Big difference, just put Q-jet on

[real4wheeler]

My latest project is a '77 Wag w/new 401. The Motorcraft carb was a fresh remanufactured unit. It ran good, but nothing like I'm used to (I've done Q-jets and super-tuning for many years on the side).

I put an Edelbrock square bore Performer intake on (couldn't find a spreadbore), and reblt an early '70's Chevy Q-jet to put on it.

The first hurdle was to find the right adapter. I didn't want to use a generic "open" adapter on a dual plane intake. I always use 4-hole spacers / adapters on dual plane intakes. Finally tracked down one that would work- TD #2034. 4 hole, 1" high. I used it upside down, fits the Q-jet great and the intake.

Second hurdle was that the throttle cable was 1/2" too short to reach the lever on the carb. I had to cut (reweld) and move the throttle cable bracket forward 1/2".

Warmed up the engine and set the air/fuel screws, engine idles with 19.5" of vacuum.

Took it for a test drive. Big difference over the Motorcraft. Now at 3/4 throttle, from a standstill, the right rear tires smokes for about
20 feet and then I let up. It wouldn't even chirp a tire before.

Now it is much more responsive. Definately worthwhile. I could never get an Edelbrock (Carter) carb to run this sharp.

I may just go Mustang hunting tonite.....

[tomd]

where did you find the adapter? i need a new carb since my motorcraft is in sad shape and was wanting a quadrajet.

[heydave]

That is what I want to run on my 360. I have always been a Qjet fan. Thanks for posting the adapter#. We have a TD catalog at work (Autozone). Now I know what to order.
Have fun! BAWOOOOOP!!!

[porkchop]

I am running the open adapter with my q-jet. What is TD? I would like to get the adapter you have. I am still tuning mine, and probaly will be forever. I think I have it pretty good but can't take it for a test drive yet. I am hoping for the same change that you got.

[heydave]

TD is the name of the company. TD Performance I think. They sell all sorts of engine accessories. Go to Autozone and look through the special order catalogs. It should be in there.

[porkchop]

Just found it here. http://www.carbs.net/adapt/adapt3.asp Cost more than I thought it would. I believe I can get it at my local speed shop as well. I should go look. I had the adapter that I am using all ready so I just used it.

[real4wheeler]

I spoke with Edelbrock before I started to make sure my opinion of the 4 hole spacer was correct.

On a dual plane intake, you need to run a 4 hole spacer, and not an open spacer ( of which I have 6 of them on the shelf...). An open spacer will have a weaker signal, less throttle response.

It took me 3 days to find the right adapter. You can order TD adapters from any parts house. Mine was $27 I think.

Also, the jetting on mine is 64 for the primaries. This is lean. I would think a 360 would need 67's, and a 401 68's. Mine runs awesome right now, but will be tuned when I can get it offroad and not get a ticket.

Your own jetting will depend on altitude, air cleaner, and exhaust.

[les78]

Dang, you're right! I just replaced my Edelbrock 600 with your Q-jet. Nice difference in low-end. The 4 hole spacer must be partially responsible, I don't see the carb alone making that much of a difference.

Thanks for the help.

[Rogue]

the qjet is often overlooked as a performance carb but i dont know why i love em

[BHT]

Great info - I've got a Q-jet that I want to put on a Performer intake. Real4wheeler, are you saying you do Q-jet rebuilds? If so, what do you charge?

[FSJeeper]

When I used to run gas AMC engines, the Qjet was definitely the hands down winner. Metering rods and small tuning were parts were hard to get back then, but now they are totally available from Edlebrock. Tuning them properly is tricky, but once you get the hang of it, you'll never want anything else. In the south we call them the poor man's fuel injection.

You can't beat the Holley for ease of tuning though but the Qjet's always give better mileage and more low end power.

[porkchop]

Originally posted by real4wheeler:

Also, the jetting on mine is 64 for the primaries. This is lean. I would think a 360 would need 67's, and a 401 68's. Mine runs awesome right now, but will be tuned when I can get it offroad and not get a ticket.

Your own jetting will depend on altitude, air cleaner, and exhaust.My jets are 71 :eek: Maybe that is why I am running so rich? Where can I find new jets at? This carb adjusting is racking my mind. It can be very confusing at times. I am reading alot of stuff but still can't get it right. It runs very rich and then when it is warmed up it won't stay running :confused: . Can someone help.

[ August 23, 2002, 09:46 AM: Message edited by: porkchop ]

[real4wheeler]

BHT Yes, I still rebuild Q-jets. I used to do peformance tuning as a side line to pay for my drag racing and four wheeling habit.

Now I just rebuild Q-jets as needed. If you need one rebuilt I would charge you $30 + parts (usually $30). Check the primary throttle shaft for excessive up and down play, it may need to be bushed which is about another $35.

There are different Q-jets, they are not all the same, so if you have questions e-mail me directly: reno1@continet.com

[Bob Barry]

Originally posted by porkchop:
[QBMy jets are 71 :eek: Maybe that is why I am running so rich?[/QB]On a QJet, it's not so much the size of the jets, but the size of the primary metering rod you're running in the jet that determines your fuel-mixture. In fact, the later ('74 and up, with the prefix 170xxxxx) carbs often ran larger jets, but also metering rods with really fat taper in the middle for a very lean mixture (for use with EGR).

Do you know what rods you've got in there now? One bad thing is that the primary metering rods changed length when Rochester went from the 70xxxxx carbs to the 170xxxxx carbs in '74, so you can't switch the primary rods between the series without having wacky mixture problems. Secondary rods remain the same, though.

It's also (remotely) possible that the vacuum port to the power-valve piston is clogged, or that it's stuck, so that your metering rods are always at full-rich.

[real4wheeler]

Barry is right about the power valve psiton. It needs to move freely up and down. Not uncommon to get gunked up.

What year is your carb?

Primary jets though can easily cause an overly lean, or overly rich condition, when using the carb on a different engine.

71 jets may be too rich, you might try 68's and see how it runs. When you take the carb apart note which primary metering rods you have (most likely "44" or "42" rods).

Also, I believe you're running an open spacer on a dual plane intake. I've never had any luck in tuning that combo. A good starting point would be to make sure the choke is properly functioning, the power piston moves freely, and you have the 4-hole spacer. Tuning from that point will get the best results.

You can get jets and rods from Edelbrock or look up an AC-Delco distributor in the phone book (larger cities only).

e-mail me directly, I don't go on this site very often. reno1@continet.com

[porkchop]

I will have to look when I get home tonight. I thought I remebered but I am still unsure. I think they are 50D or something but not sure.

[JOECOOL]

Hey PC did you epoxy the bottom of the carb?

Jets and rods can be picked off all those junk GM cars at the "up pick" places for real, err, cheap.

[porkchop]

Originally posted by JOECOOL:
Hey PC did you epoxy the bottom of the carb?
???????? :confused: ????????

[jode]

R4W...you got mail...

[JOECOOL]

PC when you remove the base plate of the carb and turn the main body of the carb upsidedown there are plugs under there that you will notice have some epoxy around then. They tend to crack and leak fuel into the intake so they must be re-epoxied.
Also double check your Float hight and the fuel inlet needle.
BTW what is your vacuum reading at idle?

[ August 23, 2002, 12:37 PM: Message edited by: JOECOOL ]

[porkchop]

My vacuum at idle is 17-19 since my carb is so sparotic it is hard to get a good reading. The needle is steady but it is never the same.

I never re-epoxied nothin' :rolleyes: I used the b-12 chem dip so I am sure that the epoxy is gone. Is it just the epoxy from any parts store? Does it leak when it is just sitting or does it leak when it is running? All the responses here are helping me make some progress, Thanks guys. I may get this licked this weekend!!!

[ August 23, 2002, 12:45 PM: Message edited by: porkchop ]

[JOECOOL]

I would find out from a carb rebuilder what epoxy works best. I used some grey stuff that was gasoline proof. Dont use JB weld as it will crumble. This is one of the reasons some Q jets have empty fuel bowls overnight.
Hey what happened to your AFB/Edelbrock carb?

[porkchop]

The edlbrock was a piece of $#!%. It would never tune right and I am pretty sure the base of it was warped. It had a constant vacuum leak and it would stumble badly on inclines. It even had the off-road kit in it. I just got fed up with it.

[porkchop]

Well I took the carb apart and this is what I got: The jets are 71 and the main rods are 47. Will this cause a rich condition? Also is a brass float better than the platic (composite)?

[Andrew]

What models of cars/trucks used Q-Jets that are good for use on our 360's?

[65 Kaiser]

I got a remanufactured q-jet for a '68 Chevelle. Very cheap, about $170CAN, with about a $50 core. Hardly worth rebuilding at a net cost of $110CAN

Interesting info on the 4hole adapter vs the open. That might account for the difficulty I've had getting the secondaries to open.