Dyno day tomorrow.

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Jan 18, 2008 | 04:45 PM

#61

BB72

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Melting Slicks

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From: Kingston Ontario

Here's the dyno print out.
How do you get a pdf file up here? Any know?

Jan 18, 2008 | 06:12 PM

#62

BB72

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Melting Slicks

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From: Kingston Ontario

If anyone is interested , I will e-mail the dyno results. Just send me your e-mail.

Jan 19, 2008 | 08:09 AM

#63

69ttop502

Le Mans Master

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From: Watkinsville, GA and Glen Cove, NY

Hey Rob, good job buddy. Would love to see the dyno charts.
sasobvo@netzero.com. How is everything else going?

Bill VO

Jan 19, 2008 | 11:51 AM

#64

gkull

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From: Reno Nevada

2024 C3 of the Year Finalist- Modified

Quote:

Originally Posted by BB72

The front and rear jets were 85 and 93, are they large for what I have?. We moved them down to 80 and 88 and didn't see much change.

You did not say which model of demon carb you have, but these are the base line for sea level 850's. Your original jets were 85 and 93 which was the correct jets. I found demon carbs to be out of the box rich in the idle cuircut. But very close to right on the primaries and secondary jetting from off idle through WOT with the installed air bleeds.

Changing 5 jet sizes front and rear would account for such lean BSCF. I also think that the super lean mixter would have cause the peak powers to be produced at such low ignition advance. 30 and 34 degrees . Richer mixtures burn slower.

http://www.barrygrant.com/demon/defa...e=29&specs=29b

Last edited by gkull; Jan 19, 2008 at 12:19 PM.

Jan 19, 2008 | 12:03 PM

#65

BB72

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Melting Slicks

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From: Kingston Ontario

Quote:

Originally Posted by gkull

You did not say which model of demon carb you have, but these are the base line for sea level 850's. Your original jets were 85 and 93 which was the correct jets. I found demon carbs to be out of the box rich in the idle cuircut. But very close to right on the primaries and secondary jetting from off idle through WOT with the installed air bleeds.

Changing 5 jet sizes from and rear would account for such lean BSCF. I also think that the super lean mixter would have cause the peak powers to be produced at such low ignition advance. 30 and 34 degrees . Richer mixtures burn slower.

http://www.barrygrant.com/demon/defa...e=29&specs=29b

So, are you suggesting I return to the original jets and go from there? It's running good now, but I don't think changing jets will affect that. The dyno room was hard to stand in after 5 minutes because your eyes were burning so much which might indicate a rich idle. At what RPM does the idle circuit stop and start running on the jets because with the dyno throttle ,which was essentially a boat style setup, wouldn't allow it to idle less than about 1300 rpms .

Jan 19, 2008 | 12:09 PM

#66

BB72

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Melting Slicks

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From: Kingston Ontario

I just went through the Barry Grant link and it says there's a 30cc accellerator pump. Is 30cc a stock size accellerator pump for a holley? This pump on the bowl is larger than stock. Maybe 50cc.

Jan 19, 2008 | 12:33 PM

#67

gkull

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From: Reno Nevada

2024 C3 of the Year Finalist- Modified

Quote:

Originally Posted by BB72

The idle circuit does not stop it is in addition to the pri and sec. and when the power valve senses low enough vacuum your ar even dumping more fuel.

Did you know that overly lean will also burn your eyes?

Unless the dyno is whacked and you can't trust the readings on the BSFC. You can't change 10 jet sizes and be even close unless the carb has different air bleed and emulsifiers.

When you get into these big motors they are so powerful that it is hard to tell when they are running bad. I was out at the track on a play day running some laps and trying this and that. So I checked a couple of plugs to see how my jetting was on such a hot day. They looked a little rich so I dropped one jet size. I went out and made the 4 mile loop and the car seemed to run fine, but it was down on power. It just didn't seem the same. I just thought that the jetting screwed me. I came back in and lifted the hood and it had the #4 cylinder spark plug wire off. I was down @80 hp running on 7 cylinders and I was still passing people.

Or your bent valve!!!!!!!!!!!!!!!!! could you tell when it went away?

Jan 19, 2008 | 01:01 PM

#68

BB72

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Melting Slicks

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From: Kingston Ontario

From the final results, I would say the valve was done right at the start. We picked up 87hp after the valve was changed. There was zero compression in #7 cylinder. From what your describing, I would say it was way too lean. Given what I paid I'm going to see if I can bolt it back up and do a couple of runs before it goes in the car. I also changed shooter cams so that the shooters stop after the blades were wide open. They were still shooting long after the blades had opened up. I would think that would bog it down.