Timing Chain Noise

[type26owner]

Adjusted the timing chain slack to a 1/2" of vertical motion between the cam gears like I've always done it before. This time the timing chain made a horrible slapping type noise when I first started the engine up. It took two more full turns in of the chain tightener adjustment screw for the noise to go away. When it did I noticed the normal clatter of the camlobes against the valve buckets decreased by about half the volume also. Surmising this can be attributed to the newly installed harmonic balancer.

Just got done applying repairs to the engine to stop the oil leaks from both ends of the 4-bolt crankshaft. After the first full heat soaking of the engine I parked it for twenty minutes this morning before getting down on all fours to see there were any new drips on the pavement. For the very first time ever there were none. Not a single drop.
My son found this smiley.

[twincamman]

try adjusting with the motor running tighten until the chain noise is just discernible - check the locking nut is tight --if the chain is too loose it will wear out the chain cover ---- ed law

[gjz30075]

<!--QuoteBegin-type26owner+Jan 21 2005, 06:53 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (type26owner @ Jan 21 2005, 06:53 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> For the very first time ever there were none. Not a single drop.
[/quote]
Keith, you know that won't last long.

[type26owner]

Keith, you know that won't last long. laugh.gif

Going to flog it on the racetrack again and really press my luck. :rolleyes:

What has me puzzled now is there a white creamy emulsion oozing from the roadtube now for the first time. First thing I checked was the inside of the oil filler cap and the dipstick for any sign of a coolant leak and there's none, it's completely dry. My buddy at work pointed out normally oil and water don't mix unless it's really mixed together. Bet it takes a lot of churning to get it to emulsify into the consistancy of whipped cream. The few drips discharged from the roadtube piled up in mound and does not flow out and away. Surmising by opening up the breather passageway to the crankcase has in someway caused this new creation of emulsified gunk. Perhaps the engine is expelling the condensation from the blowby more efficiently now. It would be nice if this solves the problem of the oil turning jet black after only a few hundred miles of driving. Planning on installing a permanent oil breather catch tank on the car today and cleanup my act by eliminating the direct roadtube.

[gjz30075]

Keith, that really is puzzling, in light of your recent work to make the webers work as efficient as they could. Perhaps alot of short trips lately? Keep us posted.

[type26owner]

Nope, only have put 70 miles in it since I had the engine mostly torn apart to install and tryout another new combination of front and rear crankshaft lipseals. Maybe I somehow got a slug of water trapped in the crankcase because it seems to be done expelling anymore gunk at the moment. I don't know for certain, it is a Lotus afterall. :rolleyes:

[rgh0]

Keith

Are you using synthetic oil ? if so I would definitely suspect a small leak into a cylinder. I had similar symptons when I cracked a bore in an engine. The oil in the sumped stayed clean but a thick greyish mousse formed in the bottom of the sump and came out the breather into the catch tank also.

Rohan

[type26owner]

Hi Rohan,
I remembered you mentioning this weird synthetic oil and water business before. The answer is yes, I just switched over to 10/30W Redline synthetic oil when I put the bits back together. I'll keep an eye on the discharge out of the breather. Went to work on Friday which is a 50 mile round trip so the engine got heat soaked twice and the cooling system also presumably pressurized to 10 psi. Hoping it was just an o-ring weeping a little coolant and by having had some force applied it has seated itself and stopped leaking.

If I drain the oilpan is the goo so viscous that it will not flow out? The stuff that came out of roadtube would be flow challenged. It took seating all day for it to discharge the mound.

As a precaution I also retorqued the FelPro fiber head gasket. The gasket which does not require retorquing except in some special cases but they have no record of what comprises the special case engines. I figure it's a Lotus so it'll require retorquing.....

Oh, since I had the camcover off anyway I checked the amount of slack in the timing chain. It's now got only 1/4" of vertical motion. Can just barely hear the valve train noise from the driver's seat now. Maybe I should make effort to get the radio working again. Nah!

[gjz30075]

Keith, 1/4" seems pretty tight. Could your sprockets be worn to the point where this type of tension is required?

[type26owner]

Due to the inertial effect of the harmonic balancer I'm guessing. It's a new chain and the all the sprockets had no signs of wear when I inspected them just 1100 miles ago. HB weighs a couple of pounds so the rotating mass has increased. Thought has crossed my mind maybe the chain tensioner spring should be stiffer then the stock one though. The chain has some slack so I'm not totally alarmed. Going to pay close attention to it for awhile.

[rgh0]

Keith

The water / oil mouse is too thick to flow and would not drain out with the oil until you have a very large layer built up in the bottom of the sump. At this point you risk sucking it in the oil pump and stuffing the engine so you want to identify the problem before then.

However if you have small water seepage problem you should be able to identify the water loss if you watch it closely and you will see the mousse continue to come out the breather, a catch tank helps identify whats comming out the breather if you dont have one . You should also be able to identify a thin layer of mousse building up on the inside of the cam cover.

The one thing I did see when I drained oil was a very small amount of free green 100% glycol in drops in the bottom of the oil. It appeared to have been separated out from the coolant with the water reacting with the oil to form the moouse and the some 100% glycol remaining free and unreacted or emulsified.

Hopefully if you had a small leak it has closed up as things settled in and you retorqued the head.

Rohan

[type26owner]

Rohan,
Thanks for the advice. Now have a Redline plastic oil bottle modified into a breather catch tank. I'll watch carefully for the emulsion. Prepared to yank the engine out again if needed to fix any problems. Last time I had it out in just two hours doing it by myself and not even breaking into a sweat. It does help to know every tool required ahead of time though. I've also modified some things like the radiator mounting into a quick release mechanism to quicken the process. One of those mods was the abilty to remove the oilpan in situ. Never have used that capability before but if the leaking stops I might just remove the oilpan for a cleaning out of the emulsion.

[type26owner]

Drained the Redline 10/30W oil and probed with a bent wire for any mousee adhering to the bottom of the oilpan and found none. Whew! No condensation to be found on the inside of the oil filler cap still. Pretty sure it's not a small coolant leak now. Drained 70 ml of the white emulsion from the oil breather catch can yesterday. Suspect it's just the moisture from the air that backflows into the crankcase when the engine cools off completely. Oil with only 200 miles of use certainly appeared to be thinner then the new stuff I put back in there. Also it was jet black and reeked of fuel and that's a real cause for alarm. Oil to water intercooler is the next upgrade to get the oil to heat up enough to revaporize the fuel. The oil should not being turning jet black within a few hundred miles.

[type26owner]

I'm looking at the instructions in the Lotus Manual for adjusting noise out of timing chain and I don't agree that the procedure described in Section E-6 will necessarily achieve the desired results. All that does is set the slack amount of the chain by means of the gap between the tensioner adjustment screw and the plunger before they come together and there is a solid connection instead of it being spring loaded. The amount of extra spring rate to be gained by closing down that small gap of about .04" is nill. What is needed is a spacer to be placed between the spring and the plunger to increase the amount of spring load onto the chain. The slack should be adjusted and left at the 1/2" of vertical motion between the camshaft gears and not used to bind up the chain. By placing a 5/16" ball bearing in there I'm able to up the spring loading by 50% from 10 lbs to 15 lbs. Be careful not to block off the tiny bleed hole in the plunger or the assembly will be prone to hydraulically lockup solid anyways. What were they thinking? The Editor must not have been qualified technically or was not paying attention.

[rgh0]

Keith

I have always assumed the main aim of the half inch movement spec was to ensure that enough movement existed to compensate for thermal growth in the block and head without the adjuster binding up. The standard spring tension around this point is obviously enough to stop the chain rattling and the hard stop is close enough to stop the chain jumping teeth.

Harmonic balancers or funny cam pofiles change the loading on the chain and may need a higher preload as you have found. Limiting the chain movement by screwing in the adjuster more so that the hard stop prevents rattle risks binding on thermal expansion as you observe.

regards
Rohan