[updated:LAST EDITED ON 17-Sep-02 AT 03:34 AM (EST)]Ok here is the senario.

86 F350 CC DRW, 460/C6, new Edelbrock 750, new Edelbrock roller timing chain set at straight up. New plugs and wires before the timing chain installation.

Immediately after installing the timing chain, I developed a backfire through the carb problem. Replaced all of the ignition components (module, coil, distributor, cap-n-rotor), and found that the only thing that made it better was to advance the timing. Retarding the timing made it REALLY bad.

Now, I have the timing advance to about 30 degrees using the hot start method, and the truck runs fantastic. But...

Today I had to take 15 mile freeway run. In the first five minutes this afternoon, it backfired once and ran fine the rest of the way. However, tonight about 11pm on the way home it was backfiring through the carb every 4 or 5 minutes.

It does it more in cool air...

It NEVER has done it under hard acceleration, or deceleration. Only high steady speeds on the freeway, say above 2500 rpm. Other than this the truck runs fantastic.

A guy at the local speed shop told me that if I installed the roller timing straight up, I could create a lean condition.

Is this true, and will this cause my backfire?

What else could be causing it. Do I need to reinstall the timing set to 4 degrees retard (don't wanna)? Plugs and wires are fairly new.

If I need to enrichen (is that a word?) my carb, will the adjusting screws do the job, or will I need to change jets?

I tow a heavy trailer with this truck, so I need it right.

Please help me out here. Thanks.

 

try timing it with a light. and also try the mixture screws on the carb to add more feul to the mixture

 

[updated:LAST EDITED ON 17-Sep-02 AT 10:37 AM (EST)]I timed it with a light, and at 15 degrees, it backfires even more. I advanced it using the hot start method to advance it as far as I can, and it is at aboout 30 degrees. Drastically reduced the backfiring, and I thought it was gone when I road tested. Then yesterday was the first extended drive I took it on.

Could I be too far advanced? I've heard of guys running this far advanced with no problems, as long as it is not pinging. I can't get the thing to ping, but I haven't towed my trailer with it this far advanced.

I will try to run it richer and see what that does.

Any other suggestions?

Thanks...

 

 

sounds like the timing chain may be in wrong
the marks should be close together top mark at 6 oclock and the bottom mark at 12 oclock
was it a 3or more key sprocket?

had a friend install new timing chain cause his was bad.
truck was towed home! the book said to replace everything as found... couldnt get it running when done, had to put dist way out and it ran poorly.
i helped him take it apart and found marks were off.
when i moved the cam he ran and got the book saying i was doing it wrong. put it back my way... and now running fine.
might not be same as your case but ''stuff'' happens



jason

 

No the gears are in right, but I am running lean. I bought some smaller metering rods for the Edelbrock carb and will get them in. The truck runs trly fantastic except for the occasional backfire through the carb. If the gears were in wrong it would be a consistent problem, and like your friends, not run at all, or at least VERY poorly.
I just was not expecting to run so lean from advancing the cam timing, but I just learned too that the Edelbrock 1411 750 cfm comes out of the box with the biggest metering rods they make, making it run as lean as possible, probably for emmisions and economy. Plainly put, this carb simply can't get any leaner.

I also was not expecting it to pop through the carb from running lean.

I've learned alot in the last week.