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Anyone know the CFM of thermoquads?

idrivemopar

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I looked at the Thermoquad Guide sticky, but did not see any CFM information.

My question, would a TQ-6322 be over kill for my 340 with just a slight bump in compression and a taller cam? Originally the car had a 6319, which i believe is 561CFM? Looking for something in the 700cfm range.
 
Most info I have seen says they are around 800 CFM but what measurement method that is based on who knows. A lot of 340's and 360's came with TQ's so making one run well is not out of the question, but don't take that 800 CFM info to the bank. Q-Jets are also said to be about 750 - 800 CFM but again, who knows how that is rated.
 
A TQ will run fine on your 340...weather it be 750cfm or 800cfm...TQ's and Q-jets are both spread bore vacuum secondary carbs....the primary bores on both carbs are small so it''s not going to over fuel your engine where it runs most of the time anyway(on the primary circuit)....Then you have a vacuum secondary, which only opens when the engine needs it, which is at WOT....
 
They are rated in two groups. 800 and 850. With exception to the early 1969 Competition versions rated at 850 and 1000 CFM. They are easy to distinguish. The 800 has 1 3/8" primaries and the 850 has 1 1/2" primaries.

The 1971 Carburetors were replaced with the 1972 style through factory service bulletins, because they were a nightmare to tune and get right. However, they were actually more powerful carburetors. They are very expensive today if you find one and are mostly used for numbers correct restorations.

The best ones to use are those from 72-74 on passenger cars and those on trucks all the way to 79. Also, from the late 70s through the 80s, Carter came out with their afretmarket high performance versions called the Super Quads. There were four numbers. 9800S which was the NON EGR phord, chebbie model, 9801S which was the Chrysler NON EGR model. 9810S which was the phord chebbie EGR version and 9811S the Chrysler EGR version. Nothing wrong with the EGR carburetors other than they had a an extra vacuum port. I like the later Super Quads best, because they all came with electric chokes and had high flow jets and better size metering rods.

*Usually* the good cores to look for are 6*** and non smog 9*** numbers. The numbers are located on the driver's side REAR side corner of the base plate. I posted The Thermoquad Guide in its entirety here some time ago:

http://www.forbbodiesonly.com/moparforum/showthread.php?t=38460

It's good readin.

To answer your question in full, it's like this. Thermoquads have a MAXIMUM flow of 800 for the 1 3/8 primary carburetor and 850 for the 1 1/2. That means that the carburetor will BE whatever size the engine needs it to be up to 800 or 850 CFM. Since they are a vacuum secondary hybrid, they only flow what the engine demands, so to look at a Thermoquad and say "hay that's a 850" or "hay that's a 800" ain't very specific. That's the main reason Chrysler used them on everything. Because pretty much one size carburetor will work on everything.
 
Excellent write up Bobby.

To answer the OP's question a little more completely, IMO, with 100% certainty, I'll say yes to the larger TQ carb for a 360. It is a large small block for starters. Secondly, the larger primary will be more powerful in part throttle operations. IE; driving around town, light to light, the corner store, etc…

The smaller bore TQ is better for mileage concerns on a 360. Or a 340. It works excellent on a 318. Use AFB rods bent 3/4 of an inch shorter to tune since OE TQ rods are very hard to come by.

The earlier the TQ the better.
 
You keep sayin that about the AFB rods.....I gotta get me some and try it.

Thanks for the kind words.
 
Your welcome. Yea, that is how I do it since there is a lack of tuning parts for these bad boys. I'd like to try and use a tap for a Holley jet, but, I have not had a TQ pop a well cover in a long time not to mention,, Holley wants a mint for there tool, what ever that size is for there jets.

Anybody know?
 
I think it's just 1/4 20. I'll see if I can find out tonight. I do remember it's nothin special.
 
You guys are assuming that the TQ is 800 and 850 CFM. Carter has always rated their carbs differently than Holley but we all think in Holley terms and you can't assume that. My point was it may not be, and doing a little research reveals this bit of info.
http://promaxcarbs.bizland.com/thermoquad.htm

I'm just saying........
 
Yeah I always read that Carter used different methods at measuring air flow. Thanks for posting that. Still though, no hard numbers from Carter. I take numbers from Galen like a grain of sand. Don't get me wrong, dude is smart, but I've read and seen him make some whoppers. ...and I ain't talkin about Wendy Whoppers.

Tell you what I'd like to do.......put one on a flow bench. I gotta friend who ports heads for a living. I'll ask him about it.
 
Mike @ MLR made an offer like that to the general public at FABO. I'm stuck at the moment in the middle of a modified TQ I'm opening up. Certainly do make that call and see if your buddy can get se accurate numbers from the two carbs. Primary and secondary if possible.
 
Tell you what I'd like to do.......put one on a flow bench. I gotta friend who ports heads for a living. I'll ask him about it.

I agree, but how will it be flowed? Wet or dry? Dry readings will inflate the CFM numbers and it's possible that's how Holley does it. I'd like to know more details about this myself. We really need to send them to someone like Edelbrock or Holley or ask if they can share flow data on different carbs. I bet you they have the flow numbers form different carbs but whether they will give them out is another story.
 
No, they do not share.
Seen a T.V. program that showed the Holley guys wet flowing there carbs. Should I think there all done this way or not, be it you believe it or not, ehhhhhhhhhh, it's just T.V.
 
I agree, but how will it be flowed? Wet or dry? Dry readings will inflate the CFM numbers and it's possible that's how Holley does it. I'd like to know more details about this myself. We really need to send them to someone like Edelbrock or Holley or ask if they can share flow data on different carbs. I bet you they have the flow numbers form different carbs but whether they will give them out is another story.

Aren't cylinder heads flowed dry? Are their numbers inflated? I'm not bein smart, I'm askin because I don't know.
 
Aren't cylinder heads flowed dry? Are their numbers inflated? I'm not bein smart, I'm askin because I don't know.

I hear ya. I believe they are, but I'm no expert either. Seems to me that getting the wet flow correct is king. It's not all about the CFM, but a balance of CFM AND velocity and getting ALL the fuel vapor delivered to the cylinder.
 
I hear ya. I believe they are, but I'm no expert either. Seems to me that getting the wet flow correct is king. It's not all about the CFM, but a balance of CFM AND velocity and getting ALL the fuel vapor delivered to the cylinder.


Ive seen several sets of several brands and model of cylinder heads flowed and they were all flowed "dry" with just air........

I seen that the bench operator could inflate numbers if they wanted too....kind of like a dyno operator....

I do know that I have brought my machinist out of the box 440 source heads, and out of the box sbf edelbrocks, afrs, trick flows, patriots and had them all flowed, only the trick flows over achieved....


I guess that is the reason that dynos, flow benches, cfm carby ratings and all that CRAP goes out the window at the 1320 with the chrondek (spelling?) comes into play....
 
Exactly. The drag strip oughtta be the end all be all for all of it.
 
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