Timing Chain Noise

[type26owner]

Rohan,
Are there normally higher force springs used on the high lift cams? The BRM intake cam we have in there has .47" of lift and the exhaust only .44". Don't recall ever having a similar type of chain slapping noise problem on the race engine before. Never thought to compare the springs.

Just hoping the longevity of the timing chain has not been reduced much with the harmonic balancer.

BTW, there is an article on the compatibility of oils with the different elastomers on the Chicago Rawhide website. For Redline Oil 100 it has silicone listed as a 4. Four means not recommended or their worst rating.

[rgh0]

Keith

High lift valve springs should be a similar rate to standard springs at around 250 lb per inch. Preload should be the same as standard at around 75 to 85 lb. The nose load on the cam is higher due to the higher lift compared to standard. This helps keep the valve on the cam at the higher revs the race engine usually runs. Typically you need to keep the nose load below around 200 to 210 lbs to avoid cam to follower wear problems. If you do the calculatons on the above numbers you will see this is possible with a .5 inch lift cam.

Chain rattle is due to a combination of vibrations induced by the cams and crank interacting to cause some sort of resonance in the chain drive. Spring rates and loadings, cam profiles, crank vibrations and hamonic balancers all can affect how the chain behaves. To hard for amateurs to model just try it and see if you have a problem.

If you have to tighten the chain so the rattle is being stopped by the physical limit of the adjuster then you will be putting higher loads on the chain how much is too much I dont know. I would certainly prefer to ensure the spring in the adjuster is still working rather than it running on the hard stop.

The race engines I have heard with a bad rattle may just have been due to poor adjustment rather than springs or cam profiles but given most race engine builders know how to tighten the adjuster properly I suspect it has been driven by what ever cam and valve springs they have chosen ( which may not have met my guidelines above as lots of race engine builders use strange components that I would not). I have never had a chain rattle problem with any of my race engine cams and spring combinations so far.

I have used Mobil 1 with silicone seals to date in my race and road engines with good results. I have only used Redline in my gear boxes and diffs. The race engine I am currently building I intend to try on Redline engine oil so I will see how well it works with the silicone seals. Redline is a ester based synthetic oil compared to mobil 1 with is a poly-alphaolefin based oil so some difference is to be expected. Redline use ester based oil due to its higher temperature resistance. These ester based oils were developed for gas turbine lubrication and to my knowledge Redline are the only company offering this technology commercially for piston engines in cars.

Rohan

[twincamman]

hey Kieth---if you want a car that wont leak oil---goes fast ---and is reliable-----buy a Caddie -- :rolleyes: ed law

[type26owner]

Hey Ed,
Play nice! I'm a lifelong Lotus Nutter. My dad put the wrench in my hands workin' on the Lotus18 when I was just ten years old and mentored me all the way until I was the crew chief doing all the work at fifteen. Brave man to totally trust a punk kid!

Should say it was my great pleasure to do the same for my son. My son wanted to put grandpa back into the cockpit to go vintage racing. I talked him through putting the lotus41 back together after it sat under the bench in pieces since the early seventies. My dad drove it again for a few years with CSRG but has retired again.

These days I'm really getting leveraged because my wife is pressing me to stop 'playing' with the Elan and start putting my Aston Martin back together again. Finally got a lead on shop space for rent so I can do exactly that thanks to Mike Ostrov. Thanks Mike!

[type26owner]

to my knowledge Redline are the only company offering this technology commercially for piston engines in cars.

Good news! There's Motul ester based oils to choose from also. I prefer the smoother feel of Motul Gearlube over the MTL in the Elan's gearbox anyway. The nearest supplier of their motor oil is at the Sears Point Racetrack which is not local for me so I don't use the Motul oil in the engine otherwise I would do so. Redline oil is to be found everywhere here.

I see they've revamped their website into stupid hype mode though only. None of the real comprehensive technical articles are linked there anymore. Good way to shoot yourself in the foot. Way to go Motul!