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Old 10-05-2008, 08:37:50 PM   #1
cmonson
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New (Rebuild Qjet) with pics

I thought I would share some pics of my rebuilt QJet.

I bought a rebuild from National Carbs. The carb was custom made with proper jets, rods and hangers for my engine. The also modded the idle circuit for my low vacumn condition. They also sent me 3 other secondary rods so I can play with 1 leaner, and 2 richer secondary rods. For the Qjet fans, I would highly encourage others to buy here. I believe I paid just over $200 for everything.

I used to have a JET stage 2, and I will say this qjet is just as good, if not better. Flooring it off from idle is deffinately better than my JET. I am sure if I knew how to mod the JET I would get the same effect, but this carb was out of the box and go. Throttle response is really quick, and has a very smooth transition to the vacumn secondaries. Absolutely no bog, and I had it up to 6500 RPM, and it would still go more.

Here are some pics below.




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Old 10-05-2008, 10:13:16 PM   #2
Damon
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I'm surprised they used the truck/boat style rear vacuum break. Nothing particularly wrong with that except..... where's the linkage to pop the choke open a little on a cold start? That could be an issue for you on cold start-up (flooding out the engine shortly after start-up).
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1990 454SS pickup. Original "tow truck motor" 454 upgraded to something a little more "aggressive." Seems pretty stout but the fuel bill is nuts.

78 Malibu. Inherited with only 35K on the odo! Mild 383 with Weiand 142 blower on top. Mid 12s appears to be the best it's gonna do on street rubber. Runs so good I may never drive it again.

"Last remaining QJet tuner on planet Earth!"

Last edited by Damon : 10-05-2008 at 10:15:44 PM.
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Old 10-06-2008, 12:17:52 AM   #3
78LT383
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Do they have a web site? If so, what's the address?
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Old 10-06-2008, 02:08:29 AM   #4
ZS10
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Quote:
Originally Posted by 78LT383
Do they have a web site? If so, what's the address?
Are ya ready for this?




www.nationalcarburetors.com
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Old 10-06-2008, 07:33:46 AM   #5
onovakind67
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Quote:
Originally Posted by ZS10
Are ya ready for this?




www.nationalcarburetors.com


The creativity of those folks....
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Old 10-06-2008, 09:55:34 AM   #6
78LT383
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Are they able to determine what carb an engine should need based on the car's & engine's specs? I'm pulling together a new combination and this would be a very nice-to-have carb.
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Old 10-06-2008, 10:04:55 AM   #7
Elpres
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where did u get the electronic choke housing thing, Im having the same carb on my 78 camaro, and i would love to switch to electronic choke.
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Old 10-06-2008, 11:10:02 AM   #8
cmonson
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Quote:
where's the linkage to pop the choke open a little on a cold start?

I am NO carb expert, but the linkage to hold the choke open on a cold start I believe is located behind the electric choke. I can tell you I started my car on Sat morning and it was about 60 degree. I was playing around with setting the elec choke position. I held my peddle down to the floor, and when I started the engine, the engine idled at 1300 RPMs. It slowly came down and settled at 900 RPM which is where this engine idles.

Quote:
Are they able to determine what carb an engine should need based on the car's & engine's specs? I'm pulling together a new combination and this would be a very nice-to-have carb.

The guy that builds the QJETs is was EXTREMELY knowlegable. He said he had been rebuilding qjets for 20 years. I told him my cam specs, current vacumn at idle, and compression as well as some other details. He built my particular carb made for my engine.

They also gave me some extra secondary rods to play with the tuning. I will have to get them out and lay post down as to which ones are riches, and which are leaner. I know one of them at home has DA stamped on it.
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Old 10-06-2008, 11:10:36 AM   #9
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where did u get the electronic choke housing thing, Im having the same carb on my 78 camaro, and i would love to switch to electronic choke.

You can get elec chokes at any auto parts supplier.
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Old 10-06-2008, 11:58:27 AM   #10
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Wow! That's a great setup that you've got. I love Q-jets over any other carburator especially when it comes to street performance and economy.

I went to the web site and sent them an email asking for a quote on a Q-jet for our youngest son's SBC powered S10. He has a Edelbrock Performer on there now and even though Carter AFB style carbs are my second favorite carbs, they are still second.
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Old 10-06-2008, 04:04:07 PM   #11
EricsZ28
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That setup looks great! I'm glad its working out for you.

Yeah, after I bought my JET Performance Stage 2 carb, I learned that they are intended for engines with cams smaller than 220* duration. I now know why that is important & what changes are needed to allow them to work with bigger cams, lol.
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Old 10-06-2008, 05:06:44 PM   #12
Damon
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The linkage to pop the choke open immediately after a cold start always comes from the vacuum diaphragm. They're different looking linkages, obviously, depending on whether it's a front or rear mounted vacuum diaphragm but they are always there.

The other alternative is to set the choke element very loose and let airflow pull it open. Not usually a good alternative- you always end up adjusting it every time you have a significant temp change.
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1990 454SS pickup. Original "tow truck motor" 454 upgraded to something a little more "aggressive." Seems pretty stout but the fuel bill is nuts.

78 Malibu. Inherited with only 35K on the odo! Mild 383 with Weiand 142 blower on top. Mid 12s appears to be the best it's gonna do on street rubber. Runs so good I may never drive it again.

"Last remaining QJet tuner on planet Earth!"
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Old 10-07-2008, 10:02:01 AM   #13
Elpres
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Quote:
Originally Posted by cmonson
You can get elec chokes at any auto parts supplier.

It depends on where u live
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Old 10-07-2008, 09:56:08 PM   #14
cmonson
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It depends on where u live

I can see where that would be an issue for you...
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Old 10-10-2008, 01:07:09 AM   #15
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Your engine and carb look very nice ! The Q-Jet is one of the finest and most accurate carburetors ever designed.

I'm curious about the finish of the metal on the main body and airhorn castings.
Is there some reason that the carb does not have its dichromate conversion on the upper and lower castings?

A lot of shops cannot do the full gold color anymore because that requires hexavalent chromium, which is extremely carcinogenic. Trivalent chromium is safer, but gives a distinctly olive drab cast to the surface conversion. I'm wondering if the state where this carb was re-built has outlawed the remaining chromium material for use.

As an aside, about metal chemistry in Q-Jets...

I've built about 400 Q-jets, roughly, over the years, and I noticed that the Carter-built versions have inferior metal chemistry in the castings. These carbs (which were built by Carter on contract when Rochester could not keep up with GM production requirements) have much greater intergranular corrosion when left exposed (i.e. junkyard in the open), but even with the trivalent chromium they "gold" better than the Rochester versions.

Never run a Carter-built Q-Jet if you can avoid it. They are inferior versions, even though produced strictly to standard.

Here's an example of how poor quality metal chemistry can do you in without every really being able to figure out why the carb runs badly:
See the punch marks in the casting to retain the power piston's little collar? This is a standard retaining technique on older carbs which have been re-built several times, but on a Carter built carb the metal will often crack during the punching without being obvious to the average shop employee. This will cause the carb to run mysteriously at times, due to vacuum leaks, erratic piston action, the effect of various temperatures on the cracked metal, etc.



No matter what, you still have a pretty nice looking setup going.

A-80
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