Blower Boost???

[Drakar]

First, I want to thank everyone who contributes to this forum. I have spent many hours reviewing the posts and have learned a great deal!
I realize that my configuration is very very mild compared to some of the configurations that I have read....but here goes:
Specs:
-1987 Sea Ray - Sorrento 24
-355 GM block (out of a 1985 corvette....reconditioned for marine use)
-forged pistons
-cast iron heads (not the original heads with block) with minimal work
-Comp Cam - Part #12-402-4
-750 Holley Carb (mechanical secondaries)
-B&M 144 PowerCharger
-Original Exhaust System: headers, risers and exhaust thru the y-pipe. I plan on upgrading the system to a "silent choice".....plus changing the headers and risers....
-Gaffrig Boost gauge ( 0-15 PSI ).
-Total timing 32
-93 pump gas
I put the boat in a few weekends ago....and last weekend started tuning the engine. When I started to plane the boost gauge did not indicate any boost?!?! After the boat planes and is around 3,600 RPM's the boost indicates about a pound (1) of boost and stays there at WOT to 4,600RPM's. I'm at a lost.....I figured with the restrictive exhaust I would have seen overstated boost numbers!?!?
I believe the boost should be some where between 4-6 pounds.....
The blower was overhauled by Holley's Supercharger department a few weeks ago. They said that the unit ran within the normal specifications of a new untit. I have a call into them to see if they can provide me some direction.
If anyone has some thoughts with this....I would appreciate all your help!
Thank you!

[Infomaniac]

I have run a few of those blowers. What pulley do you have on it? Also they squall really loud when they are loaded hard.

[DEEZ NUTTS]

Drakar, what kind of speed increase did you get with that motor over stock? Even with 1 lbs. of boost. My neighbor wants to do the same to his sea ray.

[riodog]

Draker, first of all, that's a baby blower so you're not going to see BIG BOOST. If everything is set-up correctly, cam( what are the specs?), timing,etc., then the boost that you should be concerned with will be at WOT. Your cam part # tells us nothing. If the cam has long duration and big overlap, such as would be used with a NA application, then part of your boost could be going out the exhaust. On a mild application your exhaust should not raise the boost reading that much unless there was a large obstruction where it shouldn't be.

[Infomaniac]

He has a good blower cam. 114 lobe seperation.
Drakar 4 or 5 lbs will be the max with the smallest pulley. If you have the smallest pulley it will be about the same diameter as the blower snout. Also those belts slip if the idler is not adjusted properly. As I mentioned before,it will squall really loud if it is working hard.
[This message has been edited by Infomaniac (edited May 23, 2002).]

[Tee]

Drakar
I ran a very similar setup on my previose motor. (144 B&M on 350 merc.) I had the 7" lower and 2.91" upper pulleys. My guage showed 7 to 8 psi boost at WOT. It sounds to me that maybe your belt is not tight enouph. I think I still have the B&M manual for that blower. If you need it I could fax parts of it to you. And as for the squal!!!!!holy crap that is right. It is extreamly loud when the blower is loaded.
I wouldn't recomend running it without thru hull exhaust though.. And it would be hard to diagnose until then also..
Hope this helps---------T

[Drakar]

I spoke to the Holley contact who handled the overhaul of the unit. He mentioned that there is some damage on one of the rotors. The imperfection is the size of a quarter... it is away from the edges (Teflon strips). When they tested the unit it was for air volume flow etc.....however, they do not but the units under a loaded state....to test boost. He was extremely helpful....he is new to his job and is going to get back to me after talking to the individual who actually worked on the unit and after talking to his contacts. Could this be the issue?
I found the following pulley information on Holley's web site:
Automotive Application:
Upper pulley for 350 - 9-10 lbs. boost .....90634
Upper pulley for 350 - 8-9 lbs. boost .....90541
Upper pulley for 350 - 7-8 lbs. boost .....90545
Upper pulley for 350 - 6-7 lbs. boost .....90542
Upper pulley for 350 - 4-5 lbs. boost .....90543
Upper pulley for 350 - 3-4 lbs. boost .....90544
Marine Application
PowerCharger 144 for MerCruiser 350 small block V-8 with a 10-rib drive. Polished finish. 350
4-5# 90543 (3.23" Pulley Diameter)
6-7# 90542 (3.02" Pulley Diameter)
8-9# 90545 (2.86" Pulley Diameter)
I measured my blower pulley it is 3"....the crank pulley I will have to measure this weekend. The part number is 8900209. I tried looking up the part number...but, I believe the part numbers have changed. I have had the blower since 1990....when I purchased it from a mechanic....who upgraded. Not sure when he originally purchased it..... TEE, if you don't mind I would like to take you up on your offer....
DEEZ NUTTS, Unfortunately, I have no bench marks to go by. The boat was setting in a rack for 4 years....and I rescued it from the 'graveyard'! I bought the boat from the Marine without the engine or outdrive......basically an empty hull. I did get some parts....ex. the headers, riser y-pipes....but everything else is new. I purchased a new Bravo 1 and transom assembly.....etc. Once, I get the boost issue resolved.....I will let you know the performance!
Bravo 1 outdrives have a raw water pump which is driven off the crank pulley. I'm running the blower and water pump with the same 6 rib drive belt......I believe this should have nothing to do with the boost issue.....but, figured I better bring it up....just in case.
Infomaniac is correct... the cam's Lobe Separation is 114....here is the rest if it helps:
Intake/ Exhaust
Valve Adjustment Hyd/Hyd
Gross Valve lift .44 / .444
Duration at .006 tappet lift 260 / 268
Open / Close
Valve Timing @ .006 int 20 BTDC / 60 ABDC
Valve Timing @ .006 exh 72 BBDC / 16 ATDC
These specs are for cam installed at 100 intake center line
Duration at .050 212 / 218
Lobe lift .2960 / .2960
Duration at .006 260 / 268
Sorry for the long post.....but, figured the more information the better.....Thanks for all the replies so far!

[Tee]

Drakar,
Send me an E-mail "nasTone@mindspring.com"
I will look when I get home and see if I can find my old manual......T

[Tee]

Drakar,
Haven't found my old manual yet. Couple other places I can look. Will do it this weekend. No play for me this holiday http://free.***boat.net/ubb/frown.gif
Everyone have a good one--------T