Page 1 of 1

Weber carb jetting

Posted: Thu 11 Jan 2018, 20:51
by getafix
Need help with 38 weber jetting on my Sierra. Did some work on the motor after 700k kms - RJ cam, bigger valves, unleaded. Can't seem to get the jetting right - fiddling is driving me insane. Sluggish below 2500 rpm = bigger idle jets? Runs out of breadth at 4500 rpm. Idle jets current 55s, mains 137 air 180 - rest is what it was at assembly time. Any suggestions?

'Normal' driving not too bad ... but every once in a while hooligan mode kicks in and it is WOT ... :roll:

Any suggestions will be most welcome.

Re: Weber carb jetting

Posted: Thu 11 Jan 2018, 21:10
by bmwmaniac
get modern technology on your side. fit a wideband lambda probe and guage.

Re: Weber carb jetting

Posted: Fri 12 Jan 2018, 07:50
by BIGSIX
Hi Getafix,

I am running 145 mains and 210 air with 55 Idle and a 55 spray.

just check what spray jet you have and that's the one that sprays through on both sides.

also check your lifter clearances as this can take out some power if not right.

Let me know if you get it right as mine is not 100% yet!

Re: Weber carb jetting

Posted: Fri 12 Jan 2018, 07:52
by RASSIE
Mains 145 and air jets 185 and she will run super fast!!
Rassie.

Re: Weber carb jetting

Posted: Fri 12 Jan 2018, 11:33
by BIGSIX
I will try that this weekend as well.

Thanks Rassie!

Re: Weber carb jetting

Posted: Mon 15 Jan 2018, 13:02
by BIGSIX
Tried the 185 airs the weekend and not as good performance as the 210 airs. Might be because we are a bit higher up than you Rassie?

Switched my carb settings to 142 Mains 210 Air with a 70 Spray. Works well for me not sure if it might work on another motor or carb.

Just my 2c!

Re: Weber carb jetting

Posted: Mon 15 Jan 2018, 14:07
by getafix
Thanx Rassie,

Will try this very soon. Carb City the only place to get jets and only Monday thru Friday. :(

Re: Weber carb jetting

Posted: Mon 22 Jan 2018, 19:50
by getafix
Did the jetting 145 mains - 210 air. Top end much better. Still got a bit of 'hoes en proes' from standstill - comes alive at about 2500RPM - then it is 'hou vas!!!'

:)