engine popping

[Screaming Metal]

I agree Ron, he's got a problem. If its a steady 20" its not in the valves or inside the cylinders, that was why I was thinking inside the distributor. It could be its coming and going.....dam strange!

What I would do, if I were he, we're guessing here right now. I'd pull the distributor, and take it to someone that has a distributor machine, have them hook it up and test it out. That would clear the distributor of any faults, period.
Then, he can hook up a multi-tester to the 12V. line going to the coil, take a spin and see if it fluctuates while driving.

Remember, it seemed to go away a little when he changed his coil. Could also have a grounding problem with the ignition, making it cut out.

The planets are in alignment again!

 

[Screaming Metal]

Its not the fuel, its not the timing, cam timing hasn't jumped, he's got 20" of vacuum, replaced the coil and the insides of the distributor, diff. carbs, before changing all the springs willy-nilly, test the pressure first on them all. Make sure you clean the plugs also,
You just don't want to throw money at this, you want to find out whats going on to fix it.
The springs or the slack in the timing set could rock backwards every once in a while....
I still think its something extremely simple....if it were a weak spring, you'd have a weak or dead cylinder. But with 20" of vacuum?
I'd hook the vacuum gauge up and take it for a spin also....

 

[Screaming Metal]

Well, if I were there with my tools but I'm not. He'd probably be better if he can't find it, to take it to his friend that works at the speed shop and let him run some tests.
At this point, I'd be making it personal with that V-6.

 

[Screaming Metal]

The only other thing I can think of is if there was alot of excessive distributor endplay....naaa, that can't be it. weegee board anyone?

 

[railroad]

Stick another carb on it. I have faith.

 

[Wild Mango]

"IF" he has 20" of steady vac he can not have a sticky valve. That vac gauge would be bouncing all over the place! Maybe we need to recheck that vac while the engine is doing its popping thing.

And RPM points out yet one more thing the vacuum gauge will do for you. An indispensable diagnostic and tuning tool, the vacuum gauge. I would choose one over a timing light in importance. Also quite a good in-car instrument, I put one in all my petrol engine cars.

 

[Screaming Metal]

Yes Mango, they are taken for granted. I mount a combo vacuum/boost gauge in all my personal cars, since they all have forced induction....

 

[Francis Blake]

After trying so many things, I think the chevy garage would be in order. I agree with good vacuum it wouldn't seem to be the valves.

 

[RPM]

After trying so many things, I think the chevy garage would be in order. I agree with good vacuum it wouldn't seem to be the valves.

Have you looked at or just replaced the header gaskets?

 

[Wild Mango]

Yes Mango, they are taken for granted. I mount a combo vacuum/boost gauge in all my personal cars, since they all have forced induction....

Yes, here the gas prices bit years ago, $6.00 a gallon seems like a good dream. The vacuum gauge is a great gas mileage tool too, promotes economical driving habits. Here, economy is part of the performance package and we have learned you can have both with a minimum of compromise.

 

[Screaming Metal]

And here is some basic reminder stuff, courtsey of the NTBA Tech pages....
http://www.nationaltbucketalliance.com/tech_info/engine/Enginepoping/engine_popping.asp

 

[Francis Blake]

I have tried everything suggested and everything that I could think of but nadda. I towed it to the garage and they assured me they can find the problem. As soon as I find out I will post it on here, then we can write this one in our books.

 

[Screaming Metal]

Like I said if we were there with our tools, if she's there at the Bash....we'll need to perform a Exorcism to get those 'No Cruise Demons' outta there! Hahahaha....I keep haveing a loose lower blower drive pulley thats stumping everyone, so don't feel bad.
Just got thru machining out a custom lower hub, I just got thru TIG'ing a plate onto my lower pulley, gotta let it cool off, then let's see that bitch back off after its bolted on!

POPPING???? Where is that POPPING????

 

[Wild Mango]

Clutching at straws now, its all we have left. Something with the accelerator pump making it a non squirter sometimes?.
Take it to a shop. Go home and have a few pulls at a good bottle and then a big steak dinner with mushrooms, onions and mash potatoes. Sleep happy and contented.

 

[Francis Blake]

I finally heard from the garage that is working on my car, they said three cylinders are not firing when it gets up some revs they think it is a ground problem. The engine is grounded in several places so I'm thinking it may be the ground strap in the hei dist. Will know more before the day is over

 

[Francis Blake]

I hope I'm not being a boar, but I got my car back today and the mechanic told me he put it on top dead centre and the timing marks did not line up so he put on a new mark and timed it from that (OMG) and said it was running good so I paid my money and got out of there. When I got home I checked the cam timing for myself and it is off about 15 degrees ( Screaming Metal told me to check this and my face is red)so it has jumped time for sure. Will do the repairs Monday.

 

[2old2fast]

Just askin' [cause I really don't know] but if it jumped a tooth , wouldn't it be off by more than 15* ???

dave

 

[Wild Mango]

Depending on the belt tooth pitch it could well be off by 15deg if it jumped a tooth. The cam is 720deg with respect to the crank so any degree error is doubled. On the SBC a 5th" offset bush in the cam sprocket is a degree.
The damper moving on the hub because the bush slips is also a classic throw off - I like to check the TDC mark with a piston stop as the first item in a tune up.
We are all very wise after the event but in truth the duh-uh's will be our constant irritating companion in life, count on that.......................

 

[Francis Blake]

2old2fast (me to) 15 degrees was just an estimate, taking a quick look after bringing it up to tdc, could be more but it is definitely out of time.

 

[Screaming Metal]

Blake, I know that some of the GM belts were designed to fail at approx. 35,000 miles of service. Most of them would not last 25000. Gates was asked to redesign them, and they had belts that could go to about 75,000.
Belts are good, to a point. I don't give a dawn if they're guaranteed for 100,000....what I want to know is when that piece fails in 35000 while I'm off on vacation in my Bucket, if old Joe Blow is gonna stick a new belt on for me! hahaha....
At least ya know whats at fault now.

Timing on the belt is a bitch, unless you have the adjustable pulley on the cam(s). You have to rotate it, line it up rotate, doublecheck your mark, and everytime you line things up with a cogbelt, its always a little off. It usually takes me about 4 or 5 times before I'm satisfied.
Change out your belt about every 5 years, to be safe. while your in there, replace your belt tensioner. Cheap insurance!