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Advice for thermoquad on a slant six? https://slantsix.org/forum/viewtopic.php?t=32793	Page 1 of 2

Author:	Guest [ Sun Dec 14, 2008 12:34 am ]
Post subject:	Advice for thermoquad on a slant six?
Has anyone out there had any good expirence with using a thermoquad on a slant 6? I have a couple and am considering one for my 225 build up.

Author:	Charrlie_S [ Sun Dec 14, 2008 6:37 am ]
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No personal experiance with a spreadbore carb on a slant, but: I THINK one would be nice on a dual purpose motor/car. I would use a Q-jet, myself, do to the problems with the TQ "plastic" body, and leakage in the "wells", to say nothing of the problem of getting tune up parts, to tweek the carb.

Author:	SlantSixDan [ Sun Dec 14, 2008 6:41 am ]
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The Thermoquad and the Quadrajet are both very polarising carburetors: Everyone who cares either loves them or hates them. Nobody thinks they're just okay or fairly decent. Either can be made to work well and reliably. Neither is tolerant of incorrect buildup or adjustment. Both are complex enough that many people perfectly capable of building a good-working 1bbl or 2bbl or simpler 4bbl will fail to build a good-working TQ or QJet until they've gained a lot experience. There are specialists in both types. That said: what kind of a buildup are you doing that you need that much carburetor...?

Author:	slantzilla [ Sun Dec 14, 2008 9:54 am ]
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I have used both extensively and a Q-Jet is about as simple as a T-Quad is complex. My major issue with T-Quads is that they have way too many parts for a carburator, and a series of adjustments to make them work properly that have to be followed in order or it becomes nothing more than a bogging mess. I used a T-Quad on a 340 Demon and worked on it long enough that it worked perfectly, but it was a ton of work. As Charlie said, leave the O-rings out of the bottom of the main well holes and you will have a rich idle that you wouldn't believe. I used Q-Jets on my 350 and 455 Buicks and they were as simple as you could get. The main issue with them was parts availability for tuning (rods and jets) and the small fuel bowl capacity. Someone did a buildup on a Slant here a couple years ago with a T-Quad on it. They posted a lot of pictures and talked a lot about it, but never posted any results after they got it running. We also have a member who has had good results with a Q-Jet. He used to post a lot but I haven't seen him around much lately.

Author:	Shaker223 [ Sun Dec 14, 2008 9:57 am ]
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Love the TQ. My Super Bee 340 gets 20mpg with it. I've raced them too, great carb. Biggest thing to watch for is worn throttle shafts.

Author:	68barracuda [ Sun Dec 14, 2008 10:42 am ]
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Wish I could get my hands on a small spreadbore vacsec type! Primaries 390 size secondaries 600 size.... The 450 Holley pulled like a demon above 100MPH but felt lame lowdown The 390 Does the reverse - above 100MPH it starts to run out of steam MIND - the dizzy was recurved after I installed the 390 - may I should try the 450 again....

Author:	Joshie225 [ Sun Dec 14, 2008 11:36 am ]
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I'm building a vacuum secondary 600 CFM Holley with annular primary boosters. It will flow less than 600 CFM because the larger primary boosters create a restriction. Some of the smaller Demon carbs have annular boosters on just one side, but the Demon carbs don't fit my budget very well.

Author:	Reed [ Sun Dec 14, 2008 11:54 am ]
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A carb that I have had very good luck with on my Ford v-8 is the Holley 4360 "economaster" carb. It flows 450 CFM and is a spread bore, but it has mechanical secondaries. It comes with both electric and manual chokes too. Very simple carb, very simple to tune, and it gets pretty decent gas mileage in my big heavy Ford van. I think this would be a great spread bore carb to try on a hot slant six.

Author:	68barracuda [ Sun Dec 14, 2008 12:14 pm ]
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Quote: I'm building a vacuum secondary 600 CFM Holley with annular primary boosters. It will flow less than 600 CFM because the larger primary boosters create a restriction. Some of the smaller Demon carbs have annular boosters on just one side, but the Demon carbs don't fit my budget very well. Hi Josh - I have a 4150 600CFM gathering dust - please let me know how this build goes - and what you have changed Fanie

Author:	DusterIdiot [ Sun Dec 14, 2008 1:07 pm ]
Post subject:	It works but...
I did this conversion on a Holley 600 cfm a few years back, the throttle response was good, acceleration was very good, but gas mileage was abissmal compared to the smaller bore carbs (and yes I daily drive it with the 'black' secondary spring...which would lock the secondaries out).. The speed shop in town that did the conversion estimated the thing flows about 575 'tops', which is more than enough for a slant. Too bad they didn't make a 400 cfm 4165/4175, or a TQ . -D.Idiot

Author:	Rug_Trucker [ Wed Dec 17, 2008 9:58 am ]
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I have been collecting TQ's for a while. Not an expert on tuning them by any means. You can print out the tuning manual from Chrysler on line. I did that. Google the Vaanth Thermoquad guide and print that. The TQ and the Qjet will flow as much CFM as your engine demands. That is the funtion of the air valves on the secondaries. I would think buying the non desirable models would be the key to running one on a slant. The 318 specific ones would be a good start. Lean "pollution Packer"metering rods, .092 jets. (smallest they come) Maybe look for the ones with the most fittings etc. Parts are becoming more readily available from what I have been reading on Moparts. Prices on cores are going up. If you remove the adpter plate off an Offy intake you can drill a Mr.Gasket spreadbore adapter and bolt it right on! They come in 2 sizes, 800 and the 850. I own 2 Qjets. One is on my van and the other is sitting in a Ziplock baggie. They are both Mopar specific 1987 360 truck carbs. Probably not good candidates for modding. Now maybe a 318 Qjet? Did they make them? There is more stuff out there, and more knowledge for these carbs. I used to know where there was a OHC 6 Pontiac Tempest with a factory Qjet! Maybe I need to take a ride next week!

Author:	SlantSixDan [ Wed Dec 17, 2008 11:10 am ]
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Quadrajets came on cop-spec 318s (possibly also trucks?) through at least 1984. All Lean-Burn equipped!

Author:	Shaker223 [ Wed Dec 17, 2008 11:17 am ]
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Quote: They come in 2 sizes, 800 and the 850. TQ's also had a 1000cfm+ version

Author:	Guest [ Wed Dec 17, 2008 10:30 pm ]
Post subject:	Advice for thermoquad on a slant six?
Wow thanks for all of the input guys! I will consider a Q-jet as well and maybe just save the T-quad for something else. My plans are to build up my 225 with the following parts I either have or will be getting: 9.5-10.0 comp (of course custom CP pistons, not sure on bore size yet), K-1 long rods, ported & polished head w/ big valves, Comp cams #264S, possibly custom headers(fabricate myself) and custom intake manifold, and hi-po electronic ignition. I have a factory aluminum 1bbl intake that I was planning on modifing to accept a spreadbore by way of my Moroso 2" adaptor/spacer. I was thinking a spreadbore carb would work good for street & strip hopefully

Author:	Rug_Trucker [ Thu Dec 18, 2008 7:45 am ]
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Quote: Quadrajets came on cop-spec 318s (possibly also trucks?) through at least 1984. All Lean-Burn equipped! '84 was the last year of the TQ. My 87 truck carbs aren't lean burn. The Vaanth carb guide does list the Qjets. Different rules for emissions applied to the trucks. An older GM carb from the 60's-70 would probably be a good choice. Yep on the 1000cfm carbs. I forgot about those. If I found one of those I would Ebay it fast! If I need something that big I will just run dual carbs.

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