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ARE SILVER TOP AND BLACK TOP PISTONS/RODS INTERCHANGABLE?
hornetV2 - 28/9/15 at 07:31 AM

I believe that black top pistons and rods can be fitted into a silver top, can anyone confirm this?

My problem is that I suffered some detonation with my silver top 2 litre at Snetterton a couple of weeks ago and there is some damage to the pistons. I need to get the engine running again as quickly as possible and a friend has a set of black top 2.0 pistons and rods. So, if they can be fitted into the Silver top, it would be a quick and cheap fix.

I believe the black top pistons are shorter and that the gudgeon pin is a smaller diameter as well, but the black top con-rod is also longer, consequently the overall length is the same.

However, I am only assuming the crank journals are the same for the silver top and black top, so the questions are:

1. Are the crank journals / con-rod width the same for both engines?

2. Is it true that black top pistons/con-rods can be fitted in silver top engines?

3. Has anyone ever done this?

rusty nuts - 28/9/15 at 09:09 AM

Can't help as to fitting blacktop Pistons/con rods to a silver top but the first thing I would do is check the bore size and stroke for each engine , if they are the same you stand a chance , if not it's a non starter?

hornetV2 - 28/9/15 at 09:18 AM

Have checked bore and stroke are the same, and from checking Burtons catalogue the big end shells are the same part number as well, so its looking hopeful.

BaileyPerformance - 28/9/15 at 09:20 AM

The cranks are the same, we have used silvertop rods with wossner pistons in a blacktop block, so I'm 99% sure blacktop pistons and rods will fit silvertop block

hornetV2 - 28/9/15 at 09:32 AM

Thanks for the reply, that gives a bit more evidence that the rods are interchangeable on the crank, so its looking better

hornetV2 - 28/9/15 at 02:10 PM

The silver top has flat top pistons, but I have seen elsewhere that blacktop pistons are dished - can anyone confirm this? and if so is it a deep dish?

big_wasa - 28/9/15 at 03:29 PM

Yes dished.

You can pick up a black top for £150, there isn't that much to change.

See this for pics, not mine.
eBay Item

hornetV2 - 29/9/15 at 06:41 AM

Thanks for the replies, it looks like the black top rods/pistons will fit, but the dish in the pistons will reduce the compression ratio

BaileyPerformance - 29/9/15 at 08:01 AM

If you use the blacktop head gasket on the silvertop block with silvertop head with blacktop pistons the compression will come back up.

The blacktop pistons are dished to lower the compression as the composite gasket is much thinner that the old type silvertop gasket