Discussion in 'High Tech for Old Iron' started by sailbrd, Sep 24, 2010.
changed gap from 0.038" to 0.030".
It seems to idle better.
Plan on taking it on a drive Sunday.
I read a quote from a guy on a boosted mustang forum where he said " I never lost any mileage or power from gapping my plugs really small" and he was down to .025.... Running 24 PSI with a blow through..
It is running good now but.............
Anyone have any issues with their blow through carburator?
I have the Quick Fuel 750-BAN model.
Mine is leaking gas out the secondary shaft.
I took the carburator off and found the six main body screws a little loose.
After I tighten them, It only leaks if you move the secondary shaft when the engine is not running.
It is only one year old.
Anyone have an idea???????????
I'll tell how I found it.........Being a little concerned about the miles per gallon (I know !!!!!!!!) but I ran out of gas unexpectally. I got to looking.
Just got off the phone with Quick Fuel. The tech on the phone said it was normal for it to leak when the engine is not running :eek2: .
He explaned that with it running pressure inside it will cause it to seal up.
i run a csu 750 4150hp blow thru. no issue and would spend the extra cash for another one of thier carbs. one thing is i think they oring thier shafts.. i thought i read that somwhere..
401 turbo nailhead
The tech said the the shafts were not o-ringed, but had some kind of special teflon ring that spread when pressure is supplied inside of the carburator and then seal it.
He said if it was o-ringed, it would lock up the shaft
Why would there be fuel there with the engine not running??
I guess maybe normally there is not. I was looking for any leak and found that if I moved the secondary shaft, gas leaked out and down the base plate.
Not something I would do or see with the engine running (just moving the secondary shaft).
Was starting to have a problem when the boost got uo to about eight pounds.
It was starting to back fire though the carburator.
Even called Bobb Makley to see if he thought it was intake valve springs getting weak.
Turn out the the spark plugs were getting "open" to much.
I had them set at 0.038 inch and moved them to 0.030 inch. It made a big difference.
Now I "only" need to let it run about 30 seconds when I first start it up for it to run on it own instead of over a full two minuets.
Thanks for sharing. I think I have mine at .035, will knock them down to .030 and see if there is any difference.
I put a fuel guage out on the hood so I came watch the pressure and it turns out that the fuel pressure is not climing with the the boost.
I currently have a Mallory 4309 regulator that is hooked up directly to the carb hat so it should be getting the full boost signal.
Is there some way I can fix this or should I just get a new regulator?
Thinking of getting the Automotive 13301 regulator to match the fuel pump I installed last spring.
Just for info I have always run a fuel pressure gauge and get really good response on fuel pressure. I use a Robbmc regulator. http://www.robbmcperformance.com/ Setup is -8AN to the regulator and -10AN back to tank.
The Mallory regulator looks a bit small with 3/8 in and out.
I thought it looked a bit small also, but it did have the boost port. I thought it did it's job until I put the fuel pressure guage where I could see it.
Have an Automotive (13301) on the way and I will post any difference.
The Aeromotive regulator is here. The main part looks to be about the same size as the mallory, but the referance part appears to be much bigger.
Took the car out on the main road where I can open it up and saw that the fuel pressure guage only got up to nine pounds at 6000 RPMs.
Will change out the regulator this weekend and make another trip.
First took the Mallory 4309 regulator off and took it apart next to the Automotive 13301 to see the difference in the two.
Now I can see why it (the 4309 Mallory) did not raise with boost pressure.
The difference in the size of the chambers and springs are enough in my guess.
Just with it running in park the fuel pressure will change reving it up.
The regulator is ok for being a by pass regulator for a street car and that is it.
That is not good. Mine idles at 9 pounds, touch the gas ant the pressure jumps.
Took the car around the block. And now it is a different car. I thought it was pretty fast before, but now...................
Touch the trottle and the fuel pressure changes.
The fuel pressure guage goes up to 14 plus pounds with the boost.
Doug what regulator and What size/type line do you have going to your regulator boost reference?
Made two changes. The regulator and changed the rear springs.
Not being ready I think I hurt my neck a little. :grin:
I use a Robbmc regulator. Just use 1/8th(?small?) vacuumn hose from the carb hat.
1/8" That is bigger than #3 an line (3/16"), but smaller than #4 an line (1/4").
I put a #4 stainless braided line from the hat to the regulator. I had a rubber line/hose, but thought it would give with the pressure. That is the reason I went with braided line.
I will make a new video and put it on U-tube in a couple of days.
Not sure what size would be more responsive though.
New fuel regulator.....................