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.

I talked to weiand also, they were concerned about my flame arrester, which is a 8"x2" eddie marine s/s, the carb sitting in a open scoop with good airflow, when running did not have back seat in so blower drive was right there open, no sign of belt slip, and almost no whine from the blower either..Rob

The guys are right - that blowers really really small.

As a point of reference a B&M 250 was still to small on my 383.

Even if you get boost out of it the intake air will be so hot as to bring on detonation. spin it any faster and youll start chuffing air and slipping as that setup usually uses a ribbed vs cogged belt.

DO yourself a favor and step up the blower to lysholm/whipple type deal-or at the very minimum a 6-71 - Youll be a lot happier.


Uncle Dave

Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwod nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan

The blower is small, but he should still be seeing some boost. He should be seeing 3-4lbs.

A stock 525SC uses a 2:1 overdriven ratio on 454ci and makes 5.5# of boost.

That blower should be whining a LOT at WOT. My guess is the rotors are bad in the blower.

That would be my guess also. It should show some small amount of boost.

call nickerson perf. about carb. size even a holley tech. when given all the info will say you need a larger cfm also look at at there websit under catalogs and look at there charts for blower ratios on stock marine eng. and I think you will find your answers even if your blower is in great cond. you need to change pulleys

Given hes reading vacuum Its likely not the gauge. with a small pulley it should give him at least 4 pounds but it will sound like a million bees inside the hatch.

Nickerson can help -(they did my original carb) he's is undercarbed but not drastcially- although the stock carb has a lousy signal at medium to low openings a demon would wake it up in the midrange.

He could likely need a teflon seal replacement. - pretty sure that blower uses them, and while its off the top- at minimum put an intercooler in there, or buy a biggerblower.

Uncle Dave

Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwood nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan

Spinning a blower at 2x + overdrive is certainly one way to shorten the life.

On 500 cid, an 8-71 running at about 0.94 under should be ideal. Little added heat and still enough rotor speed to prevent loss of atomization. Use a set of Holley 750 blower carbs with boost referencing.

No question a larger blower would be better. But $$$$.

The 177 was designed to be spun that fast. It has a recommended max rpm is around 13000rpms. The problem with spinning it faster is the heat it creates.

IMO, a larger carb would be better, but a friend of mine runs an 850 on his 454 with a 177 and it makes good power and boost.

my 177 did not have teflon but I had the blower shop machine and install in both also the chillers were a real heat reducer and yes they do make a lot of noise at WOT but worth it given the smile on my face

Ordered a 2.66 pulley today, will give that a shot see where it ends up..the carb is a highly modifyed 850dp flowed, 4 corner idle, boost referenced, have talked to holley/weiand and they say the combo shoulr be fine..not going to make the power of a 8.71 but it's all about $$$ may work out may not...have friend who runs the same boat, std 454, same blower, 800 spead bore carb(I know..junk) with no hole in the hatch and the boat runs mid 70's on a totally stock engine, except the blower and exhaust....trying to find out his pulley size now...

Your wasting your time with that sc, at best you'll get 100hp and world of heat under the sc so be careful. For a better filter, I found the K&N Extreme, with the element on top made a significant difference over a 10 x 3, let alone a 8 x 2. The element lets the blower suck straghit down instead of trying to get air from the side of the venturis.

belt slip = no boost

don't think I had belt slip, was running with no back seat so the belt/drive was right behind me, no noise from the belt and it's looks fine, I will also try a better filter as well, pulley should be here today and hope to retest this weekend..stay tuned film @ 11 !!!!! Rob

I had a belt slipping on my 525sc once and there was no indication other than boost was down to about half of normal.