Geez, Louise, this thread came off the rails early on and is somehow managing to get a bit crazier with each subsequent post. Open this thread in a real quiet environment and you can hear it sucking the intelligence right out of your head, I swear. A slipped timing belt in a 4.3 V-6?!?
Huh?!? Can we get a show of hands from just the people who have actually seen a 4.3 90° V-6 Chevrolet?
Francis, Ron is absolutely correct. There's not a 4.3 out there using a timing belt, unless it is a race motor with an after-market belt drive on it.. I've no idea where these guys are getting the idea a belt is causing your problem, but your engine has a timing chain and not a timing belt.
For the rest of you, a 4.3 90° V-6 is a 350 with two holes missing. Nothing exotic in it. As a matter of fact, the odd-fire (common crank pin) 4.3 uses all the same pieces as a 350. Right down to the lifters, oil pump, rods, pistons and wait for it, even the timing set.
That wee heart-breaker has a timing belt on it. But it is an after-market Jesel belt system and is the
exact same part number as used on the SBC.
Francis, part of the problem in getting this problem diagnosed is that you are leaving some really wide gaps in your description of the problem. The rest of this problem is people (who clearly know nothing about the 4.3, BTW) are making wild-arsed guesses that are sending you dancing down the wrong garden paths. Let's stop right here and start all over, using the very same diagnostic techniques we would use on any other engine. That way, we won't get all caught up in timing belt nonsense or in major internal damage on a motor with such excellent vacuum numbers.
I'll try to help you out, but I need some specific answers to some specific questions and without it, all I can do is join the 4.3 Timing Belt Club of America and start making guesses, myself.
Before we even start off, I need to know what crank your engine has in it. Is it an uncommon pin crank, which is used in the even-fire motors? Or is it a common crank pin crank, which is used in an odd-fire motor? We absolutely need to know crank design before we can proceed.
Next, bring me up to speed on this engine. Is this a new piece, something you just freshened, or a used engine you picked up? If it is new or fresh, has this problem been nagging you since start-up? If this is a used engine, did the problem recently manifest itself, or has it been doing it since you got it running?
1. Pull off the distributor cap and rotor. Now, look at the points on the reluctor. Are they evenly spaced in a symmetric position, or do three of the points look closer to the other three? Symmetric spacing means it is an even-fire reluctor, whereas odd spacing will mean it is an odd-fire reluctor. The reluctor design has to match the crank design. The engine will run with the wrong reluctor, but it will mis-fire, which might sound familiar to you. So be sure to check this closely.
2. Put the rotor back on and give that center contact tang a good pull, to make sure it will make good contact with the coil contact. And, speaking of the coil contact, is it in good shape. Increasing secondary voltage levels with an aftermarket ignition will cause that carbon to erode faster. And once it starts to erode, it will go away really quickly.
3. Turn the cap upside down and talk to me abut the terminals. They are likely spaced symmetrically, but do you see some tails wrapping off one side of the terminals. The ignition people make one cap to use in both firing orders and it actually causes problems with both. But if you have an odd-fire combination, those terminals are going to need those tails, in order to keep things firing as they should. We would take a Mallory distributor housing and machine the bowl off, which we would replace with a nylon adapter to accept a Volvo, true, odd-fire cap. They were small in diameter, as you can see in the above picture, but they were set up for a 90/150 firing combination.
4. Make sure the grounding strap in the distributor is in good shape and then make sure the distributor is well-grounded. And by well-grounded, I mean clean metal contacts at both ends.
5. If she's still popping and mis-firing, please describe that condition to me. Does it pop all the time? Or only at low RPM? Or maybe at only high RPM? Or only while you're squeezing the throttle? Or only when you're stepping off the throttle? Does it do it when the engine is cold, warm or at all temperatures? Tell us the details on this pop, so we're not guessing at it.
6. What fuel pump are you running and what output pressure have you measured?
7. Have you recently rebuilt that Edelbrock carb, or even just changed the needle and seat? If you have, what brand components did you use as replacements?
8. What are the numbers from a cranking compression test? Cylinder by cylinder, please?
9. With the plugs out, place your thumb over the #1 plug hole and have someone slowly bar the engine over until compression blows your finger off. Look at the timing marks and see if you are at TDC.
10. Knock the rocker covers off and slowly turn the engine over. Are all 12 valves opening to approximately the same height and closing the same way?
11. Please describe how you set lifter pre-load.
If we can get some of this data, we can then start making some well-informed progress on what needs to happen next. Without it, all anyone can do is go right back to the wild-arsed guesses and those just don't seem to be working real well for you. We're at Day 16 and diagnosing pitch on that non-existent timing belt has this motor running just as poorly as it was over two weeks ago.
