My Latest Carburetor (q-jet guys will get a kck out of this)

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

why junk it, Oldsmoletick said he's got it running properly now

Many of them do irreversible things to the carb castings. Such as drilling out the threads for the factory screw in valve seat and use a press in seat that are poor flowing and phrone to leaking. Heli-coil the main jet threads which also causes leaks. I already said they acid dip the castings as a cheap way to clean them but it really weakens and softens the pot metal alloy and can even make them porous enough to leak vacuum. They also drive plugs into the idle air bypass which can be very hard to remove without damaging the castings.

While it's good to hear Oldsmoletick has got it running okay, it probably still is not at it's best and never may be able to do it's best. Also the carb since once being reman may not last as long as an unmolested core.

I agree with you but for now I'd say just keep it as long as it seems to working properly and he's happy with it..

 

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

I've seen those mystery rods and jets too. A micrometer will tell you what the rods are ( all tips are .026 IIRC) and decimal drill bits will tell you what the jets are. As for the secondaries, use a micrometer for the tips, but the taper will be obvious (fast,slow,medium).

 

[olds307 and 403]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Actually, I lied. I found the numbers on them just now, 48x or k. That is the same as factory 403 carb. The APT was set at 11 or so turns, the 403 carb was about the same. One difference was the reman had 71 jets vs the 73 in the 403 factory carb, swapped them in. The power piston spring was slightly stiffer in the 403 carb, swapped that over too. The secondary hanger was a L hanger with unmarked rods. Now a G hanger and CK rods. It was missing the black cup in the corner, put it in. I am getting a new choke pull off, 72 and 74 jets, 44 primary rods and a new top gasket. I am finally going to hit the magic 9.5 in the 1/8.

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

I agree with the fear of the "reman" carb, I was leary about even messing with it when I saw the sticker, however, once I tore it down, it seemed ok, the jets and rods when OEM (had factory id markings), whether they matched each other for the application I do not know. No heli coils were used, all threads were in good shape. There was a few things that I said WTF at, but nothing I couldn't reverse, so maybe I just got lucky on this one.

The APT setting was one of the things I was worried about, whether or not they had it set right (I've never messed with one, always told not to do so), I used their setting which was 3 1/2 turns from seated, it seemed to run decent, but was consuming more fuel than it should. I don't know whether this is a correct way to go, but over the weekend I hooked up my vacuum gauge inside the jeep and went out for a drive. I noticed at a steady 60 mph the engine was only pulling about 8, which seemed kinda low. Taking note of where the APT was, I started leaning it out a tick, 1/4 turn at a time, ending at 3/4 of a turn from initial set up. Now at a steady 60mph, it pulls about 14, and has a slightly better off idle response, it wasn't bad before, but it's certainly more crisp. I should try playing with my fuel pressure a bit, maybe knock it down to 6psi? I believe it's set at 7.

One thing I did notice this weekend, my choke/secondary pull off is way too fast, takes barely a second to open. I noticed it's supposed to be adjustable (Holley part of course ), but it doesn't seem to respond any different. I overlooked this while attemting to tune my secondaries in previously, now I see why it was giving me so much trouble, lol. So back to my junk stash to find a slower one, :lol: . It's a good thing I like tinkering, .

 

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

"It's a good thing I like tinkering, ." Absolutely. Nothing ventured, nothing gained. Every unmolested APT I've ever seen has been between 3 and 4 turns, so you are on the money. I never tried watching the vacuum while underway so that's something I need to investigate, Thank's! Do you know about the little plug in the top of the air horn? It is in the air cleaner gasket ring, and right under it is the APT. So you pop that plug out, tap and thread a pipe plug in it's place, and now you have an APT access port. And if you don't have a "double D" socket to adjust it, a secondary rod holder with the edges ground off fits and works perfectly.

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Already covered, when I initially built the carb, I kinda figured I may need to access the APT screw, so I popped out the plug, tapped the hole, and installed my allen plug. I made a tool from and old busted screwdriver. For some reason, mine doesn't have the double "D" type, I had a spare carb laying around which had the same type, I found that a schrader valve core removal tool worked almost perfect, just needed extra length to get down inside the carb. Lobbed the end off the screw driver, notched the tip, good to go, lol. Like I said though, I have no idea whether or not my vac gauge hooked up on a drive would be a correct method, but I figured it was worth a shot, and since I kept exact track of what I did I could always reverse my wrong doing, :lol: . Let me know what you think Bonnewagon, if you do a test of your own... I just went out to my favorite near vacant backroad, did a steaady test run at 60, took note of vac, pulled off to the side, made a 1/4 turn, did another steady speed test run, and so on.

 

[olds307 and 403]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

I wonder why my APT on both carbs is adjusted so far out? I am going to check the other body I have out there. I adjusted that carb a 1/2 turn due to lean conditions, will also check the numbers.

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Is that 11 turns from seated, or 11 turns to remove? I'll have to look at one of my 350/403 q jet spares to see what they're at.

 

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Yeah, 11 turns seems excessive, like it would be practically removed. I'm gonna try that Oldsmoletick, it sounds very logical. After all, APT means Adjustable Part Throttle, exactly what you have at cruising speed. However, deserted back roads are pretty scarce in NYC!

 

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

this thread is great...it's bringing details of the the fine tuning we can do on these carbs that I don't usually think about..