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post #1 of 4 (permalink) Old 06-09-2010, 09:06 AM Thread Starter
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Exhausting Cam Question

The stock exhaust cam for the 80-81 2000 engine, 105200320000, is specified with the exhaust valves opening at 58 deg. DBDC and closing at 34 deg. ATDC . The 10548 “euro” cam has these exhaust events at 54 and 35 degrees respectively, very close it seems to me. Am I wrong to think that the 80-81 exhaust cam should perform substantially the same as the 10548?

The previous owner had the stock VVT intake cam replaced with a 10520 SPICA cam, year unknown., and I am contemplating using either a Centerline ‘Euro+” (10.5mm lift), or maybe even their 11.1 mm performance cam, on the intake only. The PO did have the engine rebuilt with 10:1 pistons, but I do not know of any other mods , such as porting, big valves, etc. The engine has dual Webers, a tube header, and as of this weekend will have a 123 ignition, set to use the 045 advance curve. I am looking for a nice, torquey street engine, not a banzai screamer. Thoughts?

Andy
81 Spider - 1980 VIN
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post #2 of 4 (permalink) Old 06-09-2010, 09:55 AM
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My engine spec is similar to yours. I have had standard US cams, Euro cams, CB47's, an RJR cam in the intake and a CB47 on the exhaust, and RJR cams on both intake and exhaust. The last two combinations are far superior to the others and the last combo is noticeably better than the RJR/CB47 combo. Richard communicated with me as I experimented with lobe centers and he has driven my car with it's current configuration. We are both very pleased with the outcome.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #3 of 4 (permalink) Old 06-09-2010, 02:13 PM Thread Starter
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Ed: I have been reading your old threads and posts on this subject for some time and I appreciate your posting your experiences. My decision to use the 123ignition was in no small part due to your recommendations.

I do not recall, but did you modify your head at all to use the high lift cams? Did you replace the tappets every time you changed cams? At the present time I do not want to do any head work, and my thinking was to go slow with cam changes and leave the more radical changes until some future rebuild.

Andy
81 Spider - 1980 VIN
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post #4 of 4 (permalink) Old 06-09-2010, 05:28 PM
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Hi Andy,
You can use cams with about 11mm lift without modifying the head. CB47's are 10.9 mm.
Anything higher and you have to cut notches in the tappet bores. It is pretty simple if you have the head off and the valves out. My current cams are about 12,3 mm intake and 11,5 exhaust. I bought a prepared head from Richard. He ported it and set up the Isky valve springs. I did not replace all of the followers - just any that showed wear, but I did break in Richard's cams per his advice which is also on the Webcams site.

I did not have to make much adjustment to the Webers when I switched from US to Euro to CB47. I had to make significant changes when I switched to Richard's cams. They require smaller main jets. My emissions Webers needed F34 emulsion tubes.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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