JET SIZE/SEAT OF THE PANTS

[Dave the Wave]

is it possible to actually feel a power increase by changing jets? ok, i read a long article about tuning edelbrock carbs. in it, it states, to never have bigger jets in the secondary as to the primaries. so i dropped one size, and man, it really seemed to kick ass. so, i ordered the NEXT size smaller, so, we`ll see. thanx

[Dave the Wave]

ok, .098 in the primaries, had .095 in the secondaries, put .092`s in. ordered .089, next size smaller. we`ll see.

[enigma57]

How did the jet change work for you, Dave?

Best regards,

Harry

[markm]

What carb uses those sizes a Dominator, that sounds like what is in my race car.

[Old Buzzard]

^^ This.
What do the plugs tell you?

[Dave the Wave]

as stated in my first post, edelbrock. btw, 650 cfm. never got to the .089`s. as for the plugs, brown, a little dark brown. thanx.

[markm]

On those don't you have to take into account the metering rod size too.

[Dave the Wave]

not on the secondarys. but yes, on the primary`s.

[Rick_L]

Edelbrock publishes a "tuning guide" for these carbs that shows the original jets/metering rods and the correct progression to richen or lean out from there. You can also find it online. While it might be marginally Ok to richen or lean using the progression without instrumentation, I wouldn't deviate from that progression without a dyno and and an air fuel meter.

[Dave the Wave]

you are exactly right rick, however, it`s a "guide", not gospel. to many variables with engines/components. i loved playing with it to get it right. like i said, i read this article, just got me thinking. and it`s been so long reading the edelbrock tuning guide, i don`t remember anything mentioned about WOT and jetting. as for the primaries, i went strictly by the graph that came with the "kit" i bought. and then purchasing more needles and jets.

[Rick_L]

I'd say it's as close to gospel as it gets. I do believe it does discuss WOT vs. cruise. Metering rods have a step on them. When the fat part of the metering rod is in the jet, that's a leaner mix for cruise. When the rod pulls up and the small end of the metering rod is in the jet, that's your richer mixture for WOT. So the way you tune the split between cruise and WOT is with the metering rod.

Just like with a Holley, you don't want to run a really rich secondary and a really lean primary. One step of mismatch is OK, that's how you fine tune. If you get lost, always go back to what they put in it at the factory and tune from there, and get an AFR meter or professional help.

[Dave the Wave]

yes, that`s the richer mix for WOT in the primaries, but all i was talking about is the secondaries. i actually think it went better with a leaner jet in the secondaries, thinking it was to rich. plugs are great, driving/idleing around town, so i`m leaving the primary alone.

[Dave the Wave]

just thinking it was just to rich WOT. that`s all.

[Rick_L]

Thing is, you want the mixture to be richer at WOT than you do at cruise.

Typically, cruise AFR needs to be 14.0-14.7. WOT AFR needs to be 12.5 or so.

[Dave the Wave]

yup, you`re right, rick.