Spring on engine mount.

[brufsup]

Hello all, I'll be putting the engine back in my Nippy later today. One of the engine mounts had a spring on it, but I can't remember which one. Does it matter which one ? I believe owners do this because of chassis flexing.

[Ian Williams]

Typical 750MC generated A7 folk law in my opinion, possibly some merit in certain specific circumstances but not in normal usage. Of course you will have some spring proponents who have read bulletin articles and will say oh yes essential I have run like this for hundreds of miles and have less block leaks and no broken studs etc. But there are plenty of people out there who quietly put their engines together properly, use no spring, and do thousands of miles with no issues what so ever. So put a spring on and bolt that make's you feel happy, if you arn't trailing or racing it won't make a blind bit of difference, and if you are racing it will probably make you go slower round corners.

[dickie65]

If its a Nippy it should be a rubber mounted crankcase anyway. so spring not needed.
I think the spring theory was for three bearing engines to stop chassis twist twisting the crankcase and miss aligning the crank.
As Ian has said also depends on use.

[GK5268]

spring = movement = wear

it is obvious really when you think about it, I did experiment as other owners seemed to recommend, but my experience was significant wear on the contact side of the engine mounting bolt head.

Experiment over, engine bolted hard on all four corners, NOTICED an immediate improvement to the car's handling over rough road surfaces AND a mysterious clonk every now & then disappeared (clear what that was now!).

Did not work for me and would not do this again.

   

[Alan]

Yes, and I’ve lost count of the number of crank cases I’ve seen with the mounting feet missing. Using the crankcase to stiffen the chassis is not a brilliant idea.

[Charles Levien]

Yes, and I’ve lost count of the number of crank cases I’ve seen with the mounting feet missing.  Using the crankcase to stiffen the chassis is not a brilliant idea.

Stuart Rolt who put my two bearing pressure fed engine together was a firm advocate of isolating chassis flexing from crankcase. I remember him spending five minutes trying to impress me on the need to do this when I picked up the engine.
Since then I’ve used an old valve spring under the top hat section which gives a firm but relatively flexible mounting. One or other ( or both) of the rear mounting points.
Im sure Ian is right when he rather dismisses the idea as being of limited use but I guess it’s nice to know my other car with a three bearing engine is free from crankcase distortion. 
The idea of using the crankcase to stiffen the chassis does seem a bit crazy somehow.

[Austin in the Shed]

If you cross section a scrap crankcase you will realise how weak they really are. I think it took all of 5 minutes to hacksaw one in half and at 80 to nearly a hundred years old they deserve an easy life.
When trialling we used to use the top and bottom rubbers of the later rubber mounts with long bolts and locknuts at the rear and longer bolts bottomed out at the front.

[Renaud]

What means "bottomed out" please? Not sure I understand that! (Silly frog!)

[David Stepney]

Renaud,

A bolt has a threaded portion at the bottom, followed by a plain shank up to the head., unlike a setpin, which is threaded all the way up its length.

A bolt " bottoms out" when one puts a nut on the reaches the end of the threaded portion without putting any tension on whatever the bolt passes through.

Hope this helps (and no, you are not a 'silly frog' - English is the most awkward of languages with lots of obscure idioms!)

[Tony Griffiths]

If you cross section a scrap crankcase you will realise how weak they really are. I think it took all of 5 minutes to hacksaw one in half and at 80 to nearly a hundred years old they deserve an easy life.
When trialling we used to use the top and bottom rubbers of the later rubber mounts with long bolts and locknuts at the rear and longer bolts bottomed out at the front.

At the rear, did you sit the crankcase on one rubber washer with another above the mounting flange, the whole nipped up by a through-bolt with a nylock nut to sent the squash "just so"?
When you say "bottomed out at the front" were the bolts nipped up, or just left loose to act as a form of "location stud"?