do you take the power valves out and run plugs?
In my forceful opinion you will want a power valve at least in the primarys or you will have a big flat spot. The power valve gives you part throttle enrichment, right where you need it for cruising speeds. If you do remove the power valves you will need to increase by 3 or more jet sizes to compensate.
If you open up any spendie blower carb. they have blanks in them.Power valves won't work right because of suction of blower.
I've been running power valves pri. and sec. for years and I thought the carbs ran fine. I'm running a 540CI engine w/14 lbs boost. I put a vaccuum gauge at the carb base and at WOT I only got 1 in. vaccuum so I determined that the power valves were not being affected by the blower.
Hey unchained, Do you remember what vacuum you pulled at 2500 or 3000 cfms under the carb base. I thought the blower always pulled a vacuum on the carbs. If not I would like to use power valves on my rig. thanks,
Kojac...
I took vacuum reading on my newly blown 454. I had (flat)zero at idle and as I increased the rpms, the vacuum shot up to around 25in hg. This would be the exact opposite of what the power valves are asking for(this explained why the thing idled so fat it made your eyes water and it spit as soon as you cracked the throttle), so I plugged them(all four). I took her out for the first time, today, and it seems to be ok. There is a little cough on hard acceleration(going from a 2500rpm cruise to WOT hard), but I think I can tune it out.
Kojac, At cruising speed you will have high manifold vaccuum and the power valves will be closed. The power valves only open and supply extra fuel when the manifold vaccuum drops below the rating of the power valve when you open the throttle.
Heatseeker, You must have been checking your vaccuum at the carb. metering plate. That spot is only for vaccuum advance for a distributor. Check it at the carb base or directly from the manifold. However if the engine ran better after you plugged off the power valves then maybe your cam has low manifold vaccuum and the power valves were a high number and dribbling at idle. Read the manifold vaccuum at idle and at cruising speed and then use a power valve that is a couple numbers higher than the manifold vaccuum reading. You want the power valves to be closed at idle and at cruising speed.
Good Luck,
I took the readings at the carb bases. The same on both carbs. My metering blocks don't have vacuum ports. I was told by many "experts" that the only way to run power valves is to reference them from the manifold. Is there another way?
Ah Yes the same discussions resurface quite frequently.
Boost ref is how many folks on this board run the powervalves. They have big boats and cruise part throttle under boost.
If for some reason your carbs are big enough for the amount of boost you are running, there is not an excess of vac under the carbs. Most of the time the carbs will not flow as much as the blower draws at wide open. In this instance the blower sucks hard on the carbs and the vac sucks the powervalve shut. Not good most of the time.
Some of the larger boats cruise under boost and require boost ref. powervalves.
I still prefer to block them off and jet up accordingly.
you may need to reference your power valves under the blower
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