Weber Venturi Size - what difference does it make

[Fishcop]

From what I understand, Richard (the bloke that runs the show) keeps it a small affair and is not particularly computer lierate. But rest assured, if you're after something in particular - PMO will have it.

I know thre is at least one rock show over here that can do webers properly... just can't remember who

[RoninLB]

", Richard (the bloke that runs the show) keeps it a small affair "




he spends a lot of time with satisfying many customers needs and quirks when he calls you back. If he was phone accessible to the masses he'd be broke.


I bought a running set of Weber 40IDA, then traded to nice 40IDS, then said screw it.. the more I knew the more I need PMO. They are unbelievably accurate. Keep in mind that the A/F mix among all 6 should be equal for equal piston power and the strongest running engine. Their differential between the strongest and weakest piston power is in league with high end precision FI, if not tighter.

If you're a carb nut there is no substitute.

all above a prejudicial rant.

[matty74]

Yeah I'm really consider ditching the webers for PMO's on a 2.7 should I go 40 or 46??

[RoninLB]

Carb size and venturi is a function of max rpm air flow as per cylinder size x6. Venturi should be about 80% of butterfly size.

a 2.7 at 6.5k calls for a 40 with measured 33.5 or 34 actual venturis.

[Fishcop]

What Ron said Not sure what you're plan for the engine is, but if it's not running high revs, then a 2.7 is generally better on 40's. In layman's terms, the volume in each cylinder of a 2.7 does not create enough "suck" to get 46's to do their thing in normal or street conditions.

From memory, both Anderson and Dempsey recommend 46's only on 3.2 litres and above.

[randywebb]

Originally posted by matty74
Yeah I'm really consider ditching the webers for PMO's on a 2.7 should I go 40 or 46??

You said 'street rod' but you already have fairly aggressive cams - GE60 cams. So I guess the emphasis is on 'rod.'

You also do not have particularly high compression. I guess it is single plugged?

You might want ot back off a bit (go up a level of abstraction) and think about what you really want out of this motor. That (plus what fuel you can get both now and in the future) will determine what to do to the cams/plugs/carbs, depending on your wallet. Or maybe you want to go to a 2.8L !!??

Generally, I'd say 40s tho.

Post what kind of driving you do and the traffic densities you encounter - are you in the middle of Sydney or way out in the outback?

[matty74]

Thanks guys I went with the agressive cams just in case later I wanted to race but yeah 40's are the go.

I mainly do weeekend driving in the car some times country occassionaly to work in the city, and the occassional track day.

I'm going with JE pistons and the plan is to stay single plugged.

[randywebb]

Based on that I'd either tinker with the Webers or get PMO's and I'd fax all the info to Richard -- offer to set a time for you to call him since its very LD. He'll prob. call you anyway.

You might want to start a Weber vs. PMO thread, but in summary the PMOs fix every issue with the Webers and are far superior, except for the period-cachet. But they do cost a lot, so ...

[matty74]

yeah, but from what every body says about them, money well spent

[randywebb]

I thnk so, that's why I bought them.

But you already have Webers...

[Drago]

Originally posted by Fishcop
From memory, both Anderson and Dempsey recommend 46's only on 3.2 litres and above.

So 40's should be good for a stock 3.0L SC motor?

I currently have a bone stock '69T w/ 40 IDA Webers. I know someone who is parting out an SC and I've though of buying the motor (along w/ other bits) and installing it in the '69.

Just curious...if the 40's are to small for a stock 3.0L SC motor I'm going to save my pennies (and benjamin's) and buy a set of PMO's.

[Fishcop]

In my opinion the 40's will be totally fine for what is a fairly mild state of tune (SC) 3 litre - infact I reckon you've still got a little bit up your sleeve if you ever wanted to up the duration of the SC cams. Obviously you'll need to go 34 venturies instead of the current 27. I simply had my 27mm machined to 34mm using a borrowed genuine 34mm as a template.

[matty74]

Yeah I may have webers already, but I'll sell them to buy a set of PMO's and be done with it

[TimT]

but I'll sell them to buy a set of PMO's

keep the webers.. no need to throw money away..

[RoninLB]

Hi Tim.. funny story.

when I was buying and then trading upscale with my Webers a friend was doing the $ trading as I'm the worst. Needless to say the guy flipped when I threw 1/2 the profit on them at him. He violently opposed the $ so I spent $200 on an Xmas toy for him.

WTF.. carb $ and I got PMOs.. bingo.

otherwise Webers can fine to use and you shouldn't lose $ trading them for PMOs.