bajah2x105

I'm getting tired of screwing with the fuel system on my stageII efi kit. I'm running 42lb injectors and the Aeromotive pump seems to be running out of steam along with the injector size. I'm looking into going with a carb box with this blower and wondered what I will need to complete this task along with the worry of keeping it reliable. I have a 502 with cam and head work done. I think an 850 mighty demon would work well for this combo running 7-9lbs of boost. I will be using the intercooler with the box along with the same Aeromotive pump. The only mod for that would be using a carb regulator from Aeromotive for lower fuel pressure along with my return line from the EFI.

Here are some of my questions-
1)What parts do I need from a carb marine motor?
2)What kind of tuning problems come with using a blow through setup like this?
3)What should the base fuel pressure be?
4)Single or dual plane intake?
5)Boost reference from carb box or intake?
6)Is this the way to go for more power vs. big money for more EFI stuff?
7)Am I on the correct path with what I listed above?

Sorry for all the questions!

blown formula

Been there!!
#1....buy the carb direct from Dean Nickerson Performance. He completely flow matches all the venturi & reworks all the air bleeds & fuel metering. There will be no black transoms then!! Worth every penny & will start like it was EFI!! He will run YOUR carb on his engine in the shop & set it up after all machining is done. I only had to adjust the idle 100 rpm. everything else was perfect!
#2.... boost reference off the carb (blow) box not the intake.
#3. single plane or DART intake is best (my .02)
#4. about base pressure of 7.5# is good.
#5.....a blower box, elbows & tubing, clamps, etc.

I really like the carb situation better than the EFI that I currently have. Not near as much worry about EGT, etc.
Best of luck!!

bajah2x105

Mr. BF, That sounds like a plan since the cam I'm running is from Nickerson also. His shop is about 45min. from my house. You really like the carb stuff eh? Did you get more power from switching over? Thanks!

Turbojack

blown formula

#2.... boost reference off the carb (blow) box not the intake.

I am assumming you are talking about referencing the fuel regulator? Am I right?

bajah2x105

Good point Turbojack Use the box for the regulator? Does this hold true for the boost gauge too or does that go to the manifold?

mcollinstn

Mount regulator after pump, after fuel cooler, after any other junk you run the fuel line thru (Floscan, etc..). Plumb the boost port of the regulator to the carb box (you want the regulator to raise the pressure to match the box pressure). Take your fuel pressure reading from a spot as close to the box as you can (I plan to take fuel pressure from a "tee" in the line between bowl linlets and run the pressure line to a fitting on the rear of the box, where I plan to take the reading).

Does anybody know of a doohickey that you can screw to the pressure line that has some sort of diaphragm in it to keep the fuel out of the line to a mechanical gauge? I'm uneasy about running a line to a gauge that, if it leaks, will spew fuel around. The alternative is an electric gauge, but they are never as accurate... hmmm.

mcollinstn

Boost gauge plumb to to the intake.

CheckmateF1

[QUOTE]Originally posted by blown formula
[B] Been there!!
#1....buy the carb direct from Dean Nickerson Performance. He completely flow matches all the venturi & reworks all the air bleeds & fuel metering. There will be no black transoms then!! Worth every penny & will start like it was EFI!! He will run YOUR carb on his engine in the shop & set it up after all machining is done. I only had to adjust the idle 100 rpm. everything else was perfect![QUOTE]



I agree on the Nickerson carb. I have a Nickerson 850/980cfm that was on my boat when I bought it 3 years ago, sold it to a friend, then recently bought it back. It was dirty and had been abused since I sold it. Got it back, called Nickerson(talked to Brad) and they told me what to run for jets, PV's and idle screw settings for my new motor. I cleaned it, put new gaskets on it and it works perfectly!! They know they're chit!!

Eric

bajah2x105

I just got back from a friends garage and his buddy Vince was there with his nasty fuel injected D3R blown Pat Musi 498 Camaro. I told him about this switch to carb and it turns out he used to run a carb setup at 13psi with a hat, not the box. He told me the main reason for the box is because the hat will only hold about 15psi before it blows the seal at the hat and the carb. He also said to use special floats in the bowls due to the pressure coming from the top of the carb vs. the whole carb(including bowles) being pressurized. The reason this sounds like a good idea is mainly the cost($500 less) and the fact that carb access may be easier with a hat. Does this sound right to you guys also? I should be safe with 10psi max eh? Any other reason that the box is better than the hat? Thanks.

cobra marty

The hat is not marine/ coast guard approved. The pressure will blow air and fuel out the throttle shafts and onto your hot enclosed motor. Car craft and hot rod this month had 2 articles on carb blow thrus with the ? mighty demon carb. Impressive results.