?

 

whats your fuel pressure set at?

if it uses the mechanical fuel pump u should not have any problem but some people like to put an electric fuel pump
if the electric fuel pump puts out more than about 7-8 psi, then your shooting fuel through the carb
then u need a pressure regulator, or if u have one, adjust it

u stated the motor is freshly built
has it been started yet?
if so how many miles on the new motor?

is it spraying gas or dribbling gas or do u just smell gas?

it may still start depending how bad it is
if it does, does the problem get worse as you rev the engine

if it doesnt start, check the timing

 

Most common reason for that on a fresh rebuild is timing being 180* off, after that would be misadjusted lifters not allowing valves to close, blowing compression out the intake.

 

it is a 550 eldelbrock vaccum secondary and it has a manual feul pump so its getting plenty of fuel and i asked one of my fellow shade trees about it and he stated the same thing about the timing being half way out in the dist so i will do the proper compression test tomorrow time it and turn the dist 180 i will keep every one posted and i thank you all for your help