i have a 68 camaro with a 350 in it replaced cam and new distributor. my problem is it pops out of carb. now timing is off and i cant seem to correct the problem. correct me if im wrong cuz im not a mechanic by all means top dead center is when the #1 cylinder is all the way up and rotor button points at the #1 cylinder. i have did this and still pops out the carb . can anybody help me ?

 

OK. We are going to assume that the cam is timed right, otherwise all bets are off.
Not only does the #1 piston has to be all the way up, but both valves have to be closed, otherwise you could be 180 degrees out. I don't know about a button on the distributor rotor, but the metal wiper on the rotor should point to #1 cylinder. Check that all wires are in according to the firing order and in accordance to the distributor rotation. Take the distributor cap off, crank the engine & note wich direction the distributor spins.
You could also have a lean condition which will make your carb spit back

 

not sure what your saying as far as the cam being timed right?
when both valves are closed are the valve springs open or closed?
the distubutor turns clockwise thanks for your help hopefully i will get this car running

 

The cam is timed right when the mark on the crank timing chain sprocket point directly up and the mark on the cam sprocket points directly down. In other words, they should be pointing directly at each other, crank up cam down.
Keep in mind that the back end of the cam drives the distributor.

The valves are closed when the springs are extended out, pulling the valve closed,

The firing order is 1 8 4 3 6 5 7 2. Standing in front of the car facing the engine 1,3,5,7 are on the driver side, 2,4,6,8 are on the passenger side. The frontmost cylyinder is #1. Your distributor housig or cap may be marked showing where the #1 tower is located.

To set the timing to a working state

1) Turn the base of the distributor till the rotor tip points to the #1 tower. If it is way off you may have to pull out the whole didtributor turn the shaft and pu it back in. Once it is right clamp it and put the cap back.

2) Connect a spark plug wire from the #1 tower to the plug on the #1 cylinder.

3) Looking clockwise at the distributor cap connect a wire from the # 2 tower to cylinder #8

4) contining clockwise connect a wire from the #3 tower to cylider #4

5) Continue this sequence till all the wires are in

You will have to fine tune the timing with a timing light once the engine is running steady

 

Forgot to mention.
Make sure the #1 piston is at top dead center on the compression stroke before setting the distributor. Piston all the way up, both valve springs fully extended out.

 

well still have the same problem! im not sure what to do now lol. even when the motor is turn over but not started it pops out carb. i think im gonna have to find a mechanic to come over to the house and see what he can do cuz im not getting any were. i appreaciate for every thing your telling me what to do but im not sure what going on with it . maybe the cam isnt timed corrrectly i thought for sure it was dot to dot. if there is any thing else to try im all ears , well im gonna run for now later

 

I am kinda out of ideas, If everythig is timed right, I can oly think of maybe a bad intake valve. May want to do a compression check.

 

It could also be your valve clearance. If intake valve does not have enough clearance the valve will not close all of the way before spark plug fires. Keep in mind spark fires before top dead center compression. Also you have to adjust your valves when engine is cold not warm or hot. Sorry but not lean condition. Lean condition causes lean missfire not lean backfire. If anything it would be because mixture is way too rich. Check your valves!

 

if you are at a loss on how to fix the timing, go to a mechanic and have them take a look. It might be simple and cheap. Its more important to have your camaro on the road.