Power Valves

[Henry Cloutier]

Hi all,

I'm in process of rebuilding the Holley 4053 on the Camaro. I am to the point of installing new power valves. The ones removed are marked 6.5 and I wasn't having any running issues so am planning on installing the same rating however the renew kit came with four marked 6.5. Two have 2 slots and two have 4 slots. The ones removed have 2 holes each primary and secondary. I'm assuming the 4 slot valve supplies twice the fuel as the 2 slot valve and therefore should be installed on the secondary side, or is 2 slots good on both sides? The Z is a weekend warrior and isn't driven daily but does know where the straight line country roads are. I do need to satisfy my need for speed every now and again :-)

Thanks in advance for the help,

Hank

[firstgenaddict]

I just looked in my tune up tool box and I have a mixture of double and quadruple slot PV's - I have built a lot of carbs over my life and honestly I have never paid attention to the number of slots in the PV's.

[z28z11]

Original 4053's were equipped with a 25R-591A-65AS primary power valve, which is a 6.5 - secondary power valve was a 35R-591A-85AS, which is an 8.5 valve. Gaskets are also different between the drilled valves and the slotted valves - failure to use the proper gaskets in each case can cause fuel leaks around the valve -

Regards,
Steve

[firstgenaddict]

I didn't have any drilled valves,
I will state that I do check that the gasket is in the correct position when I install the valves and I place the gasket on the PV then hold the JET PLATE with the power valve hole pointing towards the ground then raise the PV to the plate and screw in so the gasket does not become oriented "wrong".

[z28z11]

I have seen both gaskets shown below in kits, important to use the gasket visible on the right for the slotted power valve. I think Holley only furnishes the slotted power valve nowadays, but this is a "just in case" note. If the valves supplied in the OP's rebuild kit are correct, are the 4 slot valves marked 8.5 ?

Regards,
Steve

[Henry Cloutier]

Hi everyone,
 Thanks for the info you all have provided. My mistake last night (perhaps one to many Bud's), The removed valves are slotted not drilled and both are 8.5. I had to get the magnifier out to verify. Hopefully the picture attached; it shows 2 and 4 window 6.5 valves. I've been researching for a couple hrs now reading threads, articles etc. Steve is correct with 6.5 primary and 8.5 secondary from the factory. This was apparently done as the engineers feared there may be a lean droop during the transition from primary onto the secondary's. The 4 window valves as near as I can tell are termed "Quick Response Hi Flow valves." They are most often refenced when "Alcohol" is used for the primary fuel source. They are also slightly taller than the 2 slot valves.
 I'm thinking to return the carb back to stock configuration of valves; 6.5 2 slot for primary and 8.5 2 slot for secondary. Any thoughts are very much appreciated! And whoever was in this carb last time double stacked the PV gaskets on both!

Hank     

[rszmjt]

I think the original Holley PV had holes instead of slots, I haven’t seen those supplied in many years, except for in some after market cheaper generic brand rebuild kits. I have some hole type PV from Holley kits dating back to the mid 70,s. Personally I like Holley branded kits and parts. We tried some after market branded accel pumps and PV /needle & seats but they seem to fail quick & the pump diaphragms seem to petrify , I think the ethylene in today’s fuel cause this.
General rule for PV selection is it should be rated at 1/2 of idle vacumn with a vacumn gauge . Eg if you have 13” manifold vacumn use a 6.5 PV

[z28z11]

 I'm thinking to return the carb back to stock configuration of valves; 6.5 2 slot for primary and 8.5 2 slot for secondary. Any thoughts are very much appreciated! And whoever was in this carb last time double stacked the PV gaskets on both!

Hank     

I would use the original 6.5/8.5 combo as it was specced, and a single gasket for the slotted valve configuration - should not be a reason to use two, one should be sufficient. The worst problem I ever had with my 4053 was an off-idle bog, a known aggravation, easily corrected by upping the diameter of the accelerator nozzles or changing the pump cam to allow a longer duration pump shot. 302's with stock compression, cam and heads are thirsty, even when jetting and timing
are dialed in. Another suggestion - if you ever sneeze the carb, prudent to replace the power valves (pretty sensitive to backfiring).

Regards,
Steve

[rszmjt]

You can also test the power valve operation by turning mixture screws in slowly, it it stumbles and try’s to quit running PV is OK

[Henry Cloutier]

Thank you for the great responses. Based on what you all have provided I have a much better understanding of PV's and associated issues with them. When the Z was delivered in July I pulled her into the garage and there was a distinct fuel smell lasting a few days. My first thought was float levels to high so I went about trying to adjust them along with the mixture screws and wanted to check the timing to see where it was sitting. The engine ran fine, pulled really well thru the gears(although I didn't get above 5000rpm on the first outing) idled a little rough but I also knew the car had sat for extended time periods. Left side mixture screw reacted normally but the right side needed to be almost bottomed out for the engine to sustain idle. Front float was to high but did adjust correctly. The rear float didn't want to adjust without much coaxing (and a small fire) but finally got it to respond. Initial timing sitting @ about 8 degrees. Still the fuel smell after driving and then both inlet fittings began to leak and I could smell fuel while driving. That was pretty much the last straw so off the carb came for a rebuild. Course some caveman before me worked on this last as the fuel line fittings are severely over torqued resulting in damage to them and the inlet fittings during their removal. So here we are to right now and now it seems the issue of which of the plethora of PV's to install is solved I can continue on with the re-assy. Thanks to everyone! 

Henry
       

[rszmjt]

Henry, as far as the fuel line problem, make sure it doesn’t have stainless repo lines, they do not work well and cause lots of leakage problems like you are describing. I always use just the OEM style plain plated steel lines as the stainless offers no conformity to the inlet fittings, plus the expansion rate of stainless always seems to make them seep.

Mike

[Henry Cloutier]

Hi Mike,

I guess I'll just say oh crap as the replacements I ordered are stainless. I didn't figure they would cause a problem cause I've seen many different vehicles thru the years sporting stainless lines. I am becoming aware however of vastly different levels of quality when shopping parts for the classics.  Aahhh the saga continues...

Thanks for the info!

H

[z28z11]

Henry, as far as the fuel line problem, make sure it doesn’t have stainless repo lines, they do not work well and cause lots of leakage problems like you are describing. I always use just the OEM style plain plated steel lines as the stainless offers no conformity to the inlet fittings, plus the expansion rate of stainless always seems to make them seep.

Mike

Mike,

Perfectly correct. It takes a lot more torque to seat the stainless inverted flares, as the SS is usually not anywhere near as ductile as the OE steel versions - that extends to reproduction brake lines as well.

Regards,
Steve

[firstgenaddict]

I had issues with the Stainless flared tube not being concentric and would not seal well.
I ended up doing the following...
I "LAP" them in...
With the carb off the car, apply a dab of grease or oil to the flared tube end... hand tighten the fitting, spin the entire tube around and around in the fitting, tighten a little more, spin a couple of times, tighten slightly and spin... repeat with EACH connection and they should seat without leaking.
 

[Henry Cloutier]

Hello James,

I'll give the lapping a try. The fittings aren't installed yet so I should be able to accomplish this on the bench.

Thanks,

Hank