thermoquad bog

took a good carb off my truck to put on my sons car and put a reman thermoquad on my 75 440 D100....runs ok....has a stumble taking off and a bog if floored....any ideas? it didn't have these issues with the other carb...

Short of taking it apart and rebuilding it with fresh soft parts ( probably sat on a shelf too long )there is no cure for your problems. Per your description, multiple circuits with problems, all containing critical gaskets / seals. Many other issues with rebuilt carbs, not excluding misapplication of parts, bad castings, errors on assembly. The Thermoquad is a great carb, but lots of pitfalls if you are not up to speed when working on them. Hence - - - -THERMOBOG!

Have you tried tightening the secondary air valve spring yet?

Should be 1 turn for all t-quads. More than that and you are covering up another problem on the secondary side.

They call it a Thermobog for a reason.

Not sure it`s your problem but I know the jet wells are known to leak and will fill the base w/fuel and be dead rich. They`re epoxied together and I grind em flat and epoxy em and let it rip...............worth a try.

hi, check acel pump for stroke and fuel volume. also, test air door, see if its too tight or loose. the accel pump can be adjusted to throttle movement. I assume, dist timing wasn't changed? lack of proper timing will cause same symptoms. just food for thought.

^^^This^^^
Your secondaries are opening too fast.
Also look to see if you got a good pump shot coming out of your squirters. Your accelerator pump might be weak and also check to see if your small air bleeds aren't clogged up. Take them out and see if you can blow through them.

I suggest you try tightening the air door spring one turn and see if that helps. You may have to do this a few times. We usually set our race carbs with 5 to 5 1/2 turns. You may also check to see how far the air door opens. We set ours between .850 and .915, We then jet based on how far it opens. The larger the opening the leaner the carb is.

Raul

Been using JB weld for this problem with some success. Another area where alcohol laden fuel is not your friend.

If you give me the carb # off the throttle plate I can give you the proper specs for your application ( jets and needle sizes. There are 12 adjustments that need to be made ( in sequence ) for that carb to work correctly. About 6 of them are critical for a proper running carb. Again, I suggest you buy a fresh carb kit and start from there.

I second Raul's suggestion...I set my 9800 series to 1.5 turns past the secondary air valve contacting the stop.

Let me explain:
1) undo the spring, make sure you do this carefully as you do not want to remove the ring tension and have the spring un-wind and get loose

2) start turning the inner screw and putting tension on the air door, once it comes up (on it's own) I mark that my ZERO location

3) I then add another 1.5 turns here...or more if needed or you want a slower secondaries kick-in

Usually, the above adds up to about 3-4 turns in my case, but I'm running a 4K stall converter with a Performer RPM intake...so it's easy to mask the too fast of an openning...I'm actually running a bunch of O2 AFR tests to jet the carb correctly and you can really tell the secondaries kick-in point where the AFR goes lean real quick and come back to the richer mix right away. For me, I'm thinking my 2ndary accel pump shot is timed incorrectly, as tightening up the secondary air valve had no noticeable impact on the lean spike.