Need help with timing.Please

[Trunks1942]

I have a 75 chevelle with a 350. Put in a new intake manafold and a 4 barrel carb.New wires, plugs and coil pack.the problem is that i cant get this timing right.i got it set at 8*.When i go to take off it will back fire through the carb and bog down.Then when driving normaly once and awhile it will back fire through the carb again.Ive tryed 10* and even went to TDC and it still does it.

Im stumped.I asked around and still havent gotten a good answer except your timing is off.is there something else that would be causeing this problem.Any help would be gratefull.

75 Chevelle Classic
96k miles
Edelbrock Intake manifold
Edelbrock 4 Barrel Carb 600
The rest of the car has its factory parts

[mason71]

Are you sure your back on the same tooth that the distrebuter was in when you first pulled it?

[CRUZN69]

Sounds to me like it's 180 out. You need to bring it to top dead center on number one and reset the distributor.

[yenders11]

it sounds like your cam is dialed wrong. Go get a cam dial and a stop block. If you don't know what I am talking about then check out how nascar sets thier timing. If you put the stopper on your block in place of the head and set your crank to tdc, you can dial your engine to perfect timing. It is a mathematical process but it is a sure fire way to set perfect timing. I have the set and I haven't had bad timing yet. It does sound like you are 180 off. If you backfire out of the carb then your intake valves are open when your exhaust valves should be. You could also try making sure that you don't have bent valves.

[Trunks1942]

I reset the distributer it runs fine execpt for the poping on take off and when you punch the gas.I'm starting to wonder if the chain might of slipped,or the carb is giveing it to much gas.If i cant figure it out i might just have to send it to a garage.Alot of money will go in there pockets

[CRUZN69]

Are you running the HEI ignition? How much initial timing do you have with the vac advance disconnected? (Make sure to plug the vac line too)

[Ironic]

Can't the same thing happen if the fireing order is mixed up?

[Mr. Horsepower]

Remember practice makes perfect. Make sure you are not 180 off. Plus check the firing order on how your wires are set remember from 1 on the distributor 18436572 clockwise. I have had the problem to with having the valve lash wrong. Plus too thick of oil may have caused your lifters to seize. Try running some 30 w oil through it for a couple hours and then set your valves again. This would help the lifters out and then change your oil again to your regular oil weight. Try to stay away from oil additives such as Lucas oil unless your oiling system is set up...

[bowties4everamen]

I cant believe no one even asked you this. I can just about guess that your timming chain is worn out. You havent changed your cam so you never even been in the timing cover yet. when a chain gets old you get almost 10 - 20 degrees of slack that the chain moves before the distributor even moves! replace the timing chain and gears, get a recurve kit for the weights and srings in distributor, and oh yeah... check to se if vacume advance even works, and the mechanical advance system built in distributor even moves. I dont mean the weights themselves buit the shaft itself must move. As the distributor gets old the shaft starts to rust and not let the mechanical advance built in it pivot. AND.. LOL... the place where the wights pivot.. check to see if they arent all grooved up either. You can no see that there is a lot of spots that cause timming misses. everone has missed them completely. When you do go all thru that, get a advance type of timming light to check out initial, vacume and then total advance. There are 3 different totals you must dial in. Welcome to tune up 101.

[hotrod_chevyz]

The last time mine did that i had knocked a lobe off the cam.You might just have mismatched parts.Did it run okay before,and now you cant get it to tune out?It might not run correctly unless you get better heads put on it,or at least new valve guides and springs and lifters/cam..Now that you have upgraded the intake and carb,the factory heads on your engine might not let the carb and intake have what they need.You may have been blessed with a set of small valve heads,wich dont take to performance upgrades very easily.If the engine is original you might see one of these casting numbers [6259425(350-2bm)],[3970014(350 2 or 4bm)] [3970010(350-2 or 4bm)],as they are the most commonly used engines in your model Chevelle.Others were used as well,but not very often.

[Trunks1942]

My guess is the chain too.My wifes grandfather owned the car and i bought it at the auction when he passed away.It has 96k miles on it.He was the original owner of the car.So im not sure if the gears and chain where even replaced at 60k.That is my next step seeing that the distriputor can not be turned one tooth which it needs to be.Edelbrock has one i seen for like 50 bucks so ill get it and try it.As far as i can remember it started doing it before i put new stuff on it. Thanks for the replys.

[hotrod_chevyz]

you can turn it one tooth

[Trunks1942]

No i cant move it one tooth not sure why.I think the older chevelle i had wouldnt do it either.I got a used hei distriputor for it then i could turn it one tooth.But for some reason this one wont do it.

[hotrod_chevyz]

Have you tried adjusting the oil pump drive?the bottom of your distributor runs the oil pump,by using a shaft that goes from the bottom of the distributor,into the top of the oil pump.It is slotted like a screwdriver,and fits the bottom of the distributor in a slot,and you cant get the distributor stabbed,cause the slot usually moves when you pull the distributor out of the hole.Using a long flat tipped screwdriver,and a flashlight,you can usually go down thru the distributor hole,and adjust the oil pump drive.you almost always have to do this or it will try to restab one tooth off.if you dont do this you cant get the distributor to go all the way into its hole,itll fall short about 1/4-1/2 inch somwhere.

[Trunks1942]

Thanks i never knew you could do that.Next time it gets nice out im going to go do that and see if i can get it dead on.