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914World.com _ 914World Garage _ Changing empi venturis
Posted by: BK911 Oct 23 2014, 12:20 PM
'72 1.7
Pulled the FI off several years ago and installed a set of EMPI 40s.
Basically pulled them right out of the box and bolted them on.
Car runs pretty well and plugs all look good.
Over the weekend I was messing around and noticed the vents were 28mm.
Just did the calc and it said I should have 30mm vents.
So... should I?
How much of a difference will it really make?
With new vents goes new main and idle jets too?
Posted by: SirAndy Oct 23 2014, 12:23 PM
'72 1.7
Pulled the FI off several years ago and installed a set of EMPI 40s.
Basically pulled them right out of the box and bolted them on.
Car runs pretty well and plugs all look good.
Over the weekend I was messing around and noticed the vents were 28mm.
Just did the calc and it said I should have 30mm vents.
So... should I?
How much of a difference will it really make?
With new vents goes new main and idle jets too?
28mm sounds about right for a 1.7L. You want the smaller venturis to get higher air speed.
If your off idle throttle response is OK, don't mess with it. Larger venturis can create a "flat spot" where the main jets kick in.
Posted by: BK911 Oct 23 2014, 01:23 PM
Thanks Andy. She runs out pretty good. For a 1.7 with 100+k miles on her.
Posted by: rhodyguy Oct 23 2014, 01:40 PM
if you're pleased with the way it runs leave as is.
Posted by: maf914 Oct 23 2014, 02:31 PM
40mm IDF's with 28mm vents should be fine for a 1.7. I had 40mm IDF's with 28mm on my 2.0 with a mild street carb cam and it ran well and had very good gas mileage as well. Low end and mid-range were good, very drivable. Go with it.
Posted by: BK911 Oct 23 2014, 04:13 PM
Thanks guys. Just making sure I wasn't leaving lots of power on the table. 
Posted by: Krieger Oct 23 2014, 05:14 PM
Thanks guys. Just making sure I wasn't leaving lots of power on the table.
No biggie. Maybe 40-50 hp if you get it wrong.
Posted by: Mike Bellis Oct 23 2014, 07:57 PM
Thanks guys. Just making sure I wasn't leaving lots of power on the table.
You might be down 1 or 2 HP at 5500 rpm. The bigger venturis work well at high engine speed. Most of us don't stay at that rpm for long.
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