6 replies to this topic

[pete l]

Hi all,
Building up my MPI engine. New cam bearings and a brand new MED camshaft.
Is it normal for it to be stiff to turn by hand with the sprocket on ? I've oiled it all up. The original cam spins freely enough. Will it free up as it runs in ? Or could it seize ?
Any ideas what I should do ?
Pete

[OzOAP]

If somethings tight,then it ain't right...when it comes to engines that is.

[Designer]

Hi,

 

Except F1 engines which are impossible to turn over until heated to the correct starting temperature.

 

Paddy

[OzOAP]

The last DFV I did turned over. Must have done something wrong.

[Cooperman]

The cam should turn freely by hand.

[Steve220]

Hi,

Except F1 engines which are impossible to turn over until heated to the correct starting temperature.

Paddy

Thats a myth, sadly. Tolerances are tight, but not so much it cant turn over.

[Spider]

Now you've fitted t and turned it, you'll have some witness marks on the bearings, Remove the cam and give the bearings a light scrape / shave on these high spots.I plain bar of 8 - 10 mm sq HSS I find ideal for doing these. Do not use any abrasives at all here. They will shed material off the paper or cloth and embed themselves in to the softer bearing material.

The Square HSS Bar Material you can get typically in 100 - 150 mm lengths from machine shop tooling suppliers, I wouldn't suggest anything too big as you want t to sit fairly 'flat' in the bearing, if it's too big, it will dig in. These are commonly used for making lathe cutting tools from and has a good edge, as supplied, in the square corners of the bar. Pass the bar through the bearing and gently scrape with it while keeping it parallel. If you still have an old bearing, even your old Mains or Big End, practice on them to get a feel for the technique.

If you are unsure of doing them yourself, tack it back to the machine shop. Most machine shops also ask for the cam you intend to run with when replacing the cam bearings so they can check and correct them as necessary.