45 mm venturies in 48 IDA's?

[neil68]

I have a set of nice Italian IDA's on my 2332 cc street/strip engine, JPM heads with 48 x 38 valves, 10.7:1 CR,  1.75" headers, IDA's, etc.

When I purchased the carbs they had 42 mm venturies already installed, which I've left in place.  I've played with the jetting over the last couple years, but am wondering if the 48 mm JPM intake valves might work well with the 45 mm venturies that I picked up a few years ago  (I thought they were 44 mm, but in checking the Jaycee package it says 45 x 48 and sure enough they measure out to 45 mm).

Would this reduce the venturi effect too much in an IDA...even for racing?  I've heard of some racers using no venturies at all for drag racing.

My engine revs nicely to about 7500 rpm and is currently running a JPM camshaft with 274 degrees duration (at 0.050"/1.27 mm) and 10.8 mm cam lift (0.425").  Total lift is 15.24 mm (0.600") with my Scat 1.41:1 ratio rockers.

I know 44/45 vents are common with 51 mm bored out IDA's.  Anyone have experience using 44 or 45 mm venturies with 48 IDA's?

Thank you!

[Cheesepanzer]

I dyno'd a 2332 combo (FK89, 1 3/4" exhaust, 11 to 1, etc.) and picked up 8 RWHP moving from 42mm to 44mm vents.  I left them in the car and didn't really notice any difference in the overall street drivability of the car (i.e. idling, low speed, low RPM driving).  Definitely worth it for me, and I suspect 45's would probably react similarly.

[speedwell]

i already have a set of 45mm in my 48 when i've bought them 13 years ago , if i remember mine came from a De Tomaso pantera engine , i still have those one , but they're for sale

[JS]

I believe the total effective area of a 48IDA is just over 43mm when you take out the throttle shaft area. Hence why some people file down the butterfly screws and even the shaft itself to gain more flow.

[magic]

hi neil68

 You wonder right! Your JPM heads (48/38) IDA's, 2332cc., 10,7:1 cr, JPM 274deg. cam, 1,41:1 rockers , AND .... 1.75 "headers!( )..... Yelling for 44 or 45mm. Venturies! 

[Jon]

Why not go for the best of two worlds, 42 raptor venturis for good gas suction, but stil flows like a 45.

[neil68]

I removed the 42 mm venturies and installed the 45 mm Jaycee vents. My previous jetting included 180 main, 210 air and F2 tubes. Anyone have jetting suggestions to go with the 45's? Race track is at 670 m elevation.

Thanks.

[speedwell]

i don't  know if it help because mine where in a DeTomaso  but here's the jetting i've with my 48 ida and 45 mm

http://cal-look.no/lounge/index.php/topic,9723.msg200397.html#msg200397

[deano]

For what it's worth, I have driven a number of street cars with 45mm venturis and very few of them were streetable... The combination of huge ports, mongo cam, and 45s made these cars a pain to drive around town, especially around turns... They just fell on their face, unless you were buzzing them...

[neil68]

Appreciate the first-hand feedback, Dean.

There's only two more races this year, so I'll re-install the 42's after, until next spring.

Thinking about bumping up the air jets a bit more, as well...

[neil68]

Well, I installed the 45 mm venturies and ran the exact same ET's at the track, although the MPH was slightly higher (~2-2.5 MPH) more.  Didn't really notice too much difference driving around town, although the idle was smoother.

Going to have to get on the chassis dyno and experiment with some jetting...