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carb power valve

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kevin719 View Drop Down
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    Posted: October-04-2008 at 5:50pm
I am finally getting ready to rubuild my carb on my crusader.It is a 4160 holley.I purchased a pcm rebuild kit.I have not even opened the box yet but I am sure that you guys know if the power valve in the kit will be right or which sizes will work best.Also I have a manual choke on this carb and I just bought a new cable for 50 bucks at crapa! My choke assembly on the carb is missing the screw that locks down the cable.Does anyone have the holley part number?? Thanks again guys!
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81nautique View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 81nautique Quote  Post ReplyReply Direct Link To This Post Posted: October-05-2008 at 1:13pm
This could open up another can of worms but 10 to 1 says the PV in the PCM kit is a 2.5 We see this time and time again and the reasoning behind it must be fuel economy. The concensus here seems to be the 6.5 is the way to go on a 351 motor but you will need to tune and test for yourself to verify.

Even if your jetting is correct I would bet there is a lean condition under hard throttle waiting on a 2.5 PV to come in.
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kevin719 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevin719 Quote  Post ReplyReply Direct Link To This Post Posted: October-06-2008 at 10:43pm
You are excactly right! The pcm kit comes with a 2.5 powervalve.I bought a 6.5 today at advance auto.I talked to a very large carb place in Indy today and he said that they put a 6.5 in these as well.Thank you very much! Kevin
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p/allen View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p/allen Quote  Post ReplyReply Direct Link To This Post Posted: October-07-2008 at 11:04pm
    quote   The concensus here seems to be the 6.5 is the way to go on a 351 motor but you will need to tune and test for yourself to verify.

So what size should be used for a 302 ?
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74SkiNautique View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 74SkiNautique Quote  Post ReplyReply Direct Link To This Post Posted: October-09-2008 at 8:53pm
I have heard that if your engine backfires, you should replace the power valve.
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anthonylizardi View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote anthonylizardi Quote  Post ReplyReply Direct Link To This Post Posted: October-20-2008 at 8:25pm
Originally posted by 74SkiNautique 74SkiNautique wrote:

I have heard that if your engine backfires, you should replace the power valve.


This is a very interesting observation, I am glad you mention this. I am finally restoring mine and actually this weekend I got the first ride after fixing the shaft, strut and new prop. It rides really good. Now I noticed that if I gun it from idle it chokes and backfires. Could this be related to this valve? Can I go to Napa and buy one of this?

Thanks,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: October-21-2008 at 12:20am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: October-21-2008 at 12:23am
Originally posted by anthonylizardi anthonylizardi wrote:

Now I noticed that if I gun it from idle it chokes and backfires. Could this be related to this valve?


No. IF the Pv failed it would flood out in the midrange.

the lean pop/fart is likely due the accel pump linkage being sloppy. Adjust so it squirts immediately upon throttle movement.

If that is in order then the initial timing may be too low. these engined like 10 btdc better than 8, and below 8 they pop/fart when you nail it.
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