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View Full Version : Carburetor choice for a 360?


mopar_nerd
10-06-1999, 07:07 PM
Hi there,

I need some different opinions about the carburetor choice for a 360. Whats your pick? A 383 carter AVS from 1968, reverse idle model http://www.moparchat.com/ubb/frown.gif or a 1971 340 Thermo-Quad with matching manifold. My engine is a slightly hotted 360; 340 cam, headers, TRW 11:1, 587 cating heads with 2,02 1,60 valves...

Thank You

Diplomat360
10-06-1999, 08:55 PM
I personally love the TQ. Once setup properly it is an awesome carb. Even though it is rated at approx. 750 CFM or 800 (I think around there with the 1.5" primaries) the secondary air door will basically allow the engine to take in as much, and only as much air as it needs.

I think the '71 TQ though is a nasty year though...something about different metering being utilized. I'll check in my carb book tomorrow.

Christopher
10-06-1999, 11:24 PM
I'd lean toward the TQ also,but not a 71 model.If you are going to use that intake use a 72 TQ or a Holley spreadbore replacement.

new and old mopar man
10-06-1999, 11:29 PM
DEFINITELY THE TQ this carb when set up right is an excellent carb but again stay away from the 71 model year have heard horror stories on these ...

Hoov
10-06-1999, 11:36 PM
I put a Carter AFB 625 cfm, electric choke,vaccum secondaries on my 360. I have a 340 cam in mine also, but all stock intake/exhaust manifolds and heads. So far it has done everything I want out of it. My shift point is 5000 rpm in the 1/4 mile. Best time of 15.2 @ 90 mph. These are my results, but this carb does everything I want it too. I have had it 4 years and no problems, I just keep it clean. Good luck on whaterver you choose.

Marshal Carpenter
10-07-1999, 01:24 AM
a friend of mine put on a quadrajet from a gm product. on his 360 in a truck, this carb works like a holley but he gets good gas milage. i am un-sure of the actual numbers but he swares by this q-jet. choke works and all the linkage hooked up with out to much modifacation. don't yell at me for this gm thing it's only a comment of some one i know

[This message has been edited by Marshal Carpenter (edited October 06, 1999).]

Christopher
10-07-1999, 01:35 AM
Thats no big deal!! Mopar used the Generic Motors Quadrajet on 360 trucks in 1988 as factory equipment.(Carter carb was going thru changes and almost went out of buisiness then)

Hoov
10-07-1999, 02:39 AM
When I was a mechanic for the police department the Quadrajets came on the 318 powered Diplomats we had.

DartGT66
10-07-1999, 06:08 AM
I wiil also try the quadrajet in my 318 cheapo project. The problem with the thermoquads is the lack of tuning parts for it. You can find quadrajets and parts for them almost anywhere. If it's performance and ease of tuning, then Holley is the way to go.

mopar_nerd
10-07-1999, 01:39 PM
Thanks for your replies.
Could you give me some more details concerning that "crappy" 1971 T-Q ? I have been studying Dave Emanuels "Carter Carburetors" and haven't found any specific degrading info for this T-Q year...Why I'm choosing this year is because 1971 was the only year without the EGR jets in the intake manifold, and usually the tuning range for those earlier carbs are better than the later ones, (doesn't go for the performance series).
Currently I'm running the engine with this AVS carb, it works great with the exception for the idle system, which due to lower manifold vacuum than a 383, runs lean.
More tech & specs please!!

Thank You

360duster
10-07-1999, 05:16 PM
I would use the manifold you have with a later tq with 1 1/2 primaries.it won`t be good on gas but it will run like a scalded dog when you get it right.

Diplomat360
10-08-1999, 02:19 PM
Talking about the TQ, something came to my mind that I know I'll need to find a solution to somewhere down the road.

I'm putting the Edelbrock Performer RPM intake on my 360, this intake does not have the choke well cast into it. What alternatives are out there in terms of an electric assist choke? Perhaps something along the lines of the QuadraJet choke?
I'm not really keen on doing the manual choke thing with the dash mounted button...

Any ideas?

dbdartman
10-08-1999, 08:08 PM
JC Whitney sells electric choke conversions for just about every carb ever made. I think they are about $20 & the ones I've used are better than the stock units. Might take a little time to install, but worth the effort, IMHO.

My 2ยข worth!
<font color = 990033>DB</font

rb77413
10-09-1999, 01:48 PM
Just wanted to add that I have an ex-cop car 86 Diplomat with a 318 4-bbl with the infaoums Qudra-junk. I'm not really fond of this carb. Like they said before, I can't find anything to tune it with. My gas milage sucks. about 13 with easy city driving. But the car passes emissions. (I'm in Tampa). I have a '64 413 in a '77 Newport with an AVS and it runs great. about a 9.4 in the 1/8 (a 4900lb curb weight car). Good luck.

mopar_nerd
10-09-1999, 07:21 PM
O.k the classic trial&error routine will hopefully sort things out.
By the way, before closing this topic, what's the difference between a carb for a automatic and one with manual transmission? They have the same jets and rods as far as I know...What will happen if i put a manual carb in automatic?
Thank You

Christopher
10-09-1999, 08:52 PM
The differences between the 71TQ and the 72 and later is that the 71 was a air bleed type carb and 72 and later are solid fuel types.

Brian Mills
10-11-1999, 02:49 AM
You want the solid fuel on. Carburetors for manual shift sometimes have size squirt pump,( I forget the real name,you know what I mean). Man. shift also never has throttle pressure kickdown linkage.

I turffed the stock Quadra bog on my 85 Ramcharger 360 and went to TQ. The factory intake had the boss for the choke spring machined off. I got a small piece of 1" plate, cut a U shape out of it and screwed it on as an adapter. Crude but effective.

mopar_nerd
10-12-1999, 10:14 PM
Just for the record, I've checked that bad T-Q year 1971, and what I have found is that it shares the same kind of idling circuit as later models but has different main and secondary jets. It also has a different kind of metering rod construction without the mechanical step-up piston, and will therefore only respond to the vacuum.

Orange Bee
10-18-1999, 01:23 PM
The best street intake you'll find is the Weiand dual plane 8000 series! The TQ is the way to go, just be careful to find one that doesn't have warped fuel bowl. This was usually more common on vans, but it can happen to any of them.

Barry Conner
09-17-2004, 10:16 PM
Could you give me some more details concerning that "crappy" 1971 T-Q ? I have been studying Dave Emanuels "Carter Carburetors" and haven't found any specific degrading info for this T-Q year...Why I'm choosing this year is because 1971 was the only year without the EGR jets in the intake manifold, and usually the tuning range for those earlier carbs are better than the later ones, (doesn't go for the performance series).


I have a 70' Challenger w/340 727 auto, changed hood, grill & dash, along with 71' intake & thermoquad per NHRA to jump to a better class.

That said, I contacted 'The Thermoquad Connection", David Cheves built a 71' NHRA/IHRA legal thermoquad per their rules. Along with this carb I purchased one of his full race 1000 cfm carbs for testing. I ran the car this past Wed. fot shake down runs and am having trouble with idling at 1,000 rpms to around 2,000 rpms - above that to my shift point at 6,000 rpms it runs good. I'm using a 1" spacer with this carb, the motor is a "Stock Elimator" setup for G/SA NHRA class racing.

This is a new car to me, just purchased, been setting for a number of years, but when active would run pretty good numbers in MN - 1,200', ran high 11.80's @ 118.00. I'm at 5,800' here in Denver and expect this setup to run in the low 12.30's. to start.

This is what it did on Wed.:

#1. 13.966 @ 97.10 mph, 4500 rpm start, shift @6500 rpm, I screwed this run up with operator error. :rolleyes:
#2. 13.484 @ 102.98 mph, 3500 rpm start, shift @5500 rpm.
#3. 13.170 @ 101.94 mph, 3300 rpm start, shift @5800 rpm.
#4. 13.012 @ 105.51 mph, 3000 rpm start, shift @5800 rpm.
#5. 13.170 @ 101.94 mph, 3000 rpm start, shift @5800 rpm.
#6. 13.000 @ 105.94 mph, 3000 rpm start, shift @5800 rpm.
#7. 12.864 @ 105.23 mph, 3000 rpm start, shift @6000 rpm. :cool:
#8. 12.891 @ 105.21 mph, 3000 rpm start, shift @6000 rpm.
#9. 12.911 @ 105.19 mph, 3000 rpm start, shift @6000 rpm.
#10. 12.889 @ 105.22 mph, 3000 rpm start, shift @6000 rpm.
#11. 12.901 @ 105.21 mph, 3000 rpm start, shift @6000 rpm.
#12. 12.899 @ 105.24 mph, 3000 rpm start, shift @6000 rpm.
#13. 12.898 @ 105.21 mph, 3000 rpm start, shift @6000 rpm.

It seems to like the 3000 rpm starts and shifting @6000 rpm at this altitude.

We did a compression & leak down tests and found I have two bad cylinders 125 lbs (others at 150) and 30% leak down (others at 4%). The timing was set at 34 degree - int. with 40 degree adv. this doesn't seem right to me and changed it at run No.#7 to 20 degree - int. & 38 degree adv. Then the times improved a little, think a ring & valve job would give me the 12.30's or lower that is needed.

The 71' thermoquad has plenty of power for a stocker (haven't tried the larger carb yet). Oh, someone mentioned 1-1/2 pri. that would be on a 72' carb & later, the 71' has the smaller 1-3/8" pri. which seems not to hurt low end.

My only problem is figuring out the richness at idle and correct timing.

Contact David Cheves about your carb for some pointers as well as look at his web site at: http://www.thermoquads.com/

Good luck.

Barry Conner

PS

You'll have some that hate this plastic thing and others that swear by them, for me I'm not sure yet, still reading. :study:

perfmachst
09-18-2004, 12:19 PM
hello, your 71 340 stocker came with the 1 3/8 primary bores. as did the 72-73 340's. T.Q. carb numbers, 6138,6139,6318,6319 are the legal T.Q. for the 340's. a 1" spacer is not legal in stock class. to answer some questions on jets for the T.Q., you can drill out the secondary jets. another mod being done is to retap the primary jets, use holley jets, do away with the metering rods.

Barry Conner
09-18-2004, 01:38 PM
hello, your 71 340 stocker came with the 1 3/8 primary bores. as did the 72-73 340's. T.Q. carb numbers, 6138,6139,6318,6319 are the legal T.Q. for the 340's. a 1" spacer is not legal in stock class. to answer some questions on jets for the T.Q., you can drill out the secondary jets. another mod being done is to retap the primary jets, use holley jets, do away with the metering rods.

Per NHRA Div.5 Tech Director the only carb. they will approve is the thermoquad #4973S for my 1971 Challenger equipped with an automatic. Like you say it has the 1-3/8" primary bores and I know the 1" spacer is not legal, we are just doing some shake down runs to make sure the car goes straight, stops, shifts correctly, etc. David Cheves of the "Thermoquad Connection" built the #4973S carb along with one of his modified "full race" 1000 cfm carbs for testing and playing with. :smileroun

If I hadn't just spent the money for the stocker carb. I would try as you have suggested "you can drill out the secondary jets. another mod being done is to retap the primary jets, use holley jets, do away with the metering rods". But, I have a third thermoquad that has not been rebuilt - a #6139 with the larger 1-1/2" primary bores - you now have me considering trying your suggestion on. :thumbsup:

Thank you for your reply, if you don't mind I'll keep in touch with you guys on how this works out. Want to run car on the last "T&T day" on the 29th of this month, if we don't have snow.

rumblefish360
09-18-2004, 11:34 PM
Barry Conner; Do you reaize that the peron your replying questions to posted awhile back? Nearly a 5 year old thread.
"10-12-1999 10:14 PM
mopar_nerd " Is the date on it. However, the answer is the first year of the T-Q carb is an air bleed version where as the all the other T-Q carbs are a soild fuel design.

jrapp13
09-19-2004, 12:47 AM
talk about resurecting a thread from the dead

perfmachst
09-19-2004, 01:50 PM
hello, I measured all of my 6139 T.Q.'s, the primary bores are 1 3/8 " dia.as are the other 6138, 6139, 6318,6319 the rules states, replacement carbs are permitted provided, they are same as original equipment,make, model,type,throttle bore,venturi size,and external apperance, i.e. fuel inlet location. Iwould get a ruling from glendora. my tech sheet shows, 6138, 6139
carbs. the 6138,6139 are legal also. I have a NHRA tech sheet, it shows carb numbers, T.Q. 4972s, 6138, sm. 4973, 6139 auto as accepted legal carbs for a 1971 340 in stock and s/s .also, there is six intake manifolds accepted too. you can find these on NHRA.com. food for thought

Barry Conner
09-19-2004, 03:38 PM
Barry Conner; Do you reaize that the peron your replying questions to posted awhile back? Nearly a 5 year old thread.
"10-12-1999 10:14 PM
mopar_nerd " Is the date on it. However, the answer is the first year of the T-Q carb is an air bleed version where as the all the other T-Q carbs are a soild fuel design.

I saw the date as I hit 'submit' - couldn't get it back, should have did an edit, sorry. Talked to David Cheves "Thermoquad Connection" about this and he replied "Well, if you remove the metering rods, you are disabling the metering rod system and this will affect the idle, main and hi speed circuits adversely and will not work.". So it was a wasted effort all around guys.
:mad:

perfmachst
09-20-2004, 01:14 AM
hello, you mean don wann's 1974 400 plymouth,that runs 1.20 under the I/SA index is doing it wrong??? hhmm, oh well. I assumed he reworked the idle system so it would work. those darn stocker guys. can't get anything right??? tongue in cheek, my T.Q, with metering rods dropped all the way down, idles fine ,runs very good !!! I'm not a T.Q. expert, but I try to work around the problem. I figured mopar did too. just food for thought.

rumblefish360
09-20-2004, 03:50 PM
perfmachst;


At this point, I usally get up and look at the part. The T-Q. But I can't. However, isn't there a mech. device in the base of the carb that is on a cam that inturns moves a lever up which is ment to insure what they say can't be done?

perfmachst
09-20-2004, 04:20 PM
hello, yes, if the rods are still hooked to the bar. then they will move up and down with throttle opening. however, unhook the rods from the bar and this lets them sit down in the jet. the bar still moves up and down, has no effect at all. it's just along for the ride. at a race ,long time ago, there was a racer with a T.Q. on his oldmobile 455. when he made a pass, it popped and banged badly. he killed all the ducks, popping so bad. anyway, he had me look at it. first thing ,reset the air door tension, looser, not any improvment.
I unhooked the metering rods, dropped them down in the jet. he went from a 13.22 to a 12.85, no pops, misfires, nothing, ran great. anyway, just food for thought, It works for my stuff.

DEMON SIZZLER
09-20-2004, 08:56 PM
hello, your 71 340 stocker came with the 1 3/8 primary bores. as did the 72-73 340's. T.Q. carb numbers, 6138,6139,6318,6319 are the legal T.Q. for the 340's. a 1" spacer is not legal in stock class. to answer some questions on jets for the T.Q., you can drill out the secondary jets. another mod being done is to retap the primary jets, use holley jets, do away with the metering rods.

You later said to leave the metering rods in place but not attached to the metering rod tree; a very big difference in the the results. Also you would get no benefit in performance at wot if you disconnect the metering rods since you will not have the benefit of the smallest step(richens the 2ndaries at wot)and thus the intended purpose of the smallest step since you are pulling lots more air into the engine and must meter more gas.

rumblefish360
09-20-2004, 11:56 PM
If such is the fact of not hooking up the metering rods to the tree and then running better, I'd say he was way rich.

perfmachst
09-21-2004, 01:30 AM
hello, when at wide open throttle and metering rods hooked up they are in the raised posistion , which puts the small end of the rod in the jet, this will give you a richer mixture. when the rod is down in the jet, this is the leaner posistion. and yes he was too rich. as was explained to me .by mopar a looooooooong time ago, with the rods hooked up, the primary goes over rich.
that is why they recommended dropping the rods. also in their manual is a picture of machining AFB metering rods to use. they refer to them as club foot rods. I made up two sets. they seemed to work also. the lower end is bigger diameter versus the middle. at low rpm, provided a richer mix for idle, at WOT, the bar pulled the rod up, and it leaned the mixture down. I've followed mopars ideas on my T.Q. and it works very well. just food for thought.