I have about 15 minutes on my new 454. It doesn't idle well. The person I bought the carb from said he thought the power valve was blown. Any way to tell for sure??

What size power valve should I use?? I had heard that I should put a larger one in it. It is a 700 dbl pmpr on a 454.
It has been a long time since I have messed with a holley so any help would be greatly appreciated.
Thanks


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Mr. D
72 454 El Camino
68 RS/SS Camaro
73 RS/LT/Z28 Camaro
99 Firebird TA WS-6 A4

The best way to test a power valve is to run a new one. Most carbs come with a 6.5 stock, but measure your idle vacuum, and run a power valve about 2.0 lower.

RH

Ryan
Thanks for the reply. So I should take a vacuum reading and pick a power valve 2.0 below actual vaccuum reading?

So if it reads 8.0 then I should go with 6.0?

Anyone recommend a good holley and Qjet book?
Thanks
Mr. D

When you back fire through the carburetor most people assume the power valve is blown due to it's lack luster performance.

I was told, and it kind of makes sense to me.
"When the carburetor backfires it produces enough pressure to upset the metering block gaskets and create a minor vacuum leak between circuits or somewhere in the system" http://www.chevelles.com/forum/confused.gif He went on to say that before you run out and lay down your kids lunch money on a new power valve, just grab a screw driver and tighten all of the float bowl bolts.
In the past I have found the bolts on the floats to be loose, but I cannot confirm his theory though.


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Lowered '67 Elcamino
ZZ430HP / 4L60
"Canyon Carver"
www.chevelles.com/showroom/elkydriveway1.jpeg (http://www.chevelles.com/showroom/elkydriveway1.jpeg)

[This message has been edited by Cardiac (edited 03-07-2000).]

Why not do a quickie rebuild on the carb? If someone suspects a bad power valve the carb is obviously not in tip top shape anyway. You can get a kit for under $30 at Summit.

I've been told that the power valve and primary ( or secondary) jets in combination set the air/fuel mixture. Intuitively, it's hard to argue with that notion. Consequently, I;ve been given advice to run a "fat" power valve to give a bit more midrange to the carb.It definitely works that way. I run a 8.5 valve in an engine that idles at 15" of vacuum, so even if you don;t use the 2" below idle, you can set the carb up properly. I'll see the dif when I bolt on an 850 with 65 and 45 valves, vs the 750 I have with a 95.

Anyway, the only way I know of to test is to "suck" oj the power valve. Rinse it is water first and simply suck on it, making sure you "lip it" to seal efectively. You'll notice whether it actuates or not right away. The Holley rebuild kits come with a 65 valve, so you'll end up using that one if you buy a kit ( which I would do anyway).

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Chaas
Gold #62/ACES
67 SS396/L88
www.chevelles.com/showroom/chaas1.jpg (http://www.chevelles.com/showroom/chaas1.jpg)

Mr.D.

Get yourself a new power valve. If you have 8 inHg at idle, I would run either a 6, or a 5.5. A 6.0 may open at part throttle, making more power, but if you care about economy, I'd try a 5.5.

As far as the "suck-test," power valves are very fragile, and I have not been clearly successful in determining if they are ok with the suck test.

However, I am not experienced in "sucking."

http://www.chevelles.com/forum/biggrin.gif Gene?

I knew I would catch some flak for that one http://www.chevelles.com/forum/wink.gif, but it works OK, it's simple and it'll tell you if it's "BLOWN" http://www.chevelles.com/forum/biggrin.gif!

Gene,

If you are so skilled, I have a few "power valves" you can check over here... http://www.chevelles.com/forum/smile.gif

I hate blown power valves. I've changed so many of those things - I'm hoping that my 1050HP has the checkvalve to prevent power valves from blowing. Anyone know for sure?

RH

Cardiac
Thanks, I will check out the bowls. http://www.chevelles.com/forum/smile.gif

Kevin,
I hope not to rebuild it. Right now $30 added to the $5,000 spent on the motor doesn't amount to much but I spent all the money I had set aside and still need exhaust, a new engine harness, tires and a paint job. http://www.chevelles.com/forum/frown.gif

Gene
I plan on checking the vaccumm this weekend. I looked at a kit and you are right. . . they come with 65's. Do you think I need both power valves replaced??

I might as well buy the kit (Holley trick kit for $39 at a local parts store) and replace both PVs.

Ryan
LOL . . . ya I'll pass on the check and just replace them http://www.chevelles.com/forum/smile.gif

I read that the new carbs have the Power valve savers installed already so your new carb probably has it.

Thanks
Tim (Mr. D)

I agree with cardiacs theary,back firing though the carb can distort metering blocks,If you change power vavles,go to 8.5s,this should work for you,but take a vacuum reading to see what ya got,dont overrun the vacuum reading with the power valve number,as in 7.0 vacuum reading,8.5 power valve,plus,lets send all our power valves to gene to have him test them!just ribbin gene,THIS DOES WORK,best easy way to check them.have a good one--67RAT member #199

Mr. D,

If you already have the blue non-stick gaskets in the carb, I would forgo the kit and just buy new valves. 67Rat is right, I just bolted on an 850 dbl last night and my mill loves it. Only thing is that I used the 065 in front and a 045 in back. I have a bit of a stumble at the 10" range. Either my squirter is too big up front (37) or I need to put the 095 valve from the 750 dbl back in. Point is you'll get much better mid range if you run a fat PV up front. Like Rat says, just check and make sure your engine vaccum at idle isn't too low.

Mr. D, you a member here at TC? If so email me before you buy anything.

[This message has been edited by Gene Chas (edited 03-09-2000).]

I bought the trickit kit at Checker auto ( I work there part time so I get a discount). It has the blue gaskets and power valves. I did not get a chance to install new valves or gaskets yet. I hope to do that this friday.

I know this question may sound stupid, but I removed the 4 screws to take the bowl off (fuel line off) and I couldn't get the metering plate to come lose. Am I forgeting something?? Last time I took a holley apart was in 1983!! Shouldn't it just "tap" off??

Gene, I guess it is because it doesn't have the 'blue' non stick gaskets in it yet. http://www.chevelles.com/forum/frown.gif

thanks again for the help. http://www.chevelles.com/forum/smile.gif http://www.chevelles.com/forum/smile.gif
Tim (Mr. D)

[This message has been edited by Mr. D (edited 03-13-2000).]

Yep, I don't know when Holley changed the surface of the gaskets they use, but some of them require dynomite to get them off. That's just the beginning of the fun, the scraping off of the old stuff is even more fun.
VHT made some spray gasket remover that worked good for removing the old gasket.

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Wally
Gold #67
67 Malibu "Small Block" second owner
90 SS454
71 Malibu "Small Block"
93 torch red vette(crashed)Bad day at Blackrock! 6 grand in damage!