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Hey Guys, Happy Fathers Day! Trying to tune my Holley 850 to my blower. Dean Nickerson blower referenced it for me. Last year I had a problem with my oil getting dark and carbon on the swim platform. No matter what I tried,(pv,jetting) I couldn't get rid of it. Took it to Dean, Changed the air bleeds and opened things up a bit to a 900cfm and fixed my problems. Now with the addition of the blower its a bit sloppy in gear up to 3200 then clears out and runs fine. Think I have a lean miss. Plugs look good. In neutral no issues at all. Also have carbon all over the swim platform again. Is happening more so on the secondaries so I jetted down from 88 to 87 and still the same.Talked to Nickerson and was told to keep playing with the jets.
The motor had a vac of about 9 inch lbs in gear before the blower. I did notice a 4.5 pv on the rear block. I checked the vac on the carb and I was getting 10 to 15 (blower surge)in the drive way flushing the motor. Any Ideas? Is there such a thing as blower p/v versus standard?
Motor seems to have plenty of power. Turning a 24 3 blade to 5700 and getting 72 mph. Need a bigger prop to drop some r's

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I know the carb was referenced internally. There is no hook up for vac from the out side of the housing for the power valve.

MILD THUNDER

iTrader: (3)

Only way for the Power valve to be "manifold" referenced that I am aware of, is to have a separate vacuum line connected to the intake manifold. Otherwise how will the power valve get it's manifold signal. Also, not sure what you mean when you say its "happening more on the secondaries". The secondaries really shouldn't be opening below 3000rpm unless you have a 1:1 linkage.

Lets start from the beginning.

What engine do you have?

What Supercharger?

What carb?

nonstop

Its a 496 stroker that I built last year. Gen V block. Scat Steel crank. Scat rods, Forged piston 8:5, Crane cam 571/556 with a 114 Hyd, Harlin Sharp rockers, Upgraded springs and push rods, 502 marine rect port heads, B&M 174 blower with Supper chiller, water pump cross over tube, Holley 850 d/p done my Nickerson. Now is about a 900 cfm. Eddie Marine oil cooler.
As far as I have been able to come across Dean is one of the only ones to figure out how to internally boost reference a holley. I had the carb apart and there is alot of internal work done to them.
When I mentioned the secondaries I meant from 3200 and up. I did some more tuning with the idle mixture screws (4 corner) and have just about eliminated the blower surge. I am about 1/2 to 3/4 turn on all 4. The spark plugs look great. All the carbon on the swim platform is driving me nuts along with the oil getting dirty/dark again. Where would you go with jetting on this set up? the boat is 3400lbs. Thanks Mild.....

nonstop

Ok, So after some carb tuning yesterday ran the boat tonight and hit 77.2 on gps at 5900/6000 rpm/, thats with a 24/3 blade. Still having issue with secondaries(soot on swim platform). Talked to the boys at BDS and I need a bigger carnb. At 6lbs of boost pulling fuel from base plate. 850/900 can't give enough air. Need to try a 1050 Dom (boost referenced).
If anyone has any leads please let me know. My best guess with current set up and a 27 I should hit 80ish!!!! Man, Am I having fun!!!!!!!!!!!!!!!!!!!!!!!!!!
P.S. Plugs look good on primary83/84.

Don Johnson

Couple of initial thoughts;

1. That is a pretty small blower for that motor and I am guessing the blower is pretty much done by 5,000 RPM on that big inch motor
2. What timing are you running? I assume iron heads with a chiller you should be able to run 32 total on 91 octane. You might consider locking out the distributor and run 32 degrees which will make the motor more responsive in the low end.
3. Agree carb is too small but so is blower. If you do not want to invest in bigger blower and carbs put a bigger prop on it and slow the motor down. I bet it helps, right now at 6,000 RPM the blower is pulling so hard on the carb it is going rich.

MILD THUNDER

iTrader: (3)

Couldn't agree more.

nonstop

Thanks for the in-put guys. Stops pulling at 57 to 5800 rpm. The heads are cast iron. I'm running thunder bolt 4 ign with a v6 module. total is 28. This same motor struggled last year to hit 62 with out the blower. I know the blower is small but I'm REALLY happy with the gains so far. With the right prop, 80ish? That's alot of gain for such a small blower, don't you think? I have never had a blower motor so if I seem more enthusiastic then I should be its because I didn't know I would pick up 15 mph.(so far) Im not sure how much hp gain this works to but I think I picked up 175 to 200 with all the mods. (exhaust, cross over, rocker arms, blower and chiller)
I talked to Dean today and he said my carb IS flowing better then 1000 cfm with all the work he has done. I am going to go down one more jet size in the rear and see how it runs.

MILD THUNDER

iTrader: (3)

Let me ask, what exact size bottom pulley and what size top pulley do you have on it right now?

I wouldn't jet down too much. That tiny blower and 28* of timing has to be close to making those pistons glow red.

Boxer

The only way to tune the engine properly is with an air fuel ratio meter. I would lock in the dist. at 30 degrees, and tune the carb to 11.8 to12 with 93 octane fuel at WOT. You are only guessing without a guage. Good luck.