911ST specs by year

[obrut]

hi all

i'm reclassing my rally car and will be using the 911ST as my "base" specs. the permitted engine and wheel sizes are based on the sizes used on the base car.

My questions are:

1a. what was the biggest engine size used in 1970?
1b. what was the biggest engine size used in 1971?

2a. what was the biggest wheel sizes used in 1970?
2b. what was the biggest wheel sizes used in 1971?

I should also mention that our rules refer to actual dates of usage not model years. (e.g. as 1972 model year 2.4's were first released in the last few months of 71, then this is classified as allowable for a 71 spec car)




ps. the short version of the above questions is when did the ST first use 2.5 litre motors and when did they first use 7" rear rims.

[CamBiscuit]

Ryan

Some good info to be found here, not sure if you have seen these sites:

http://www.toadhallracing.com/oppenh...e%20911st.html

http://www.911handbook.com/articles/e_davem911.html

It looks like the 2.5 was produced when the 915 trans was first produced so maybe late '71?

I hope those in the know will chime in here, interesting questons.....

[a911s]

For the 1970 racing season Porsche needed a new 911 (ST) for the Group 4 GT class. Initially the ST motor was 2.25 liters, then 2.38 liters, and finally 2.5 liters (to stay within its class). The 2.5 race motor was developed for the 1972 race season, initially as a long stroke version (70.4) and later as a short stroke (66). I think 1971 is correct for time of development of the 2.5.

[a911s]

As far as wheel sizes for the ST, I believe that for both 1970 and 1971 the widest wheels used were deep 7R 7x15s Fuchs on the front and 9x15 Minilites on the rear. I have seen some vintage photos of 8x15 Fuchs on the front and 9x15 Fuchs on the rear of 1972 STs - not sure if those were used earlier in 1971.

[Chuck Miller]

Looking through my references it seemed 'things' were changing pretty fast from '70 to '72 … and it looked like the Kremer Bros. were always on the sharp end of it all.
Engines, fender profiles, tires and wheels…. Whatever was next, was best… (in most cases.) The last iteration of the late '72 ST looked just like an RSR except for the tail and front cooler…and they were on 9's and 11's.

I love'm all .......

[OliveR]

Spoke with Mezznarie about the Larrousse ST,appears engine was close to 2.6 ...

[kenikh]

Harvey Weidman will have some valuable input on this if you ask him.

[a911s]

Looking through my references it seemed 'things' were changing pretty fast from '70 to '72 … and it looked like the Kremer Bros. were always on the sharp end of it all.

Yup, Kremer's '72 LeMans 911ST had 8 & 9 x 15 Fuchs.

[boba]

From the day.

[obrut]

thanks for the replies guys

"I think 1971 is correct for time of development of the 2.5."

ok, any ideas as to how i can verify the above? our rules allow a 17% displacement increase. if my starting point is a 2.4 i can run a 2.7, but if i start from a 2.5 i can build a 2.8.