quick fuel q 750

[wrench87]

I purchased a quick fuel q 750 for my 445 fe, i was wondering if it will be ok out of the box for my first start up?. i will eventullay have it dynoed but wanted to know if i could do better then with the following

1) primary jet 74
2) sec jet 84
3) idle air bleed 73/73
4) hi speed bleed 33/33
5) pri nozzle 31
6) sec nozzle 31
7) needle and seat 110
8) power valve 4.5

my engine is for the street 10.0 comp ratio stage 1 keith craft edelbrock heads 2.09 and 1.6 valves, performer rpm intake port matched, comp cam hydraulic roller .598-.617 lift 230-238 duration at .050 112 lobe sep
msd 6al box msd dis 13 degrees initial timing 38 total timing

[FWB]

hard to guess at this point, my seat of the pants tells me the secondary will be a little fat at 84, and that cam may produce more vacuum than a 4.5 may like. i would have a 5.5 PV and 78 thru 83 jets on hand. the jets can wait but you may have some off idle and stumble issues with the wrong PV

[Clois Harlan]

I think you will be ok as long as you don't rev it up to 4000 rpm's but I am sure there are others that know more. I dyno'd my FE 427 with a 750 mechanical holley w/ a 4.5 pv. I am running a much higher lift cam and a torquer intake EB Heads with about 11 : 1 compression. I did switch to a 850 holley to max out my hp and power band. Next build I will dial everything back a bit but I will keep my solid lifters and roller rockers.

Clois Harlan


Clois

[FWB]

what you may not be figuring is the Quick fuel metering blocks also have screw in emulsion orifices, these also will have to be tweeked, i believe there are 3 to play with, which also come into play with the idle and WOT fuel metering. they will go hand in hand with the air bleeds in the airhorn

[wrench87]

it is hard to tell what the vacuum will be until you start it, i have e mailed quick fuel a few times never received a response. i was hoping some one had a similar set up so i could get a better set up until i am able to get it dynoed.
i dont think the 4.5 power valve is right . i am planning on dropping the engine in tommorrow so it will be a while before i start it i am converting from a small block efi, have to wait to see where i can ,mount the msd box and fuel regulator.

[Dwight]

Call Keith Craft and ask and then call Quick Fuel and ask.



Coach did this last week for a Quick Fuel on a 408 that had been dyno'ed, 530 hp 540 tq. Keith and Quick Fuel told him the same sizes to start with.

But Mike was getting 6 to 7 mpg. And the car ran great! It did run a little rich at idle. He called us and set up a day he could drive up and let Coach check the carb. Coach is our carb guy.

On the 130 mile trip to Coach's shop he got 8.4 mpg. A lot of interstate hiway cruising. After changing the jets, and I don't know what size to what size, but I do remember he jetted everything down 4 to 6 sizes.

On the 130 mile trip home Mike got 13.5 mpg. And it still ran great.
What we learned was just because they dyno' it for max hp does not mean they tune it for street driving. They don't know what exhaust system you will use nor the air cleaner.

Dwight

[Gaz64]

I would have gone for an 850 for your engine, I fitted a QFT 750 to my mates 355, runs perfect straight out of the box.
Wideband O2 sensor readings smooth and consistent, A/F ratio through the power band at 12.8, cruising 14:1.
Might drop both sides by one jet size.

[wrench87]

i emailed keith craft got a generic answer that the quick fuels are good out of the box?, i bought mine from mike forte it was not set up for any thing.

i went back and forth on the 750 and 850 talked to a guy with a ford 460 in a cobra went 850 said it was to much carb for the street, talked to another guy with a 445 in a cobra same thing bought a 850 got it dynoed wished he would of bought a 750. the guy with the 460 did switch and likes it better.

e mailed quick fuel 3 times no response?

guess i should of bought a pro systems carb.

[FWB]

i have never emailed quick fuel, i always just call, and i have always gotten a body to talk to........and a answer that helped...

[PurpleVenom]

I've been out on vacation, so didn't have time to get you the specs on mine yet. Will get those to you soon. You will be happy with it out of the box. The dyno will tell you what you need to dial it in for more power. Same as above, I've just always called them and gotten a response. Will get back to you soon...

Tim

[Varmit]

Patrick at Quick Fuel has always been very very quick to respond to any inquiries I had on my set up

[COACH MIKE]

In response to your question concerning the Quick Fuel carb on your Keith Craft engine. I recently "tuned up" a friend of mine's Quick Fuel 780 on his 408 storker. I also have a Keith Craft 408 stroker. I checked the vacuum at idle, adjusted the idle air mixture jet screws on the primary metering block. I first closed them completely and unscrewed them 1 and 1/2 turns as a base start.
Once the engine was warm the screws were adjusted in (clockwise) 1/4 turn at a time, each side. Once the vacuum began to drop I then turned the screws out until the vacuum came up as high as possible and leveled out. Once I determined this vacuum at idle (12.5) I divided it by 2 to determing the power valve size (6.5). I then removed the front bowl and checked the jets. I found them to be too large and reduced them from the 74's they came with to 71's. The secondary's were 86 and I reduced them to 80's. The reason I made such a large scale adjustment (most carb guys will tell you to drop or add two sizes at a time) was the size of the jets in my 408 which was about the same identical engine. I had 68's in my primary's and 80's in the secondary's. I did nothing with the air bleeds. Those are probably the least of your worries. I also checked the accelerator pump. There should be
.015 between the pump arm when fully pressed and the accelerator cam arm when fully open.
I have found that engine dyno's are set up to get the most power out of the engine with no restrictions at the carb and little back pressure on the exhaust end. Depending on what type of air cleaner and exhaust set up you have, the size of the jets could have a considerable effect on performance.
Hope this helps
Da Coach

[Barry_R]

You cannot just pull a jet number out of the air. Depending upon the emulsion and air bleeds in the fuel package you can have the "right" mixture with jets that are 10 numbers apart in different carbs.

I have run a lot of Quick Fuel carbs on the dyno mostly right out of the box to start. Once you get a handle on wide open throttle mixture (often a couple jets leaner based on experience) you can start tuning on the power valve channel restriction versus primary main jet relationship. Leaner main jetting can sharpen throttle response and improve cruise mileage when coupled with larger power valve channel restrictions to maintain wide open throttle mixure.