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914World.com _ The Paddock _ SVRA RMVR HSR 914/6 gt vintage engine questions.

Posted by: jmz May 16 2023, 05:24 PM

Thinking of putting together a 2.3 or 2.4 914/6 gt spec engine that will be vintage legal

Anyone here running one? Looking over different rules it’s hard to decide on short strike (66mm crank) or long stroke 70…

Logged a call to SVRA tech waiting on a a call back

Anyone have any experience or thoughts?

I have a set of large port racing heads (41 mm intake ports) some RSR sprint cams, twin plug distributor and 46ida carbs already. …plus a donor 2.0 litre. (Matching #s to my six)

Hope to hear some thoughts and/or experience.

Posted by: BillJ May 16 2023, 06:55 PM

I am having a legal motor built now. It is 70.4 with custom 85 pistons. If you go long stroke that is the only size that will keep you under the 2399 limit (well techncially you can do 86.2). Otherwise just got with 2.0 ltr 66mm crank and have fun in that class. Staying under the 2399 limit makes you legal in several orgs without competing with the 3.0 RSRs.

I see you have a 2.5 already. What is your experience there?

Posted by: jmz May 16 2023, 10:31 PM

QUOTE(BillJ @ May 16 2023, 07:55 PM)

I am having a legal motor built now. It is 70.4 with custom 86 pistons. If you go long stroke that is the only size that will keep you under the 2399 limit (well techncially you can do 86.2). Otherwise just got with 2.0 ltr 66mm crank and have fun in that class. Staying under the 2399 limit makes you legal in several orgs without competing with the 3.0 RSRs.

I see you have a 2.5 already. What is your experience there?

I race in the big bore class including the 3.0 RSR with 1974 IMSA rules with my local club and it’s a lot of fun.

I’m just looking at options plus I may use the 2.5 for something else. SVRA published rules do not specify if short strike ~2.4 is legal. HSR rules seem to specifically allow for it.

Posted by: BillJ May 17 2023, 04:35 AM

I do think the <2400cc is the sweet spot for classification for many orgs thus why i am building one. PCA is specific about it (not that they really are checking all that hard), HSR as you note bumps the 2.5 to the big bore but keeps under that in a reasonable class.

Posted by: jmz May 17 2023, 07:52 AM

Bill, any specs on your build? Port sizes, cams, compression?

Posted by: BillJ May 17 2023, 08:41 PM

46/41 for ports and the cam is a DC60 or DC43-102. We are looking at right around 11:1 compression. I think we did 85s with a 70.4 crank.

Hoping to get somewhere around 240hp but more importantly a nice wide useable power band.