Cam woes

[kob666e]

Think my cam is lunched, checked valve lift last week and the worst offender, no.4 inlet, is 2.5mm off recommended and another, no.1 inlet, is 1.5mm off. Did a cold compression test, worst affected cylinder is 165 psi compared to average 180 psi. Hot it was 195 against 205.

 

Also that valve sits 1mm lower in the head, a couple of others 0.5mm lower which have full lift.

 

No point in messing about, just rip it out. Has anyone managed it successfully from below, would prefer if I could drop the sump (I can buy 15 sump gaskets for the price of one head gasket!), and there's a lot less ripping, BUT do the followers fall out the bottom?

 

Should I have a look at the valve seat for no.4 inlet, or is that an acceptable discrepancy?

 

I know I'll have to hook the followers out of the way to remove the cam, I'll figure that out when the time comes!

 

Any suggestions greatly appreciated.

[RogerH]

Hi Justin,

it can be done from below but!!! It really is easier from above. Plus you will be able to have a look at the valves as well.

 

You have to take so much off anyway, the head is of little consequence..

 

Roger

[Fireman049]

Hi Justin ~

 

Roger is quite correct. It's far easier with the head off. Have you got an unleaded cylinder head?

If not, then I would be inclined to have it converted.

 

Tom.

[graeme]

If you are changing the cam, you will need to change the followers too. So, removing the head is the way to go.

 

The other thing to consider, if the cam has lost a lot of metal, that metal has gone somewhere in the engine.

 

Cheers

Graeme

[RobinTR6]

Defo easier with head off , did mine recently. I was advised to check cam bearing surfaces even though I was changing from a 125 to 150 cam, ie the cam wasn't worn.

[TR NIALL]

Defo easier with head off , did mine recently. I was advised to check cam bearing surfaces even though I was changing from a 125 to 150 cam, ie the cam wasn't worn.

Hi Rob,you've a PM from me.

[kob666e]

I've made a start ripping the engine, cam was definitely goosed, 1mm gone off no.4 inlet lobe and equal amount off follower, and a few others were looking a bit worse for wear.

 

I've dropped the sump and removed the pistons for inspection, and there are a few numbers I'd like some assistance with:

 

On top of the pistons is 205498 D67 and a capital G

Con rod bearings are Moss standard.

 

If all continues well I may as well fit new rings and bearings while I'm in there......

 

I'll take a few pictures and post them later.

 

 

 

Majority of the damage was to the inlets, valve guides also showed wear with no. 4 by far the worst. There was carbon build up on one side of the face of that valve, I think due to the wear in the guide caused by the cam lobe, the valve was seating at an angle on compression stroke leaking air before it then sat correctly.

 

 

These two bearings came from one and four, both are the lower bearing, little or no wear on all the other bearings (none that I would notice!)

 

Edited July 12, 2015 by kob666e

[Speed]

certainly worn stuff, she will welcome the new bits, defo change to unleaded while head off and double check all other bits carefully some extra cash now could save loads if anything not quite up to the mark goes back in and always with new parts and old going back check all tolerances carefully before you hit the start button again, good luck with it.

[DaveN]

The shells have lost some of the white metal bit, but don't look too bad. Check the crank for scores while you at it. Replace the shells with Vandervell (I got mine from Revingtons). Check the crankshaft end float, if out of tolerance replace them, again could save a lot of grief later.

I can highly recommend thrust washers from Scott Helms in the states iirc about $60. Including delivery!

Worth also replacing the main bearing shells, again easy to do.

Clean the sump! And assemble all the bearings with graphogen grease.

With the new cam and followers don't forget to assemble with copious amounts of cam lube.

[Motorsport Mickey]

Buy the camshaft and followers from the same supplier and follow their fitting and particularly lubing instructions to the letter, otherwise you'll have trouble claiming from them if they prove to be faulty.

When you start the engine make sure the revs stay OVER 2000 revs for the first 20 mins, (use the search facility loads of info)and make sure you use the correct oil and add ZDDP to it, unless your choice of oil has enough.

 

Mick Richards

[McMuttley]

My wife has cam woes, or at least that's what I think the neighbours lad calls them

[Tom Fremont]

Hi Justin,

 

Make sure your tappets are absolutely flat on the bottoms. With a very slight amount of oil on them they should stick together. If they're crowned, they won't stick and will positively fail along with your cam ( just like the pics you show ).

 

I had one of the better known TR specialists supply me with (2) sets of crowned ones. On the 2nd set wear set in after 150 miles. These are correct for other applications, but not TR engines.

 

Cheers,
Tom

[Stanpartmanpartwolf]

You may have been one of the unlucky victims of a certain aftermarket supplier of cam followers, which for a few years sold poor quality steel (!) items, instead of chilled iron. That wear pattern is depressingly familiar.

Before you go any further, measure the size of your crank journals carefully & accurately, then report back here- crank sizing & cam wear are linked.

The currently available new chillcast cams & followers are of excellent quality. Failures with these are never materials-related.

SPMPW

[Motorsport Mickey]

Stanpartmanpartwolf

 

Hi Jon,

 

You have a PM.

 

Mick Richards