jetting extremes

[Jetdud]

1050 Phase III, Buck 50's, coffman with 15/24 swirl on 85 exit nozzle at sea level. I was at 175 main and 130 pilot. I was close to fouling a plug. Could feel it. I found the Y line barb that came with vapor separtor had a 60 return jet so I feel was overpowering the carbs. I changed return jet to 110 and rejeted to 170 pto and 165 mag w/120 pilots. I was loading up pretty heavy. You can say all you want, but most plugs will read decent at 73-7500 unless you are way, way, off. Considering this, what in your opinion min and max main jetting my setup. I am thinking a max of 175 on mains and and minimum 160 min on same. So I should be somewhere in there.

The pilots I always set up so as to take off clean.

Yes. I would like an egt setup. .. How fast does a siezure happen. I was running around 7250-7300 with aforementioned jetting. I figure was way to rich.

[Bill O'Neal]

So are you saying it siezed with that jetting?

It doesn't matter what size jets, return jets or fuel pumps you run if it isn't pulling the fuel from the diffusers in the throat of the carbs.

We have had nothing but trouble with BRM 50's actually pulling the fuel from the carbs the way they are susposed to. Some modifications to the diffusers may be necessary to get them to work (almost) properly.
I highly reccomend Novi XR48 P9's with "F" boosters. They were made for the 1050's, we have tons of experence with them both on the water and the dyno, using detonation sensors.

The unmodified BRM 50's lit up the deto sensors like a christmas tree display. At least 40 % more detonation than the Novi's with F boosters.

We just recently did some testing in the past two weeks, using Novi's, BRM's and Full Spectrums. All can work, but only the Novi's worked well without modifications and not needing to back down the ignition timing.

You may be headed down a rough road using BRM's, a 1050 and twin pipes, if you are really squeezing the motor for ultimate power. If you have a recreational setup, with a single pipe and low compression, you probably can make the BRM's work well enough. If you don't have an EGT, you are running blind.

[Jetdud]

No it did not seize. It ran well. It pulled well. I know I was running rich cause a plug tried to foul, I could feel it, I was able to prevent it by grabbing the throttle a few times. That was at low rpm (2000) and probably caused by return jet of 60. The B50's have been updated with latest metering block (they seem to be working fine). I turn the electric fuel pump on at 4500. I have the 70 liter per hour novi pump installed per dir. I run a coffman, not twins. I'm on pump gas, running +2 (24) to 4000 and plotted for 15 at 7500. I am running around 155 compression. I have no plans for twins. Would I like novi 48's? Sure. But those are major $$. I need do best with what I have. I don't have novi's. Looking for min and max jet specs based on your xperience with this setup.

BTW, u phase III has wicked, wicked porting. Very cool stuff.

[Bill O'Neal]

Jetdud,
I do not have my jetting spec book here at home. Could you call me tomorrow at work?

626 914 9509

BTW, we will do the machining updates to the air horn and bombsites for $125 per carb set of two BRM's for anyone interested in having it done.

[ April 23, 2003, 09:51 PM: Message edited by: Bill O'Neal ]