I am considering resurecting my car. It has scored cylinders that blow tons of oil. If I rebuild is scoring just going to happen again especially if it is modified and tracked on occassion or is there real ways tp prevent this from happening?

 

U.S. Chrome.. they will hone and re-plate the cylinder walls.. then you just need a set of Nicasyl compatible pistons (much larger selection).

PM Chris White for more info!

 

I'm talking about stock alusil. I know about the nicasyl. But I am wondering about the stock bore condition. Does this happen to all these motors and why?

 

I don't mean to thread jack, but I am in a similar situation. My car still runs fine, but it has low compression in one cylinder and burns through oil like crazy. The person I had do the compression test told me I would probably be best off just buying a new engine.

Going with a rebuild kit would be cheaper as I do want to keep the 2.5L, but will it be as reliable as swapping a low mileage engine with the one I have now?

If the only safe rebuild route is to change the stock bore, then is the extra cost of swapping engines worth it?

 

Why not contact some builders and compare prices? That would give you an idea of cost of a rebuild vs swap.

 

If you know the bores are scored, they will need to be honed back to restore the finish. This isn't a "if you want to".. as the scoring WILL destroy the new rings in short order.

The stock bore doesn't have to change, it CAN be rehoned and stay within stock tollerances, or Nic plated and have the finished bore any dimension you want, even stock.

Excess oil consumption / low compression ISN'T an indicator of a badly scored cylinder wall, it could just a likely be a bad oil ring, or out of round cylinder.

The only way to check the cylinder walls is to pull the motor apart, and measure / inspect everything.. when my motor was torn down it was down on compression on 2 cylinders, but the walls were pristine, and measured within tolerance (barely).

I elected to go ahead with the Nic plating for a multitude of reasons, #3 and #4 were barely within tolerance for out of round, and barely within tolerance for bore.. I could have just slapped it back together, but given my goals, and driving I decided to build it to better than I could.. also the reason Chris White has the motor right now, and should shortly be assembling it!

Home DIY rebuild... expect $2500-3K, if no machining is needed.. I would consider this as a complete all inclusive rebuild, or what I would do were it a daily driver, stockish, street car... it can be less, but you will be wondering about that extra $500 or so you could have spent to have this or that done...

swap... market price depending on condition of the motor, source, mileage etc..etc..etc.. $1-$10K depending on what is available and what you want (recently seen a full rebuilt motor / trans for $4500 and 2.8L built with 20K street use for $6K IIRC, a ready to run 3L... likely $6500+ depending on who built it, what it was built using, age, mileage etc..)

Professional rebuild... sky is the limit depending on what you elect to have done.. basic rebuild.. 4K.. full race 3.X liter.. 10K+ and yes that just for the motor, not considering the engine management, larger turbo, exhaust, intake, or any other special considerations (fuel system, intercooler options, clutch, etc..)

FWIW, my 951 resurrection will easily top $15K, is 2.5 liter, and will include every modification to allow bolt in of a 3L+ motor in the future.. BUT, included are the big FMIC, large pipes, bigger turbo, exhaust, EMS, fuel system... these are all on top of the suspension mods already done, and all other work performed last year!

 

Ugh...I could have had a V8! Boy that joke just never gets old!

 

Scored cylinders don’t usually have a severe impact on compression tests or oil consumption. They will show up more on leak down tests. Typical scoring does not create enough of a unsealed area to have a profound effect on blow by.

Scuffed, tapered, out of round or just plain worn cylinders and worn rings have a much greater impact on blow by than scoring does. If you have no evidence of blow by (high crank case pressures and leaks) then it may just be valves/guides.

In the good old days an engine swap was an acceptable solution for a worn engine…but now all the used engines are at least 22 years old. Even a low mileage 22 year old engine is not a safe bet for a quick swap. With all the costs and effort to R&R an engine in these cars it does not make much sense to just pick up a used engine and swap it.

BTW – the Nikasil finish is much more ‘score’ resistant than the alusil. If you want close to bullet proof go with the Darton sleeves – some of the toughest steel I have had to machine!

 

I guess I did not make my point so thgat every one understood. I am not wondering what to do about a block that currently has scored bores. I am wondering if scoring is inevitable on these motors. If I do a complete rebuild or buy a good stock bore engine is it inevitable that the bores will get scored? I see so many posts with scored cylinders. What can prevent this from happening?

 

No they do not all score, but they all do wear out over time..

Proper maintenance will extend the usable life, but EVERYTHING wears out!

The origional blocks, while revolutionary (sort of) for their time, were also so prone to wear that Porsche quit using the Alusil bores, in preference for Nicasil plated bores in an Alusil block / cylinder...

Prevention requires proper maintenance over time...

 

The engine I have just started running had scored cylinders from a previous metal contamination. It was enough to catch your fingernail on. They also had 90K miles on them. I cleaned the pistons/rings/cylinders thoroughly, re-assembled. Engine is running fine. Compression is 188,188,184,180 after 50 miles of break-in (if they even need to break in).
This is an S 16v not a turbo.

 

I'd say not inevitable on a factory motor with factory tuning and factory boost levels -- if the motor is well maintained, not allowed to overheat, and not run with air pockets in the coolant. Take away any of those assumptions and the risk goes up...

 

I am also in same situation. Scored some and low compression and now increased blow by. Motor was scoped, but not broken down yet. I assume rings are bad and/or cylinder issues as mentioned and scoring is not the sole issue as it is getting more blow by and crankcase pressure as time goes by. I assume if scoring was the sole issue it would not gradually get worse and worse??

I also have done the research on rebuild vs. swap and DIY vs shop, sourcing parts and different shop's ball park estimates, etc. etc. etc. lol After a while your head starts to spin when taking into consideration all the possible paths and bare bones vs. top dollar, etc.

So, Tom/John/Chris: Could you guys break some of it down to a more Rebuild 101? or "if I was going to do a rebuild in a cost effective way......" ?

 

For a rebuild, what parts would be acceptable used? Just the block? NA block?

 

I posted this back in April. In May I rolled the dice and bought a recent rebuild. Life gets in the way sometimes but I keep pushing. If Irene wasn't about to come by my house Sunday which meant that tonight I had to get my yard in order and stow away my outdoor stuff in the back yard and then do the same tomorrow at my mothers I could then get on to plucking the old motor off the crossmember and dropping the new one on and throwing on a new timing belt. Got the old one out last weekend.