Zenith rebuild

[Rob Pritchard]

Hi,
I'm having my Zeniths rebuilt to match up with a 2.7L S cam, 10.5:1 piston, 2.4 crank rebuild, on a previously stock 2.4T engine.
I've bought 34mm venturis, 145 main jets, and 65 idle jets. Do I also need to upgrade the air correction jets or anything else, and does the combo of jets and venturis sound like a good choice? I wasn't sure whether to just go for 60 idle jets.
Thanks in advance to everyone who gives me some advice on this.
Cheers,
Rob.

[Daugaard]

Hi Rob.

When I renovated my zeniths i had good use of these threads:

Zenith TIN Idle Air Jet Modification

And

Zenith 40 TIN Carburettor Manual

[Rob Pritchard]

Thanks Daugaard - I'll take a look. I'm looking forward to trying out the carbs with the venturis I bought from you.

[VFR750]

I'd say you would probably be happier with 60 idles. 65 will be too rich

145 mains seem a little too small. 150-155 might be better. The S cam is going to need fuel.

Going the carb route normally means playing with jetting.

[Rob Pritchard]

Any ideas on the air correction jets? I've read one article recommending going up 50 from the mains, so I'd be starting off with 195s.

[VFR750]

Zeniths are not like Webers. They tend to lean out more at high power. Hence a smaller air correction is probably better.

I found 165-170 air correction jets are best with 160 mains for my 3.0 with a milder DC20/19 cam.

I also drilled out the acceleration jets from .3mm to .46mm. And I've experimented with a revised bellcrank profile to get the acceleration jets to squirt more earlier in the top in.

All my experiments are documented here. Search "Zenith TIN" the stuff from 2010-2011 goes into a lot of main and air correction interaction.

[Rob Pritchard]

Thanks VFR750