texlmc

Ok here is the scoop. I have an 84 Z that i purchased two years ago and after a long list of struggles finally got the dang thing running like it was when i bought it.

Now the problem is I can't get the darn thing timed right. I can set it by ear halfway but always has a stutter or backfire in carb. If I try to use the light its way off timing mark. I have no idea what cam is in the car I thought it was a stock cam, could this be the problem or am I overlooking something stupid. I had to change intake gaskets and a new carb. Also changed plugs, wires and rotor cap. Please my Z is depending on you to save it from an almost certain fire ball to he)*.

It is 305 HO with 5 speed standard trans, 600 edelbrock carb other than that i was told by the seller he didn't know what was on it. Apparently the guy he bought it from told him it was stock.

Thank you for any assistance.

cars3

Did you unplug the connector by the passenger head with the brown wire before you timed it. You have to do that with any computer controlled car. Your car has a computer even with a carb for the emissions. Alot of people don't think so. I had the same problem with my 83 trans am and I had to bring it to the dealer and that's what they told me. In 5 min. they had it running like a champ.

cars3

I believe I was wrong. I'm looking in the chiltons manual right now page 2-34 and it says for a carb engine you need to disconnect the 4-wire connector at the distributor. This will bypass the ecm est.

texlmc

Yes this was disconnected for timing and it almost killed the car when it was.

Rice Killer87

Since you replaced the intake and you cant get it timed right now,it sounds to me like it may be off a tooth on the dist. It will have enough movement to get the timing "close" but not where it really needs to be like your saying.

~Take the #1 plug out and bump the motor (with finger over hole...its safe I swear) over until it gets to the compression stroke and the air will push your finger off and maybe scare the $hit outta ya.

~Then check your timing mark and it should be on or very close to TDC (Top Dead Center).

~Now pop the dist. cap off and check where the rotor is pointing. It should be pointing right at the #1 plug wire terminal. If its not,you know your off a tooth.

jayman350

yeah i would say you are off a tooth

you may have to turn the oil pump shaft a little so that the gear on the bottom of the dist can engage with the gear on the cam as well as the oil pump shaft

90rocz

A not so common problem for some SBC's is harmonic balancers that the outer ring spins causing the timing mark to be way off.
And if you time by it it will be off.

Put the timing mark on "0" and make sure the piston is up as high as it goes. I use a small screwdriver inserted in the sparkplug hole and feel the piston rise and fall, turning the crank very slowly by hand.

Or check a new one and compare, see where the mark is in relation to the keyway in the balancer. My IROC timing mark was off by 2 inches.

And whenever there's a timing issue, double check TDC, verify number one plug @ distributer too.

texlmc

Ok thank you for all your suggestions. I have now got the timing set where the light should be and after alot of tweaking it is running pretty good. With a smaller problem now it will only backfire through the carb if you load rpms to about 2500 and then pump the pedal down for a second. Or very rarely when you hard accelerate from an idle.


I have a guess to what this might be whats your input on the matter. I was thinking it sounded alot like a valve adjustment needed. I prob need one anyway because have a little lifter clatter. What do you think? Could valves needing adjusted be the reason setting the timing was so difficult?

Thank you for the suggestions so far and thank you in advance for any help you can offer.

Rice Killer87

Sounds like a spark plug is fouled or is cooked. Pull them and check.

Going through the valvetrain is a good idea,but shouldnt cause a backfire through the carb unless its off a pretty good amount...which it could be.

Check the plugs first. Where is the timing at? Maybe w/ the timine your running you need higher octane gas,which could make it run funny also.

Marc 85Z28

600cfm Edelbrock carb with the stock computer controlled distributor?

If you do in fact have the stock computer controlled distributor you'll never get the timing correct, no matter what you do. You need a standard HEI with vacuum advance.

You cannot mix and match computer controlled carbs and distributors with the standard carb and HEI distributors. Either both must be computer controlled, or neither are computer controlled.

Rice Killer87

Good looking,I didnt even notice that

texlmc

No it is HEI distrib

Thank you all for your suggestions and looking.
I did finally find out what the problem was and it WAS NOT the carb or the timing but all the symptoms of both.....lol

And only a 50 cent fix, my magnetic pick up inside the distrib was the problem. Not that it was bad just that the male prong ends had a little tarnish or corrosion on them. 50 cent piece of sand paper and she fired right up and my carb adjustments and timing were not to far off despite all the changing them trying to over diagnose the problem.

Oh well that will be one of the first things i check from now on when i have set timing and something still isn't right.


Thank you all again.