TomZ

iTrader: (2)

454, Dart 360 heads (don't judge, they were set up for a 468 alky motor and they were a gift) Bob Madura 525 EFI cam, 8.75:1, 250 blower with a 2.75 upper pulley, twin 850 Nickerson's, and CMI headers.

578 HP on 87 octane at 5500 (and that was on 87 octane because we couldn't get cylinder temps up on 93). Springs might be an issue too (not that bad to deal with... using a 953 Comp spring now which should be fine). A real disappointment.

The blower would only produce 5 to just about 5.5 lbs of boost with the "set to kill" pulley.

First pull after run-in... really fat but definitely doable with the induction. We made four pulls and couldn't get any more out of it. Changed jets and gain 4 HP (on 87). Yes, 4 HP. Might be chasing a valve spring issue too, but I'll play with that going forward (easy enough).

Going to run it because I want my boat in the water. And it's safe and workable right now. Next season, I'm getting the blower rebuilt or putting something bigger on it (I can fit a 420 under the sun pad).

Word to the wise.... With used parts if someone says it did this and that, it probably didn't. The blower is tired. Fortunately, I have a very good guy here locally to rebuild it, but after spending almost $3K on a complete "ready to run" set-up, needless to say I'm a little disappointed. Heck, I was still dealing with the shipping of stuff from the deal just days ago.

TomZ

iTrader: (2)

Just to add... my guy runs more than a few of these builds per year. His thought was that even if it was thrown together and pushed off a cliff it would make 625 HP, then tune from there with a goal of 650, safe tune. His first question after the second pull, "Where did you get that blower?"

We were all scratching our heads.

masi242

that should make the 242 move right along, are you thinking high 70s with this engine.

260Velocity

Hi. I am a new member here at OSO. I have been reading threads for years. Anyway, I just wanted to put my experience in this thread. I had a 509 with 320 pro topline heads with JE 8.5-1 comp and crane hyd roller. I had a 250 charger with no intercooler and small pulley. It made 8-9 pounds at 5200 with a 26 4blade in my260 velocity. Roughly 650. Hp.

JRider

iTrader: (1)

I do not think your supercharger is tired if it does not have strips, really what can get tired? If it does not have strips you need to send it somewhere to get stripped, you should pick up a lb or so just by doing that. One thing you might run into is belt slip with a ribbed belt, doubt you have a gilmer drive, a new belt will help. That will definitely kill your HP.

Also, what is your timing at?

MILD THUNDER

iTrader: (3)

The 250 b&m have strips. The 256 weiand doesn't .

TomZ

iTrader: (2)

I'll be happy with 75 but 78 would be good too!

TomZ

iTrader: (2)

This blower is stripped. Checked the belt during set up and all was good there. I have a brand new belt to try also, but there was nothing wrong with the one that it had.

Timing is at 30 degrees with a V6 module.

One cool thing.... she sounds absolutely bad a$$ at idle!

800XCR

iTrader: (2)

IMO, Pretty big heads for the cubic inches at that compression and not much cam for the rpm range you are at with forced induction and way more carburation than required. More timing probably wouldn't hurt either.

TomZ

iTrader: (2)

I'll agree on the cylinder heads being on the large side, but the blower should help offset that to some degree. Carbs... big but not too big for a roots set up per everything I've been told. The cam should turn 6K in this setup so I'm thinking there might be a spring issue. That cam is supposed to work very well in this set up, and it was falling off a cliff at 5500.