76 Chevy blazer full sized 4x4 w/350 that is backfireing thru the carb...

I have recently put an Edelbrock cam and lifter kit in my brothers truck since the last one the rockers were over tightened and flattened the cam. Well since we were going to take it apart any way and we've had success with
the Edelbrock carbs in the past. We thought we'd change things. Now its back firing thru the carb and I can't figure out why. The timing is set about 12 BTDC. I think it could have been the adjustment of the rocker arms on when we put it back since everything else checks out. But I was wondering if there is some stuff I could try.
Thanks, D.L. Man
P.S. There is not emissions stuff on the truck.
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Is it starting or just backfiring through the carb? If its not starting then the timing is WAY off, plug wire sequence backwards on the cap, and/or lifters set too tight. If it is starting drop the second one and back the timing off, check that there are no crossed plug wires, and loosen the rockers and reset.
That should give you a good starting point...

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I don't know if its important but it is running and it doesn't backfire when at idle. Or when I have it floored. Only about mid range on the foot feed while driving at anyspeed.
Any ideas on rocker adjustment? the books say put 1 ant TDC and then tighten spin the push rods in your fingers while tightening them down. When they start to have pressure then tighten them a full 360 more and then turn the engine over 90 degrees and do the same for the next set in the firing order.
How do I know when its too much? When the push rods are spinning with allot of force or what?
"Shades" <shades_1970(at)netins(dot)net> wrote in message

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1 turn is standard. I have gone as little as 1/2 turn and as much as 1 1/2 turns. The pressure on the pushrod is minimal...it is more like slight drag than real pressure.

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1/2 turn is standard , comp hydraulic lifters enjoy 1/4 turn preload max.
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Mad-Dog
'79 Chevy K-10
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You are overtightening the rockers by a wide margin. Start with Cyl #1 and rotate the engine until the Intake valve is completely open then adjust the exhaust until there is no play then tighten 1/4 turn more....... then rotate until the exhaust has opened fully and adjust the intake. no wonder the cam went south.! the intake valves are staying partially open and sending a flame front back up thru the intake manifold, pocpocpocpocpocpocpocpocpocpocpoc does this sound familiar by chance?
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Mad-Dog
'79 Chevy K-10
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Another possibility is the carb is running way too lean and he's getting preignition while the intake valves are still open on the intake stroke?
Doc
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That's a thought, with the intake valve not closing completely on the compression stroke the sudden loss of cylinder pressure would most likely quench any preignition.
for a moment i thought he might have a wire crossed but now i know he's just a loose nut behind the wheel.....
How's that silverado comin along Doc?
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Mad-Dog
'79 Chevy K-10
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Still kickin' ass at 171K on the clock. She's gunna need a tranny rebuild soon enough, and I'm likely going to dump a 383 in there at the same time. Haven't had the time and it's been too damn cold anyways to get at it so far. If it quit I'd be more motivated to get out there and get going, but so loing as it keeps running as well as it does I'll just wait for the warmer weather!
Doc
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A guy from edelbrock that I was emailing said that my carb maybe to small for my application. But he wants to send me a set of metering rods and setup springs. I hope he sends instructions too. I don't know what to do with those things. Last night I was going to adjust the rockers but I was called away. So I told my brother what he should do to adjust them. He hasn't gotten back to me yet to tell me if it worked.
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leaning over the fender and looking across the engine the intake valve will line up with the intake runner...... and the exhaust valve will line with the exhaust port or hedder pipe.
It makes no difference which valve on which cylinder you start with as long as the reference valve lifter is resting on the base circle of the cam b4 adjusting the companion valve rocker.
It's always a good idea to start with #1 and follow thru to #8 or follow the firing order 1,8,4,3,6,5,7,2
Hope everything turns out well.......!
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Mad-Dog
'79 Chevy K-10
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Standing in front of the truck with the hood open, the first cylinder on your right(engine left) is #1, the first cylinder on your left(engine right) is #2. It goes back and forth across the engine. Odd numbers being on the drivers side(engine left) and even numbers being on the passenger side(engine right).

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A flat cam lobe will cause it to backfire through the carb. You don;t say if you replaced the bad cam, but it will do this untill you do. Dan
wrote:

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Also this could be an effect of the backfiring but... I noticed when I had the intake manifold removed from the truck there was plate on the bottom of it that was coming off. This is the stock manifold and we really didn't see a reason to change at the time we put the new carb on. But I was thinking that the backfiring that was going on before we changed the camshaft might have blown out that plate. Is there a problem with leaving it on there? Or should we change the manifold now? Thanks

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I made the same mistake of using the stock manifold when I first installed my performer carb. A big difference when I replaced it with a Performer intake! I later went as far as installing a 4-hole thermal spacer gasket. Not as big of a difference, but noticeable.

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