Lotus Elan

Simple carburettor advice?

PostPost by: blueseamonkey » Mon Nov 14, 2005 1:29 pm

Since buying my +2 a couple of months ago, I have been avidly reading every word of Keith's (and other's) posts on this forum about how to tune the carbs. I have barely understood a word of it :oops: , but was until today satisfied that my car was well tuned and in good shape. The previous owner had fairly recently taken the car on a rolling road dyno and managed to get 100bhp at the wheels. So for me at the time, ignorance was bliss.
Unfortunately I had a problem on a longish journey yesterday that both myself and the RAC man thought could be carb related... turns out it wasn't and the actual culprit was the electric fuel pump - this problem is now rectified, but not before the RAC man had adjusted several things on the carbs. I wasn't able to see all of what he was doing as he kept needing me to turn the ignition etc...
The eventual outcome was that he got the car running again, but it does seem to be lacking a bit of the power it had before, and certainly sounds different. :(
So... my questions are these: Is there anyway I can sort this at home? (I've read the relevant workshop manual section, but it doesn't sound much more accurate than what the RAC man did) What equipment will I need? Is there a book that explains this in very simple language? (I am aware of the 'how to tune Weber's' book, but worried it will be way over my head like all the discussions on here about carbs) Am I best off leaving it (after all, it is running) and waiting until I can save the money to go back on a rolling road again? Or would my money be better spent starting a fund to buy Keith a plane ticket to come over to the UK for a trip to tune mine and all other contributer's carbs? (Go on Keith, you know you want to! :wink: )
Set-up of the car is as follows: Weber 40s with K&N filters, big-valve conversion. Lumenition ignition with sports coil... don't know if you need any other details?
Anyone who can point me in the right direction would be a great help, and if anyone does have the patience to write an idiots guide to simple carb tuning I will be very grateful.
Rick
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PostPost by: type26owner » Mon Nov 14, 2005 2:24 pm

The eventual outcome was that he got the car running again, but it does seem to be lacking a bit of the power it had before, and certainly sounds different. Sad

You'll have to be more descriptive then that to get help from me. Did he change the jets? If the adjustments were done with a screwdriver you can do those and set it back with some coaching no problem.
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PostPost by: twincamman » Mon Nov 14, 2005 3:05 pm

I'm assuming the assistance man changed the balance and/or fiddled with the idle screws so the easiest way is to adjust the balance screw [ found between the carbs on the throttle linkage ] turn it out or in until there is no rocking of the motor at idle and then when the motor is warm turn each idle screw in to the bottom [ gently now or you will screw up the points on the idle jet screws ] and turn each one out 1 and 1/4 turns ----oh yes put some new plugs in or clean the existing plugs with carb cleaner before you start ----remember carburetter is French for leave it alone----the problem will be somewhere else contrary to popular belief once a carb is set correctly it wont change --even Webber's --look to plug wires --spark plugs-- points condenser--[your wiz bang replacement part where the points used to be] or other distributor faults or bad gas [burp] also check the carbs are snug to the 'o' rings --as in no air leaks note snug NOT tight or the ear on the manifold will break off ----or take it to France where the rabble will solve your problem by burning it :shock: ed
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PostPost by: blueseamonkey » Mon Nov 21, 2005 8:48 pm

Ok, sorry for the delay in relying, but I've been away a few days. Have now had chance to drive the car further and see if I could add any more details.
The RAC man did look at the jets, but I don't think he adjusted anything there. He was using pliers, but I think he just adjusted some of the screws. As I said, it was difficult to tell because I was sat in the car while he made most of the changes.
The slight loss in power seems not to have affected the lower end of the revs range, that is fine, it appears to be just in the mid-range. Having taken the car on a further long drive it doesn't seem to be as big a difference as I first thought, but it is still there.
The change in sound, seems to be that at higher speeds there is a louder noise of air rushing, which as far as I can tell may be coming from the carbs. The increased noise is not present at idle or I would be able to localise it better for you.
The only other hint I can offer is that the engine is running at higher temperatures than previously, I don't know if this is related at all to the change in weather (its well below freezing here now) but the engine temp is 10- 15 degrees higher when driving in traffic than it used to be. I've got a direct water temp gauge and the electric fan kicks in at 90 degrees, but even with this the temp is now rising up to 105 even 110 which is worrying me a little.
I haven't yet got round to the tips suggested by Ed, will this weekend if I get the chance, unless these hints suggest otherwise to anyone?
Thankyou for the advice
Rick
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