Dynra Rockets

I've had this Holley 6210 spreadbore double pumper for more than a couple of decades now, been on a few cars. Never had a problem with it and its never been cracked open. With my new engine refresh (ZQ3 with 58cc 128 heads and '80 alum intake) I am too rich at cruise and not rich enough at WOT. Thought it was about time to give the Holley a good cleaning and open it up for a kit, possibly a rejet.

To my surprise it has #57 jets on the primary and #86 on the secondary (Holley pdf says comes with #62/#83) so I should not have the rich condition in theory. Few moments later discovered my rich at cruise is because of a stuck power valve on the primary side - easy fix.

The 6210 has no power valve on the secondary side. I've read that there isn't really a need for one as the extra large jets will take care of the fueling. My question is, would I benefit from adding a power valve and corresponding block to the secondary side? IIRC, squarebore double pumpers have them. I've Googled and youtubed and cannot find an answer.

R

resdoggie

The power valve does not come into play at cruise. Running rich at cruise is another problem. Secondary power valves are not fitted on all Holley square bore dp carbs. My Holley 650 street HP DP with mech'l secondaries doesn't have one.

Dynra Rockets

It was stuck open

OK. Thanks

71VetteLover

In my 50+ years of wrenching I have never heard of a "stuck" power valve. Was the bottom of your Holley full of mud?

Jebbysan

The answer to your question is no....you will not benefit.
The only time I have seen power valve on the secondary is in offshore boat applications......
The power valve is a vacuum operated "jet".......it is worth about 8 jet sizes......
Your spreadbore probably has a buttload of "signal" at the booster due to it being smaller.....this would increase velocity and pull more fuel through the jet than a even sized venturi......

Most rich running conditions are due to a blown power valve after a backfire or a bad power valve gasket......
The primary metering block gasket can also create an extreme rich condition if it is dried out and leaking....OR....if you have the wrong gasket in it, which is not hard to do.

Jebby

resdoggie

Yes and Holley has had blow proof PV's fitted in their carbs since the mid-'90's I believe.

Jebbysan

1997 actually and they do not always work.....a massive backfire or nitrous backfire will still window a power valve. I have seen it first hand so cannot rule it out.
But you are absolutely correct....and they did solve most issues....

Jebby

Dynra Rockets

Thank you Jebby. The answer I was looking for.

Dynra Rockets

I see you are in arid California. Have any of your 50 years been in the humid southeast like Georgia and northern Florida? The carb sat on the shelf for a couple of years in between cars in my humid shed (down by a creek). There was a lot of corrosion on the valve. I can only assume when I reinstalled the carb the power valve attempted to work on its first call to duty but then got stuck open. Regardless, it is replaced now and functioning.

71VetteLover

So it was full of mud. If I was going to store a carburetor I would dump the gas out and put it into a box or bag to keep dirt out of it.