Help with diagnosis of whine from front of engine

[pharriso]

Hi Robbo,
May I chip in here as I have just done this as instructed by the engine builder.
Give the chain a smack downwards with something like the back end of a hammer shaft to move all slack to that point and rotate the jackshaft a little if necessary. It needs something like a karati chop.
Now at the midpoint between the cam sprockets, measure the vertical distance from the chain to the cylinder head top surface.
The whole chain should move up and down by half an inch.
I hope this is clear
Best of luck
Eric in Burnley
1967 S3SE DHC

I like this method as you're not trying to hold something still in the air!

I'm in the middle of a head change so I will follow this routine

[Craven]

Seems fairly unambiguous to me.

[billwill]

Hi Bill

Thanks for the further detail.

May I task a couple of questions for further clarity, and avoid any ambiguity, pls:

The timing chain adjustment I have is as I read the illustration in the workshop manual (just seeking to be sure I have it correct)... in that with finger pressure in each direction alternately: from the 'high' point the top of the chain reaches to the 'low' point the bottom of the edge reaches is 1/2". Correct?

and regards the oil on the chain, aside of it being dry (it wasn't) can you give me a guide as to how much oil should be present? (I will try the oil can idea too, thanks.) The sprockets looked fine, btw, though to be fair I didn't really examine them, I'll take a closer look when the cover's off next time.

Thanks again

Actually I don't recall any more precise detail about the tension in the timing chain, I personally would not fuss so much it isn't that critical provided that the chain moves as described about a half inch, but the dimensions of the chain are not involved. choose ,say, one of the pivot pins midway between the cam sprockets. that pivot should be capabable of being moved up & down about a half inch, with the rest of the chain taut on the sprockets. I usually do this by doing the tensioner up tight which will force the cams to rotate slightly if necessary, then slacken it a bit pressing down in the centre at the top until it can move about a half inch.

Again as to the quantity of oil to use in a test, just make sure the whole chain is oily not dry. You may need to turn over the engine by hand with a spanner (clockwise when viewed from the front) to get at all of the chain.

[rgh0]

did you see my reply in the other thread before this one started ?

The top edge of the chain needs to move up and down a total of approx 1/2 inch max and this needs a little force to bring all the slack to between the cam sprockets. The blocking of the oil lube hole I believe should not be a major problem. This was a left over from how ford lubed the chain to the original cam and is not really needed in the twin cam with all the head cams draining oil down the chain cover

cheers
Rohan

[Robho]

Thanks all. Will revert..

[2cams70]

Whilst the engine is running and making the sound you are concerned about back the tension off the chain a fraction to see whether there is a change in the pitch of the sound. No change = timing chain and related components are not suspect. Change = timing chain and related components are suspect. Simple.

Regarding the oil lubrication hole that exists in the block for the timing chain. It most certainly is required in the Twin Cam application. In the twin cam application the oil is fed through this hole and redirected into an oil channel in the timing cover backing plate and then directly onto the crankshaft sprocket. It is important that the oil hole in the block has not been covered by excess sealant applied to the paper gasket fitted between the backing plate and block. It's easily blocked because the opening is very small.

[david.g.chapman]

I came up with a test to see if the chain oil hole is working:

1. Take off the camshaft cover on the engine.
2. Spread newspaper over the front wings.
3. Start and run engine for 5 seconds.
4. You should see a black line of oil being deposited on the front wing newspaper either side of the timing chain.
5. Clean up!

Cheers,

Dave Chapman.

[Robho]

Cheers Dave..

[rgh0]

..... It is important that the oil hole in the block has not been covered by excess sealant applied to the paper gasket fitted between the backing plate and block. It's easily blocked because the opening is very small.

I politely disagree with the criticality of the Ford chain oil lube system in a twin cam. The original Ford cam drive was enclosed in a small cover between the crank and cam with the main source of oil to the cam coming from this oil hole or from oil mist in the sump or oil slosh under braking which the later two Ford in their wisdom clearly thought was inadequate and thus added the direct oil spray onto the chain and crank sprocket in the block design.

In the twin cam however the chain and its drive sprocket are continually doused in oil draining back though the chain cover from the overhead cam bearing feed system. IMHO this is totally adequate for chain and sprocket lubrication without the spray onto the sprocket from the hole in the backplate.

Lotus kept the oil spray system as Ford had it but it is not critical and if blocked will not affect chain noise or wear to any significant degree in my opinion.

I am right and maybe wrong. I make sure it works when I rebuild an engine but I would not pull an engine apart to see if it was blocked if I had a whine from the front of the engine which has a number of other possible causes.

The top 4 are as below and all 4 can be easily check without pulling the engine apart

1. overtight chain
2. water pump or dynamo / alternator bearings
3. chain tensioner pivot wear resulting in misalignment of the tensioner sprocket
4. sprocket wear, which is normally worse in the crank sprocket versus the cam sprockets but if you have visible wear on the cam sprockets you can guarantee more wear on the crank sprocket

taking the cam cover off and seeing how much oil sprays off the chain will certainly confirm whether you have adequate chain lubrication !

cheers
Rohan