340 Chugging instead of Reving

TT5.9mag

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I even like a curve for a race engine. For what he’s doing he can lock it out about anywhere about 30 and get some kind of direction.

He’s got a really nice distributor.
Yea but you’re a stick guy. :poke:
And if you have a good box you can dial the timing anywhere you want it for power management. I think to eliminate some variables here locking it would be a good test but I’m leaning towards the box being the issue.
 

1969GTS340

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That’s true. And I forgot, he’s running a 685 box. If he wants to lock it out at 35 or even a bit more he can as that box has a built in start retard that he can activate and adjust. I think up to 20 degrees.

^^^^^ Correct
 

1969GTS340

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Really it’s just for testing. I like a curve in a street car. But for a race car with a decent converter I dont see why anyone runs a curve. I’m not familiar with the Mallory magnetic pickup distributors though. I’ve only used their optical pickup distributors. @1969GTS340 do you have a part number on that distributor?

The distributor is:
Comp S/S 32 series YH single pickup model which used keys to set the mechanical advance. I just checked the keys and found that I set it at 28* I may misspoke earlier.

Just so I am clear on locking the distributor... there is nothing in the instructions. If I need to dis assemble the distributor and set 32* mechanically, I'll need to measure the size of each key and come up with a spacer to reach 32. The keys only go to 28. I read someplace that if you don't have the keys you can use a drill bit in the size needed.
IF I do not need to set it mechanically, but only need lock the side set screws and turn the distributor to 32* with a timing, that would be easier IF it can be done that way. Or I could turn the rotor clockwise to reach the current 28 setting and lock it there... again just for testing purposes. Any thoughts, concerns or direction on these 3 options?
 

1969GTS340

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For all who strongly advised a fresh set of plugs. I picked these up today for the next round of testing, hopefully today or tomorrow.

20220915_145430.jpg
 

TT5.9mag

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The distributor is:
Comp S/S 32 series YH single pickup model which used keys to set the mechanical advance. I just checked the keys and found that I set it at 28* I may misspoke earlier.

Just so I am clear on locking the distributor... there is nothing in the instructions. If I need to dis assemble the distributor and set 32* mechanically, I'll need to measure the size of each key and come up with a spacer to reach 32. The keys only go to 28. I read someplace that if you don't have the keys you can use a drill bit in the size needed.
IF I do not need to set it mechanically, but only need lock the side set screws and turn the distributor to 32* with a timing, that would be easier IF it can be done that way. Or I could turn the rotor clockwise to reach the current 28 setting and lock it there... again just for testing purposes. Any thoughts, concerns or direction on these 3 options?
If you set it to 32 internally you’ll have 32 degrees of MECHANICAL advance. That’s not what you want. You want “0” degrees of mechanical advance. I’ve never had my hands on that distributor so I don’t know how big the slots are, but basically you want to adjust it with no keys if that makes sense. You want the distributor shaft and the reluctor plate to be “locked” together. Then you’ll have no mechanical. Make sense?
6745E614-F34A-4849-A992-DB1A239A7A1C.png
 

TT5.9mag

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The opening sentence suggests he’s been through troubleshooting the easy things for 2 weeks. I do agree with “one change at a time” though.
 

TT5.9mag

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A little oil in the chamber, a couple fouled plugs, or a vacuum leak ain’t gonna make an engine hit a wall at 3000rpm consistently.
 

1969GTS340

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Oh boy .

Personally, I try to make changes one at a time, so you know what repaired the issue . jmo.

Agreed.

My plan of attack in order:
1. Change the plugs (test run)
2. If 1 failed > Change coil (test run)
3. If 2 failed > Lock distributor (test run)
4. If 3 failed > Send the ignition for repair.

The first two steps are quick and easy.
The third is more involved.
The fourth, I already have a Mallory engineer lined up for test and repair if it gets that far. I may squeeze a leakdown test in there somewhere if my buddy brings his kit over in the middle of all this.

If 4 fails I might have a large liquidation sale and buy a Hell Cat lol. Just kidding of course.
 

1969GTS340

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If you set it to 32 internally you’ll have 32 degrees of MECHANICAL advance. That’s not what you want. You want “0” degrees of mechanical advance. I’ve never had my hands on that distributor so I don’t know how big the slots are, but basically you want to adjust it with no keys if that makes sense. You want the distributor shaft and the reluctor plate to be “locked” together. Then you’ll have no mechanical. Make sense?
View attachment 1715985968

Yes, makes sense. It's a little involved to dismantle this distributor but being the second time, should be easier.
 

inertia

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A little oil in the chamber, a couple fouled plugs, or a vacuum leak ain’t gonna make an engine hit a wall at 3000rpm consistently.

All my schooling and experience has taught me to eliminate all the obvious easy stuff before going deep .
I'm not saying the plugs are THE cause, but that oil fouled plug will likely misfire under load .
If it's still sucking oil, that's a vacuum leak, is that okay, let's ignore it !
Do you, would you run those plugs in your car, and ignore them if you had a misfire ?
And are you suggesting locking the distributor is the cure, and now many times in you career have you cured a 3000 rpm wall with a timing adjustment ? ?

If detonation blows it up, are you gonna pay to fix it ?
 
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That drawing in post 80 is too small for me to read, but you just loosen the screws, slide the stops all the way in and lock the screws. Pretty simple to lock out.
 

inertia

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The opening sentence suggests he’s been through troubleshooting the easy things for 2 weeks. I do agree with “one change at a time” though.

Yet he is still running those plugs, does that suggest a novice .
The original post states "plugs are rich", is that how YOU read them ?
 

TT5.9mag

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All my schooling and experience has taught me to eliminate all the obvious easy stuff before going deep .
I'm not saying the plugs are THE cause, but that oil fouled plug will likely misfire under load .
If it's still sucking oil, that's a vacuum leak, is that okay, let's ignore it !
Do you, would you run those plugs in your car, and ignore them if you had a misfire ?
And are you suggesting locking the distributor is the cure, and now many times in you career have you cured a 3000 rpm wall with a timing adjustment ? ?

If detonation blows it up, are you gonna pay to fix it ?
Not sure why you sound so offended. We all are merely offering suggestions to help diagnose his problem. If anyone comes on the internet and says “I KNOW what’s causing your problem, you NEED to do “THIS” we should all stop listening to that person. And yes, I had a very similar experience with a Mallory (optical) distributor and locking the timing helped me diagnose a bad xr700 box. I’m not suggesting he should run it locked for anything more than testing.
Yet he is still running those plugs, does that suggest a novice .
The original post states "plugs are rich", is that how YOU read them ?
As to the plugs, they look like ****. But trying to “read” a plug that is oil fouled or has been in an engine with long idle times, or lots of no load situations is a fools exercise. Your experience should have taught you that. I can get a plug to fire at 9:1 AFR with 15 pounds of boost on top WHILE spraying it with methanol. And if you read back a few posts you’ll notice I suggested sticking a new set of plugs in it very early on. And there ain’t no way in hell detonation is going to blow it up locked at 32 going for a test drive.
Now back to our regular scheduled programming.
 
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1969GTS340

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Just a brief update so ya know I didn't abandon the forum. I should be back in my shop over the weekend to begin the series of changes and I'll update until this is car is running like it should. One misperception in my original post, is that I have been chasing this problem for a couple weeks. In my garage 2 weeks equals about 7 hours lol. I get small windows of time in-between other obligations. I built this drag car completely over a 3 year period which could have taken 3 months in some of your shops I'm sure. But this my retirement hobbie and I appreciate all the advice that's been offered.
 

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Ok...back in the garage for the rest if the evening. So Far...
New NGK plugs - No change in cutting out. But it started quicker and idles better. Adjusted the timing and couldn't stop the stumble.
Next swapped out the coil. Same results as above.
Now im about to remove the distributor and trying the lock out suggestion. If this doesn't stop the issue, I am shipping the ignition out for test and repair tomorrow (Monday) morning.
 

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If you set it to 32 internally you’ll have 32 degrees of MECHANICAL advance. That’s not what you want. You want “0” degrees of mechanical advance. I’ve never had my hands on that distributor so I don’t know how big the slots are, but basically you want to adjust it with no keys if that makes sense. You want the distributor shaft and the reluctor plate to be “locked” together. Then you’ll have no mechanical. Make sense?
View attachment 1715985968

Inside of the distributor the picture shows the slot alignment after moving the plate to 0* . I'll lock the adjustment there. Since the springs are obviously not doing anything when locked, I am removing them.

20220918_174738.jpg
 
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1969GTS340

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I am setting the reluctor to pickup gap at .008"
Are there any other setting I should consider?
This is the same gap I have been running.
 

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Locked distribtor and immediately saw/heard an improvement. Took the rpms I to the 5000 range but got some popping out the exhaust. Changed the timing from 32 thru 38 and the popping stayed. I then watched the timing light while increasing the rpms.and it retarding as the rpms increase. When locked at 34* the timing goes down into the 20s. I believe the only thing that could cause this is the ignition box. Any other thoughts before I ship the box out tomorrow????
 

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Locked distribtor and immediately saw/heard an improvement. Took the rpms I to the 5000 range but got some popping out the exhaust. Changed the timing from 32 thru 38 and the popping stayed. I then watched the timing light while increasing the rpms.and it retarding as the rpms increase. When locked at 34* the timing goes down into the 20s. I believe the only thing that could cause this is the ignition box. Any other thoughts before I ship the box out tomorrow????


And that’s why you don’t lock out a distributor. For one all engines need a curve, however short it may be. And two, ALL ignition boxes retard like that. If you don’t test for it you have no idea how much timing you really have.

6 or more degrees of retard is not uncommon. I think I would lock timing out at 38 for now and start working with the rest of the tune up. IIRC, the plugs looked fat. That can some of the popping you are hearing.
 

1969GTS340

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And that’s why you don’t lock out a distributor. For one all engines need a curve, however short it may be. And two, ALL ignition boxes retard like that. If you don’t test for it you have no idea how much timing you really have.

6 or more degrees of retard is not uncommon. I think I would lock timing out at 38 for now and start working with the rest of the tune up. IIRC, the plugs looked fat. That can some of the popping you are hearing.

I put new plugs in, ran for 5 minutes with no change, swapped coil, ran for 5 min with no change. Then locked the distributor. Tried timing from 32 thru 38 and it ran much better but popped. Maybe I'm full circle back to carb settings?
I see what your saying about needing some.curve. others have said to set initial high with a slight mechanical around 8*. Now that I know that I'll loose around 6* in tne box, I could set initial at 32* with 6* advance (like I read others descibe) it makes much more sense now. In that example, I'd be adding back in the amount of degrees I'm loosing.
 
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TT5.9mag

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Have the box checked out. A few degrees of retard from box is normal. 14 degrees is not normal. I think you have a faulty box.
 
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