I got #72 jets that came with the Holley 750vac. That was WAY too rich. I went down to 70 and now am at 68 jets and my A/F guage (if it is somewhat close to right) reads in the high/normal range.

With emmissions comming up next month, I was wondering if I could switch to #66 or so and help my chances out all the more. If the A/F gauge says I am running close to normal (not lean), then are they OK? Does that sound too small for a healthy 350 engine?

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

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1985 ASCD Ram Air Trans Am
http://www.execpc.com/~karpsta/home.html
to find out more
-=ICON Motorsports=-

 

you're not too lean until you start getting lean misfires (you will know it). Changing the jets probably will not help with emissions testing though.

 

Okay your are talking about 72's in the primaries. No 66's won't be too small as long as you jet the secondaries right. I assume you have a metering plate on the secondary side, right? Get a metering block kit and put it in. This allows you to jet the secondaries as well. You want to fatten up the secondaries a little, not much. Do plug checks and sniffer checks if you can while at WOT. Good Luck!

 

Changing the jets will help with emissions testing!

 

i put 66s in my 650 DP on a not so healty 350 and it back fired, start with a 68 or 69

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when the green flag drops the bull$hit stops

Curent: 350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast
Spring 01: 406, Comp 282 solid cam, 2400 stall converter, every thing else the same.

R.I.P #3

 

They're easy to change; just drop them 2 sizes at a time until it gets to where ti surges cruising, then go back the the prior size.

It's extremely difficult to predict what size jets to use. Lots of things affect that, sop just experiment until it's the way you like it.

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"So many Mustangs, so little time..."
ICON Motorsports

 

I did the drop down 2 jet size thing from 72-70-68 where I am at now. I have definately seen an improovement too, but I can smell gas and I don't get the best gas milage (about 15 mpg).

In NC, they rev the car up to about 3000 rpms for a minute to do the sniffer. I have plans on doing a vacuum leak to lower the emmissions levels all ready, this is as much for gas milage and daily driving as it is for emmissions I guess.

Thanks for the replies guys!

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Just so u get an idea i am running 68# jets on primaries on my 454 which is putting out 400+horsepower.My secondaries are 86. I 've got the metoring block on secondary side instead of metering plate.

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Big 454 72 Chevy Nova
383 86 Camaro Z28

 

I don't know for sure, but I think I do not have a metering block in the secondaries... yet. I'll have to look into one I think.

So maybe I could go even to #66 jets to see what that does. I think I'll also remove my floor mat so I get better acceleration!

 

Emissions tests run the carb 95% of the time on the IDLE CIRCUTIS, so jetting will have little effect on the tailpipe sniffer, but they will help in that little part of the test that actually uses the primary circuits.

The best thing you can do is lean out those idle screws as far as you can, without causing the idle to miss or stumble. I start with my idle set to the OPTIMUM point for warm engine idling and then start to lean it out a little bit at a time (evenly on both screws!) until I've chopped about 100 RPMs off the idle. That's gonna help cover up the excessively rich Holley off-idle circuits and give you the best shot at getting through without a problem. Remember to adjust the setting on a FULLY WARMED UP ENGINE- 10 miles of driving minimum before adjusting anything.

Really, as long as your cat is in good shape, passing a tailpipe sniffer is no big deal for most engines.

 

What power valve are you using? If you have a lumpy cam, try going to a 6.5 power valve, rather than the stock 4.5.