 SVRA RMVR HSR 914/6 gt vintage engine questions. |
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| jmz |
 May 16 2023, 05:24 PM
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#1
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Member  Group: Members Posts: 165 Joined: 11-April 16 From: Lone Star State Member No.: 19,886 Region Association: None  |
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. |
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| BillJ |
May 16 2023, 06:55 PM
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#2
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Senior Member Group: Members Posts: 1,091 Joined: 4-March 13 From: charlotte, NC Member No.: 15,610 Region Association: None 
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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? |
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| jmz |
May 16 2023, 10:31 PM
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#3
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Member Group: Members Posts: 165 Joined: 11-April 16 From: Lone Star State Member No.: 19,886 Region Association: None |
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. |
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| BillJ |
May 17 2023, 04:35 AM
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#4
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Senior Member Group: Members Posts: 1,091 Joined: 4-March 13 From: charlotte, NC Member No.: 15,610 Region Association: None
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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.
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| jmz |
May 17 2023, 07:52 AM
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#5
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Member Group: Members Posts: 165 Joined: 11-April 16 From: Lone Star State Member No.: 19,886 Region Association: None |
Bill, any specs on your build? Port sizes, cams, compression?
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| BillJ |
May 17 2023, 08:41 PM
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#6
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Senior Member Group: Members Posts: 1,091 Joined: 4-March 13 From: charlotte, NC Member No.: 15,610 Region Association: None
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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. |
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