Engine stuff (7 articles)


Valve clearances and explanation

Normally they get bigger over time, as parts of the valve gear wears. With OHV's (not OHC's) with rockers, there are *many* places where it wears, so the clearance changes a fair bit; set them every 10k miles. With direct acting OHCs like ours, there is *one* interface that wears; and that has a big area so the wear rate will be s l o w .

If clearances get too big, it'll get noisy. If *very* big, you'll lose a bit of power ... you might just measure it on a dyno, you'd certainly not notice it in driving! You'd be wondering what that godawful top end racket was, long before you got to that point.

If valves hammer themselves into the valve seats, clearances may get a bit less. A *bit*. And this will most likely just offset some of the wear above. One or two thou - not the 10 thou that would give problems. Assume the worst ... clearnces way too tight. Valves would start leaking and you'd lose compression, lose power. Spark plugs go mucky (black, oily and sooty). Continue to run it ignoring all these warnings and you'd burn a valve seat, that would be serious - but even that's not going to make pistons hit valves.

If you're really bothered (and why not! It's caring :-) ) then why not remove the valve covers and measure the clearances. Very easy - just the valve covers. Take advice about what sealer to use when you put them back, and *don't overtighten the bolts* - a *very* low torque is specified but I forget what it is. (I'm pretty useless today, all in all!).

The figures in my general data for the clearances are

(cold): inlet .005 to .007 inches
ex .010 to .012 inches
verbally: inlet 5 to 7 thou, ex 10 to 12 thou.
BTW, 'cold' means ... engine has stood overnight since it last ran!

Then we come to interpretation of results, and it's personal views and guesswork! The racing boys would shoot me but for road use I'd say that 1 thou under the limit or 2 thou over is perfectly OK, just note to check again at the next service and reckon you might need to set them then. 2 thou under, or say 5 thou over, and I'd say drive it with a touch of care till a convenient time to do the job. 4 thou under ... limp about and do the job more or less at once 5 thou under ... that's zero clearance ... the engine shoulnt be running!

It's not a bad addiction; there are worse. Have fun.


Valve clearance figures

According to the manual, the valves should be checked every 10,000 miles and adjusted as required to keep them within spec:

005" - .007"
Intake .010" - .012" Exhaust


Engine smoke

About smoke from the breather:(Mark's 76 Eclat) This *must* be getting past the rings, this is the only route for combustion gases to get into the crankcase. Crud and oil in the cylinders should burn in the combustion chamber and go straight out of the exhaust.

Smoke from the breather may not be a concern in an engine that hasnt been run for several years, esp. if you believe the engine is basically OK.

Guesswork suggests the following:

a ring or two stuck in their grooves; quite possibly they have scraped up some muck off the bores and this has got compacted between rings and grooves

poor surface finish to the bores Either/both could well be self correcting with luck, by running the engine.

I got my Elite 501 engine running after several years laid up; I dont remember the same problem but then I think the breather remained connected to the airbox or wherever it goes, so I would not have seen this problem. What I can say is, it ran a whole lot better after being run for a few hours in total over several occasions.

So, I'd say if it runs, run it; *gently* but often.

the bores will get polished just by being run

rings could well get freed by being 'heat cycled' and by being shaken about, esp with oil about.

Myself, I'd suggest a few cc's of light oil (10/30 or thinner) down the plug holes each time you run it. Run it at a fast idle till up to full temperature; let it get fully cold and repeat.

After this, you could try a compression test (if you can find a tester with a long enough neck to fit the 907 engine!).

The 907 engine being canted over may be problem - oil put into the cylinders will stay at the low point. It may pay to run the LHS wheels onto ramps to compensate, when putting oil down the plug holes. I *am* serious even though it's still April


Head gasket testing

The standard checks for this kind of head gasket leak are usually fairly reliable (but this may not be much use to you while the car is out of your hands):

. compression check B&C are going to do this
. look for oil in the water
. look for 'white smoke' at the exhaust

The white smoke test (IIRC) tends to show up on the overrun, it's like this. Take an engine with a leak between a cylinder and the water jacket (and let's hope it's not your engine). When the engine runs, gases under pressure are forced into the water and over pressurises the system. But, on the overrun, there will be *loads* of suction in the cylinder on the intake stroke (throttle closed) and no pressure in the cylinder on the power stroke. This will (on the faulty engine) suck water in through the leak, and the resulting steam mixed with the bit of exhaust gas gives the 'white smoke'. So, with a warmed up engine, you rev it to the max you're comfortable with (I'd say 4500 for you. assuming a new cam belt properly tightened). Then close the throttle and when the revs are just about down to idle, give it just a bit of throttle. This burns up whatever has been sucked into the cylinders! This is a pretty harsh test because (as above) you are deliberately doing all you can to suck crud into the engine. It's more severe than the MOT in this way! So don't be alarmed if it gives a bit of blue smoke (oil) or black smoke (fuel), these (oil esp) are fairly normal for an oldish engine; you're looking for white smoke (or not, we hope).

If compression tests / oil in water / white smoke tests are hopeful, I'd say it's worth giving the cooling system a good flush. I asked the list about using flushing compounds and got no answer so I can't help there. I've emptied my system about 3 times (to do timimg belt, heater valve) and did it after running the engine, this shifted some muck and it seems ckean now so I'll leave well alone. In your case, if the gasket seems OK, I think I'd flush with a compound and then rinse thoroughly. Seriously, get the engine hot then put the stuff in; fast idle for 20 mins (or whatever *minimum* time they say) with the fan running; turn off, let it cool for a short while, ensure it's not at boiling point and drain it carefully. Take care over safety. Then fill with water and flush. *NOTE WELL: dont put COLD water into a dry HOT engine*, water from the hot tap is OK. I'm not sorry for shouting if it avoids a cracked or distorted block. And flush several times to get the corrosive agent out. And keep your face well away from the filler cap at all times, esp when pouring water into a hot engine. Run the engine for a few mins each time you flush it. Oh, and turn the heater to hot !!!!!!


Head gasket testing

If you put the engine to TDC you will see some dots on the cam pulleys, these will be in line and in line with the centres of the cam pulleys.

Expert tip: there is an idler pulley which drives the distributor; I didnt see any marks on this one so I painted one on. If it moves, the ign timing will be wrong; and the distributor is such a tight fit you might not be able to move it to get the timing right. So ensure it stays in the right position. IIRC the crank pulley has to come off; anyway, it's fairly obvious. And - a rad hose has to come off! So 'roll' this job in with some of the cooling system work to save effort and antifreeze. Getting the belt tension right is to me a 'black art'. Feel what the old one is like before you take it off, similar tension will be a starting point. The belt is in tension, not like a fan belt which is not. The tension should just allow you to twist it, at its longest run, about 45 degrees; so I'm told. These approximations should make it OK to run gently until it can be checked properly. Tension is set by the small idler pulley which is eccentrically mounted and clamped by a lock nut. It's easy to see, not quite so easy to see how it works. After lining up all the marks, with engine at TDC, slacken the lock nut and turn the bigger nut behind it, it *should* go anticlock to slacken but dont rely on this, do it gently and check .... the belt will go slack. When you get the new one on, tighten the belt to what you think is the same tension and do the lock nut up. Then turn the engine by hand (spanner on the crank pulley) a few times, get it to TDC again and check the marks again. Also check the tension and tighten it if necessary.

That's what I did. I *think* it's OK. But treat it gently until you can get the tension checked; even if it's only by feeling other peoples timing belts!


Oil leaks

If the leak is high on the engine, it could also be coming from the oil passage that takes oil from the pump, across the block-to-head joint and to the the cam bearings.

There is a rounded rib or ridge (looks like a mole tunnel in the grass) running vertically along the front right side of the cylinder block from the auxilliary housing (oil pump housing) to the head. It's located near the #1 intake manifold runner. That mole tunnel is an oil passage.

The head gasket runs around the top perimeter of the block to seal the water jacket. The aluminum wall thickness around the oil passage hole pretty narrow (probably only 3/16 inch / 4.5 mm or so). That's not much to seal on. It's not uncommon for an oil leak to start at that point.

If it leaks to the outside, it just makes a mess. You can live with it if you wish. If it leaks to the inside (between the oil passage and the water jacket), oil can get into the coolant or coolant can get into the oil... or both. Either way it's bad and you should NOT try to live with it. The fix is a new head gasket and requires removing the cylinder head.

If it's an internal leak, it needs to be fixed as soon as you can get to it. Oil in the coolant will attack all the rubber hoses, turning them soft and gummy. Eventually they will rupture. Water in the oil will get into the bearings and corrode precious metals (bearings and journals).

You can tell if water and oil are mixing by the brown mayonnaise scum that it creates. Keep an eye peeled for any sign of it in the catch tank, on the oil dipstick and on the inside of the filler caps (both oil and water). The mayonnaise in the cooling system can also reduce cooling efficiency and lead to overheating.

If this oil passage is the source of your leak, it could also be indicative of a more extensive head gasket failure. If the head gasket is also leaking between the cylinders and the water jacket, it would most likely be responsible for the overheating symptoms you have been chasing.


Plugs and ignition advance

I found the Champion Gold 2405 is a good runner in my 907 powered Elite (running rich Dellortos).

Prior to this, as Harry will confirm, I was using Champ Gold 2415 -- apparently a bit cool for the setup -- yet, amazingly enough, never seemed to foul (sparks from stock Lumenition electronic). They even helped Harry get home from LOG-18.

Since Champ. Gold had proven to be so flexible (all traffic, all weather) I wanted to continue.

On doing some research, I found a span of four heat ranges (apparently 1/2 steps, not certain). The 2415 was coldest, with 2405 two steps up. So, I tried the 2405, figuring I could step down or up a half range from the 2405 and still have a warmer plug than the 2415. These plugs are pre-gapped around .035" which is a good range. I have to say they are running very well. And I've always been able to let my car idle for a long, long time -- even when set up a bit rich (not "lean best idle" -- about 1/4 turn richer).

BTW, plugs don't work in a vacuum (yeah, they work under a lot of pressure!) -- yuk yuk yuk!

I do tend to run my ignition pretty far out... I'll recall Kosko's "44 at 4400" (actually he said 4500 but it's full ahead at around 2500.

My NGK manual says "Advancing ignition timing by 10 degrees causes plug tip temperature to increase by approx. 70 - 100 degrees Celcius.


Replacement shims

Do TR-7 shims fit 907 engine?

1. Yes TR7 shims do fit.


Replacement shims 2

It's in our mutual best interests to support our independent Lotus parts suppliers. They've always been able to take care of my shim needs. Sometimes it's taken more than one of them to cover a single order, but they've covered me. However, if you need to look elsewhere, Triumph TR7 and Saab 99 shims will both fit.

Lotus .060" - .150" (odd & even, .070, .071, .072, etc.)
Saab 99 .090" - .120"
Triumph TR-7 .070" - .120" (even sizes, .070, .072, .074, etc.)

BTW, never trust the markings on the shims. Use a micrometer to measure the thickness at the center of the shim.

Try your local British car specialist or the following sources for Triumph shims.

The Vicky Brit catalog lists a full range of Triumph shim sizes. Victoria British Ltd. P.O. Box 14991 Lenexa, Kansas 66285-4991
1(800) 255-0088 FON, Orders, Catalog Requests
1(913) 599-3299 FAX, 24 Hour

The Roadster Factory P.O. Box 332 Armagh, PA 15920 (800)
678-8764 Level 1 (you know the Part No.)
(800) 234-1104 Level 2 (you need help w/ Part No.)
(814) 446-4491 Tech Asst (answers to problems)
(814) 446-4495 CustServ (after you've received part)
(814) 446-6729 FAX Orders (24 hours)

My local Saab dealer used to let me come over with a handful of shims and a micrometer and pick through his shims. Delta Motorsports is a Jensen Healey specialist and could also supply you with shims.

Lotus Ltd. used to have a shim exchange program.

Save the shim job for a day when you have an abundance of patience !


Neoprene gaskets for cam covers

(http://www.jaeparts.com/new1.htm)
Never used them myself but they're supposed to seal better than the original style.


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