Lotus Elan

Static Compression ratio (on California gas,91 octane)

PostPost by: holywood3645 » Sun May 16, 2021 8:19 pm

Couple of questions regards optimum Compression ratio (on California gas)
Q1
What is the highest static compression ratios are people on the west coast of the US building there engines to that are intended to run on the 91 pump gas?
Q2 what was there dynamic CR measured after build?
Thanks
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PostPost by: 1owner69Elan » Sun May 16, 2021 8:29 pm

10.3 CR California pump gas 91
'69 Elan S4 SE
Street 181 BHP
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PostPost by: Mike Ostrov » Sun May 16, 2021 9:36 pm

I concur with our Napa lad. I can do 10.5 with B cams. Dynamic compression numbers can vary depending on: displacement, cam profile, etc. My 1725 cc LB block, Stromberg head will provide 195 psi. This is in my Elite/Elan MK II with a C-4 automatic gearbox. Elan S2 frame, stretched 4.125 inches to accommodate the Elite wheel base, full adjustable suspension and re enforced, all on our 15 inch wire wheels. She did gain a bit of weight. Had to use the Stromberg head as the C-4 is vacuum controlled. Hope this is helpful. Cheers. Mike, only 45 minutes from Napa.
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PostPost by: holywood3645 » Wed May 19, 2021 12:16 am

Please... I appreciate some additional feedback
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PostPost by: bitsobrits » Wed May 19, 2021 1:25 am

While I'm not in California, we have 91 octane locally, and my 1720cc twincam (fully ported, large valves, high lift/short duration cams) runs just a bit over 10.3 static with no issues/pinking etc on the 91 octane. It does run a custom curve in the distributor with total advance listed to something like 28 degrees IIRC.
Steve

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Elan S3 1967 FHC pre airflow

Formerly:
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Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
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