996 engine mounts interchangeable with 997 part?

Hi eveyone, first post but owned Porsche's for 5 years now. So i realised my exhaust on one side of my 996 C4S was hanging down and low and behold a quick inspection has revealed the right engine mount is shot. I've gone to look up the mounts and found they should be part 99337504908, was a bit dismayed to see they were £200 a side everywhere but the USA, especially seeing past forums where people got lucky enough to come across them for under £50 a side. So after some digging I saw pretty much all aftermarket listings for engine mounts were interchangable between 996 and 997 but stock eqivelents of the mounts for each car with part numbers 99337504908 and 99737504908 had a large price difference. Thinking this may be similar to how 996 C4/C4S top mounts are interchangable with 997 C4/C4s top mounts even though porsche didn't make the old item obselete but the 996 equivelent costs a huge premium over the 997 part I kept looking. comparing the two pictures of the mounts and mounting points the only difference appears to be the 996 mounts have ridges at the bottom of the mount and the 997 doesn't, the mounting ponts look the same and that bottom surface doesn't make contact with the car so it must only serve some function to the intenal structure of the mount or just a design limitation of the time. So my question is, is the 997 mk1 part a suitable replacment on a 996? is 99337504908 interchangable with 99737504908? as they can be had for half the price. I'm sure most of us know 997 mk1 shares so much with the 996 mk2 it's been jokingly compared to the as a body kit, I assume Porsche would only inprove a parts design over time and porsche aren't above selling all their old stock off before replacing a part number in the past.

I can't talk specifically about the 996 and 997 engine mounts, but a good value upgrade is to 993 'RS' specification mounts with a mounting kit which comes to £125. Available here: https://type911shop.co.uk/epages/de...ca1-377e-432e-84fd-bdccf2206766/Products/9792 Although currently out of stick - doh! Looks like they supply the same kit for the 996 and 997 so another data point also supports your suggestion they are the same.

Thanks for the reply I did look at the RS mounts and was sold for a time, but put off by the URO branded mounts as I read on a forum and another person on an amazon review that they experienced the mounts sagging 8 months for one and two months in the other review both needing replacements and when I asked my local Porsche centre they wanted £600 for the OEM parts. My original mounts came from the factory have lasted 16 years and 90k miles so I biased to get somthing from Corteco who make the Porsche OEM ones as I was happy with the driving experience I had before with them, being my daily I wouldn't want any more vibration, my latest mods were autodimming mirrors and footwell lights and the new PCCM stereo to give you an idea of the kind of driver I am. I'm just after a comfortable and a little sporty driving experience with the peace of mind I probably won't need to replace the mounts again at least for a very long while. But yeah, that was primarily why I thought these mounts may be interchangable.

Just updating as I go along. more research is showing the parts all fit the same and operate just with various levels of stiff ness. - Corteco mounts are Porsche mounts without the Porsche sticker, same product from the same factory (not even a metal stamp on a porsche one to differentiate it, just a white sticker with the Porsche part number slaped on top), this is the case with both the 996 and 997 mounts, Corteco also go by CRP and Rein depending on region and distributer, they are the same product, same factory too. - from what I read it is speculated 996 turbo mounts are stiffer than standard 996 mounts and 997 cabrio mounts are stiffer than 997 coupe mounts though I don't know how 996 mounts relate to 997 mounts in stiffness though in the forums I read no one is 100% sure and are assuming in both cases with no evidence for what they say and if repeated in another forum they refer back to the same original 1 person who said it in speculation so equally could just be the same mount with different part number. Corteco themselves list their own part number that is compared to the 997 coupe part as being for the 997 cabrio too so that would indicate to me if the factory that makes the part for porsche has autherisation to sell the part themselves that if they differentiated the coupe and cabrio version as porsche do they would sell two different products rather than the same product under two listings however the 996 standard and turbo mounts sold by corteco are listed differently - I think I'm going to try installing the 997 coupe mount equivelents in my car, if i do so I'll report back on how it is after, I'll wait a day or 2 before I order incase anyone comes with any new revelations in this thread. - my though are the 997 part is just an improved/updated design for the same part for the 996 but susperseeding the 996 part would make it hard to shift old stock for porsche or would require them to test the part on 996's and spend money there to be fully confident in suggesting the swap over. also may be worth noting but could be just the 996's are older car in general but I found a hell of a lot more 996 threads with mounts leaking that 997 ones. if you look at the ridged edge of the 996 one its far less perfect the the 997 one, I'ts like the 997 design is what they wanted to make and the 996 mount is like this due to the limitation of the tooling for the time, not to mention the 996 was built at a time when porsche were limited finacially and the 996 mount is essentially a 993 turbo mount so they already had the tooling but the two parts are designed a decade from one another from 1995 to 2005 where there was a huge leap in technology. part numbers as follows: 99337504907 - 996 (non Turbo) 99337504909 - 996 Turbo - maybe firmer than 996 (non turbo) 99737504908 - 997 Coupe 99737504907 - 997 Cabrio - maybe firmer than 997 coupe if anyone has any old shot 997 mounts or turbo 996 mounts they wouldn't mind sending to me I'd be interested in disecting the different varients and posting the results so we conclusivly tell if there is a difference between the two. I'll hold onto my original 996 mounts incase, only one has actually failed so can compare a working though used mount.

your car and money etc but even the newest 996 is 15 years old and will have been used far more than is likely in the future for a fun car. I fitted the items from type911 (helpfully just down the road from me!) and have been very pleased with them. Try and give type911 a call, Matt has been there packing deliveries on the two occasions I have phoned during lockdown and will be able to give you some advice. I seem to recall something about bolt lengths when I started reading up on aftermarket kits but for me its a no brainer to buy these.

Thanks for the advice. just seeing what I could find about the URO mount really put me off them and Porsche wanted £600 for the real set so for me its a no go. sounds great but not for me. Just looking if anyone knows if these 997 mounts will fit I'm almost certain they will they will at this point. plenty people out there are driving air cooled cars daily and to be honest I'm quite happy with the car, even saving for a potential EV conversion come closer the time we can't drive ICE's anymore which in some of the countries I drive to is as little as 10 years away. Just a further heads up, I found a forum where function first said the two mounts are essentially the same in and out so I've gone and ordered the 997 mounts and will give a heats up when fitted on how it went.

Just thought I'd finish this up in case anyone was interested and came across it. the 997 mounts are a direct swap everything lines up perfect, the square notch fit exactly. side by side they are the same, the older mount just had some ridges on the bottom to do with the internal competition and had nothing to do with fitment. work great and far nicer than my old sagged mounts.

Appreciate your feedback on this, interesting results