View single post by discogodfather
 Posted: 07-10-2020 05:33 am
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discogodfather



Joined: 09-17-2007
Location: San Francisco, California USA
Posts: 221
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 Major discovery today- as I was doing my usual swapping of jets and tubes I decided to change back to the 38mm chokes. I have long intake trumpets and since my top end rebuild I had fitted a set of "filter socks". They are just a foam element cut into a little cap like shape and then you simply put them on the trumpet.

This time I didn't put them back on, and didn't fit the trumpets on either, just a naked DCOE. I immediately noticed the idle was different and readjusted, then realized my AFR's were completely different. Running her around the AFR's had shot up by 2-3 points and transition was great, and now VOOM- big RPM's pulling very hard up to 7000+. So those awful air socks had really screwed up my tuning.

Using F3 emulsion now and she is running very nicely, the best ever really since I got her. Running 125 mains seemed awfully lean given the setup with the 104's and the high compression, and naturally it was way to lean and sneezing without the restricted intake. Went up to 145 mains and now she pulls like a horse in the higher rpm's, but I still feel it's a bit lean. New ratios are:

Idle = 13.5 to 1
Light throttle = 14.5 to 1
WOT = 12.5 to 1
Cruising most rpms and loads = 13-14 to 1
Closed throttle - 15-16 to 1 (some popping still)

Years ago when she always had this setup (before the wideband):

125 mains
170 air correctors
F3 emulsion
55 pump jets

I remember Judson telling me years ago that the pump jets seemed really big and the mains a bit small, and I think without the wideband the original setup was fooling us in the sense that the pump jet was hiding some major flaws in the main circuit. I also remember reading Tim Engel's advice on how the pump jet is often diagnosed as a problem when it's really the mains. Too bad that didn't sink in!

New setup:

145 mains
170 AC
F3 emulsion
45 pump jets

Really starting to scream! Transition is a dream with no flat spots or issues, she just blazes through it. Going to try 150 mains and slowly see if I can raise the air correctors up a bit, should help with mileage.

FYI those sock puppet filters really suck. I'm working on an airbox with a cold air feed, so may dust off some old K&N filters until I get that system up and running.