High mile 3.4 street build
 

The car – 85 Carrera 3.2 with 915 – Stock fender mounted oil cooler

I’m interested in gaining a better understanding prior to having my motor professionally rebuilt in the near future. That being said, I have come to the conclusion based on my limited researching of the subject that the 3.4 low compression Mahle set up is most conducive to my needs. With the idea of high mileage and with the limitations of realistic rev. capabilities, I think (again think) I am on the right track to commission a build that will prove the test of time. I just want to have most of my ducks in order prior to consulting with a professional.

What is the consensus regarding a mild mannered 3.4 street motor utilizing Mahle (98mm) 9.8:1 compression. Motronic will be kept and the idea of twin plugs in not out of the equation. The primary goal is longevity, reliability and the limitations of running on 91 octane fuel and relatively hot weather 90 – 110 degrees give or take. Detonation is a primary concern based on the increased bore size and the said operating conditions. Is it advisable to stay with single plug with matched components or is it wiser to “fork-out” the extra money for the twin plug again with all components designed to work in unison.

Thank you,

John

Upon further research, I think the answer to my question(s) is that twin plug is required with 91 octane fuel.

Absolutely, at that CR and displacement. :) :)

You will also need custom software to make all that run properly.

Thanks Steve:):)