454 blower update.
 

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.

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.

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

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.

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?

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

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

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!

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.

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.

I'm not an expert here, but I have run a 454 with a small blower for a while now. What were the exhaust temps? The boost is lower than expected because the heads probably flow well.

Tom what kind of Torque numbers did it make? At what rpm did the Torque start coming alive?

I don't have the numbers in front of me to be exact, but I believe we were 1190-1200 across the board on the last pull.

Yes, the heads flow really well, but the blower was being overdriven about 2:1. It should have made a good bit more even with the big cylinder heads.

630 at 3600 was the peak. The spreadsheet was capturing from 3500-up, but we were well over 600 under 3K. Very flat too.

IMO, that small supercharger is not doing much but building heat spinning that fast and it still can't keep up with the heads along with cam timing mismatch for the setup. Put some timing in it and see if it helps.

Also, there is a reason Merc used a larger supercharger for 600sc.

I know it's not common practice these days but what did the plugs look like? Heat range? Did you ever try 93 and some timing?

It has been suggested that upping the timing some might help (thanks Joe). I might try that when I've got the boat back together in a week or two.

Tom, I certainly think with 2:1 overdrive, and only 5lb of boost range, the blower is severely tired, or something else is wrong, like valvetrain issues. How did the boost look at 3500rpm compared to 5500 rpm?

I can tell you, on my 468's when I had 250 B&M's, that 63% over, netted 5lbs. 80% over, netted 7lbs. 100% over, should have netted 9lbs of boost theoretically. The only reason I can see that blower you have having a 2:1 ratio, is if it was on a big ci engine, or had an intercooler and was running over 7psi in the manifold on a smaller ci .


I can tell you from some testing data I have here from when B&M developed the 250 blower, that increasing overdrive from 60%, to 110%, the manifold temperature at 6000RPM, increased from 140* at 60% over, to 230* at 110% over. Hot air kills power.

If you find no valvetrain issues, or any other issues, and get the blower rebuild back to spec, and make that 5lbs of boost with 60% overdrive, you'll find your horsepower you are missing.

Heres a thread you might like Tom.

http://www.offshoreonly.com/forums/g...0-refresh.html

Joe, no change in boost. Flat at 5 to 5.5. That's why my buddy asked me about where the blower came from.

Exact setup except for cubic inches (his 496) made over 700 HP with a larger pulley. Same heads, 250 B&M, 525 EFI cam, 30 degrees of timing.

Just out of curiosity, how much effort should be used to turnover a 250 by hand? This one is extremely easy to turn. Anyone have a rolling torque spec?

Tom, does the blower get hot after a couple pulls? You would think that with a blower being over driven so much that it would make it easier to get the egt's up... That's what doesn't make sense to me. Unless the blower is so loose it just doesn't make heat.

46 more cubic inches can easily = 60 HP or more.........

Peak tq at 3600 is way low in the way of rpms.

It was warm but nowhere near hot. If I had to guess, maybe 95-100 degrees?

Agreed, but 46 cid doesn't equate to a difference of 125 HP. Also, I agree that peak torque is way off the mark. I was expecting 4200 or so.

A Jim Oddy 468 blown alcohol motor can make in upwards of 1500-1800hp.

Which begs the question, how damn big / worked are these heads ?

And do we know the comb chamber size and where they figured into the actual compression ratio. Some blown bbc's use some pretty damn big combustion chambers.

They were setup to work on an NA 468. Nothing crazy. They were worked over pretty well to work on the 468, but nothing crazy.

Haven't heard that name in a long time. My buddy use to work for him.

With my limited roots blower experience... When you really start spinning them babies they turn into a heat sink and you can hardly put your hand on them.

Tom, can you measure the gap from the rotor strips, to the case, at the bottom of the blower with a feeler gauge, and post the results ? Do it on all 4 strips. You should be looking for around .004-.006 range.

Yep, that was my understanding too. But not hot at all.

Joe, I'll need to get the blower off the engine to check it. I might be able to do it this evening.

How about resistance in turning it? Should it be super easy to turn or offer some resistance?

Tom I think what you have is a intake charge cooler rather than a supercharger.

Yay. A glorified cooling fan. Not.

Generally, they are pretty easy to spin, compared to a 8-71 type of blower. I'd definitly pop the blower off, and check those clearances with a feeler gauge. Check it across front to back of case on all 4 lobe ends. Let us know what you find.

The only way to determine actual air temperatures in the manifold is with a temp probe/gauge. The blower case feeling thing can be misleading.

Couple other things. The 250 blowers mounting setup kinda sucks. Very often, guys would overtorque the 4 bolts holding it on, and distorting the case. The teflon doesnt like that. I've actually torqed the blower down to spec, and felt the binding from the stripping when turning it after mounting. I had to loosen bolts, and tighten them in a fashion where the teflon did not rub the case anymore.

The o-ring that seals the blower to the manifold, sucks. I'd run the gasket RBS sells for them. I've ran both, and the RBS gasket simply seals, the o-rings didntt. B&M actually came out with a tech bulletin at one point, advising customers to stop using the o rings and use the gasket. not sure which one your using, but just thought i'd mention that.

I'm not far from Va Beach, if you don't mind who is / was your engine guy? Just curious as there are not many good ones around here.

I built the engine. Jeff Riddle ran it on his dyno for me.

Joe, you might have it nailed with the o-ring gasket. I was going to replace it, but it got really well so I went with it. Crap. Still shouldn't be falling off at 5500, but that's probably a separate issue.

I did torque the case to the manifold correctly (12 ft lbs).

OH S#it, I better get updating that thread.

The blower in the pics in the thread that Joe referenced basically free wheels, little to no resistance. My other blower has resistance and actually makes a pumping sound when turned over. It's pretty tight and was rebuilt/stripped recently. You can definitely can tell the difference. The Blower Shop had the best pricing on the rebuild kits and the Teflon stripping. Pretty easy to rebuild and can do it in a day if you have the parts and pullers. You would need to remove the front bearings before ordering parts. There is a double or a single row version for the bearing.

http://www.theblowershop.com/store/b...60_63_127.html
http://www.theblowershop.com/store/t...-c-60_103.html

Pm commandersander on here if I'm a liar. I bought the motors from him. And he told me the blowers were brand new beside basically dyno time and made 653hp on 5psi I believe. It pushed my boat to 94.8 on GPS and I literally only ran it for maybe 15 hrs.

Wasn't commandersander outed as a liar selling a new part that wasn't ? Or do I have the wrong guy ?