Is there a way to rebore 1979model 928 to 4,7 liter without altering the intake feeding system?Can the factory ring be used on cats iron liners?

 

Sleeving the block is a rather high risk operation and once it is done you run aftermarket pistons and rings. There have been numerous attempts over the years with a limited number of them succesful. The 95 mm 4.5 can usually be bored and honed to 97 mm making it a 4.7. That requires Mahle original pistons to run on the alusil finish.

 

Or just buy a 4.7 engine from 928 International....seems like that would be cheaper than boring the block and finding pistons.

 

based on the "4,5" I'd bet the shipping cost is pretty high.

oh yeah, and welcome aboard Fras

 

Fras is in Australia so shipping costs are a big consideration.

 

So is the price of doing the job, more than once.

 

I know a fellow with a great 4.5 liter short motor, he is in Sydney, if shipping proves too expensive from the States, maybe this fellow will sell it. I also have a set of brand new 98 mm pistons, you will need a 4.7 liter block most likely, I know somebody with one of those too but get ready to spend some cash for that combo.

Greg

 

Yes i am interested to buy the pistons and 4,7 block from somone,Are they iron plated pistons? If so can they run on cats iron sleeved motor?I think one option would be to buy the pistons and sleeve my block to 4,7 liter

 

How thick is the Alusil finish? Can new surfice be honed using Sunnen paste?

 

By Fras As I should have said the pistons I have are brand and Genuine Porsche pistons in Porsche boxes, that means they cost more I don't know what the plating is, it is irrelevant if you are running them on the Alusil bores. The Alusil goes all the way through but you need to maintain a certain wall thickness, my engine after boring has 5.5 mm and produces according to the Porsche Club of NSW 290 kw after it was tested during one of their tech days, it has on other occasions gone over 300 kw. Other 928's tested on the same day are around 50 to 100 kw less but I do have a nice exhaust. If Jim can't help you out you could just buy that engine.

I have brought quite a lot in from the States and a couple of belly pans from 928 INTL and I used Halfords international at Banksmeadow, they are quite reliable, NNR is used at the U.S end.

I don't know what you mean by a cats iron engine? If you have steel sleeves which have a mixed reputation, that being some successes and some failures you don't need Porsche pistons, just get them custom made for around $1500 to $2000 AUD, my pistons are $2,500 AUD or if you buy them this coming week I will do you them for $2250 AUD, It will make approx 4.8 litre engine. I believe they are around $3,000 USD or $6,000 AUD from the dealers here. Boring will cost you $750 AUD from someone who knows what they are doing. So around $3K for a new piston bore surface which will last around 20 years of normal service.

Greg

 

Greg
the the machine shop will put iron sleeve in the block so can i put iron coated Porsche genuine pistons to run on Iron sleved block or should i grind of the plating of them to get aluminium piston on iron sleeved bore?Is there place in Au who would Nikassil plate or made custom pistons?Or file of the coating of Porsche piston to back to the alumioum core on them?

 

i think you need to do more research on the M28 block if your intending to go this route.

You can bore and and get to the silicon finish and i would suggest that a million and 1 times before i ever suggested sleeving. Your only boring 1mm off the surface and i think you jeopardise the integrity of the block to sleeve. You bore the block (there is a process to do once you bore to get to the alusil with paste, i am really unfamiliar with it but someone here knows what to do.) then you can just run a stock porsche piston thats already made to run in the alusil. Much easier, much cheaper, fewer steps and PORSCHE already engineered the whole thing.

This has been covered and i suggest you read further before proceeding with your idea on how to do it.

I think there are much better alternatives then what you suggest. But its your project so have fun.

 

I would concur with Ryan, clearly your machine shop has no experience with this type of engine, may I suggest you get hold of the workshop manual before this turns into a disaster both engine wise and financially.

Please reread my post, Around $800 for boring and then you will need new or used pistons, decent used pistons getting hard to find, the last two sets I saw had problems that meant they were unusable, then if you use the second hand ones you will need to buy new rings. The pistons I have are ready to be used after the block is bored and lapped and they have new rings and pins. There is no Nicasil service in Australia unfortunately, there was going to be a plant built with a Gov grant but fell through, the quoted price was $2,400 to do the plating, this place can replate cylinder barrels on motorbikes etc but not car engines.

Greg

 

The alusil is part of the entire upper block casting the bore are honed to final size using a paste and felt pads which cut back the aluminum leaving the silicon for the pistons and rings a very durable surface to ride upon.

 

bore the block with new/used pistons, up to the 98mm pistons that are for sale.
someone that bores the block must know how to do the boring with the silicon paste.

Otherwise, your only other choice is to just buy a used short block, probably from 928 international and just re-ring it by yourself. nothing would have to be done and Ive done this a few times with no issues. the block cylinder condition is easy to see if it is sutable for re-ringing and 928inl would be able to send you a block that is ready to go or just needs reringing very easily.

sleaving, nicasil, etc, is not the way to go for what you are trying to do.

mk