QUOTE(ablesnead @ Jan 12 2018, 12:25 PM)
I think GTU was 2.5 in 76...maybe GTO, as a non porsche special...?
correct
1976 IMSA had the GTU, and GTO cut off is at 2.5Liters
however the race club that mike is asking about (RMVR)
only adopted IMSA rules that include 6cylinder and 8cylinder cars
so within rmvr, no 4cylinder IMSA cars are currently accepted under current rules
the rational at the time those IMSA rules were adopted by rmvr was that no gtu cars were interested and the person writing and researching the imsa rules saw no reason to write gtu rules and do the work for a class that no one was interested in.
(its a lot of work to adopt rules and go through them with a fine tooth comb)
so 6 and 8cylinder cars are currently legal.... 4cylinders are not until someone puts in the hours to write and refine the rules, and then puts it through the board.
(only 50 to 100 hours of volunteer work)
sometimes vintage rules are weird... because the person volunteering all of their time is only willing to do so much free work.