Thread: SB400, Dyer's blower, dual Holley 4160's puzzle, Help!!!

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Hello all, new to the forum and looing forward to participating.
I am primarily a motorcycle guy, but got involved in a customer's hot rod project after a previous mechanic abandoned the project. after months of work wiring, plumbing, interior and exterior finishing, got to the point to start the motor. It strted, ran, then I heard a bad noise... clicking in the cylinders. The previous mechanic left what looks like a small washer in the blower. I pulled off the top end, and found pieces in cylinders 3 and 2. Made the necessary repairs, inspections and re-assembled the top end. While I had the engine apart I checked over the "rebuilt" carburetors and found that the previous mechanic had left them way out of ajustment, 3 floats high one low, Idle air screws all unbalanced, etc. Adjusted everything on them to give me a starting reference setting according to Holley instructions (more on that later).
Now, on starting, the motor will run for about 5-10 seconds, then shut down. Generally, it will restart immediately, occaisionally blows back, then stops again 5-10 seconds later. This is bad, but just as an experiment, I have started it and as it dies, hit the strter again, and it will continue to run for another 5-10 seconds.
I have read that the blower requires more fuel from the carbs, but these seem to be out of the box Holleys, standard size fuel valves, jets, pumpers, etc. no mods to the primary and secondary butterflies. I'm getting 6 psi at the fuel regulator. All of which would lead you to believe that the engine is starving for fuel, but the carbs seem to be overly wet, and the plugs carbonized.
Any suggestions, further questions, anything to help me move in the right direction would be greatly appreciated. Experts help for a newby on this setup, please!!!

6lbs fuel pressure is pretty much where you want to be for Holley carbs. This doesn't sound like a fuel issue, have you checked the ignition for a loose primary connection?
Also chech for vacuum leaks..

Originally Posted by cafenoir

I have read that the blower requires more fuel from the carbs.

The blower doesn't necessarily require more fuel alone, it requires more CFM than a similar naturally-aspirated motor.

Originally Posted by cafenoir

I'm getting 6 psi at the fuel regulator.

Is this a pressure that you have seen on a gauge or are you saying that the regulator is set at 6 psi and you haven't really monitored the fuel pressure at the bowl entry?

Originally Posted by cafenoir

All of which would lead you to believe that the engine is starving for fuel, but the carbs seem to be overly wet, and the plugs carbonized.

None of what you have said would lead me to that assumption. Tee off at the carb inlet(s) and install a mechanical, liquid-filled 0-15 psi fuel pressure gauge. I'm thinkin' that what you're seein' at the regulator ain't what the needle and seat are seein'.

And by the way, what exactly does this mean? " the carbs seem to be overly wet"

.

Originally Posted by cafenoir

as an experiment, I have started it and as it dies, hit the strter again, and it will continue to run for another 5-10 seconds.

This makes me think it is an electrical issue.

Which side of the blower is the drive on??? rotors need to turn outwaeds not inwaeds-----

An engine will fire on static air but if blower is running backwards will die 4 or 5 seconds (or quicker)

Whats the over drive ratio? whats timing set at? static, locked? curve?

Are the carbs boost referenced?? Jerry is dead on, make sure the blower is turmimg the right way, try to get rid of your back fire or blow back at all cost, I knocked the rotors out of phase for a $800 rebuild of my blower several years ago doing just what you are doing. If your blower is fairly "loose" you can start the motor without the belt as a saftey measure to check your timing. Get your cam specs and your info and don't mess around call Holley, they have a great supercharger dept (aka Wieand) Supecharger carbs are generally not off the shelf carbs, not saying that with small modifications off the shelf carbs can't be used, boost referencing Holleys is needed (as far as I am aware of, I run Edelbrocks) as the carbs are always under full vacuum on a blower motor, at idle, part throttle & full throttle due to the vaccum the blower creates. The power valve needs to gets it vacuum signal from below the blower. Therealso is a formula for figuring out what size carbs are needed depending on amount of boost used.

(DxR) divided by 3456 x (B divided by 14.7) + 1 = C

D=Cubic Inches
R = Maximum rpms
B = Maximum boost
C = Maximum CFM required

Keep in mind the blower crams in more fuel & air making the intake charge that of a larger motor, which makes the fuel demands more. Feeding two carbs under boost also needs larger fuel lines as well generally (more volume not pressure) and some carbs need higher flow needle & seats also, I personally would run all that by Holley, get your parts and carbs set as they say then come back on with any questions as the damage done experimenting can get costlly. Best of Luck

Thanks for everyone's help. One major problem with the carbs found: leaking fuel valve on the rear secondary bowl, kept fuel from the primary bowl and the front carb. Also allowed fuel to run down to the cylinders... I'll start by contacting Holley, get their suggestions first. I'll keep you posted.

If your fuel system did not supply the front carb due to a stuck float, you may have a bigger issue. One float stuck does not even come close to both carbs wide open.....