Thermoquad issue

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midnight340

midnight340

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Location
Lawrence, KS
I've been running a really well dialed in 440 TQ on my 340. I have an A/F meter on it, and keep an eye on the plugs. I have nothing but ultimate praise for the TQ!!! Once I finally figured out how to set up and adjust this carb, I find it much more tuneable and easy to tweak if necessary. A/F #'s are impressively steady under all conditions.

Now, TQ preaching done, here's my issue:
Even with no choke it normally starts easily with a pump or two, but I may have an electrical problem plus the starter is failing, so I was struggling yesterday to start it. Thus some extra turning over, extra pumps etc. I pull the air cleaner and find the secondaries nearly FULL of fuel !!!!!!

What can cause this????
Is this likely dirt in needle and seats? Can that cause this?
Or a gasket issue? (Haven't had time to explore today... but when I built it I did make sure the body surfaces were flat, and the wells securely affixed.)

Anyone ever experience this???
 
Update: I had rebuilt the TQ 1-2 years back with a ("Made in USA") Walker kit. I pulled it apart to find one float sloshing half full of fuel. Intake had standing puddles of fuel. Checked the oil and it was a quart+ high. Yikes!!
I had done a compression test yesterday and all were very good. So I'm assuming this was very recent failure or I would have seen it on the A/F meter or felt/smelled it.
New kit on the way. And I'll test the floats before using!! :thumbsup:
 
I'd have to drill a hole to drain it, but thanks! I'll consider doing that. I can certainly solder up a hole.
 
Congrats on using the best 4bbl ever made!!

That is certainly a flooding problem that you have. But if only re-built 2 yrs ago, should not need a rebuild kit [ unless it has done huge mileage ].
I would check some other things first:
- fuel pressure. Over 12 psi, is too high, might cause flooding, faulty pump?
- filter. Or quality of. A filter is useless if the element inside is not sealing & lets debris get through to the carb.

Other suggestions;
- Using E fuel? Might not be compatible with n/seats.
- float fuel logged. One fuel logged float is enough to cause BOTH sides to flood
- binding n/seats; binding or rubbing floats; loose n/seats
 
Bewy said:
Congrats on using the best 4bbl ever made!!

That is certainly a flooding problem that you have. But if only re-built 2 yrs ago, should not need a rebuild kit [ unless it has done huge mileage ].
I would check some other things first:
- fuel pressure. Over 12 psi, is too high, might cause flooding, faulty pump?
- filter. Or quality of. A filter is useless if the element inside is not sealing & lets debris get through to the carb.

Other suggestions;
- Using E fuel? Might not be compatible with n/seats.
- float fuel logged. One fuel logged float is enough to cause BOTH sides to flood
- binding n/seats; binding or rubbing floats; loose n/seats
Click to expand...

One float definitely sloshing fuel inside, fortunately my local NAPA could get a single brass float in tomorrow morning. Should solve that problem.

MoparLeo said:
Most Carter type carbs are rated at 6.5 lbs max. Always best to use a regulator regardless of carb type.
Click to expand...
I do have a regulator set at 6#.
I'll reassemble the TQ tomorrow and am installing a new starter. Hoping I built the 1-7/8" such that I can do that without pulling a header.

thank you all for the comments!!
 
Be VERY careful buying replacement brass floats. There are a LOT out there that have been soldered on the float brackets UPSIDE DOWN. So make sure you don't get those.
 
RustyRatRod said:
Be VERY careful buying replacement brass floats. There are a LOT out there that have been soldered on the float brackets UPSIDE DOWN. So make sure you don't get those.
Click to expand...

Thanks Rusty, it turns out the float NAPA ordered is exactly what you said!!!! Float bracket soldered on with the float upside down!!
Who's doing this?!! Really!!?
Ed, my parts guy is determined to find me another float by tomorrow if at all possible. Good service by NAPA!
(And it's great to have known your parts guy for 16+ years.)

And the Dakota V-6 starter that I run on the 340 DID come out with my homemade headers still on. Yay! It was damn close but wiggled it out of there. :D
 
Another TQ question.... When the primaries are completely closed where should they be in relation to the the idle ports (the vertical slots) Should I have about a square shape showing below (like Holleys) and the like?? Though it's been running really great the primary blades were closing those off completely, so thought I'd better check on that.
 
The answer to post #15 is an 'if' answer.
IF:
- the engine idles ok & the mixture screws [ either screwing in or out ] have control of idle quality
- & if there is no off idle flat spot & smooth transition from idle to main cct.
- then there is no problem with the t-slot closed off by the t/blades.
It is actually a benefit in my opinion because more of the t-slot is available for the very sensitive off idle metering & transition to the main cct.
 
Bewy said:
The answer to post #15 is an 'if' answer.
IF:
- the engine idles ok & the mixture screws [ either screwing in or out ] have control of idle quality
- & if there is no off idle flat spot & smooth transition from idle to main cct.
- then there is no problem with the t-slot closed off by the t/blades.
It is actually a benefit in my opinion because more of the t-slot is available for the very sensitive off idle metering & transition to the main cct.
Click to expand...

I really appreciate that information. It was running fine, good idle, good off idle. So this is obviously one more example of my over-thinking things. (Bad habit I seem to have...)
 
For a streeter, with an automatic trans;
If you shut the transfers off completely; you may experience one or more of several problems;
>A tip-in sag as the transfers take time to come back on line.
>Stalling, going into gear.
>A rich AFR throughout the low speed circuit because by the fatly adjusted mixture screws.
>The only way to make the engine run with the transfers shut off, is with a lot of Idle-Timing. This may and usually does, cause problems in trying to build your other timing curves.
> Cold-start issues.
> hot-running issues
> did I mention the dreaded tip-in sag? You can cover this with pumpshot, but then two other things happen; First, you use it up when you should be saving it for later, and Secondly; because the pump is pissing more gas than it needs to; the engine is a gas-hog in town. My goal is always to use as little pumpshot as is possible.

But if a manual trans;
You can't hardly get away with anything below 2000rpm; yur tune has to be pretty right on.

But if a racecar;
You can get away with a lottachit, that won't fly on the street.
 
AJ/FormS said:
For a streeter, with an automatic trans;
If you shut the transfers off completely; you may experience one or more of several problems;
>A tip-in sag as the transfers take time to come back on line.
>Stalling, going into gear.
>A rich AFR throughout the low speed circuit because by the fatly adjusted mixture screws.
>The only way to make the engine run with the transfers shut off, is with a lot of Idle-Timing. This may and usually does, cause problems in trying to build your other timing curves.
> Cold-start issues.
> hot-running issues
> did I mention the dreaded tip-in sag? You can cover this with pumpshot, but then two other things happen; First, you use it up when you should be saving it for later, and Secondly; because the pump is pissing more gas than it needs to; the engine is a gas-hog in town. My goal is always to use as little pumpshot as is possible.

But if a manual trans;
You can't hardly get away with anything below 2000rpm; yur tune has to be pretty right on.

But if a racecar;
You can get away with a lottachit, that won't fly on the street.
Click to expand...

Thanks, AJ! I've learned a lot from this site over the last couple of years!! Pretty damn happy with the TQ!! Here's an overview:

-Yes, transfers have been previously shut off. And it is primarily street (strip 2-3 times a year) and is an automatic.
-No cold start issues as it's set up, nor hot start problems. (Choke removed, temp controlled garage.)
-No stalling going into gear.
-No notable tip-in sag. (could it be better?? maybe.) Cam is Lunati solid 235/243 at .050, .526/.546 lift.
-I can reach in the car and turn the key from outside and starts right away when warm, so no issue there.
-My timing is set at 18/38. It likes the 18, the 38 is set from doing timing loops at the track (quickest/fastest there.)
-Plugs read very good now. Light grey/black on ring, small tan ring at base of porcelain, timing mark right on the bend.
-A/F tends to be 13's with light throttle in slow traffic, 14.7 steady :), drops uphill to 15-16.
-Yes, transfers probably covered by my drilled nozzles. (.034 or .038 based on old Demonsizzler posts... Jets are .101/.149.)
-Yes probably burning more fuel in town than necessary with a TQ, not that I'm too worried about that.

So now, I have to decide if it's worth it to mess with what's working just to open the transfers a bit...
As a carpenter I used to work with used to say: "Don't F**k with it. ...If you F**k with it, it'll look F**ked with!" :rofl:
 
Last edited:
@Bewy knows his stuff, so if your junk is working, don't mess with it.

38*seems like a lot for street; if you can make it work more power to ya; but it is telling you something about the efficiency of your combustion chambers.

For reference;
with the transfers shut off;
where are your mixture screws set?
and do you happen to know what you set the float height at?
and if you have a fuel-pressure regulator; what have you got it set at?
Do you know your cylinder pressure or your compression ratio?
And finally, do you know what your cam specs are, or what cam is in the engine?
I just want to know what works for future story-telling.
 
AJ, you may be right about the 38* timing being some indication of combustion efficiency. The weak spot in my "formula" isn't the heads (X-heads ported and chamber work by Bob Mullen back in the day) but definitely the old #2385 TRW pistons down in the hole. Probably should have changed them when I did cam and all new bearings, but cylinders were still in good shape.

I have a cc'd compression ration of 9:1 due to pistons down in the hole. (The TQ sits on opened up LD340, 1-7/8 headers.)
Mixture screws in the 1-1/2 to 2 turns out.
Float height is set at the recommended 1" setting
Fuel pressure has been at 6.5# (may lower it a bit)
Static cold cranking compression 160#
Cam ground on 110* and is 235/243 at .050, lift is .526/.546 (smallest Lunati Voodoo solid lifter)

So, how does that fit for future story-telling information? (Love to read your posts!) :)
 
If your damper is off 1 degree and your timing light is off 1 degree you have 36 total. Nothing out of the ordinary. There are videos on the web showing two identical timing lights being different by 3 degrees. Give the engine what it says it wants and don’t live and die by a number. You are fine.
 
Midnight,
Holley owners would kill to have an engine run as smoothly & effortlessly as your TQ equipped engine.
I don't see anywhere that you need to tinker further with it.
Comp ratio is pretty low for what is a sizeable cam, which would explain why it likes, & needs, a lot of timing at idle. Enjoy!
 
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