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914World.com _ 914World Garage _ Experience w/46mm Weber or PMO’s and 36mm venturies on an otherwise RS spec 2.7L?
Posted by: Rufus Jan 2 2024, 07:09 PM
Does anyone have firsthand experience to share on running 46mm carbs and 36mm venturies, either Weber or PMO’s, on a street driven 2.7L engine that’s otherwise built to RS specs; I.e. 8.5:1 P&C, ‘S’ cams, 6500 rpm power peak? Thanks in advance for any input.
Posted by: mepstein Jan 2 2024, 07:44 PM
PMO’s are better track carbs than street. They aren’t great at low rpm’s. The new ones are pretty expensive and quality control isn’t great.
Posted by: Rufus Jan 2 2024, 07:56 PM
PMO’s … quality control isn’t great.
Thanks Mark. That answers another question I’ve had. I had a long chat with Richard Parr soon after he sold to EMPI. I was trying hard to find a set of PMO’s made under his ownership, and expressed that sort of concern based on my career experience.
Posted by: mepstein Jan 2 2024, 08:11 PM
PMO’s … quality control isn’t great.
Thanks Mark. That answers another question I’ve had. I had a long chat with Richard Parr soon after he sold to EMPI. I was trying hard to find a set of PMO’s made under his ownership, and expressed that sort of concern based on my career experience.
It’s what the owner of the machine shop that we’ve been using for 20 years has said to me. He sets up carbs for race cars at summit point. He knows Richard. He said every new empi pmo has required hours of work. The old ones were RTR out of the box. He said empi let go the employee who built the carbs for pmo and now they are just thrown together.
The nice thing about Webers is the availability of parts all over the world. Tried and true.
Posted by: infraredcalvin Jan 2 2024, 10:11 PM
Why not 40s? I think you may be choking down the 46s a bit too much for a street driven engine…
Posted by: Rufus Jan 2 2024, 11:03 PM
Why not 40s? I think you may be choking down the 46s a bit too much for a street driven engine…
Before encountering fuel system problems related to debris, vapor leakage, etc., my 2.7L RS spec engine ran great (idle, cruise, wot, transitions, low speed tractability, etc) with 40IDA’s and 36mm venturies.
I more recently saw this:
http://www.performanceoriented.com/throttle-body-and-main-venturi-sizing
My understanding from that is a 46mm throttle body’s a better match to my 36mm ventury than the 40’s. Asking for 1st hand experience as confirmation.
Just doin a little winter dreaming during times when I’m unable to work on my 914.
Posted by: BillJ Jan 3 2024, 07:48 AM
That was the config on my 2.7 with PMOs and that engine ran great. Mechanic has since changed them to match with the new 2.5 twin plug, but was a nice combo. Not sure on jetting.
Track only however.
Posted by: Rufus Jan 3 2024, 10:04 AM
That was the config on my 2.7 with PMOs and that engine ran great. Mechanic has since changed them to match with the new 2.5 twin plug, but was a nice combo. Not sure on jetting.
Track only however.
Thanks Bill. Great info that begins easing any doubts I’ve had.
Now, anyone have experience with this in driving on the street?
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