vacuum @ WOT?
 

I have a 91 baja 240 sport with a 630hp 509. I bought the motor complete, so I do not know all the specs on the motor. I do not think I am over propped, but I am running a 26p B1. I am only able to turn 4600rpm, and have no vacuume at full throttle, I pull about 12-15 at idle. The motor was not dynoed with the carb that is on it now, and I think the setup may be my problem. It is a 950 proform body with quickfuel blocks and base. The vac guage is hooked to the base of carb. Runnind 80 primary and 86 sec. , and 3.5pv on carb. Stainless marine dry exhaust, and I do not know cam specs, but it is not small. I am at about 3000ft above sea level, does anyone have any setup advice, or know what my vacumm should be at full tilt?

Vacuum should be close to zero at wide open throttle. You need to find out the cam specs, possibly you're not hitting peak RPM because of the altitude.

You could be running rich, we wind them up and shut the key off, drift to a stop and check all of the plugs.

I think I am running rich, the altitude is not that high, I am in the norther part of Texas, not Colorado. I will try the shut off the key at WOT thing, it was just very windy yesterday and kind of worried me to do that. Does this sound like the corrrect PV for my application. I know the cam specs would help, but the motor was built some time ago and the motor bulider, Mesa Balancing, could not remember the specs. It had been sitting in his shop for some time till I bought it off a friend of his.

tx911 i have 540dart 624hp on dyno. 850 holly 84 jet 3.5 pv in front 96 jet no pv in back . timing 36 degrees at 3000rpm . 136 bravo one drive. runnig 21mirageplus .78mph5500rpm i run a 24 trubo 75.6 at 4900rpm . check your timming try a 25mirage prop . your rpm are to low iwould prop the motor 5200 to 5500 that will wake your motor up and check the plugs after . good luck

Thanks for the reply bajabob, timming is 34deg fixed, I have a 25 mirage prop, it just handles better with the four blade. I have not tried the mirage with this motor, I guess I will throw it on and see. I am just not certain about the carb setup, but that may not be my problem, maybe I am over propped. Motor before this was a 540 merlin with almost same power on dyno, but I was swinging a 27 mirage plus with that motor.

I'm not a carb guy, but the plugs would tell you what you need to do. Couldn't hurt to check the timing before making a run.

It can't be much of a cam if you're getting that much vacuum at an idle

well i had 82 jet in fr91 in back no power vale dyno 600hp put 84 f 96 in back now got 624hp all i did was jet change.. .i ran the boat and gps the speeds the mirage 3 blade gave me the best speed . recheckthe destribertor make shore it on number one could be a tooth off ??did you check for intake leaksor carb???

I am running 34 deg timing with a fixed MSD distridutor, my timing is stable up to the 4000 rpms I have checked it at, I do not see how I could be a tooth off?

The 540 merlin had a big cam, 632/632, and 309/318 duration, and made more vaccume at idle then this motor, so I do not see how the cam is not that big. It has a pretty mean idle, and made 630hp on dyno.
I will try killing it at WOT and checking plugs this weekend and see where that gets me.