Thread: Thermoquad question

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So i just got my friends 850 cfm thermoquad on my car and i got a few questions on what could be going wrong. At about 5000 rpm in third gear it feels like it is choking out and i was wondering what could be the problem anything will help need all the suggestions i could get thanks. Also the carb is rebuilt.

What engine? What mods? Maybe its just running out of revs! Did it work better with whatever was on it before?

I would also add what transmission, it makes a difference if we are talking about a 3 speed or 4 speed transmission.

okay its a 350 bored .30 over the compression is 10 to 1 the cam is .450 lift 274 advertised duration and it had a edelbrock 600 cfm that ran good on it before and the transmission is a th-350 and i take this motor to 6000 rpms easily

I thought that all thermoquads were 1,000 cfm, in any case, do a plug run, take it up to the point of choking/stalling an then slip in neutral, and shut off motor, coast to a stop, pull a couple of plugs to see if your leaning out or over rich condition, its one or the other..

It would really help to know which thermoquad you have. There are basically three, the first series was introduced for the Mopar 340 engine these are all 850 CFM, then the Competition Series came along ( all CS thermoquad are 1,000 CFM) and then there is the later or 9000 series thermoquad, The 9000 series were avaliable either as a 750 to 800 CFM identified by the front throttle bore at 1 3/8 inch's and the other is 800 to 850 CFM indentified by the bore size of 1 1/2 inch. All thermoquads have a rear or secondary bore size of 2 1/4 inch. The type and place ment of the choke will also help in telling you which one you have as well. There also was a model # stamped on the lower left rear bolt flange. Some thermoquad also had tags attached to a front screw and some have a Bar Code sticker usually long gone with a model #. Forget the stamping # on the body of the carb they are parts # and could have been changed.

Also you mention you were running a Edelbrock 600. Sense all thermoquad 's are spread bore Carburetor's did you change to a spread bore manifold? Or are you using a spread bore adapter? If so and you "ARE" doing one or the other could that be the problem? Manifold installled correctly? Same for the adapter!

Roland

From the description it's hard to tell exactly what the problem is, but it sounds like one of three things fuel starvation, too rich or too lean.

If you can rule out fuel starvation, an overly rich condition could be caused by either too big of a jet in the secondary’s and/or the air valve being set too loose.

An overly lean condition will likely be too small of a jet in the secondary’s or the air valve being set too tight.

Here’s a link to one of the better Thermoquad references if you’re interested.

http://www.imperialclub.com/Repair/L.../290/index.htm

Hope it helps. Mike