4160 carb help on 302

jimmy wayne · 02-20-2009

i was wondering if a blown power valve in a holley 4160 would effect the performence , and how about fuel economy, if its a bad power valve is it hard to change out, could this have put gas in my oil, any help will be great , thanks alot to all

The Greek · 02-21-2009

The power valve can be accessed by taking the front or primary fuel bowl off. It can be removed with a 1" socket or box end wrench. Pay attention to the numbers stamped on it as they come in different opening rates. Most carbs use a 6.5 (The P/V is stamped with a 6 and a 5 with no decimal point). The 6.5 opens when vacuum drops, as when accelerating, to 6.5 inches of vacuum.

When they go bad, it's usually the diaphram that's ruptured. You will usually have a dead spot when trying to accelerate and an unsteady idle and surge. The fuel will have a tendency to leak from the fuel bowl, past the ruptured diaphram and down into the intake through the P/V's vacuum port. There could be fuel leaking past the piston rings and into the crankcase oil because of the ruptured diaphram. Fuel economy will suffer, too.

It's easy to replace and it's not expensive. If you suspect it, replace it. Use a Holley branded valve as there are some cheap replacement valves that will flow poorly. These are usually found in off brand rebuild kits. The 4160 only uses one. The one on the primary side.

cushman350 · 02-21-2009

If the power valve diapham is cracked, the vacuum source that holds it shut will be sucking whatever gas is leaking through right down the engine, hurting economy and running rich.
Added note, rule of thumb on power valves and hotter cams with low idle vacuum. Measure idle vacuum, divide by 2, + .5 to get the correct power valve number. My Holley came with an 8.5 PV and the cam I had measured 8-9 vacuum, so the power valve was trying to open at idle, running too rich. Switched to a 4.5 and it smoothed out the idle.

FordLover18 · 04-17-2009

i have a 1979 Ford Mustang with a 1969 boss 302 we put a offenhouser tunnel ram on it we are running dual holly 4160 carbs. we can't get the thing to idle worth a crap and was wondering if we could get help with how to tune the carbs to get it to idle. we get it started and it is idleing about 2500 rpm's and when we back down to 1000 where we want it the motor starts to shake and it finally dies. if we could get some help with the tunning of the carbs we would really appreciate it.