new engine combo, no blower boost
 

finally got my checkmate in the water with new engine package, 454 1/4 stroke=482 ported 781 heads, KB blower pistons, comp blower cam (114 centerline) full headers, flowed blower 850 carb, weiand 177 blower, engine runs fine but produces no boost ?? new gaffric vacume/boost gauge, shows about 18 vac @ idle, goes to 0 under load, but no boost. we took the line off shot a little air in it shot right up..running a 3.50 upper and 7.0 lower pulley set, which according to weiand should make 4 lbs ? any idea's ?? thanks Rob

Is the blower new?

Not the ideal blower for close to 500 cid. To get it to put out you have to turn it so fastthat it produces a ton of heat, which is real detrimental to making power. If it's worn or scored, you're just not going to be able to overdrive it fast enough.

While you're at it, not enough carb either.

dumb ? is your point of ref. for gage is under blower ? new a 177 an a stock 502 would be about 3.3 with your 2.0-1 drive 5.2 an a stock 454 with your eng mods you may need to step up in ratio check with you builder and see what boost he wants you to run I run 2.44-1 on my 472 bbc and get 8lb boost

3.50 upper pulley? That is your problem. You have a large CI engine for that blower anyway. Put on an 2.85" upper pulley. Just for reference my engine (525 SC /intercooled) has a 2.85 and I see 6.5 psi below the chiller @WOT.

the boost taken at manifold, according to weiand, the blower size and carb are fine to 5500 on up to a 502, but I was thinking pulley size as well, just seeing if anybody had run a simular set up..thanks Rob

My setup is very similar. 469cid, 1050 dominators, 177, rect port edel heads, livorsi boost/pressure gage, etc. I started with a 3.74" upper pulley (7" lower) and was getting 3.3psi. Moved to a 3.5 pulley and the gage reads 5psi but the calculation says it should be about 4.8psi. Picked up 8mph. Something is wrong somewhere with you getting no boost. After a run with no boost stop and feel the blower pulley for excess heat to see if maybe the belt is slipping. Also I would think about that carb and the ventilation in your engine room. You need a lot of air in to get air out although I would not think an 850 would be that restrictive. Just a thought.

I have 2 small pulleys 2.85" I think that I would sell if you come to need some. They are the type with the splined bore. I switched out my blower input shalves to keyed so I could more readily change pulleys.

BT :cool:

I switched out my input shaft to the keyed style also. The only splined shaft units are the OEM Merc blowers, which makes pulleys hard to find. I also did not like the way the splines engaged, seemed prone to failure. I ended up with 2 splined pulleys before I gave up on them.

You really, really need a larger supercharger. If the supercharger is turning internally, and your getting enough air into the hatch, and your boost gauge is not kinked, or reads 0 when key is off, then you need more airflow from the sc, via a pulley or larger sc.

What cam are you using?

My 525SC is 60 over (468), with SRP flat tops, 088 heads, comp hyd flat tappet #11-404-4 (232/237, .547/.547, 114 LSA), stock 177 blower with 2:1 ration gives me 5psi boost.
This combo pulls 400rpm more than my HP500 carb with the same prop.