3 litre engine rebuild

[David Reynolds]

Could anybody give me a idea as to what clearance is needed between the front No1 cylinder crank web and the first main crank journal should be ?, the Technical facts manual just says the is is the important clearance, with NO figures as to how much it should be. I'm just checking my engine over prior to fully rebuilding it, and I had the bearing's re-white metalled and line bored by a well known company who specialises in it, and I'm sure they have not left enough clearance between the crank webb and the No1 journal so it would pretty shortly after starting to run be running metal on metal between the crank journal and the bearing.

[John Murch]

I’m not sure if NDR (the WO spares scheme) would be prepared to give you some advice.......

[JohnWilliams6437]

Are you looking at the Big Binder Technical facts as that seems to give more info than the 'old' book.

[JohnWilliams6437]

Are you looking at the Big Binder Technical facts as that seems to give more info than the 'old' book.

[David Reynolds]

I was using both the big book, binder version and the older version and neither of them mention how much. it just states that this is the important clearance.

I've now spoken to Ced Cook and he seems to think that approx .0010 thou would be enough and I'm just about to speak to Jimmy as well.

[Nicholas Simons]

Do you really mean 0.001 thou, or do you mean 0.001 inches, ie, 1 thou?

[Nicholas Simons]

In an effort to assist, I have read through the relevant section of the big green book and note that the answers are in there.

Part 1. p34 Table at the top of page gives minimum clearances after bevel gear meshing operations.
Part 2. p17 Section 5 gives warnings about giving adequate clearances especially to the rear of the flanges, due to the differential thermal expansion rates of the crankcase and crankshaft.
Part 2. p34 Diagram 2.1.15 shows the relationship between the front main bearing and the crankshaft thrust bearing assembly.

If you leave insufficient clearances to the rear of the main bearings there is a grave risk of the bearings tightening up and running on the radii. The minimum required clearances increase as you go away from the thrust race, which is right at the front, as more expansion is taking place.

I suggest you set the bevel gear meshing first and then ensure you have sufficient clearances to the rear of the flanges.

[Quentin Chases]

Just joined the forum, I have nothing to add, but I need to say something if only to see if the damn thing works,
my 1924 3 litre is going fine, Neil Davies is very helpful, and Jimmy Metcalf has also helped me immensely
Regards

Quentin

[John Murch]

Welcome Quentin, always nice to have a new contributor.
Glad your car is going well, do tell us more about it.

[Quentin Chases]

Thank you John,

I use the three litre most days, up to now I have been used to driving 30-98s and Twin Cam Sunbeams, having owned two 30-98s and 3 1/2 Twin Cams. I have only owned the 3litre for five years, swapping it for a Talbot 105.
I am unsure how much Camshaft rattle is acceptable, if it gets a bit excessive, I put the headlamps on to act as a damper. Neil reckons the answer is to fit the 4 1/2 camshaft drive, but this entails taking the block off. He reckons it is an expensive job, probably double Ouch !!!
Thankfully i live near the wizard of Watford, and all the parts seem to be available.
So far I have been to France and Ireland in the beast.
Whilst it is more agricultural than the Twin Cam, it is far easier to live with. nearly all the parts are on the shelf.
Regards
Q

[John Murch]

I have started a new thread to avoid hijacking this one!