Thermoquad - 1974 440 Engine - Today's Fuel

[Wile E Coyote]

I searched the site for Thermoquad threads and read the post from April 2019.

My question is this; Say you restore a 1974 vehicle, new engine, new everything, rebuild the original TQ9016S carb, everything is hooked up like its 1974 (EGR, water pump sensor, radiator sensor, all vacuum lines/hoses) - all back to Day 1: "Will todays fuel (different specific gravity from old fuel, ethanol in it, etc) allow the TQ internal circuitry to work as it was designed, or will it never run "correct" because of todays fuel?

Is anyone running a 1974, 75, 76 440 with a Thermoquad and all the emissions stuff hooked up - and its running fine/perfect?

Thanks for your inputs!

Ron

 

[Davea Lux]

I searched the site for Thermoquad threads and read the post from April 2019.

My question is this; Say you restore a 1974 vehicle, new engine, new everything, rebuild the original TQ9016S carb, everything is hooked up like its 1974 (EGR, water pump sensor, radiator sensor, all vacuum lines/hoses) - all back to Day 1: "Will todays fuel (different specific gravity from old fuel, ethanol in it, etc) allow the TQ internal circuitry to work as it was designed, or will it never run "correct" because of todays fuel?

Is anyone running a 1974, 75, 76 440 with a Thermoquad and all the emissions stuff hooked up - and its running fine/perfect?

Thanks for your inputs!

Ron

Assuming a stock T-QUAD is still solid, which a new one should be, it will work. Today's fuel tends to cause the engine to run leaner than it otherwise would, so you will need to go up the equivalent of about one jet size, on a big block maybe two sizes. It was difficult to get these cars to run right even when they were new, the cars were set to run as lean as possible to pass emissions. If the New T-Quad has those plastic limit caps on the idle circuit, those will probably need to be removed to fatten up the idle The EGR valves did not play well with the carbs of that era because there was no compensation for the introduction of inert material into the combustion process which tended to leave the engine with a lot of dead spots at different throttle positions. You can disable the EGR valve by putting a blockage in the vacuum line to it. That retains a stock appearance and makes tuning the engine to run correctly a lot simpler. You will need to play with the timing settings to see where your car will run the best as today's fuels also require more advance than what was suggested on the emission stickers and shop manuals of 1974. Hope this helps.

Dave

 

[Newport 66]

Just a side bar thought....I have often wondered what affect ethanol will have on the TQ carb body or phenolic floats commonly found. Anyone have an experience?

 

[cbarge]

Just a side bar thought....I have often wondered what affect ethanol will have on the TQ carb body or phenolic floats commonly found. Anyone have an experience?

No effects on those parts in particular but eats up the accelerator pump,corrosion on the jets and metering rods.
I have to rebuild the TQ this spring on the wagon because of flat spotting from the carb running lean not being able to shoot gas upon accelrating.
Not fun driving feathering the gas with a standard trans.

 

[73Coupe]

Use a leather accelerator pump cup too, I went through about 5 of the synthetic rubber cups over a period of two years 'til I found a leather one, no problems since. I don't know if the rubber doesn't agree with the alcohol or not, however the cup was sticking to the pump cylinder walls which caused it to detach from the plunger.

I also changed the floats to brass. The plastic floats tend to degrade over time and sink.

 

[Wile E Coyote]

Assuming a stock T-QUAD is still solid, which a new one should be, it will work. Today's fuel tends to cause the engine to run leaner than it otherwise would, so you will need to go up the equivalent of about one jet size, on a big block maybe two sizes. It was difficult to get these cars to run right even when they were new, the cars were set to run as lean as possible to pass emissions. If the New T-Quad has those plastic limit caps on the idle circuit, those will probably need to be removed to fatten up the idle The EGR valves did not play well with the carbs of that era because there was no compensation for the introduction of inert material into the combustion process which tended to leave the engine with a lot of dead spots at different throttle positions. You can disable the EGR valve by putting a blockage in the vacuum line to it. That retains a stock appearance and makes tuning the engine to run correctly a lot simpler. You will need to play with the timing settings to see where your car will run the best as today's fuels also require more advance than what was suggested on the emission stickers and shop manuals of 1974. Hope this helps.

Dave

Will read and study this! Thank you Sir.

 

[70bigblockdodge]

the original TQ9016S carb, everything is hooked up like its 1974 (EGR, water pump sensor, radiator sensor, all vacuum lines/hoses) - all back to Day

Honestly with the emissions and miles of vacuum tubing it will never run correctly. 74 is actually a good one, no cat, no lean burn, and still has ported spark advance. With a O2 sensor/air fuel ratio meter you can make it run spot on.
I have a 76/81/and some unknown year Hodge podge small primary one on my 68 Charger. It spanks the hell out of the 1406 Eddy that was on there. Seems to get better mileage, I'll find out through this season.

Just a side bar thought....I have often wondered what affect ethanol will have on the TQ carb body or phenolic floats commonly found. Anyone have an experience?

I will let you know. Against my better judgement and because I'm so cheap I put the plastic floats in there. So far so good. My air door needs a little slowing. Other than that I have no complaints.
I will be hooking up A/F guage this spring I'll see where I'm at with my guessing.
I ended up with 1981 heavy truck (like a 350+) 360 cid float bowl and throttle plate switched air horn for a more contemporary 76 lean burn car style with side fuel inlet ( truck had rear center fuel in).
I kept the lean burn secondary jets because these were bigger than the truck stuff my cammed 440 is more fuel demand than a 360 truck engine. The primary side which is where the lean burn is, I used the larger jets and smaller rods that came with the truck carb.
The carb has none of the hateful bugs that give TQs a bad rap. I do need to hook up a manual choke (heat crossovers blocked and RPM intake), because cold starts are a bit of a pain.
I have never experienced ethanol problems like others. Some steel parts will get some rust on them, but I'm not convinced it isn't just because they sit alot. The worst I have seem repeatedly in Holleys and Eddy's is the jelly like sludge that forms in the float bowls, again not convinced this is from Ethanol, because alcohol evaporates very easy/faster than gasoline. The sludge may be due to moisture in the liquid because of the ethanol, again water evaporates, especially with heat. I believe the sludge is from all the additives they have to put in gasoline to make it a viable fuel, like octane boosters, stabilizers, oxygenators, etc. hell the oxygenators have shown up in drinking water and roadside creeks just like good old lead did years ago, after passing through the combustion process.

 

[Stern70]

Thanks for the info guys, I'm at the same point on my 440 so we are all learning here!

 

[commando1]

it will never run correctly.

Thank you.
I'm tired of repeating myself.

 

[thrashingcows]

The sludge is from the ethanol since it pulls moisture/water out of the air and then it settles in the bottom of the carb.

 

[Wile E Coyote]

Thank you.
I'm tired of repeating myself.

Sorry. I searched for previous threads. I apologize I missed more than the one I found.

 

[70bigblockdodge]

The sludge is from the ethanol since it pulls moisture/water out of the air and then it settles in the bottom of the carb.

I did have a couple of bubbles in the rear of the Holley. With that car anything is possible. I guess I will have to mash on it a bit more to try and keep that tidied up. That makes sense since it is always at the bottom. The other additives that are suspended can't all evaporate, I still think they are part of the issue.
Best advice is keep the thing running as much as possible.

 

[CBODY67]

The basic short block of those motors still had a good bit of old-time hot rod factory parts in them. Main thing was the 8.2CR and pistons .125" "in the hole".

From what I've read, the best A/F ratio for E10 is about 14.2, whereas for E0 it is 14.7. So the richer jets Dave mentions would be a good place to start. As for the total timing, aim for the normal 38degrees BTDC total mechanical, then see where the hot base idle initial timing might be. A "dial-back" timing light comes in very handy for these things.

Mopar Perf and others used to sell a bag of vacuum line block-off plugs for unused vacuum ports on the carb. ONE of them is the correct size to fit inside of the EGR vacuum supply hose, as I recall. The EGR was modulated by the thermovacuum switch in the radiator's upper tank, as I recall, to keep EGR from happening until the engine got to a certain operating temp. There might also be a CCIE (coolant controlled idle enrichment) valve on the carb, too, which might be run by s similar thermovacuum switch?

Basic thing is to keep the OEM look as much as possible, without diluting the stuff that matters more than necessary for good performance, throttle response, and highway fuel economy. It might take a bit of tweaking here and there, but it'll be worth it.

To me, the orange silicone accel pump cups were or should have been more responsive than the older-style leather pumps were. But in the ethanol era, the leather pumps seem to work well longer.

Seems like the old Carter Strip Kits for the T-Q had a selection of accel pump shooters? Another tuning bit that might help?

I'll concur that the brass floats might be a good deal, too.

Keep us posted on how everything works,
CBODY67

 

[road chicken]

Supposedly the newer rebuild kits for any carb had the proper material to deal with crapinol fuel....guess not. I've found bumping the Jetting @15% works well. 2-3 sizes. Have to do a little figuring on the metering rod steps. I'm doing the same adjustment s with a couple street demon carb. They basically are a hybrid using alot of TQ design features.

 

[CBODY67]

In the S-A Designs Rochester Carb book, it goes through the procedure to change jetting on metering rod carburetors. Rather than "jet sizes", it mentions using jet diameter area minus metering rod diameter area. Probably need a calculator for these "numbers". This can yield much more accurate metering calibration changes than using just the jet size or the metering rod changes.

(This might complicate things a bit) In one of the Holley Carb books, it mentions that the number on the jet might not always apply to the physical diameter of the orifice, but to the FLOW through the particular orifice. AND that when using a non-beveled jet, any changes should be with a non-beveled jet. Similar with beveled-orifice jets. Due to the flow differences of beveled vs non-beveled jets. There was mention that replacing a beveled jet with a non-beveled jet three numbers larger might actually result in less flow through the jet itself. BTAIM.

In general, at least in Carters, the jet number is the jet orifice diameter, I believe.

In the same Rochester carb book, it details how to meter the various steps on the metering rod. KNOWING, of course, how the vacuum level phasing of the power piston spring that runs the metering rods up and down. Using a vacuum gauge, stop watch, and a measured distance of road. Similar procedures are in the Edelbrock AFB manual, as I recall (all 30+ pages of it). LOTS or "road time", which might be shortened with a road-load chassis dyno?

Enjoy!
CBODY67