Pulling my hair out! Why is my Elan so down on power?

[M.J.S]

I really would appreciate some advice here folks, before I spend a lot of time and money pulling apart something that may not need pulling apart.

My 1972 +2 130/5 on Dellortos, belonged to a friend until I bought it a few months ago. I know from borrowing it in the past it has always been down on power and a bit lumpy. I assumed it was through lack of use, being coked up and in need of some TLC, although looking back through history and receipts this is nothing new.

The car has done a genuine 31000 miles, and 1500 miles ago the engine was stripped and rebuilt with new rings, bearings, valves and guides etc, at a cost of ?3500 by a local garage using parts supplied by Christopher Neil.

It has excellent oil pressure, does not rattle, smoke, burn oil or overheat and starts first time, every time with just a couple of blips on the throttle. There is no water in the oil or vice versa.

If you just drive along sedately at 40 to 60 mph it's actually quite smooth.

However it ticks over lumpy, drinks fuel, misfires and coughs and farts occasionally if you floor it and is quite slow; I doubt it will pull more than about 85-90 mph or so, although I have not tried.

When you put your foot hard down it makes a great growl, misfires now and again but goes nowhere. As it reaches approx 4000 rpm and you wait for it to come on cam and pull strongly, it just flattens out and nothing happens.

I thought it was a carb issue, but here's what I have done so far.

New plugs, leads, rotor arm and cap (it has electronic ignition), all to no avail. I have tried the timing both advanced and retarded from the standard setting with little change.

My friend must have also have an idea it was a carb issue because a year or two ago he bought a brand new pair of Dellorto dhla e 40's from Christopher Neal, all jetted and set up as per the manual.

After checking them over I have just carefully fitted them with new petrol hose and fuel filter, with new deep K & N's and rampipes (it was already on slightly shallower K & N's).

After hours with my carb balancer, colourtune and many miles of road testing, so that all barrels are pulling approx the same volume of air and all plugs are coloured brown instead of the usual black, she is no different.

In fact now she pops and farts through the exhaust on the overrun; she never did that before, and the tick over is even rougher and seems to alter of its own accord. I can see no signs of it sucking in air anywhere on the carb mounts.

I did a compression check and all 4 cylinders show a uniform 125-130. No brilliant I know but not overly dreadful either.

I drove her up to a local Lotus Europa specialist who was too busy to look at her, but he heard her running, commented how rough it was and said the compressions were too low for it to run properly and it sounded like it had a couple of bent valves. When I said all 4 cylinders had uniform compressions he suggested to me that the cam timing was possibly out.

......

Surely if it had any bent valves the compressions would be very low on the offending cylinders.

If the cam timing was out from the engine rebuild (or can they jump teeth?) surely it would not start first time and run quite smoothly when held on a steady throttle.

If the bores were worn enough to be losing compression into the block then why isn't she smoking?

Although I don't mind too much removing the cam cover to check the valve timing, I really don't want to start removing cylinder heads or stripping and rebuilding the engine only to put it back together several thousand pounds and dozens of hours later, to find it's exactly the same because there is something I'm just not seeing.

I am a virgin to Lotus Twin Cams so any suggestions will be greatly appreciated.

Thanks folks, look forward to your replies,

Mark.

[JJDraper]

Get a cam cover gasket ready and then check the cam timing. My +2 ran reasonably until I checked the cam timing and found it just one notch out. Ran much better after that was rectified. Without variable timing sprockets, or offset dowels, it is difficult to get perfect cam timing, but it is still easy to get it a notch out.

Could be carbs, but for the cost of a cam gasket you can eliminate one possible problem!

Jeremy

[john.p.clegg]

Mark

I'll second Jeremys reply,get yourself a timimg disk and check your cam timing....

John

[miked]

Mark,

I am no mechanic but would agree and had this with a plus two. Smooth but not guts. 1 tooth out on cam timing. Sounds like maybe something else as well. If this car has sat (low miles), is it possible that there is some blockage in the exhaust silencer. May sound stupid, but who knows, worth eliminating.


Mike

[types26/36]

The car has done a genuine 31000 miles, and 1500 miles ago the engine was stripped and rebuilt with new rings, bearings, valves and guides etc, at a cost of ?3500 by a local garage
I did a compression check and all 4 cylinders show a uniform 125-130. No brilliant I know but not overly dreadful either.
Mark.

Got to agree with other posters and the Europa man........sounds like cam timing.
Got to disagree with you quote "a uniform 125-130. No brilliant I know but not overly dreadful either".........I think it is dreadful as its only done 1500 miles since a rebuild.......cam timing will effect the compression readings.
Any idea why the engine was rebuilt ? could uprated or modified cams have been fitted at the rebuild?
I know you have advanced/retarded the ign. but have you checked that it is actually advanceing with revs?

[pamitchell]

My two cents; Get a leak down test done to verify valves & rings are seating correctly. May corroborate the theory on the cam timing if the leak down reading is low at TDC.. Are you using an adjustable timing light?
Phil

[tdafforn]

Agree with all the above. Cam timing well worth a check. dizzy advance as well. Had an old triumph spitfire that wouldn't go over 3500 rpm. pulled it to peices, and eventually found a screw lodged in the advance mechanism!
free'd it up... new car!
Tim

[ppnelan]

Yes, check the cam timing - not too difficult to do. It can make or spoil (but probably not break!) an engine... If it needs correcting, it may even improve the compression readings?...

Matthew

[M.J.S]

Thanks folks. I've ordered a cam cover gasket so I'll pull it off and check the timing marks. I hope that is the problem, because I don't fancy a rebuild at the moment.

Could it be the chain has been wrong since the rebuild or is it possible for them to jump teeth if there is a tensioner fault?

Also what is a usual, reasonable compression for a twink to run at?

Many thanks

Mark.

[john.p.clegg]

Mark

To do the job proper you need to get hold of a dial gauge with a thin finger and mounting plate so you can check the cam buckets at max travel (cam on peak)...

John

[types26/36]

[quote="M.J.S"].Could it be the chain has been wrong since the rebuild or is it possible for them to jump teeth if there is a tensioner fault?Also what is a usual, reasonable compression for a twink to run at?
Mark.[/quote

I think it quite probable that it could have been assembled incorrectly although why the garage let it go and the owner accepted like that is a mystery.
I dont think it could have jumped a tooth or two in service as the chain would have had to have been very loose and as such would have made a hell of a noise but anything is possible. May be it was worked on later (to recheck/adjust the valve clearence?) and not timed correctly....who knows?
From memory Lotus quote in access of 160 psi @ sea level for the compression pressure, I would have expected the engine to have at least that after 1500 miles.

[andyelan]

Mark

You're way down on compression. My 130/5 has done 35000 miles and has never been rebuilt but I'm getting 190-200psi.

I do agree with everyone who's suggesting incorrect valve timing though. Think logically for a moment. When the piston begins to rise on its compression stroke, the inlet valves are still be open for a while. The compression you measure therefor is only that for the remainder of the stroke after they've closed. If the inlet cam is "late" closing the valves, there will be less of the stroke doing the compression and hence a lower reading (tight valve cleareance give a similar effect but would generally affect individual cylinders differently). The knock-on effect to low compression is that the fuel mixture would now burn much slower than intended, this would make the standard ignition advance all wrong and the max pressure generated in the cylinder on the power stroke would be trying to push on a piston that had already gone. Hence no power.

When you do come to check the cam timing, you be looking for an error of more than 1/2 a tooth (I couldn't get any better than this on my car and that runs fine). If you're no worse than this, then you're problem must be elsewhere

Good luck
Andy

[pauljones]

have you tried putting a little oil down the bores then doing a 2nd compression test.if this is done and you get an increase in compression then the rings could be installed wrong,ie too much gap.
no compression,no bang,no power.could be a cheep (er) fix.

[types26/36]

I did a compression check and all 4 cylinders show a uniform 125-130. Mark.

Just to check...... you did do the the compression test with the engine warm and the throttles wide open...........?

[oldokie]

The chain will most certainly jump teeth if the tensioner goes slack! Mine came a drift and popped completely out in a car park one night. Luckily I was able to find all the pieces restore the timing of both cams and the dizzy in the dark.