89formula#1

Hey guys I was wondering what the deal is with the power valve block offs they sell? in what kind of application would I not want to run a power valve?? also I can get a 750 double pumper with the choke horn cut off that needs a rebuild for 100 bucks is it worth it?? thanks guys

IHI

iTrader: (1)

IMO any carb that needs rebuilt is worth passing by and getting one that works. Too many problems buying second hand carbs, it's different if a buddy lets you try one out and then you buy it, but knowing buying a carb that needs work is not a smart choice.

As far as the PV block offs, mainly a drag race only application. Some guys "claim" to see more consistency blocking the power valves off and compensating with jets-you must go up 6-10 jet sizes when removing the power valve otherwise youo'll go extremely lean.

Trying to street drive a carb without power valves is miserable. Bad enough in the pits when warming up you car as it always wants to load up.

TA5LiterHO

For street do run a power valve.

As far as the carb needing a rebuild, if you could get the carb for a bit less money and you don't mind spending a couple bucks to rebuild it yourself, go for it.

It's not hard to rebuild carbs and it saves you a lot of money if you can do it. As long as the hard parts are good and all it needs is a cleaning and gaskets it won't cost you much to fix. Some peoples definition of a rebuild is needing new gaskets so you may get lucky. Ask him why it needs a rebuild is what I would do.

89formula#1

well i say it needs a rebuild because one of the gaskets on the long screws holding the bowls on was leaking when we hooked it up on his car. He said he didn;t know why cause he watched some guy rebuild it when he got it a while ago. I just said rebuild cause I can get a rebuild kit where i work for 20% off so i was just going to rebuild it for the hell of it. just make sure its all in working order. Also for a powervalve I need one that is half of the vacume i pull at idle right??

IHI

iTrader: (1)

As a general rule of thumb on the PV-yes.

Sounds like your getting yourself into a can of worms with this carb Hopefully it's just something really simple, but as the story unfolds with somebody else aready having it apart, based off ecpereicne it's not looking to be a happy ending. Good Luck!!

TA5LiterHO

I have rebuild quite a few Holleys and they are not complicated. The main things that I have run accross in my experience is clogged passages which are easy to fix.

If you want to spend $300+ on a new carb go for it. If you want to invest in a Holley repair manual and buy a cheap rebuild kit that would be a lot cheaper. These carbs usually don't go bad to the point that you can't rebuild them.

If it's been rebuilt and it's just a bowl screw gasket you can replace them for a couple bucks and it will be fine.

F-BIRD'88

Blocking off the power valve in a holley is for an engine that has little or no manifold vacuum at idle. ( takes some vacuum to close the power valve)
A radical drag engine with a cam about 280 or 290+@.050" would need to have the power valves eliminated.
When blocking off a power valvre the main jetting has to be made larger to account for the fuel that normally goes through the Power vavle channel restriction at WOT. (About 8 to 10jet sizes larger)
The car will be on full rich power mode all the time.
Will enrich the apparent jetting during part throttle cruise and idle.

You don't need to do this on your car.