Big Valve Twincam

[micha]

hi. i purchased a westfield se with 1600 lotus big-valve engine. as i dont know much about these engine type, i would kindly ask if you can foward me any infos about it:

is it reliable?
is this engine rare?
spare parts still available?
where?
any weak points?

thanx in advance,

[ELAN+2]

Lotus made about 50,000 of these engines, The factory "Big Valve" had slightly oversized inlet valves (1mm) over standard, higher lift cams and raised compression(10.3-1) and the carbs(dellorto or webber) jetted to suit. Output rated at 126bhp.
The early engines had rounded main caps, a four bolt crank and weak conrods, all up rated for the S2 Elan and Lotus Cortina a six bolt crank, stronger main caps and stronger (125E) rods introduced.
Lotus cast alloy Twin Cam 8 valve head on a Ford pre crossflow bottom end, identified by a raised cast "L" behind the engine mount.lotus front alloy chaincase.
There were quite a few conversions to fit these heads to the later crossflow block (refered to as the tall block), easily identified by an alloy spacer between the head and timing chaincase. these can be taken out beyond 1800cc
If properly built, these engines are very strong, powerful and reliable, pay particular attention to the cooling system (they dont like overheating) and do not over tension the fan belt, as the waterpump will fail (only real weakness).

Most of the "problems" with these engines are down to lack of maintenance, bodgery or abuse. The factory had no warranty issues during its production run.

Suggested reading The Lotus Twincam by Miles Wilkins.
Parts available from various sources, Burtons, QED etc

A lot of what you hear about these engines is a load of old tosh!!

regards

Mark

Edited by ELAN+2 on Monday 4th December 00:15

[micha]

"There were quite a few conversions to fit these heads to the later crossflow block (refered to as the tall block), easily identified by an alloy spacer between the head and timing chaincase. these can be taken out beyond 1800cc"

this is interesting: how big (thick) is this alloy spacer? on mine the headgasket seams very thick (about 2mm), or its maybe such a spacer? the next interesting thing is that the V5 says 1750cc!! the engine has lots of torque from low revs (unusual for a 1600) and is fitted with 45 dellortos.

will try to locate the engine no´s and post it soon.

[Sam_68]

micha said:

is it reliable?

Yes, if properly built.

micha said:

is this engine rare?

I'd query Elan+2's production figures - 50,000 seems a hell of a lot to me - and the Big Valve variant will account for only a fraction of total production. Also, bear in mind that there are plenty of 'Big Valve' engines out there that are just a Big Valve cam cover on a 'standard' Twin Cam.

micha said:

spare parts still available?

Yes, at a price!

Micha said:

where?

QED (Quorn Engine Developments) are the top specialist, probably followed by Burton, but Elan-specific parts are not cheap. There are also a couple of specialists in America (Dave Bean, for example, is very highly respected) that might be cheaper at the moment, given the weak dollar.

micha said:

any weak points?

Apart from the water pump that Elan+2 mentions (which is mainly a problem because to change it properly means removing both head and sump - an engine out job, in practice, in an Elan), they all tend to leak oil unless recently rebuilt. The crossflow bottom end conversion can be done one of two ways - either by fitting a spacer plate between the front cover and the head (cheap, but introduces another joint for the oil to leak out from!) or by buying a new, tall front cover (more expensive, but does the job properly!)

Also, and more seriously, they have quite short valve guides and no valve stem oil seals. As a result, they wear valve guides quite quickly. If the guides are worn, oil drains down into the cylinders when the car is not running and you get a big cloud of smoke when it is started. When new valve guides are fitted, they are reamed to size, and it's easy to overdo this job so that the engine burns more oil than it did on the old guides. For this reason, I'd suggest that if you need a cylinder head rebuild, you should get it done by someone who knows the Twin Cam engine well - QED or Nick Stagg, for example.

Expect head rebuilds with new guides maybe every 35,000 miles, and a full engine rebuild every 70,000 miles... they don't do the astranomic mileages between rebuilds that we have come to expect from modern engines!

They can be marginal on modern unleaded fuel, particularly if the head has been skimmed, because they are prone to pinking with the cr@p octane ratings we have to suffer these days. I'd suggest you always run the car on Super Unleaded and/or use an octane booster.

They're a great engine for their day and, again as Elan+2 says, they are very torquey for their capacity and power output. QED will sell you the cams and bits to get an easy 145bhp out of a Big Valve and the cam profile (QED420) actually makes them even torquier than the standard Lotus Sprint cams!

I'll be honest, though - there are cheaper, more reliable ways of getting the same power in a Westfield these days, so it wouldn't have been my engine of choice. In the long term, unless you like the cachet of having a Lotus engine under the bonnet, it would probably make more sense to sell the Twin Cam to a Lotus owner and replace it with a Ford Zetec/Duratec or Toyota 16 valve.

Edited to add: Re production numbers - Miles Wilkin's book gives total production as 'around 34,000', but this is for all Twin Cam variants from the original 105bhp version, through to the final, 126bhp Big Valve.

Edited by Sam_68 on Monday 4th December 18:14

[ELAN+2]

Sam,

I couldnt remember the exact production figures and i was under the influence of the "vine" at the time, I'd dispute the mileage between head rebuilds (my mother ran one daily for 5 years,)ive seen one run over 40,000 miles with no visible signs of wear (she wasn't Stirling Moss, but she didnt hang about either! posibly modern fuels could be the problem now adays?

the tall block spacer is I would guess about 5-10mm thick (theres one on Ebay now) and needs a longer timing chain.

Interestingly Europa waterpumps can do over 80,000 miles (brother ran one for several years) but there is no side load applied from the alternator on these as they are cam driven.

Nice Sprint Sam

[Sam_68]

They do vary quite a bit; it depends on how accurately reamed the guides are to start off with and the quality of the material they are made from (which can vary a lot even between guides that are allegedly of the same material specification), as well as number of cold starts, frequency of oil changes, average revs, etc. The sort of useage most Twin Cams get these days (left for long periods for the oil to drain down from the head) is not the best treatment for them.

For a head properly rebuilt using Colisbro guides, I am probably erring well on the side of pessimistic, but then for every good head there's another one with bronze guides that have been a bit over-reamed.

Never the less, the short valve guides are a definite and unavoidable design fault and I'd stick by a figure of 35-40K miles as the average at which you should budget for a head rebuild (by which I mean new valves, guides and valve springs - not necessarily cams, tappets etc). Depends how much a smokey engine with high oil consumption bothers you, of course - they'll go on a lot longer if you can turn a blind eye to the blue haze in your rear view mirror - I rebuilt the head on my second Elan at 66K miles with valves that could be rocked side to side by about 1mm and that layed a smokescreen across the whole village when I started the engine after a week off the road, but it was still running sweetly enough apart from the smoke and the 1 litre/700 miles oil consumption!

I'm sure that a good QED head rebuilt with Colisbro guides would give you a comfortable 60K miles in general road use in an Elan, but I'm conscious that a Westfield will probably end up being thrashed a lot harder. Mind you, the mileage between rebuilds in a Westfield is probably pretty academic, 'cos the chassis will have rusted away long before the car has done 60K miles, in most cases!

Edited by Sam_68 on Monday 4th December 21:20

[ELAN+2]

Fair point Sam, My old man rebuilt the engine as per the Miles Wilkins book, heating the head in the oven to do the guides and valve seats!! Mind you he was an engineer (He built a long case clock and I swear he used a vernier when measuring the timber!!)
If I do half as good a job that he used to do, I'd be well chuffed to be rebuilding my "lump" in 30K miles, I'm planning on rebuilding the engine next winter as the seats arent unleaded ones the old mans attitude was "if it was good enough then, its good enough now" The engine on my car is still in bits, dad did the head 5 years ago and it still hasn't been assembled yet!
I'll have it on the road for the summer though.

Mark