after much deliberation on the best way forward (for the orange car) i have decided that a GTS engine is my solution and i have found one from a wreck that has 30,000 km, a 1992 auto.

ive been advised to replace the head gaskets and rings as the mileage is so low and there is a risk of them leaking/'sticking' - respectively. if i do go to this trouble, what else should i do and in particular does anyone have information on modification to the pistons to prevent excess oil consumption?

what did the factory do when it rebuilt the GTS engines under warranty? i understand a piston modification was introduced in 1993, do i need to upgrade the pistons or are the earlier ones sufficient?

i would be commisioning the work to a mechanic but i like to be well informed prior to doing so, TIA.

 

I would replace all bearings and seals, especially #3 main bearing to be sure it's perfect and do not show signs of dreaded TBF.

I think original piston can be modified to work like earlier models by drilling oil return passages all the way through. Didn't factory use same only partly drilled piston design on all GTS's? Did they ever change pistons to replacement engines as first replacement wasn't always enough?

Regards,

Erkka

1992 928 GTS 5-speed new everything some day
Oak Green Metallic 22L
Classic Gray MX

 

erkka, is your engine in pieces? is the point at which the piston needs machining (the oil return passage) obvious to find, how is it identified? i did read where mark@devek describes drilling GTS pistons in a couple of different ways...

i would have thought that at 30k kms the crank could be left alone and end float could be measured to preclude thrust bearing wear.

any other mods to the stock engine recommended?

can the ports in the head be 'cleaned' of casting marks etc without complete disasembly?

 

Yes, there are pieces all over the place. Can't really dismantle it much more if interior isn't counted. Only gearbox and TT left and they're next in line.



Unfortunately so far do not have pictures of pistons but there is several (4 or 8, can't remember for sure) holes under oil ring and in GTS's case they are only partly drilled, maybe 4-5 mm's deep. It looks easy job to drill them through like on all other 928/944/968 pistons. If there is some other way of doing it would be interesting to know. Possibly even more holes on perimeter or something totally different?

I would open up block no matter how little use it has had. Just to see there isn't anything wrong in there. Would hate to do it twice just because some minor detail.

Having any machining done to heads without thorough cleanup (washing on a machine) afterwards sounds sure way to disaster. Same thing applies here also, it's not so big deal when you're almost there anyway.

Regards,

Erkka

1992 928 GTS 5-speed small deal
Oak Green Metallic 22L
Classic Gray MX

 

erkka, thats probably good advice to completely tear down the bottom end and clean/measure to confirm everythings in good working order. it may be more than my budget allows to completely redo the heads (even though the idea of mild porting does appeal -that, some GT cams and a carbonfibre intake..!).

i might email mark@devek and see if he has any advice to lend from his experience, i have the feeling that first hand knowlege of GTS rebuilds is not that common... although i do hear stories of cylinder liners...

 

with a lot of advice along the way, heres a pic of the engine as it is nearing completion. we elected not to separate the lower block and left the crank in place during the process as the engine had a very low mileage and there was minimal evidence of wear on any component - i could probably have gotten away with simply installing it to the car and changing the oil!

the only modifications at this point include re-profiled cams, drilling of the oil control holes and revised sump baffle. all else is stock however there will be no cattylitic converter and instead an ott-x pipe with 2.5" dual exhaust. the EZK has a GT program although the intention is to re-map the chips on a dyno after break-in. hoping to begin installation in a couple of weeks and at the same time convert from auto to manual using a twin disc clutch.

i think the header wrap is good for 3-5 bhp!