#67694 - 12/14/11 05:34 PM
Re: snowman4839 turbo build
[Re: Boucher]
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tlowe #1716
12 PORT ADVERTISER
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Registered: 04/01/04
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Loc: Dysart, Iowa
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The 250 dyno carb was set to factory specs at first and then only jetted it up by 2. Stock squirter.
Your stumble sounds bad. Like something else is wrong.
Tell us about timing setup. At idle with or without vacuum line also. How about total timing at 3500 rpm without vacuum.
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#67768 - 12/18/11 07:47 PM
Re: snowman4839 turbo build
[Re: Mean buzzen half dozen A.K.A. Hank]
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tlowe #1716
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MBHD, How do you figure 24HG is really 12 inches of vacuum? 24 would be 24" of mercury. Vacuum in Inches is in reference to mercury most of the time.
Either way, I do not think his guage is reading correct at idle or boost. Most engines will not produce vacuum reading that high at idle. Iregardless his carb tune is off and needs to get under control.
Snow, You reaaly need to do tuning , one step at a time. This includes timing and carb.
My 292 has O2 readings like this. idles at 12.75, cruises at 12.5 and full boost is 11.25 or so. Timing 23-25 at idle (total) , 48 cruise, 27-28 under boost.
Your meter will read different than mine, they all do. Best tip is to add fuel at first and then lean it up slowly with tuning. Start with a stock setup, unmodified carb(PVCR). Then get started.
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#67793 - 12/20/11 05:42 PM
Re: snowman4839 turbo build
[Re: tlowe #1716]
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Mean buzzen half dozen A.K.A. Hank
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Registered: 09/23/04
Posts: 4585
Loc: Ca
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I do not think his guage is reading correct at idle or boost. Most engines will not produce vacuum reading that high at idle. I agree Iregardless his carb tune is off and needs to get under control. I second that,, the A/F ratios @ semi throttle accelerating, hard on the throttle & under boost are all off,,, he needs to be careful before the engine goes KABOOM!
I wonder what his intake air temps are running 10 psi & no intercooler? Snow, You reaaly need to do tuning , one step at a time. This includes timing and carb. I would think he knows this by now. :/
My 292 has O2 readings like this. idles at 12.75, cruises at 12.5 and full boost is 11.25 or so. Timing 23-25 at idle (total) , 48 cruise, 27-28 under boost.
Tlowe, just curious how much total timing you have run @ cruise & when you have gone over 48*,,, what happens, does the engine start to buck & not like it , or ?
MBHD
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#67795 - 12/20/11 06:17 PM
Re: snowman4839 turbo build
[Re: Mean buzzen half dozen A.K.A. Hank]
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tlowe #1716
12 PORT ADVERTISER
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Registered: 04/01/04
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My engine starts to get a small buckiness to it, almost like it is missing. Been a while since looking at it timing curve, but may have high as 52 degrees.
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#67797 - 12/20/11 06:49 PM
Re: snowman4839 turbo build
[Re: Mean buzzen half dozen A.K.A. Hank]
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tlowe #1716
12 PORT ADVERTISER
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Registered: 04/01/04
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Bet yours has a little more than 35 at cruise. Might be hard to measure. Are you able to set the computer timing?
I have always had a intercooler. Bet with 10PSI Snow is seeing 250 degree intake temps. Try grabbing that charge pipe!
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#68096 - 01/14/12 06:12 PM
Re: snowman4839 turbo build
[Re: snowman4839]
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tlowe #1716
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Registered: 04/01/04
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Thats great its running better. You also changed atleast 2 or more things with your carb. Harder to tell what really did make it run better. But to give you more tips on tuning the Holley. Harry is right, the PV needs to be relatively low in #, like 3.5-4. The 10.5 PV you have is open practically all the time. So you are getting fuel from 1. Main jets 2. PV and its channel restrictions.
What I am wanting you to do is. Jet the mains for normal driving (cruise). Have the PV open only when the vacuum is low (like 3.5-4) ,IE when you starting to get into the throttle and drill the PVCR to supply the fuel needed when under boost.
Lets see some video of this car under boost. Tom
Edited by tlowe #1716 (01/14/12 06:14 PM)
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#68106 - 01/15/12 05:20 PM
Re: snowman4839 turbo build
[Re: RedMan*]
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snowman4839
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Registered: 03/26/10
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Loc: Memphis, TN
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