Thread: Blower carbs

Tweet

I could not find what I was looking for. Do I have to run a Boost referenced carb(blower carbs). Or is the two 750 DPS GOOD? Do I need to mill the chokes off, or are they fine just being up there?

are they blow thru or are they mounted on top of blower??? blow thru need to be bust referanced or preferrably totally enclosed in a chamber

Originally Posted by jerry clayton

are they blow thru or are they mounted on top of blower??? blow thru need to be bust referanced or preferrably totally enclosed in a chamber

Na, just some 750 dps mounted on top of a 671 in my avitar? Sucking throgh

If they are double pumps then there is no 'boost referancing'; what you might want to do, or be aware of, is that i have best luck making them pig rich at idle. If you have replaceable idle air restrictors then drop them to about a 68 or so, i keep riching the idle circuit until it affects the plugs and lean it from there. Do it like this and you'll be able to go from light to light without engine getting too hot.

So pretty much youd rather have the carbs rich than lean? I am running a freshend up Vertex Mag.

Originally Posted by PRO53

So pretty much youd rather have the carbs rich than lean? I am running a freshend up Vertex Mag.

A lean condition can quickly spell death to a supercharged engine. Very ugly--melted pistons, etc.

Blower motors make a lot of heat, the carbs are your friends and can help you deal with it. I make the idle ckt extra rich, the idle ckt runs constantly so you can cut back on the main jet to compensate for the fat idle, doing that when you are cruising the fuel won't be excessive. Pig rich at idle will let you go from traffic lite to lite and creep in line without overheating.
I set up a '32 with a blown BBC and i've never seen it go over 180 deg.
I do like them blower motors.

i built some blower engines the boost referencing BG carbs /use this but boost psi off the intake base with a line to the carbs . helps with load sensing i played with a set over 10 years ago but all most all blower builds i have used AFB /edebrock . some with holleys and dominators .one predator .as for dumping more fuel we did that on my 548 we made up limit blocks to keep the power rods from going to the thick idle part /off idle part lost idle circuit hard to tell was some time ago. but at the time it was dumping allmost raw fuel out the ex .your eyes would burn never drop the engine temp that much to deal with the burning eyes so i pull it out. at that time we did have EGT on it was fine before trying to cool the engine with more fuel at idle .went thru and did vaccum at the carbs at WOT. when i said we as a freind did the reading why i drove .i played with the timing water speed . went to purple ice a stewart water pump did get were i wanted the temp to be at( somewhat )this way i left the engine were it was happy .i have the AFBS on it jump up on a power rod / for a thinner one when the power rod is down. the 548 been in the chevy now for 9 years with the afb carbs over all i am happy with tune on it and the carbs.i used them on other street blower builds . i drive this car very hard ... like bounce it of 7500chip. its never mist a beat . has GREAT throttle response. i think i still have pistons with tops on them in the engine

you could make any holley boost reference if it has power valve s your not using vaccum to work the power valve in a blower engine . vaccum port is pluged in base plate and boost is used to work the power valve.AFBS work with set up springs and power rods they work good with this set up as soon as the vac drops the power rods go to the thinner part of the rod just have to make sure at W.O.T that your not making vac at the carb base it w.o.t so it will not lean out

So, I can use my 750 dp, if I put in a boost referenced power valve, run the idel jets fat, run alittle lean on top end?

Originally Posted by PRO53

So, I can use my 750 dp, if I put in a boost referenced power valve, run the idel jets fat, run alittle lean on top end?

air bleeds can flatten up idle .yes you can rework you holleys for boost reference or send them there no idle jet on holleys just meter block s you do not lean any engine on top end less you want new pistons

In my humble opinion, for the street this works for me...
Put a vacuum gauge between the blower and carb and make sure the vacuum is not high enough to keep the power valves shut at cruise. (usually only the case under boost)

If it is you need to get the signal for the power valve from below the rotors.

Originally Posted by Yellow72

In my humble opinion, for the street this works for me...
Put a vacuum gauge between the blower and carb and make sure the vacuum is not high enough to keep the power valves shut at cruise. (usually only the case under boost)

If it is you need to get the signal for the power valve from below the rotors.

well you just get a faster response from boost referencing and not reading at the carb base is you not going to see the real vac drop with the blower/vac pump .. but in the reall world for the street abit slower response.. lag... is not going to hurt.as your going to blow the tires off any way you go. as the blower is a big vac pump at idle mine thinks at the base of carbs thinks there on a mild street engine. at intake it making 2.5 inchs of vac race engine. how fast you spinning the blower at idle and how well its seals up would come in to play i haded good luck with the afbs on blowers you can play with power rods and set up springs trying them on a run then pull over and swap them out very fast with out getting in the carbs