73 340 and the Thermoquad

[Beekeeper]

Picked up a nice complete 340 today along with the matching 727 trans.

It has its original iron spreadbore intake and I’m wondering if the original intake is a decent piece. I dont need to squeeze every last horsepower out of the motor but I don’t want to use it if its gonna rob me of 25 hp versus a newer aluminum design.

On the carb, I’ve limited knowledge of the Thermoquad but I know lots of Mopar guys love them. Are they difficult to rebuild?

 

[moparleo]

Download a Service Manual. In 1972 Compression dropped to 8:1 . rated @ 240 hp.
The earlier performance 340 was 10.5:1, better cam, heads. Underated @ 275.
To get to 350 Horse to the crank will require all things but the crank/block to get there.
Much cheaper to do a 360. Externally all LA motors look the same.
Either way, plan on a complete rebuild to do it.

 

[Beekeeper]

I removed the last part of my post since that wasn’t really what I was after.

How does the 73 340 intake compare in power to the earlier 70-72 versions. I don’t want to use it if it’s a dog.

on the Thermoquad, are they easy to rebuild?

 

[Challenger RTA]

RockysRoadshow on youtube is a good place to start to understand the Thermoquad rebuild.

 

[ted s]

i have used the 73 intakw with very good results

 

[fasjac]

I removed the last part of my post since that wasn’t really what I was after.

How does the 73 340 intake compare in power to the earlier 70-72 versions. I don’t want to use it if it’s a dog.

on the Thermoquad, are they easy to rebuild?

The T-quad would be a bit more difficult to rebuild than say Holley. Like anything, there’s plenty of published instructions out there. Most importantly is that the body isn’t warped. I personally love the T-Quads.
And I also believe that you would gain 25 or more HP with a Holley and an aluminum air gap type intake. JMO

 

[moparleo]

Remember, the more air you put in, the more air you must get out or it acts like a funnel. This is where after an intake and carb change, the heads/cam become the next restriction. The final piece is the exhaust header. Good headers would be next for the money. Head work/cam/lifters etc.. the biggest cost, but give the biggest gains.

 

[Chryco Psycho]

TQs are a good carb if they are in good condition , the intakes are decent design also , I would certainly try what you have before you ditch it

 

[Challenger RTA]

Pick you cam and build from there.I would say it's a draw in performance between cast iron and aluminum. only weight being the difference. If you really want to keep it street able and a cruiser.keep the duration under 300. That's just my opinion and experience I leaned from others.Others may have a different opinion.

 

[Beekeeper]

I started Tearing it down to see what I’m working with. Looks like it’s all original components and never been rebuilt.

 

[Titan1969]

I removed the last part of my post since that wasn’t really what I was after.

How does the 73 340 intake compare in power to the earlier 70-72 versions. I don’t want to use it if it’s a dog.

on the Thermoquad, are they easy to rebuild?

I had two supposedly knowledgeable TQ people take a shot at rebuilding my 73 TQ, both failed as it just would not idle well enough for my preference. So I kept the TQ for originality in case I ever sell the car and bought a Edelbrock 600 CFM with auto choke. Best thing I ever did, installed it, set idle...never touched it since.

 

[moparleo]

Woodruff Carbs

Carburetor Restoration in Youngstown, OH | Woodruff Carburetor Specialties

Woodruff Carburetor Specialties offers Carburetor Restoration in Youngstown, Ohio and surrounding areas. Contact us today for more information and a free service estimate.

www.carburetorrestorationyoungstownoh.com

 

[Challenger RTA]

Carter Thermo Quad part.Can you see the difference? If you can't see the difference you need to find out before you touch a Thermo Quad. That's why it's misunderstood. Not knowing how it is put together. Even the manufactures of parts and re builder.
First picture is of a new set of brass floats. Well there made wrong.black ones are correct and original.second picture is original float installed. Third picture is the new float installed. Forth is the the new float on top and an original on the bottom. I contacted the vendor and had to show them other pictures and from Chrysler pictures that they were made wrong.I don't fault the vendor. It was put in the jig wrong when made.

 

[i_taz]

I had a Edelbrock 1411 that I hated so much just for spite I wanted to see what a TQ would be like and it's much better. Runs more like a factory carb should rather than an aftermarket, if that makes sense.
I know of one on a '77 New Yorker and it's never been off the car in all these years even with ethanol fuels so don't listen to all the put downs. They put 100's of 1000's of them on Chrysler's and Scouts used them for awhile.

Used a stock '73 intake which replaced a '68 and they were identical except for the throttle bracket bolt down ( and EGR stuff) Factory intakes weren't slouches, intakes are a give and take affair like most performance upgrades. You won't miss 25hp til you know what you have anyway...