Which carb for a 144 B&M Blower????

Ok guys I came across a old B&M blower for basically free. I sent it to B&M to go through hone/reteflon/seals and bearings. I know NOTHING about blowers and have never ran one so for you guys that know blowers or this particular small one any carb info would help greatly. I have read tons of forums and a bunch of articals and have have so many diffrent ideas of what can work. This will be a around town cruiser not a strip runner. Here is the info on what I have and will be running:::::


B&M 144 Supercharger 6lbs boost pulley
CHEVY 350 10:1 compression, flat top 4valve pistons, the cam has 218 duration on intake, 224 on exhaust at .50 lift
HEADS are double hump heads that have mild porting and 202 intake valves and 1.6 exhaust., steel crank, je rods.
TRANS is a 700R with a B&M shift kit
REAR end is a 9' with posi and 4.56 gears
TIRES on rear are going to be Hurst Cheater slicks 31" tall
SCOOP will be a firberglass surfer scoop


Hope that is everyting you need to help me out.....to get to the question, Which carb do you guys think will work the best????? Just a standard old holley 750 double pumper(which I can pick on the cheap) OR do I need to spend to money on the 750 Holley that is set up with blower reference?? I was told that the one with Blower reference will run better around town and at idle.

On the standard 750 I will have to mess around with the jetting. Once the jetting is dialed in it will run just OK but still not as good as the carb with blower reference. I have also been told just to run the standard 750 Holley becuse the blower is so small and I'm only running about 6lbs of boost it is not going to make a bit of difference which carb I run.

Thanks guys for any further help on a good carb choice!!

Tony

 

I'd go with a smaller 650 with vacuum secondaries and add a secondary metering block with no power valve... That way you can tune the jetting on it as well as the primary jetting..

 

bump^

 

Thanks Dueces.......you think the 750 is too much carb for that small motor and head combo?

Tony

 

Yeah.... Kinda BIG for a street small block.. Get a 650 and play with it.... Your motor will love you for it!!..

 

I built one of these a few years ago. 8.5:1, RV cam. Holley 750. I did everything that Holley specked out for me to do and it worked out great. Call Holley tech line and they will tell you what you need to know. I have built a lot of motors but never one with one of these blowers. I figured I didn't want to reinvent the wheel when Holley has been there done that with these setups. I had a slight carb problem that they told me how to fix it first try and even the part number of what it took. I would have had a week of trial and error work to find the problem had I not called them

 

I run two 650s on my mild street blown 454. I doubt one of them would sufficiently feed a blown 350.

 

Thanks Cryobug.......that's what exactly I did. Holley came up with one of their blower type carbs, MINIMUM 750 double pumper they said and one with blower reference, manual secondaries and manual choke. $540(dammmmn) Wasn't looking a spending that kind of money.

Thanks again

Tony

 

You did mention it was just a street cruiser.. I figured a smaller carb would give you better mileage and better low end torque...

 

Running a sim setup 174 weiand on a 306 sbf this is what worked for me
750 demon mech sec check your power valve.. if like mine vacum reads 8lb at idle i went with the 6.5 powervalve ......jets ..well i put a wideband gauge in the car and dialed in in that way you want the AF to be in the mid to low 11s under full throttle i dont like mine to go much higher than a early 12 AF
this setup has let me drive everywhere better to be a little rich then lean
and post a best so far of 11.7 at 118 leaving the line light MAKE sure your timing is not too much mine is set at 30 full advance unless you have a boost retard this is the safest way 10 to 1 is a little high comp i am 9.58 so in the same boat and run good fuel.. driving 2 hrs to the track i do run 91 oct but never floor it once closer to the track i put in 94 oct and good to go any other help let me know you will love this little blower it really wakes up when set right

 

heres a few pics

 

I think I would try the 750 if I had it. Remember your velocity is being built by the blower, not the pistons pulling the mixture in by vacuum.

Edelbrock suggests setting the carbs up 10% richer than they come out of the box for blowers, I'd figure Holleys could probably use the same thing.
Larry T

 

Well in that case, I'll recomend a 750/vac/sec. with the same mods I mentioned earlier..

 

LOL just like fish in a bowl going diff directions go with mech sec only

 

Thanks guys for all the info and diffrent points of view I do always appreciate the help. Especially on something I know very little about. What I'm leaning towards is the 750 with the mechanical secondaries.....Just don't know if it is worth spending all that money(which I don't have) on the one with blower reference or going with the standard one and messing with it. Some where one one of these forums(can't find of course) someone said I can take a normal 750 double pumper(part number 0-4779c) which I can find use and rebuilt for $200-$300 and do some work on it to convert is to work like a blower reference set up and not spend the money($550) on a holley blower carb(0-80573s). I know its only a 150 to 200 price diffrence but when your on a budget thats a crap load of money.

 

I've been running normal old 4777 650 DP carbs on my blower motor for 20 years...maybe it would be more perfecter if I did the boost reference thing? but it works just fine without it. But it's your money, so I say spend the extra $$$. If it were my money, I wouldn't.

 

I definatly don't want to spend the extra money......

 

How about a Carter carb? No need for boost ref and simple enough to tune that even I can do it. I would start with an out of the box 750 and go from there.

I would DEFINATELY hit your local chassis dyno shop for an afternoon worth of tuneing. Your compression is borderline high for a street engine with iron heads and no blower. 6lbs of boost is only going to create more cyl pressure that will lead to detonation, the biggest thing you want to avoid.

Some dyno time will tell you if you can back off anough timing and flow enough fuel to keep from making big holes in the pistons. Money well spent.

Honestly, if it were me, I would hit ebay for a used set of aluminum heads with a bit bigger combustion chamber. Aluminum heads can live with about a point higher compression than iron. If a 500 dollar set of used aluminum heads with the right chamber cc could get you to say 9:1, you could flog that thing at 6# of boost and never have to worry.

Good luck, -Abone.

 

Call me nuts,but I run an 850. boost referenced,mechanical secondaries. Almost same engine, trans,just different gearing.Got plugs to read correctly throughout rpm range=max of 6K, runs like a striped ass ape(never seen one),idles all day long,don't smoke/load up,overheat..... You can jet accordingly,but when that lung want's some air, only advise is to not bring a bb gun to a gunfight. Depends on what your doing though.
I might be fortunate in my combo though. Pulls about 16-18 in vac at idle w/ a hyd cam just a tick over 1/2' lift.

 

I would think 850 would be good, 930 would be better

 

Or throw any old secondary metering block inplace of the metering plate. You should be able to find one for around $5 or $10 at a swap meet

And truthfully when it really comes down to it a carb really doesnt care all that much what is sucking the air through it, but how much

 

Do a search - there is a link on here to the Holley tech article on updating a carb to boost referenced power valve. I just wonder how you run 10:1 static plus 6 PSI boost on street gas - even if you do bleed some compression off with the cam? E85??

 

I would run 750d/p boost referenced and no smaller .Also because its a small blower does not mean you can get away with a small carby.6lb of boost from a 144 is the same as 6lb of boost from a 871.

 

I ran a 650 Holley on a 355 chevy.. used 62 main/68 secondary (tuning will vary with engine) used a 10 in/hg power valve. I was running 12lbs of boost in s (gasp)'84 camaro
I would watch predentination with 10:1.. that's very high for a boosted engine without forged pistons ..
two points of caution
Make sure fuel delivery is good as it can get.. Lean it out to far and it pop the blower..
And spark needs to as strong as you can get too.. MSD is pretty good for this.

I was running a 6AL and MSD coil

 

Thanks guys for all the info....heads are something I would love to say I have the money for and in the future I will definatly purchase a set. I was hoping to just get the carb and run it how it is until I'm at the point to where I can purchase those bigger heads. For now I'll try and figure out this carb set up and when I get back from vacation get started on the frame for this truck.

Thanks again guys for taking the time to help me out!

Tony

 

Perfect

 

650cfm would be fine on that motor without the blower. 750cfm would be minimum on the street. Boost referenced carb is preferred. That's a bit of compression for a blown street car, as someone else mentioned, maybe grab a different set of heads with bigger chambers to knock down the CR so you can run a decent supply of pressure without worrying about anything.

If you don't have the money to set it up properly, wait and get the parts you need over time when funds allow. Cutting corners with a forced induction system will only lead to more money to fix the damage.

 

Will this thing work on a 390 Fe Ford

 

My questions are:

1) How much cfm's of air are being pumped to the engine when the blower (this one in particular) is making 6 lbs.

2) Boost referenced?---'splain.

3) Does a smaller blower like the 144 put as much strain on the crank nose as say a 6-71?

 

6 lbs is about half of atmospheric pressure, so you're using about 50% more air, so at high rpm you'd probably need 900 cfm or so. This is a really rough guess.

Boost reference is where you connect the vacuum source for the carb's power enrichment system ( metering rods or power valve) to the manifold, instead of above the blower. This prevents the engine running too lean under certain conditions. I've never bothered on my blown 454, and I've got over 100k miles out of a set of pistons...so it may or may not be necessary. (I do have a wideband O2 sensor, and while the numbers are interesting, they're not scary, it is always sufficiently rich under full throttle conditions)

Strain on the crank....hmmm....I doubt it's as bad as a 6-71, I haven't heard of too many problems with the small blowers losing dampers