Nobody ever talks about 5R cases, Differences between 5R and 7R ? |
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Nobody ever talks about 5R cases, Differences between 5R and 7R ? |
michel richard |
Jun 18 2005, 08:26 AM
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#21
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Senior Member Group: Members Posts: 1,291 Joined: 22-July 03 From: Longueuil, Québec Member No.: 936 |
Whenever a discussion comes around as to which /6 engine case to use for a high peformance engine, the talk always revolves around the early aluminum case, the early mag cases or the 7R cases.
My 2.2 E is built on a 5R case, which is the case that was used for most 2.4 engines, including most 2.4S engines, I believe. I've never done a detailed side by side comparison of 5R and 7R cases, but I could'nt see differences between a 5R in my hands and pictures of 7R cases. I could see a number of differences between 3R (early mag) and 5R, however. And I did have to get creative to fit the 2.2E distributor to the 2.4 case (the hole was too big, and the locking mechanism different). So what is it? Do people forget the 5R because it's close to the 7R, because discusssions have just not gotten around to it ? because it's a little rarer ? or another reason ? I'm asking because I'm beginning to contemplate a short stroke 2.5 project, and I would really like to keep my case. The advice is often: go to a 7R, it'll end up cheaper etc . . . But I had to go through 4 cases before finding the one I have - finding good cases is harder when you're not in California, so that starting with a known quantity is a definite plus. So, the question really is: can anybody help me figure out what the differences are between 5R and 7R cases ? TIA Michel Richard |
ArtechnikA |
Jun 18 2005, 09:28 AM
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#22
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
yes - and those 92mm-spigot '73.5 7R's are pretty highly prized by guys trying to build up HiPo <2,7 engines...
there are many guys on the Racing List who actually prefer the 5R - or even the 3R cases. all the cases need prep machining, and they're all a bit fragile when pushed to the edge, so (as their thinking goes...) you might as well start with one that's had a much easier and less stressful life as a street engine. i think the point of diminishing returns hits with the 1R (i think it is...) that was the first case to have piston squirters. IMO these are essential, and are simply nonnegotiable for any Nikasil P&C. it will cost a bit more to have 3R or 5R cylinder spigots opened up to 97mm like the '74+ 7R's but it's a drop in the bucket to the full cost of a race-prepped engine... and that presumes you're building a 2,7 or a 2,8. if you're building a <2,5 you want the 92mm spigot case, and if you're going bigger, you should be starting with a 3,0 SC case... |
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