I'm thinking of building another small block (meaning paying someone to) and am very interested in using a spread bore carb and intake. Mild performing 360 street engine. I REALLY miss that sound of a Qjet or TQ. I realize tuning one isn't the easiest, and parts sourcing can be difficult but if there's not a big dropoff in performance due to the intake and carb itself versus something like an edelbrock performer air airgap with Holley 3310 than I'd love to have that sound again.

Problem is I don't know if there are good intakes available, especially aluminum to accommodate a spread bore carb and if I'm sacrificing lots of power.

Also not a fan of any carb adapters but what do I know? Not much.

Spread bore carbs are a good design for a street car but good luck finding parts these days. If you can find a good carb then you'll want to track down an old Mopar Performance aluminum dual plane intake. They had a spread bore flange on them.

The new Street Demon carbs are a great carb. I have installed several and all have done a good job. They are a spread bore design that will fit both spread bore AND square bore intakes. Available in 625 and 750 CFMs.

www.holley.com/products/fuel_systems/carburetors/demon/street_demon/

www.youtube.com/watch?v=TRpmtLb_9dI

the q-jet are readily avail and there are 3 versions. 750, 800 and the elusive 840. the 840 came on 455 pontiac sw. i will be using an 800 on a magnum with aftermarket intake. i bought the q-jet book and am really excited about it.

I had a carter on my A38/E58 Aspen and a Quadrajet on my '89 Diplomat AHB and was happy with both for years, and as I mentioned oooohhhh that sound.

Enjoyed the video Dave thanks. VERY nice Demon carbs! I really like the second one with the polymer center. Both with their HUGE secondaries. Might be a better choice than the beloved carter or QJ just for simplicity. I was really impressed when he took it apart.

Thanks all. Larry

It's been awhile since I bought from them but quadrajetparts.com sells parts and kits for TQ's. Thermo Quad Parts

I read the designer of the Street Demon carburetor worked for Carter back in the 60s and 70s. He took the best attributes of the Thermoquad, the AFB and the Rochester Quadrajet when he designed the Street Demon. Cant go wrong with a new carburetor with a revamped design.

Forgot the Ford VV carbs? Nothing inherently superior in a revamped carb. It all depends on the design, new is not always better.

I have run a few of them on my SB trucks. I like the early-mid 70s q-jet to swap a mopar throttle plate or lever on and run them (327-350 chebby carbs are bestest)

I have on the shelf a

edelbrock 1905 Q-jet which list for 85 d150/auto correct throttle linkage hook up with stock 85 q-jet 318/360 engines.

NOS/NITB military surplus Holley 650cfm spredbore list for 86 d150 3604v engine. again correct throttle linkage hook up on the stock 85 d150 linkage

Mercruzer chevy 305 CI (boat q-jet non-emissions only has 2 small vac ports.1-choke pull off, 2- dist vac can & NO PCV) I ground the throttle lever off a 88 police 3184v q-jet (feedback carb) tack weld it to the throttle shaft after removing the GM style throttle lever..

IIRC, thermobog 3 piece PTK linkage will be the stock PTK linkage you will be looking for to use with a stock intake on your 79 truck you can mod the 79 2v 3 piece rods to fit and adjust out or adapt any 3 piece set up to it if need be. you can mod a 1 piece to work with a couple of the slotted flat bars bolted together (carb stud to bellcrank)


I know for sure the 85 q-jet stock 1-piece PTK linkage works with these intakes and are bolt on/adjusts with no mods.

stock 318/360 cast iron 4v intake (best on 360 heads for port size matching)
Edelbrock RPM air-gap large ports

for a small port head 273/318

stock 273 cast iron intake
273 duelquad intake
LD4B
Edelbrock performer 318/340/360
Holley Street Dominator

there are other intakes but will all be the 340/360 port size so pick your poison

my new 318 build is getting the Holley STREET Dominator with the brand new holley 650cfm spredbore. I added a QFT adjustable vac pod to it so it will be easy to control the big 2ndary opening and give that big Q-jet howl
I have a set of duel feed bowls/fuel line on another Holley 6213 800cfm spredbore I may swap on...it makes the spredbore carb LOOK HUGE sitting there on an intake.

your police cars should already have the 4v PTK and the stock 4v intake would look more correct. the hardest part is always finding the PTK linkage when swapping things around or having to mod some linkage up to work correctly

PTK working and adjusted correctly is very important or just go manual. but you know this.

Absolutely loved my TQs when I was running 340s. Pulled one off my last 340 and put on a 3310. Seat-of-the-pants dyno didn't notice any difference so I put the TQ back on.
I think the reason many folks don't like them is that a Holley is just so much easier to work on although once you tinker on a TQ for a while, they are not much harder. Granted, high HP engines probably need a Holley(s). Can't recall ever seeing a big inch stroker with a single TQ or 2 TQs on a tunnel ram but that would be cool.
Had my '65 Valiant project not fell through I would have been running a 360 with a TQ.


Tim

just love those thermoquads !
it took me a looong time to figure out how to tune them, but after i figured that out, i was in hog heaven !
as said, parts for those can sometimes be hard to find, so i have a bunch of them on the shelf, and every so often, i can pick up another one for next to nothing.
if i need to use an adapter, i use the ones that are nicely cast, or i machine one out of 3/4, 1", or 1 1/2" plate chunks i have laying around here. blended in to the intake of course.
i have always wanted to try a tunnel ram with twin thermoquads, but have never had the opportunity to do so.

Factory 340/360 spread bore intakes are at least equal to eddy performer. RPM and Air Gap are a different story. Step up from stock intake if justified would be a holley street dominator spread bore intake. If you are going to run AC with a sanden style compressor, you will need a late 70's 360 intake that has the thermostat offset for it.

That said, how often will you be above 5000 rpm on the street? Not very much I suspect. A properly tuned thermoquad will give better gas mileage than any other, followed by the quadrajet. Both are excellent street carbs.

Dont be put off by others telling you how hard they are to tune or get parts for. Rebuild kits are available, and parts are available from the thousands of tq's being used for door stops or paper weights.

Won’t be running a/c. Hoping magnum heads. Shooting for something very similar to the Mopar performance crate 360/300 hp. I owned two of those in the past and was extremely impressed with the combination. Very mild-mannered for daily driving but tons of torque. Only change I would expect to make is the intake and carburetor going for a MP M1 dual plane which from what I’ve read was not all that great anyway and instead of Holley 3310 a different carb. I would love to use a TQ but the more I look at those Demons the more I like. The huge bowls are a benefit it’s a little more ethanol friendly and we have 10% ethanol here in Florida and I love the huge dump from those secondaries when you open them up. I think they call it goggle valve. Check out the video Dave posted if you don’t know much about those demon carbs.

I called Brevard Cylinder Heads yesterday (Vic) but no answer. It was afternoon so maybe that's why. Try again Monday. I'd like him to build engine.

On Demon carbs; I'm really interested in them and think I might put one on my stock '79 Power Wagon 360-4 right now. Currently has Edelbrock 1406. Granted not a performance engine but would love to go back to something closer to what it came with, with the little primaries and the big secondaries and that sound. When I look on their website they make it appear the 625cfm in the video Dave linked is not compatible as far as kickdown linkage. They show Ford/GM parts but not for my application. I'm showing my ignorance but what gives?

Larry, be sure to check ebag for refurbished ones. They pop up ever so often. That's what I grab if we have the time to wait for one to come up. And the black center ones are the way to go in areas like yours and ours where it gets hot and have alcohol in the fuel.

I have never tried the 625. All I have ever ran are the 750s because I have only put them on 360s and 440s. The only difference between the carbs are the primaries.

Lots and lots of reviews and information on these carbs on the 'net. Just have to Google it.

www.forabodiesonly.com/mopar/threads/750-street-demon-linkage-issue.400773/

Yep already decided I like the polymer center after watching the video you posted Have to admit I'm too anxious and want one on my truck now but don't quite understand the applications part of their website; as if I'm going to have trouble with linkage. Also, I figured the 625 was plenty for a stock smog engine

If I was sure which one to get and that it would be no issue with linkage I'd order one now for my truck.

Just saw your additional link...thanks! reading now.

Seems to me it someone that can't follow directions that's the issue in that link.

Yes, and also seems they'd have Chrysler specific applications by now.

Would you think a 625 or the 750 would be best on my stock '79 W150 360-4. Well it does have Hedman Ultra headers and dual exhaust now but stock engine.

Bolt on kickdown adapters have been the norm for decades. Hasn't been an issue for me. Holley uses them, Edelbrock uses them. Just have to remember to use one if you need it.

My experience with a 360 running a 625 or 7550 carb is limited to the Edelbrock Perfomer carb. FWIW, the 625 gave better mileage, the 750 better top end. Since I didn;'need to exceed 115 and I daily drove it I went with the smaller carb on a mildly warmed up 360.

No idea how useful that would be with a Street Demon