Austin Branson Posted April 8, 2019 Report Share Posted April 8, 2019 Greetings, Oh Sage One’s! My ‘74 CF starts readily, and runs well when warm, but the 5 or 10 minutes in between are awful, firing on only 4 or 5 cylinders. I’ve changed all the usual suspects. Has anyone got any ideas? I am running a single 2 inch SU and a supercharger. many thanks, Austin Quote Link to post Share on other sites
Waldi Posted April 8, 2019 Report Share Posted April 8, 2019 Austin, it could be a fuel issue. Running lean maybe? A bit related: I have a CP car with original Lucas System, with an AFR sensor in the exhaust and a gauge in the car. Yesterday when I started the car it ran reasonably ok (for a cold engine after not having run for several weeks) but suddenly ran or 4 or 5 cylinders. AFR was like 15-16, so it was running lean. Suddenly, while I playd the choke, the engine run ok on all 6, and I could see an immediate shift in AFR to 13. Waldi Quote Link to post Share on other sites
Mike C Posted April 8, 2019 Report Share Posted April 8, 2019 I guess you've checked the fuel enrichment system works. Last SU carburetted car I had (50 odd years ago) this was a cable operated lever that lowered the main jet. Quote Link to post Share on other sites
Tim D. Posted April 9, 2019 Report Share Posted April 9, 2019 I have the Holly supercharger setup and I get the odd backfire when cold. I have checked with the AFR meter and it is running a little lean. Trouble is the enrichment on the Holly isn't great. Have partially solved it by running a little rich at idle. Could be a similar issue with your SU. You may want to richen it up a tad. Tim Quote Link to post Share on other sites
stuart Posted April 9, 2019 Report Share Posted April 9, 2019 Put some thicker oil in the dashpot. Stuart. Quote Link to post Share on other sites
Austin Branson Posted April 10, 2019 Author Report Share Posted April 10, 2019 Thanks for all your responses. Waldi - I have an AFR guage, I’ll take a good look next time out. Mike - yes, I’ve checked that and it appears OK. Tim - I can try that, thanks. Stuart - I have some EP80/90, will that be OK? Again, many thanks. Austin Quote Link to post Share on other sites
stuart Posted April 11, 2019 Report Share Posted April 11, 2019 13 hours ago, Austin Branson said: Thanks for all your responses. Waldi - I have an AFR guage, I’ll take a good look next time out. Mike - yes, I’ve checked that and it appears OK. Tim - I can try that, thanks. Stuart - I have some EP80/90, will that be OK? Again, many thanks. Austin When I used to race Jaguars back in the 70`s and 80`s we used to make up a version using anything from 3in1 to 20/50 engine oil or 20/60 and in cold weather thin it with a bit of diesel, I think gear oil maybe too thick on its own but it would be trial and error, you would be surprised what a difference it makes, damper spring poundage also makes a difference. Stuart. Quote Link to post Share on other sites
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