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1150 cfm Dominator on 250 blower

Old 07-30-2006, 04:03 PM
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Default 1150 cfm Dominator on 250 blower

A couple of years ago I purchased for my 38 īCigarette (Merc 425 HP 454 engines) a pair of 250 blowers and two (one for each engine) Holley dominators # 0-9377 following a hint in an old B&M manual.

I modified among others the pistons to CR 8.0:1 and have just installed the blower which should produce 7 pounds of boost at 5500 rpm.

Actual jet size from the carb.box is 94 / 94, power valve acc. to Holley data sheet is not required.

Anyway I would like to install the PV # 125-65 in the primaries & secondaries in order to avoid plug fouling in the lower power range.

I plan to reduce main jets by six numbers and vacuum signal for the pv shall be delivered from the manifold.

Has anybody experience with such a configuration.

Thanks

Joee
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Old 07-30-2006, 07:02 PM
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Default Re: 1150 cfm Dominator on 250 blower

I don't have personal experience in what your doing BUT I would not drop the main jets down to 88's from 95's on a 1150 cfm carb until you have it running and can look at the plugs after a w/o run. You are going to want your afr's in the mid 11's under boost ,if not you may melt the pistons or detonate. If it is rich while running at cruising speed start by leaning primary jets slowly,better yet drill and tap your exhaust manifolds somwhere and install 02 bungs and buy a air fuel ratio meter,this would be accurate and keep you safe,Smitty
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Old 07-30-2006, 07:04 PM
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Default Re: 1150 cfm Dominator on 250 blower

this will help you,just over 300$,a little work but will take guess work out,Smitty
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Old 08-03-2006, 02:36 AM
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Default Re: 1150 cfm Dominator on 250 blower

Itīs a nice device but I assume that there is no sufficient space in the GIL manifold to install the sensor before the cooling water injector.

I was just happy being able to install a 3 mm exhaust gas thermocouple through the manifold flange.

Joee
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Old 08-03-2006, 09:40 AM
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Default Re: 1150 cfm Dominator on 250 blower

We just got my brothers boat on the water last weekend. 468's with B&M 250's and single dominators. He is running low boost.(2-4 lbs) The carbs are not boost referenced. They put 96's in both rears and 94 in the front of one and a 92 in the front of the other. The one with the 92 is close but still fat. The 94 is very fat. We are now going to put 94's in the rear and 92's in the front.

I doubt this helps but maybe.
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Old 08-03-2006, 09:48 AM
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Re: 1150 cfm Dominator on 250 blower

"""""NICKERSON PERFORMANCE IN PA.""""""""""""
Will Build A Carb For Your Application

95% Of There Carbs Are Dead On Out Of The Box Just Set The Idle And Adjust The Floats If Needed ""or"" Keep Fiddling With Jets Till You Meld Down Or Flood Out.

They Reworked My Bg Carb And It Was Dead On

Good Luck

Last edited by Badtoon; 08-03-2006 at 09:52 AM.
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Old 08-03-2006, 10:46 AM
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Default Re: 1150 cfm Dominator on 250 blower

I agree with Badtoon.

What was wrong with the original Dominators ? More than enough carb.

===================

BTW: Most Domiators have such a large power valve channel restriction that a regular PV will become the restriction itself.

Holley has high flow PV's for these cases. They are about twice in price also. Usually around $14-$16 each.
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Old 08-03-2006, 12:17 PM
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Default Re: 1150 cfm Dominator on 250 blower

Originally Posted by joee
A couple of years ago I purchased for my 38 īCigarette (Merc 425 HP 454 engines) a pair of 250 blowers and two (one for each engine) Holley dominators # 0-9377 following a hint in an old B&M manual.

I modified among others the pistons to CR 8.0:1 and have just installed the blower which should produce 7 pounds of boost at 5500 rpm.

Actual jet size from the carb.box is 94 / 94, power valve acc. to Holley data sheet is not required.

Anyway I would like to install the PV # 125-65 in the primaries & secondaries in order to avoid plug fouling in the lower power range.

I plan to reduce main jets by six numbers and vacuum signal for the pv shall be delivered from the manifold.

Has anybody experience with such a configuration.

Thanks

Joee
8.0 to 1 is a nice low static comp.
You didnt mentioned if your intercooled.
if you are not then.
I would leave the secondarys alone. No P/V. then add and boost reference the primary p/v. I like to see 1.1 linkages aswell.
Drop the primary jets down 4.
Boost reference will require drilling the 9377.
Checking plugs is a must. Total timing should be in the 28-30
vicinity.

Make sure you check plugs at different throttle settings.

Gerry
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Old 09-13-2006, 07:38 AM
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Default Re: 1150 cfm Dominator on 250 blower

I havenīt yet installed an intercooler, air temperature after charger was measured with 153 F @ 7 lbs

Anyway I started similar to the carb configuration that Mercruiser used on their old 525 SC engines (with 1050 Dominator and 177 Weiand blower)

Acc to the Merc manual they have modified the 1050 Dominator carb (# 8082) by rising the main jet size from 88 to 98 and by replacing the standard flow power valve # 125-65 with the high flow #125-165.

This looks very rich, is the fuel distribution on that 525 SC engines so bad.

I hope the B&M blower produces a more evenly cylinder distribution not only in respect to quantity but also to air/fuel ratio.

Which cylinder could be expected to be the leanest.

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Old 09-13-2006, 09:57 AM
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Default Re: 1150 cfm Dominator on 250 blower

I third the motion on Nickerson Performance. His experience with the B&M 250 Blower/Holley Dominator configuration is second to none.
He does not boost reference.
He reworked my 4500 series carb for my B&M 250 and it was spot on. Just had to adjust the idle. Well worth the money spent.
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