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Finally found time to replace the tired Qjet carb with a Street Demon 625 cfm. The install went OK with only a few issues that had nothing to do with the carb. Lets just say as I get older simple things seem to be not so simple anymore.
This was my first time using steel braided fuel lines with AN fittings. I tried it without any special tools and did not have any success so as luck would have it I was smart enough to order the Koul Tools jig which made it simple. With more practice I feel sure I could have done it without the jig but it is so easy and fast this way.
The throttle linkage and kick down cable went on without a hitch.
First drive after the install, it felt like a different car with smooth idle and no hesitation at wide open throttle right out of the box.
Now to install the new Dizzy and reset the timing. Will make sure full advance is in by 2800 rpm.
Here are some pics before and after.
I want to say thanks for all the advice I received on this forum.
First two pics are before the install.
Thanks for the writeup. I've only read good things about the performance of this carb for street use. The promo ads always talk about an increase in mpg, will be interesting to read your results comparing it to your Qjet when your quad was running well.
Demons quality took a nose dive a few years back. As for your carb are the boosters correctly placed with perfectly 90 degrees perpendicular to the throttle bore?
625 cfm is a good size although VS carbs and dual planes can get away with being bigger like 750
Yes unusual looking but if it works well, congrats...
Just wondering why you picked the street demon over other Qjet spreadbore carb replacements, especially the Holley 4175 650 CFM vacuum secondary Qjet replacement?
This looks suspiciously like an old Thermoquad updated......
They even offer it in a composite bowl version......
It looks like an excellent alternative to the Edelbrock for not so radical V-8's......
Time will tell.
The Demons quality issues were well known to me when I ran the Speed Shop.....The Speed Demons were assembled in Mexico and were absoluter garbage.....sometimes the jets were laying in the float bowl.....
The Mighty Demon was assembled here and were much better, but the only one I could ever make work correctly was the Annular model.
Barry Grant ran the company into the ground....extorted it for big money and skipped town.....nobody has seen him in 4 years or better.....
A brilliant but goofy guy.....who let his issues catch up to him.
This was designed after the fact.....there was even a Road Demon which I have never seen anyone use......
Holley owns it now.....like they own everything......
A brilliant but goofy guy.....who let his issues catch up to him.
Jebby
My buddy who owns a machine shop- had a guy there that had worked for Barry Grant. Supposedly has like 27 patents and Holley sued him over one...
I did have a Speed Demon 575 - on my warmed over Bodix headed 327 on my 65 C2. I ran the car over 3000 miles on the Hot Rod Power Tours - never had any issues- but that was before all of the problems at BG.
On my 73 with a basically stock L82- was prepping it for the Hotrod Power tour - the fuel inlet/filter was stripped out on the Quadrajet. I ordered a Street Demon 625 from Summit- got it the next day and just bolted it on. Ran great- out of the box! And even after sitting in many a traffic jam on the tour w/ a lot of heat- never had a hard hot start- lit right up every time. Gas mileage was up - and in the last couple years have put about 12K on the carb- no issues.
From: At my Bar drinking and wrenching in Lafayette Colorado
The trend in "performance" carburetors absolutely cracks me up. In 1969, if you had a '66 GTO with a Carter AFB, you yanked it off and threw it in the trash can for a Holley or a Q-Jet. Everyone new it was the worst possible performance carb on any car.
In 1974, if you had a ThermoQuad on your Dodge, you ended up with nothing by problems, so you yanked it off, threw it in the trash, and got a Holley. The ThermoQuads only stayed in production for a few years due to problems with reliability, twisting float bowls, and a bad reputation.
Now, Edelbrock is re-making those horrible Carter AFB Carbs and calling them "Performer" carbs. People hail them as the most wonderful street performance carb on the market. Fact is, they run just as bad as the originals...
Now, Holley, under the nameplate Demon, is re-making the ThermoQuad and calling it a Street Demon: It's the most wonderful carb ever...
You gotta' give these marketing guys credit: They can turn a pile of S into a perceived bar of gold. I guess the people buying this stuff now are too young to remember how bad these carbs were when they came out the first time. And most people have old carbs that are running so badly, and are so far out of tune, that even these new re-issued old bad design carbs run pretty well compared to what some people are running. But they run no better than what they did back in 1964 and 1974, and that was recognized back then to be pretty bad...
The trend in "performance" carburetors absolutely cracks me up. In 1969, if you had a '66 GTO with a Carter AFB, you yanked it off and threw it in the trash can for a Holley or a Q-Jet. Everyone new it was the worst possible performance carb on any car.
In 1974, if you had a ThermoQuad on your Dodge, you ended up with nothing by problems, so you yanked it off, threw it in the trash, and got a Holley. The ThermoQuads only stayed in production for a few years due to problems with reliability, twisting float bowls, and a bad reputation.
Now, Edelbrock is re-making those horrible Carter AFB Carbs and calling them "Performer" carbs. People hail them as the most wonderful street performance carb on the market. Fact is, they run just as bad as the originals...
Now, Holley, under the nameplate Demon, is re-making the ThermoQuad and calling it a Street Demon: It's the most wonderful carb ever...
You gotta' give these marketing guys credit: They can turn a pile of S into a perceived bar of gold. I guess the people buying this stuff now are too young to remember how bad these carbs were when they came out the first time. And most people have old carbs that are running so badly, and are so far out of tune, that even these new re-issued old bad design carbs run pretty well compared to what some people are running. But they run no better than what they did back in 1964 and 1974, and that was recognized back then to be pretty bad...
Lars
Well said. I've felt the same way for so many years ...
Here are the pics of my yesterday install.
Carb works great. The engine pulls great. No stuttering under hard acceleration. The engine comes alive above 3500rpm. A music to the ears at high revs!
The only issue I have is with the vacuum hose that was attached to the front of the rochester and now it is attached to the rear. It's a squeeze because the manifold vacuum is attached there.
An now with the new carb even the brakes are firmer which suggest that I had a vacuum leak with the old carb.
Finally found time to replace the tired Qjet carb with a Street Demon 625 cfm. The install went OK with only a few issues that had nothing to do with the carb. Lets just say as I get older simple things seem to be not so simple anymore.
This was my first time using steel braided fuel lines with AN fittings. I tried it without any special tools and did not have any success so as luck would have it I was smart enough to order the Koul Tools jig which made it simple. With more practice I feel sure I could have done it without the jig but it is so easy and fast this way.
The throttle linkage and kick down cable went on without a hitch.
First drive after the install, it felt like a different car with smooth idle and no hesitation at wide open throttle right out of the box.
Now to install the new Dizzy and reset the timing. Will make sure full advance is in by 2800 rpm.
Here are some pics before and after.
I want to say thanks for all the advice I received on this forum.
First two pics are before the install.
Hi, I am installing a Demon on my 80 C3, and your pics are awesome. What did you do with the hose to the charcoal canister on the top front of the quadrajet, just eliminate it?
Hi, I am installing a Demon on my 80 C3, and your pics are awesome. What did you do with the hose to the charcoal canister on the top front of the quadrajet, just eliminate it?
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Street Demon 625 cfm Installed
