Polybushes

[Reckless Rat]

My God Baldrick! There are spies everywhere!

[dickie65]

Hi Folks,
I have been using Delrin engine mounts for the last couple of years with no problems.
My car is Roadgoing / Hillclimbing.
I use old valve springs on long studs to hold the engine in, the spring tension can be varied by winding the locknuts up and down.
Delrin is quite hard and turns easily,
I used Delrin as we use a lot of it at work ( free offcuts )

Cheers Richard

[Ruairidh Dunford]

My God Baldrick! There are spies everywhere!

[Reckless Rat]

Well after a morning in the workshop I have given up trying to machine the inserts for the engine mountings in poly bar. Even with a mandrel the material just is too soft to machine down to 1.5mm thick. I have taken the easy option and ordered some silicone rubber tubing 13mm o/d and 10mm i/d from that well known auction site. A one metre length will make enough inserts for the next millenium.

[Chris KC]

Interested to hear how you get on, Reckless. Just an observation, but the fundamental issue is that the rubber in general use for these mounts plainly does not have long-term resistance to engine oil. I don't know what grade it is, nor what Austin originally specified. There are of course rubbers with superior oil resistance - nitrile rubber, for example - but in practice it might be difficult and costly to produce a batch, or even a small quantity.

[AustinWood]

I use Nitrile rubber on my 1929 engine. Originally solid mounted but seems a good idea to add a bit of resilience.
all I do is cut some washers from nitrile sheet. One between engine and chassis and another above the engine with a penny washer to hold it.
Seems to work fine.

[Reckless Rat]

That's the main reason why I have gone for Polyethylene, to avoid the oil contamination issue. I wonder if the original reason for Austin going to rubber mounted engines was purely to reduce vibration between the block/crankcase and the chassis, which I guess would become intolerable in the cabin, particularly with the greater emphasis from 1933 onwards for saloon cars rather than open tourers? Does anyone have any info?

The standard set-up is still pretty firm if bolted up tight so I can't really see there'll be a detectable difference with the poly, apart from durability. Shame I couldn't turn the little inserts out of the same material but I'm sure the silicone rubber I have ordered will do the job just as well.

Now, when I eventually get round to removing and replacing the engine (it has to come out because the clutch release bearing is knackered) should I :

a) bolt everything up tight and see how it goes
b) leave one of the rear mountings a little loose to allow for chassis flex
c) add a used valve spring to one or both (or all) of the mountings.

The car is only used on the road and I have grown out of the need to drive it "banzai" all the time.

If option 'C' is the majority view I will happily accept any springs that might find their way down here because I don't have any other than the ones in the engine.

B

[Chris KC]

That's the main reason why I have gone for Polyethylene, to avoid the oil contamination issue. I wonder if the original reason for Austin going to rubber mounted engines was purely to reduce vibration between the block/crankcase and the chassis, which I guess would become intolerable in the cabin, particularly with the greater emphasis from 1933 onwards for saloon cars rather than open tourers? Does anyone have any info?

The standard set-up is still pretty firm if bolted up tight so I can't really see there'll be a detectable difference with the poly, apart from durability. Shame I couldn't turn the little inserts out of the same material but I'm sure the silicone rubber I have ordered will do the job just as well.

Now, when I eventually get round to removing and replacing the engine (it has to come out because the clutch release bearing is knackered) should I :

a) bolt everything up tight and see how it goes
b) leave one of the rear mountings a little loose to allow for chassis flex
c) add a used valve spring to one or both (or all) of the mountings.

The car is only used on the road and I have grown out of the need to drive it "banzai" all the time.

If option 'C' is the majority view I will happily accept any springs that might find their way down here because I don't have any other than the ones in the engine.

B

Personally I do them up about finger tight; 3 that is, the fourth is inserted but distinctly loose. Never used valve springs. If you did I guess you'd want a steel washer to stop them eating your engine feet. No evidence that my way is the best! But I've not had any particular problems.

[Steve Jones]

All my cars (including the trials car) have a used CLUTCH spring under the rear, near side of the chassis rail, Bruce. I use a longer bolt, a washer and a Nyloc. Tighten the Nyloc up until the spring is fully compressed and then back it off a turn or so. Other three corners bolted down hard. Been doing it that way for over 25 years and, if it wasn't for the fact that it would be the kiss of death, I'd say I'd never had any issues.

If you want a spring, let me know.

Steve

[Reckless Rat]

Thanks Steve - I was thinking along those lines. Bolting down hard does seem to reduce a lot of vibration. I should be able to source a clutch spring or something similar from Monsieur O'Reilly et Fils, (It'll be ready on Thursday) garagistes in the village. There's no rush for the time being as I've got other jobs to do on the car.