The Sputtering Thermoquad

[aceofspades]

....and no I'm not getting rid of it.

So the starter went out as soon as my engine swap was done. At long last I can start driving my truck again after having replaced it.

So, let's get to it. The engine is my 360 out of the former Chrysler 300. Now that the lovely lean burn is gone, a bigger cam is in, etc. I feel like they turned the timing up too much and the idle looks to be all the way down.

Problem: when the T-Quad is warmed up and I punch it, it sounds like a rocketship launching and is awesome for about two seconds, then starts to sputter.

I'm not sure if it's the timing, the T, or what.

So, I can......

A: tinker with it until it's more gooder
B: wait for advice from you fine folk
C: prank call Craigslist sellers

 

[khryslerkid]

I'd do all three

Was your carb rebuilt?

Is your carb the original lean burn carb?

What shape is your fuel tank in?

Who's doing the timing on the engine?

 

[aceofspades]

All three...got it.

A: no
B: yes
C: plastic, good except for small crack on top which plan to fix.
D: a backyard guy that's been doing mechanic work for years and has yet to fail me, however, may not be Thermoquad savvy.

 

[khryslerkid]

Did your carb have wires going to it?

 

[aceofspades]

I don't believe so.

 

[Photon440]

I think I've got that album too.

 

[aceofspades]

I think I've got that album too.
View attachment 549620

I think I just pissed myself

 

[khryslerkid]

It's the original carb, engine ect that ran ok before you installed it in your truck?

 

[Cranky]

A lean burn carb is calibrated differently than one that wasn't on a lean burn system.....so I hear. Shoot, the best street carb I've ever had was on a 71 Cuda. 3.55 gears, 17mpg and 14.0's in the 1/4 mile.....

 

[khryslerkid]

I think I've got that album too.
View attachment 549620

 

[aceofspades]

It's the original carb, engine ect that ran ok before you installed it in your truck?

Yes. It worked great on the Chrysler. The only problem I ever had it instantly tromping it at takeoff. It would just cut out. Otherwise it was a beast.

 

[aceofspades]

In it's former lean burn glory.

I'm actually thinking a new accelerator pump would help.

 

[khryslerkid]

Could be dirt or corrosion in the float bowl. Float levels too. Might be worth a look see.

I'm not too sure if it would be the electronic carb or not. I had a 318 with lean burn and it was going to be a hassle when I looked into taking the setup off. It had wires going to it as part of the system.

 

[tomlin]

I have not worked on a lot of Thermo quads but I have tuned a Street Demon and worked on a bunch of quadrajets. It sounds like your secondary air valve (flap) is set too loose. Does it have a vacuum pull off that is connected via a link to the air flap? I think most did. Make sure that pull off is functional. Look and see if the air flap is adjustable, if so try to tighten it in very small increments. This is the adjustment that solved my Street Demon's bog. BTW the Street Demon is closely related to the Themo quad.

 

[aceofspades]

I have not worked on a lot of Thermo quads but I have tuned a Street Demon and worked on a bunch of quadrajets. It sounds like your secondary air valve (flap) is set too loose. Does it have a vacuum pull off that is connected via a link to the air flap? I think most did. Make sure that pull off is functional. Look and see if the air flap is adjustable, if so try to tighten it in very small increments. This is the adjustment that solved my Street Demon's bog.

Take a peek at the pics I posted Tomlin. I think there is. And yes I'm sure it's probably in need of adjustment. I don't think there were any wires connected.

The "computer" was the compartment attached to the air cleaner

 

[mopar 3 B]

1. Check meter rod function
2. Spring tension on secondaries
3. Accelerator pump and set at max squart
4. Fuel flow
5. Where is the crack in the fuel bowl?
6. Check all fuel bowl vents
7. Fuel bowl floats. Brass or foam? In other words do the floats float?

You have removed all the lean burn crap from the carb?

 

[aceofspades]

1. Check meter rod function
2. Spring tension on secondaries
3. Accelerator pump and set at max squart
4. Fuel flow
5. Where is the crack in the fuel bowl?
6. Check all fuel bowl vents
7. Fuel bowl floats. Brass or foam? In other words do the floats float?

You have removed all the lean burn crap from the carb?

Good checklist. Yes all emissions are gone.

 

[mopar 3 B]

Good checklist. Yes all emissions are gone.

It does have air-fuel adjustment screws? Some where capped and not adjustable.

 

[aceofspades]

I believe these are it up front...

 

[rumblefish360]

Whoa! Good advice & check lists.

IF it were I, ..... I would not run the leanburn carb and seek an earlier low to zero emissions carb. The less on it the better.