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Hey all,

This is a bit long-winded, but the issue is becoming increasingly annoying so I'm putting it out there to see if anyone may have a possible solution. I'll list all relevant details below...

Car has been running really well, but lifters were a bit noisy so checked into my mechanic for an adjustment. Motor has done @ 6,500km's since rebuild. At the same time it had a new set of plugs installed, & a tune up. Mechanic drove it just prior to me picking it up, & said it was going well.

On the way home, it seemed to be missing a little but I put it down to the heat & wasn't too concerned at that stage.

Next morning, it was a bit rough at cold idle & was definitely missing on immediate throttle opening, and at slow cruise speed. Hard acceleration it seemed all good. Car ran pretty poorly, so I stopped in to fill the tank (took 80l, so wasn't empty enough to have dragged any shit into the system). Seems a little better after that, but not much.

Anyhoo...60' 389 rebuilt to 400 (all the details & specs I have but don't think will help here?).

New distributor, fuel sender, fuel pump, carb. Plugs have been checked & cleaned, lifters have been re-adjusted, carb has been stripped, checked & cleaned and retuned, so dirt in there isn't the problem. To be honest, the car ran exactly the same after this was done! Coil & leads have been been replaced since also, to no avail (although the new leads look good😃).

As stated, missing occurs just on throttle opening, & slow cruise (idle/primary circuit)? Will pull easily to 80mph & beyond with no problem, if you boot it.

Thanxx 🤷‍♂️

 

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paul, justA go through the basics... one thing i note is you havent changed the plugs ? what brand are they ? 

i would be replacing them !

i am using these ngk 

also, check your points, and same there, if in doubt, replace them 

 

image.jpg

Edited by 64 kiwi boni
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Hey @Frostyand @64 kiwi boni,

Thanks for your replies-fuel filter is clean, carby has been stripped & cleaned, base gasket is new, plugs (BP5S) were replaced, & have since been pulled & checked a few times now (I even swapped the them over in case that might highlight something), points look as new (as Is distributor, rotor & cap), there is no arcing or witness marks inside the cap or on the rotor, the vacuum lines from the brake booster & distributor vacuum advance are both in place & secure.

Anything else I could be missing (no pun intended)?

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4 hours ago, Last Indian said:

Ok, a couple things. First is it a miss or is it a stumble/ hesitation? They can seem similar, but the causes are very different. I would tend to agree with Frosty. Your description sounds more like a vacuum leak. Why? A miss doesn’t go away. Doesn’t go away on a power increase usually. But a vacuum leak can be like that! You need to get a can of spray ether. Than methodical check your intake gaskets & the carb gasket. There are a lot of variations in carb gaskets & I have seen a lot of carb gasket leaks that cause havoc to people because they never suspect that gasket. Also I would suggest checking your fuel pressure. Just because you replaced it doesn’t mean there isn’t a problem with the diaphragm. I have seen new fuel pumps have a small hole in the diaphragm.

Thanks for that-I’ll chase the vacuum solution.

As for fuel pressure-prior to this issue the pump (Holley mechanical) was working perfectly. Also, if it was fuel pressure wouldn’t it deteriorate rather than improve as the revs/speed increased, due to poor delivery?

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When you are running points, this is what is supposed to happen: 12V is routed through the ignition switch when you start the engine. Once it's running and you release the key, it springs back slightly to the 'run' position which now uses a different contact on the back of the switch and sends voltage to the coil but through a factory 'resistance wire' which drops it down to 6V or so, to allow longevity of points. Constant 12V to points will make them burn out quite quickly. So, with engine not running and ignition 'ON' you should have 12V at coil + terminal. Once it's running, you should have 6 or so. I suppose it'd be prudent to check that your earth lead from coil to distributor is also in good condition. A good earth is vital. If you ever peered into your engine bay and wondered why GM fitted so many little earth straps, they are all there for a reason.

If you happen to ever go to electronic ignition, then you'll need constant 12V to the coil + which means running a nice new wire from the ignition 'START' feed so as to ensure 12V. Phew!

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20 minutes ago, Fitzy said:

When you are running points, this is what is supposed to happen: 12V is routed through the ignition switch when you start the engine. Once it's running and you release the key, it springs back slightly to the 'run' position which now uses a different contact on the back of the switch and sends voltage to the coil but through a factory 'resistance wire' which drops it down to 6V or so, to allow longevity of points. Constant 12V to points will make them burn out quite quickly. So, with engine not running and ignition 'ON' you should have 12V at coil + terminal. Once it's running, you should have 6 or so. I suppose it'd be prudent to check that your earth lead from coil to distributor is also in good condition. A good earth is vital. If you ever peered into your engine bay and wondered why GM fitted so many little earth straps, they are all there for a reason.

If you happen to ever go to electronic ignition, then you'll need constant 12V to the coil + which means running a nice new wire from the ignition 'START' feed so as to ensure 12V. Phew!

So, earth lead from distributor to coil is new, as distributor is also new.

Any ideas why I should have 6.5v with ignition on, but 9v when its idling? This seems backwards doesn't it?

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Paul, first off the electrical. Irrelevant of what any of us say, you can find out in 5 minutes how your coil/distributor system works with respect to voltage. That said, what Peter is indicating to you is you have two wires that feed the + side of coil. One is a resistance wire the other comes from the ignition, the other can come from the ignition or the starter, both are acceptable. What Peter indicates occurs is correct. On starting the non resistance wire supplies 12- 9 volts depending on battery condition, ground wire condition, etc. once started the starter switch springs back as he says to the resistance wire. In my earlier post said running, I was rushing not paying attention & it should have been starting. So the point is by what you described as happening something is not right. It’s actually backwards in occurrence of voltage. The 9 volts on starting is acceptable, 6.5 is not, but 9 volts at idle while not what you want should not be causing the problems you are describing. So I still have to question the vacuum leak! While brake cleaner can work to chase vacuum leaks it’s not nearly as effective as ether/ starter fluid. Furthermore grease on the base gasket of a carburetor won’t seal anything. You need a vacuum gage connected to the engine than you chase the vacuum leak & watch the gage. Also don’t assume it’s an engine gasket. It could be a hose or a diaphragm. Do you have a vacuum advance distributor? 

 

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  • 4 weeks later...
On 11/17/2023 at 6:02 PM, Fitzy said:

When you are running points, this is what is supposed to happen: 12V is routed through the ignition switch when you start the engine. Once it's running and you release the key, it springs back slightly to the 'run' position which now uses a different contact on the back of the switch and sends voltage to the coil but through a factory 'resistance wire' which drops it down to 6V or so, to allow longevity of points. Constant 12V to points will make them burn out quite quickly. So, with engine not running and ignition 'ON' you should have 12V at coil + terminal. Once it's running, you should have 6 or so. I suppose it'd be prudent to check that your earth lead from coil to distributor is also in good condition. A good earth is vital. If you ever peered into your engine bay and wondered why GM fitted so many little earth straps, they are all there for a reason.

If you happen to ever go to electronic ignition, then you'll need constant 12V to the coil + which means running a nice new wire from the ignition 'START' feed so as to ensure 12V. Phew!

So, earth lead from distributor to coil is new, as distributor is also new.

Any ideas why I should have 6.5v with ignition on, but 9v when its idling? This seems backwards doesn't it?

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Hello again all,

I've been laying low because up until yesterday we haven't been able to solve the problem, & TBH I've had the shits!

However...after checking, testing, rechecking, replacing, etc, etc, etc, it appears as if the bloody NEW distributor that we installed after the rebuild has an internal issue, & is not supplying spark to #8 (there's a bloody long story as to what was done before discovering this, & how it was discovered, but I don't want to bore you all).

It was a Cardone distributor, that up until this issue has been running perfectly (still looks new, which it essentially is). Not wanting to go electronic or remanufactured I've just ordered a new one through Rockauto.

Which hopefully will be the end of this one!

Thank you for all of the suggestions & advice - I've learned a lot from you guys yet again.

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2 hours ago, Fitzy said:

Paul - please give us a rundown on what the issue was. I'd like to know how a dizzy refuses to fire only one cylinder.

Hey @Fitzy, even the mechanic who built the motor said he has never seen a distributor do that. Ever!

He pulled & checked every lead as it was running, & saw that there was no spark on #8. To be certain, he reversed the firing order & sure enough...no spark on #1. Then he bench tested it, again nothing on #8. Bench tested another V8 distributor he knew was good to make sure the issue wasn't with the tester, & it worked fine.

So after all of that he believes that there must be an internal failure with it, for whatever reason🤷‍♂️

Given that we have checked, adjusted or replaced everything else, I hope he's correct...I guess we'll know soon.

The distributor is a new Cardone, which seemed to be the best available at the time (still is, it seems?). So I've just ordered another one through Rockauto (due 29th December), hoping that this is just "one of those things". 

The reviews are overall positive, but mixed. But the reviews on everything else available seem to be the same. There just doesn't seem to be a consistent, decent quality product out there that most people have used and are happy with.

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While I'm here, has anyone used alternative components to make their original horn work? Maybe Holden or Chev?

I have the wheel and horn bar, but only the contact that is mounted to the wheel, 1x spring and the nut.

Hence, when the wheel is tightened, the horn bar won't "rock", and there isn't enough in there to make the horn work anyway.

I know there are other solutions, but I'd really like to get this working.

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Surely that’s just a faulty dissy cap Paul ? 
the only other way a dissy can’t  throw power to one terminal would be if there was no lobe at that position on the main shaft to actuate the points ? 

Edited by 64 kiwi boni
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17 hours ago, 64 kiwi boni said:

Surely that’s just a faulty dissy cap Paul ? 
the only other way a dissy can’t  throw power to one terminal would be if there was no lobe at that position on the main shaft to actuate the points ? 

The cap was swapped for the one off the original distributor - same issue. And...it was running just fine for about 6,000k's, then this issue raised it's head. So I'm left with the mechanics diagnosis at this point, until proven incorrect. Have a new distributor on the way, so fingers crossed 🙏

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Like I said, and please take note: I also have a new Cardone and the supplied points & condenser were garbage. The car broke down and I gave up and had it towed to my mechanic. Replace the innards with Bosch ones.

Have you heard of Performance Ignition Services, in Melbourne? They have an excellent reputation and I have used them before. They can do anything that's required including recurving to suit your engine's specs, fit electronic ignition and/or overhaul. I continue to use the Cardone supplied cap & rotor without issue so far, but keep spares in the trunk.

No spark to one cylinder - crazy.

On 12/15/2023 at 8:39 PM, Bonne61 said:

While I'm here, has anyone used alternative components to make their original horn work? Maybe Holden or Chev?

I have the wheel and horn bar, but only the contact that is mounted to the wheel, 1x spring and the nut.

Hence, when the wheel is tightened, the horn bar won't "rock", and there isn't enough in there to make the horn work anyway.

I know there are other solutions, but I'd really like to get this working.

Ah yes, Ye Olde Horn problem. I fiddled for hours and eventually gave up and retro fitted a discreet button just under the dash to activate a shrieking air horn. That'll get the bogans out of the way.

Good luck.

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