Hi guys,
I'm starting yet another topic on DCOE 45 jetting for a modified stroker L31 engine. The reason is that I would really like some feedback from someone else with a similar setup as after 2 years of driving / tuning / jetting it I still have not managed to get rid of the "bog" if flooring it below 2500 rpm.
Engine specs: L28 bored / stroked to L31, ported head & intake manifold, MSA 6-1 headers with 2.5" exhaust, Schneider "270-80F" cam (270/280 duration, .460" lift), 10.5 to 1 compression, ZX dizzy, a set of rebuilt Webers DCOE 45
DCOE jetting: 38 chokes, 155 main jet, 185 air corrector, F11 emulsion tubes, 55F9 idle jets, 60 pump jets, closed back-bleed valve
So the engine runs nice, dyno showed 242 HP@6600 rpm (calculated crank), AFR is around 11-12 at idle and cruising, 12-13 at WOT.
If I floor it below 2500 rpm the AFR gets really lean and all power is gone. I tried to fix that with a bigger pump jet (60) and a closed back-bleed valve and it helped a bit, but didn't really solve the problem. As the idle/cruising AFR is already on the rich side I don't want to increase the idle jets.
My theory is that the 38 chokes are a bit too big, or that the cam is too mild and doesn't produce enough flow to correctly draw fuel at low rpms. Any other ideas how I could improve the low rpm acceleration phase? Any other hints on the jetting setup?
Many thanks for all the help! :)