[snbush67]

Originally Posted by Bobboloo

Hi guys,

I could use some help on jetting for a 3.5L engine I built with PMO 46 carburetors and Mod S cams from John Dougherty.

The engine started as a 3.0Lbuilt as follows:

3.6 crankshaft
3.6 oil pump
Mahle 98mm high compression P+C set.
10.3 to 1 CR
Patrick Motorsports Twin Distributor
Heads ported to 40mm intake 38mm out
Mod S camshafts
MSDS headers

Current jetting PMO 46's

190 air corr.
F11 emulsions
155 main jets
38mm chokes
55mm idle jet?

The car runs great but it's a bit rich.
Here's some numbers I got with my LM-2.

RPM's AFR
Idle 12.3:1
2500 11:1
3000 11:1
3500 12:1
4000 14:1

Any suggestions on leaning out the 2500 to 3500 range?

I think your chokes are way too small, typically smaller chokes will mask improper set up and balance. The mod s cam is docile for your 3.5.

190 air corr. Probably good
F11 emulsions. Maybe
155 main jets. 165 maybe bigger
38mm chokes. 40’s and maybe 42’s (more air in, better Signal)
55mm idle jet? Maybe try a 56.5 or 57

Your AFR 14:1 at 4000 is bad. That lean at 4000? That means you’re likely going receive lean damage at 6500.