COMET CENTRAL

poboyjo65 wrote:I agree with Roy. I have a street driven 347. it ran good with a 600 edelbrock, but I needed the 600 to put on a 302 so I put a 650 edelbrock on the 347 & does good with it too. to me, it seems like mechanical secondary's would drink more gas on the street. Your going to have to fine tune what ever you use,,,so I would dial in what you have for the street ,,,, maybe get a big one for the track later on.

I think that is a myth that mechanical secondaries use more fuel, the fact is it take x amount of fuel to make x amount of hp. I had a 750 on my gto and got 21.5 mpg on the highway, I did have freeway gears in it but I have also run a bunch of quadra toilets and they never did any better on fuel.

My 2 cents

Ant

CALIFORNIA CALIENTE wrote:Anthony;it is your car to do as you wish! I still feel for a street combo a 750,mechanical secondary is too much carburator!! This is just my opinion based on my experience with 347s!! Good Luck , ROY.

Roy,

I did job mean to start such a big debate! I truly respect your input! I have run the car with the 750 demon and also the 650 Holley and have to say the overall manners of the 750 were better. I'm going to try to adjust the accelerator pump on the 650 if that does not work to my liking then I've got a couple things to try on the demon. I did call them today and their tech suggested that I try a 45 power valve, he thinks that maybe causing all my issues. I think it's a long shot but a power valve is cheap and easy to try. I'm just not ready to fork over another 650.00 yet. I'm sure with enough time and the right guy either carb could be made to run good.

Ant

How much vacuum are you pulling at idle?

Rocket989 wrote:How much vacuum are you pulling at idle?

10ish

Can't hurt to try a 4.5 then! And hey, if we all agreed ALL the time...it'd be pretty boring!!!

JH

Ant said: "Quadra Toilets"!

I gotta use that one on my Pontiac buddy!

Joe

I always heard called "Quadra Junk". Hate to admit it but if you understand them and set them up right they do actually work pretty well. I have experimented with them and had one work well for me. Of course it wasn't on a ford.
Ron

Comechero65 wrote:I always heard called "Quadra Junk". Hate to admit it but if you understand them and set them up right they do actually work pretty well. I have experimented with them and had one work well for me. Of course it wasn't on a ford.
Ron

They actually are a great carb they have a few things that need addressed, like epoxy the bottom side of the float bowl where the plugs are they like to leak and will drain a float bowl overnight. And they have a small float bowl so a high volume pump is a must for any performance use, we had a 71 Pontiac t37 with a 455 ho in it that ran 11.72 in super stock with a q jet on it. So they work but NOT on a Ford though I have seen that done!

Ant

Comechero65 wrote:I always heard called "Quadra Junk". Hate to admit it but if you understand them and set them up right they do actually work pretty well. I have experimented with them and had one work well for me. Of course it wasn't on a ford.
Ron

SAME here,tore 1 apart and cleaned it,put back together and had a couple of small parts left over,it went on an uncle's big GM product,,after uncle left,I put those parts in a sheet of paper and wrapped and taped them up,carried it in my shirt pocket for a few weeks,,,waited on uncle to call me and complain,instead he called me and said the damn thing ran better then it had in years,,,I thru the parts away and never touched another one,,,,,,pop

popscomet wrote:

Comechero65 wrote:I always heard called "Quadra Junk". Hate to admit it but if you understand them and set them up right they do actually work pretty well. I have experimented with them and had one work well for me. Of course it wasn't on a ford.
Ron

SAME here,tore 1 apart and cleaned it,put back together and had a couple of small parts left over,it went on an uncle's big GM product,,after uncle left,I put those parts in a sheet of paper and wrapped and taped them up,carried it in my shirt pocket for a few weeks,,,waited on uncle to call me and complain,instead he called me and said the damn thing ran better then it had in years,,,I thru the parts away and never touched another one,,,,,,pop

Pop great story as always! Dad made a fortune rebuilding them in the 70's he kept all the parts in Stock for them.

Here's and interesting tidbit the first production car to get the qjet was the 66 pontiac ohc 6 sprint and they were a 750 cfm! In fact from what I have read they never made one smaller the that! I had a 74 gto they also had the 750 on a 7..8:1 compression 350 pontiac that made a huge 210 hp!

Ant

And they were vacuum secondary equipped!!! ROY.

Mine was on a 454 in a motorhome i used to own. I installed an o2 meter on it. And since the engine was next to me I left the cover off, stuck a coffee stirring stick with a flag in it down the tube on top of the power valve so i could watch the valve while driving. By watching the o2 monitor and the power valve I could see what it was doing. Played around with different needles and jets and setting up the power valve. I had that thing running like a clock. I could run all day and the only thing that passed me were greyhound busses. Even the trucks couldn't keep up with me and they used to run pretty darned fast. And for a heavy vehicle it climbed hills better than most trucks of the same weight. I averaged 8-9 mpg after the changes. It would only do 4-5 mpg when I first got it. It was a dog when I first got it.
Ron

I don't really know squat about Q-Jets but I didn't think they were vac. sec. carbs?

My memory is vague on the Q-jet but I don't remember them having vacuum operated secondaries. Pretty sure they were mechanical. I still have one so will have to take another look. don't know why I still have it though. will never use it again.

For those that don't know there were some SBF engines that had an intake that fit the Q-jet carb back in the 70's. I think they were on ford vans but that's only vague info. So there were intake manifolds made for the Q-jet to fit a ford engine. Probably rare and hard to find these days if a person were so inclined to want to use one. I wouldn't!!
Ron

Rocket989 wrote:I don't really know squat about Q-Jets but I didn't think they were vac. sec. carbs?

the throttle plate open mechanically but the upper flaps were pulled open by engine vacuum, there is a small spring on the passenger side of the top plate that controls how much vacuum it take to pull them open. set to loose and you get a nice bog then they scream, to tight and they don't open all the way. most left the factory not opening all the way.

as for using one on a ford why? even all the high hp GM stuff came with Holleys for a reason.

Ant