Harms Rebuilt '71 Thermoquad - Wondering Idle, Stalls when Put in Gear

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Syleng1 said:
How many miles on engine. Cam walking from loose timing chain, vacuums leaks, base gasket leaking. Lots of stuff could be going on but carb may have gotten a small bit of junk or maybe those epoxied pots at the bottom broke loose. Hard to fix over internet. Lots of questions.
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Unknown mileage on engine but doesn't smoke or behave like a high mileage motor. All vacuum access points were plugged when I was tuning carb and engine ran essentially the same with everything hooked up. I suppose I should pull the carb and check the pods.
 
Frank Cole said:
Timing was steady at idle, maybe plus or minus 1/2 degree. I had a vacuum gauge hooked up to both manifold pressure and the carb advance port time. Manifold was 9-10 and fluctuating, vacuum port pressure was 0-3 degrees depending how I was playing with idle screw but even at 3 degrees, timing was steady and did not move. Advance started pulling in when I got to about 5 inHG at vacuum port.
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Do you mean 3 inches of vacuum at the ported spark fitting? That should be 0 at idle. But steady timing mark is good. Sounds carb related but fluttering intake vacuum signal could be a valve or lash adjustment.
 
AJ/FormS said:
at idle the rods have to stay down.
in Neutral the rods should stay down with gently increasing rpm, to over 2000rpm or more, so long as the manifold vacuum continues to increase.
If the needles pop up when you put it into gear, the engine will flood and stall.

Here's a trick; Just take the springs out. At idle and in neutral, this should cure both problems. If it does, then you know to install weaker springs.
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Now this is interesting. I'll go back and double check but the rods and tower were moving up and down slightly when idling but mostly stayed at the TOP.
 
66Valiant528 said:
I'm thinking the high idle is starting to pull advance . Check your timing at idle. Should be rock steady. If mark jumps around make sure your advance springs aren't stretched or too weak .
And putting your hand over carb and idle increases is an indication of a vacuum leak. Could be a leak on the bottom of the intake runner to head port. WD won't find that.
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Advance was either plugged or T-ed off when tuning. I'm sure distributor advance wasn't contributing. If the problem is vacuum related, it's either internal in the carb or under manifold which I'll pull as a last resort.
 
Frank Cole said:
Correct gaskets, not quadrojet gaskets. I didn't check float level. New rebuilt so I just installed it as-is. Metering rods move up and down slightly at idle. Regarding mixture screws, engine stalls out when either screw is turned all the way in so i don't think idle jet is blocked. All good points though.
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Bewy said:
1971 was a one year only model of the TQ. It should still work. Correct gaskets used?
Float level? Do the metering rods stay down at idle [ they should ]?
Four turns out on the mixture screws seems a lot. Maybe one idle jet is blocked.
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Reread your post.
Frank Cole said:
Now this is interesting. I'll go back and double check but the rods and tower were moving up and down slightly when idling but mostly stayed at the TOP.
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CORRECTION - I just checked and the metering rods stay mostly DOWN down. Fluctuate but mostly down.
 
Bewy said:
Something not right here, getting drip fed info....
Now you say the Edel wandered at idle.
And the engine is 'bone' stock?
Stock engines will have 16-19" of vac at idle, not 10-11".
A stock engine should idle at 5-600 rpm, not 900....
Since this problem has occurred with TWO carbs, & from what you have done so far, I suspect the engine has had a larger cam fitted. That would also explain the 16* init timing [ which is good, not a problem ].
The high idle rpm could be activating the centri curve in the dist, especially if the springs are stretched. This could explain the varying rpm & needs to be fixed first. Check by monitoring the ign timing with a timing light.
One last thing to try: initial timing is at 16*. Loosen dist, engine idling, turn dist slowly CCW; keep going until rpm stops increasing & THEN see what the timing is.
I suggest you try the above & report back.
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Edel wandering but much less than TQ. Bone stock visually and listening to exhaust note - no lopey cam noise. I highly doubt the cam if not stock, is close. My low vacuum is likey internal carb or under intake. Vaccum advance is not being activated. Tuned with advanced plugged or T-ed with gauge. The factory emission decal says 900 RPMs for idle. I believe CCW is advance. This is a 340 but I had it as high as 24 degrees but idle was very erratic. Seems to run best at 16 degrees. Much lower and power started dropping off.
 
Frank,
The carb looks beautiful! I'm jealous! Looks brand new.
Since the problem has occurred with TWO carbs, you probably need to look elsewhere:
- sticky lifters
- worn cam lobes
- lifter pre-load not adjusted properly.
 
Frank Cole said:
I didn't pay to have the carb rebuilt. It came with the car when i purchased it.
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So rather than FIND OUT, you're just gonna ASSUME that he won't stand behind it or help you out. Ok. I got it.
 
abodyjoe said:
for what he charges it should install itself and run perfect.
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I agree, except the ONE thing I touched on. There's NO WAY you can get the metering rod tower adjusted right on the money without being on a running engine. You can get it close, but not spot on.
 
Bewy said:
Frank,
The carb looks beautiful! I'm jealous! Looks brand new.
Since the problem has occurred with TWO carbs, you probably need to look elsewhere:
- sticky lifters
- worn cam lobes
- lifter pre-load not adjusted properly.
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Bewy - I have another 1971 Challenger with the same carb. I'm going to swap carbs this weekend and see what happens but your probably right.
 
RustyRatRod said:
So rather than FIND OUT, you're just gonna ASSUME that he won't stand behind it or help you out. Ok. I got it.
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I assume nothing. I am not the original purchaser of the rebuild and therefore don't have a vested interest from Scott Smith's point of view. It would be like if you bought a car from someone who bought a car from me and thinking I owe you. I would not make such a presumption but that is just me.
 
RustyRatRod said:
I agree, except the ONE thing I touched on. There's NO WAY you can get the metering rod tower adjusted right on the money without being on a running engine. You can get it close, but not spot on.
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I'm not even close to being "spot on" or "on the money." I would graciously settle for the car not stalling when I put it in gear. I have another '71 Challenger with the same carb and mostly stock. I'm going to swap carbs this weekend and see what happens. At least I should be able to confirm or eliminate the carb as being the problem.
 
Frank Cole said:
I assume nothing. I am not the original purchaser of the rebuild and therefore don't have a vested interest from Scott Smith's point of view. It would be like if you bought a car from someone who bought a car from me and thinking I owe you. I would not make such a presumption but that is just me.
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I know what it's like. I'm also not presuming anything. I don't even know what that stupid crap means. It doesn't hurt to ask. He might do it free...he might not. But don't ask. That's one way to never know. My carburetor runs great. So your junk is pretty far down on my list, especially if you don't want to listen to sound advice.

To expound a little more, you act as if the world is coming to an end because the carburetor won't idle. That's a VERY SMALL part of the equation and one that very likely the adjustment I outlined might fix. I would try it first. It costs nothing and may fix it. If not, you've lost nothing.
 
You have two different brands of carbs doing the same thing: varying idle speed.

Something not right with only 11" of vac. It is low, for whatever reason. It is probably causing havoc with the PCV valve. I would disconnect the PCV hose at the carb, & plug the carb port. See if you can then set the idle.
 
Bewy said:
You have two different brands of carbs doing the same thing: varying idle speed.

Something not right with only 11" of vac. It is low, for whatever reason. It is probably causing havoc with the PCV valve. I would disconnect the PCV hose at the carb, & plug the carb port. See if you can then set the idle.
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Yeah, I had every vacuum port plugged on the intake and carb. I mean everything and the idle was hunting and the car stalls when I put it in gear. I'm going to try a carb swap with my other '71 340. The Edelbrock750 would not stall when I put the car in gear but the idle wasn't great (hunting). A TQ swap for a good running TQ should tell me for sure if it's the carb. If that doesn't work, then it's probably engine related like intake gasket underneath or a valve from what the feedback I'm receiving. Thanks to all posters for your input. I plan to do this tomorrow and will report back on my findings.
 
A Chrysler type ECU conversion would have required changing the distributor.
That factory stuff from that era is very tight and there's not much latitude.
Map out the timing and compare with factory spec.
By that I mean measure timing vs rpm from the lowest rpm you can. Do every 200 or 250 rpm, or every degree or two, whichever is easier for you. Take it at least to 1800 rpm, and preferably as high as you feel comfortable.
Plot that on graph. That's the timing
Now take the initial and remove it. This will leave you the advance curve in crank rpm and degrees.
Compare with the FSM advance specs which is in distributor rpm and degrees.
 
How old is the gas in the car?
You need good fresh gas in the system before you attempt to tune the engine.
I've seen people try to tune an engine with old gas and are pulling their hair out by the roots.
A change to fresh gas and bingo!
What a difference!
 
Bewy said:
You have two different brands of carbs doing the same thing: varying idle speed.

Something not right with only 11" of vac. It is low, for whatever reason. It is probably causing havoc with the PCV valve. I would disconnect the PCV hose at the carb, & plug the carb port. See if you can then set the idle.
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If at a Manifold port the vacuum is 11" then you have one of 2 things. A problem or a not stock build. If it's stock and in somewhat good mechanical condition I would expect to see a minimum of 15" and I'm on the low side.... Figure that out and your carburetor may not be the issue.....

JW
 
Where is your initial timing set?
 
So I swapped a perfectly working '71 TQ and the problem persists. I'm getting about 9-10" vacuum with both carbs and I tried several base gaskets. After everything, the leak is coming from under the intake or what? Bad valves?? I'm going to perform a leak down and compression test once the engine cools. I'm dreading removing the manifold as the car has AC and it looks like I have to remove the compressor to get to the hoses and front manifold bolts. The system is charged so I guess I'm going to need to have it evacuated too. Sucks.
 
Frank Cole said:
So I swapped a perfectly working '71 TQ and the problem persists. I'm getting about 9-10" vacuum with both carbs and I tried several base gaskets. After everything, the leak is coming from under the intake or what? Bad valves?? I'm going to perform a leak down and compression test once the engine cools. I'm dreading removing the manifold as the car has AC and it looks like I have to remove the compressor to get to the hoses and front manifold bolts. The system is charged so I guess I'm going to need to have it evacuated too. Sucks.
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Low vacuum. I would do a compression and if that shows good and your willing to put in the work do a leak down. If they show good then you need to make sure everything is in order on the timing side and "then" I would look at the intake. If it has a power brake booster cap that off FYI and recheck vacuum.....

JW
 
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