SC Power poly engine mounts - experiences?

[GreenV8S]

I'm still toying with the idea of replacing the OE rubber engine mounts with the poly ones from SC Power, but I'm concerned that they could be stiffer and transmit more loads to the engine mounting brackes. I'e already had problems with one bracket cracking and don't want to make it any worse.

If anyone here is using the poly mounts, have you noticed any more noise/vibration transmitted to the chassis as a result?

[rev-erend]

Not tried them yet but thinking of it.

When I last had my mouting brackets off - I added a bit more seam weld to the parts of the bracket that had none. Often the underside of the bracket.

Also spotted one of the cars racing at the Brighton Speed trial who had fitted an additional tie rod type device between the front on the engine and the chassis - to stop the engine twisting. It was a very powerful RV8 ..

[stevieturbo]

Bolt it in solid. Never worry.

[GreenV8S]

stevieturbo said:

Bolt it in solid. Never worry.

Not for you maybe, but I drive a TVR and enough bits fall off that as it is!

[That Daddy]

I fitted some of these a few months ago,engine vibration is ever so slight only around 1500rpm though and when moving you dont notice any change,i am not really hard on my car but i replaced the sagging originals 18 months previous to fitting the SC mounts and they had detearated already about 8k(not good)its early days so far but i was concerned with vibrations but they have been fine,i check the engine mounting bolts for tightness about once a year anyways but would imagine as long as they are tight that they should not come looser any sooner than stock(the SC mounts are not that stiff) to sum up,yes very slightly harsher but not to be even a slight concern unless your motor is badly balanced.

Edited by That Daddy on Thursday 2nd October 20:45

[leorest]

As I'm sure you are aware, vibrational frequencies (and their harmonics) can be amplified, or damped, by very subtle changes. Even if the alternative mounts are designed to be the same stiffness they will almost certainly have a different natural frequency. It is hard to predict if this would give better or worse results for your particular installation without using exotic (V expensive) instrumentation. The only thing that is for sure is that it is unlikely to be the same. Whilst it is a good idea to canvas the opinions of someone with a similar installation the only real way to find the answer is to try it out. Maybe if the suppliers are sure enough of their product they would let you have them on a "sale or return" basis? I presume they are not a trivial cost.

[stevieturbo]

GreenV8S said:

stevieturbo said:

Bolt it in solid. Never worry.

Not for you maybe, but I drive a TVR and enough bits fall off that as it is!

Solid = a little DIY, and free.

Ive had my engines bolted in solid now for about 6 years or more. RV8 and LS1.

You'll be surprised.

[BB-Q]

I'm currently looking for (cheap) poly mounts for my car.

can anyone point me in the right direction?

[GreenV8S]

BB-Q said:

I'm currently looking for (cheap) poly mounts for my car.

can anyone point me in the right direction?

Don't know if they're what you'd call cheap, but these are the ones I'm talking about:

http://www.sc-power.co.uk/Polyurethane-engine-moun...

[Chassis 33]

stevieturbo said:

GreenV8S said:

stevieturbo said:

Bolt it in solid. Never worry.

Not for you maybe, but I drive a TVR and enough bits fall off that as it is!

Solid = a little DIY, and free.

Ive had my engines bolted in solid now for about 6 years or more. RV8 and LS1.

You'll be surprised.

I've been thinking of this on the racer, I know Cliff did it on his twin turbo Tasmin but that had an iron block not ali. I'm just concerned about loading the block as the engine would be the only thing bracing the chassis around the wishbone rear mount, you reckon it will be ok?
Regards
Iain

[That Daddy]

GreenV8S said:

BB-Q said:

I'm currently looking for (cheap) poly mounts for my car.

can anyone point me in the right direction?

Don't know if they're what you'd call cheap, but these are the ones I'm talking about:

http://www.sc-power.co.uk/Polyurethane-engine-moun...

Yep,those are the ones i am using

[stevieturbo]

Chassis 33 said:

stevieturbo said:

GreenV8S said:

stevieturbo said:

Bolt it in solid. Never worry.

Not for you maybe, but I drive a TVR and enough bits fall off that as it is!

Solid = a little DIY, and free.

Ive had my engines bolted in solid now for about 6 years or more. RV8 and LS1.

You'll be surprised.

I've been thinking of this on the racer, I know Cliff did it on his twin turbo Tasmin but that had an iron block not ali. I'm just concerned about loading the block as the engine would be the only thing bracing the chassis around the wishbone rear mount, you reckon it will be ok?
Regards
Iain

I dont understand the question ?

If the engine is currently bolted in with rubber, why would bolting it in solid weaken the chassis ?

If you seen my engine mounts, you'd be very surprised. Im amazed they havent broken yet. But they were a cheap and easy DIY when I installed my engine.

With the ET Streets, I can pretty much do a 5000rpm WOT clutch dump in a 1600kg car, with virtually no wheelspin, yielding some 1.5x 60ft times.
Which is fairly vicious for a heavy, manual rwd car.

I have 4 x M10 bolts bolting each of the 2 mounts to the side of the block, and a single M10 bolt at each side to the crossmember !!!!!

[GreenV8S]

stevieturbo said:

If the engine is currently bolted in with rubber, why would bolting it in solid weaken the chassis ?

I suspect the concern is that the chassis is relatively flexible and liable to flex under suspension loads. The rigid engine mounts would result in the engine acting as a structural member connecting the two sides of the engine bay together which would effectively make it a structural member. The concern is whether the engine block will be happy with those loads on it. I don't know whether it's a valid concern or not.

[stevieturbo]

GreenV8S said:

stevieturbo said:

If the engine is currently bolted in with rubber, why would bolting it in solid weaken the chassis ?

I suspect the concern is that the chassis is relatively flexible and liable to flex under suspension loads. The rigid engine mounts would result in the engine acting as a structural member connecting the two sides of the engine bay together which would effectively make it a structural member. The concern is whether the engine block will be happy with those loads on it. I don't know whether it's a valid concern or not.

Lots of racers use the fact that an engine block is a rather strong piece of kit....to strengthen the chassis.

Some race cars, although designed around it.....actually use the Engine block and trans to mount susp components from, simply as it saves having a chassis in some areas.
You already have a big solid structure there....why not make use of it !

[GreenV8S]

stevieturbo said:

Lots of racers use the fact that an engine block is a rather strong piece of kit....to strengthen the chassis.

Yes that's true, but I suspect in most cases that's done after careful analysis of the stresses. In this case we have a big soft flexible aluminium casting which is already being heavily loaded by the engine internals. I have no idea whether it's a problem in this case, your experience seems to suggest not. The engine block is going to expand quite a bit when it gets hot - do you rely on your chassis bending?

[stevieturbo]

GreenV8S said:

stevieturbo said:

Lots of racers use the fact that an engine block is a rather strong piece of kit....to strengthen the chassis.

Yes that's true, but I suspect in most cases that's done after careful analysis of the stresses. In this case we have a big soft flexible aluminium casting which is already being heavily loaded by the engine internals. I have no idea whether it's a problem in this case, your experience seems to suggest not. The engine block is going to expand quite a bit when it gets hot - do you rely on your chassis bending?

All things considered....I'd say my chassis bends quite a bit lol