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 Posted: 06-24-2008 01:45 am
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couter06
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I'm having my 40s rebuilt. Does anyone know the correct jet sizes for a 2.0?

Thanks,

Last edited on 06-24-2008 01:45 am by couter06

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 Posted: 06-24-2008 12:28 pm
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Brett Gibson JH5 20497
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The numbers I was given and believe Greg recommends are,

Choke 33, Main jet 145, MJ emulsion tube 7772.5, MJ air correction jet 190, Idle jet 55, Idle jet holder 7850.7, pump jet 45, cold start jet 70, CS emulsion tube 7482.1, Float assembly 7298.2, Butterfly's 7481.2,

This is what I'm running also along with the anti-popping flanges on a stock engine with the cams 110 to 110, seem's to run a tad rich with a bit of hesitation if I tromp on the gas pedal, if I play the pedal works just fine, top end speed is great with no breaking up smooth all the way.

Brett

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 Posted: 06-24-2008 01:54 pm
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Judson Manning
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There is no 'correct' jetting....only starting places for you to begin tuning your specific engine and driving style.

IMHO the Dells available through the JHPS (145 mains) have a MUCH better starting point than the Lotus Spec5 & Spec9 (160 mains) available through previous sources. 

Lotus with all of their resources began with 142mains with Spec1, went 'down' to 130mains, back 'up' to 160 mains, then finally ended up with 135mains on the Spec10.  Of course they were changing all of the other jets, camshaft profiles, displacement, timing, etc. so it really is a crap-shoot.

It took me years of research playing around with different jet combinations and utilizing O2 sensors and EGT gauges to get where I wanted to be.  Without the aid of such devices, running a bit rich is cheap insurance.

 

 

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 Posted: 08-27-2008 06:06 pm
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Judson Manning
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This is an update after we put John Cronin's rebuild on the DynoPak last week.

John went with an extremely 'streetable' combination of 107 cams 104^ HTD sprockets fed by Dellortos and breathing through the standard tri-Y header.  I'll get around to posting the actual torque, HP and air-fuel ratios graphs one of these days.

The results showed an almost perfectly flat torque curve from 2500rpm to just over 5200rpm.  The intermediate dip in the curve corresponds to a/f ratios dropping to 11:1 from an ideal (full power ideal that is) 12.5:1.  The dip is right in the middle where the carbs are running out of the range of the a/c and idle jets suggesting the 145 mains are a tiny bit rich at full throttle.

For comparison my 2.2 running essentially 104 cams on 135 mains showed a steep  rise from 2000rpm to over 5000rpm.  That was until we smoked the clutch!  A dynoPak WILL find the weak point in your driveline.  At full throttle my a/f ratio was skirting the low 12:1 range.

The more dyno runs we get across the country and more data we collect on various combinations will most definately help us find better and better jet combinations.  Anyone else have dyno data they can share???

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