New Carb

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Grover72

Grover72

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Hey guys, Looking for some opinions on a new 4 barrel carb. Engine is a 318 with a 904 trans, mild cam, stock 318 heads, 340 intake p# 3671918. Hooker headers to full 2 1/2" dual exhaust. Currently has a holley 8400 650 carb with vacuum secondaries this carb really doesn't seem to fit wellI've been having some for issues between the carb flange and the intake. I believe the original carbs that mounted to these intakes were TQs? Looking for something that will fit well onto the intake manifold in the 600-650 range with vacuum secondaries. looking for some input.
 
How about a thermoquad since it's the correct carb for the intake? I love the look of an original thermoquad! And they can be quite effective when tuned properly.
 
another vote for a properly built and tuned thermoquad! Mine handles my 440 with 284/484 cam quite well!
 
Hey guys thanks for the thoughts. Any idea where to attempt and get a TQ or are there any repros out there?
 
625 street demon will bolt on, and you can buy them new for a little over $300.
 
There are sveral nice thermoquads in the for sale section here. Also, i have heard lots of good things about that street demon.
 
mopower440 said:
There are sveral nice thermoquads in the for sale section here. Also, i have heard lots of good things about that street demon.
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I bought one of the first ones when they came out, it is a truly set and forget carb, they work great, would even start at 0 deg F on the first crank, and 90 deg f after being run.
I had issues with a holley boiling fuel in the heat of the summer here, the carb took care of that, buy the composite body one.
I sold the truck it was on, but thinking of buying another one to replace the 700 double pumper on my duster. They just street drive so smooth.
 
Use the small primary TQ. There are electric choke versions that would be excellent with a mild 318.
 
I went with the Edelbrock 650 AVS2 and it was super simple setup and hasn't required any further tuning. Excellent idle quality and throttle response. That Street Demon was in my shopping cart a couple times too. Really a coin flip situation. Unless you know what you are doing an old Thermoquad could be problematic. Great carbs, but most anything used you buy is going to need to be rebuilt and there aren't many tuning parts available. Guys are having to salvage old cores for parts to modify to tune with. Doesn't seem like where you want to be.
 
Grover72 said:
Hey guys, Looking for some opinions on a new 4 barrel carb. Engine is a 318 with a 904 trans, mild cam, stock 318 heads, 340 intake p# 3671918. Hooker headers to full 2 1/2" dual exhaust. Currently has a holley 8400 650 carb with vacuum secondaries this carb really doesn't seem to fit wellI've been having some for issues between the carb flange and the intake. I believe the original carbs that mounted to these intakes were TQs? Looking for something that will fit well onto the intake manifold in the 600-650 range with vacuum secondaries. looking for some input.
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Are you saying you need the spread board adapter? So the carb will actually seal and fit?
 
gzig5 said:
I went with the Edelbrock 650 AVS2 and it was super simple setup and hasn't required any further tuning. Excellent idle quality and throttle response. That Street Demon was in my shopping cart a couple times too. Really a coin flip situation. Unless you know what you are doing an old Thermoquad could be problematic. Great carbs, but most anything used you buy is going to need to be rebuilt and there aren't many tuning parts available. Guys are having to salvage old cores for parts to modify to tune with. Doesn't seem like where you want to be.
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Any specific mounting gaskets for those carbs?
 
Grover72 said:
Any specific mounting gaskets for those carbs?
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I used the Edelbrock 9266 Isolator on my RPM Air Gap Dual Plane. It is about 5/16" thick, provides thermal isolation to keep the carb cooler and doesn't require any other gaskets. Comes with studs. They make the same thing for a single plane.
 
Another vote for the Street Demon here, I have the 750 cfm version on my built 360 Magnum. I've messed with ThermoQuads, Carters/Edelbrocks and Holleys and the Street Demon is like a combo of all 3. Secondary air valve and primary metering rods like a TQ or Carter/Eddy, available plastic main body like a TQ, but is made by Holley and uses some Holley parts (secondary jets for example). It also has dual mounting bolt patterns so it will mount straight-up on either a spread bore or square bore intake. You'd need to check the throttle bore alignment if putting on a spread bore manifold though, might still need an adapter if it's a factory iron TQ manifold.
 
If I remember right, the new street demon I bought came with a plate for either a spread or square bore.
One thing that truly sucks though, to put the holley mopar throttle arm on you have to dissemble the carb, maybe the new ones are different. A factory mopar throttle arm will not fit.
I even confirmed it with holley tech before tearing into it.
Not hard, but I could see a person not familiar with carbs having issues.
 
sireland67 said:
If I remember right, the new street demon I bought came with a plate for either a spread or square bore.
One thing that truly sucks though, to put the holley mopar throttle arm on you have to dissemble the carb, maybe the new ones are different. A factory mopar throttle arm will not fit.
I even confirmed it with holley tech before tearing into it.
Not hard, but I could see a person not familiar with carbs having issues.
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Good point, I converted to Lokar throttle and kickdown cables on mine. It also sucks you have to remove and disassemble the whole carb to change jets.
 
YEA! Whats with that? Not user friendly IMO. It doesn't make me happy thinking about it. It is the only draw back (IMO at least) to the Carter/Edelbrock carb for major jet changes. But once you have it, your done, rods fine tune it. Good to go. Jet it, set it, forget about it. Done!
 
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