rebuild or replace engine

[911tracker85]

posted this on the 951 forum but no posts yet. not purely a 951 issue.

made the mistake of digging into why I lose a small amount of coolant. had not seen any dripping in the past, just loss of coolant from the tank. I had put a small bottle on the overflow to see if that was the cause but not that.

so decided to figure it out. found what I was afraid of, a very slight leak/weeping from the head gasket on the intake side.

fight for several days getting the head off due to corroded bolts at the water bridge.

when I started to look at the block to clean found my #2 cyl BADLY scoured. ironic in that if it had been #1 or #3, at #1 TDC would never have seen the damage. I was really surprised because not having any noticeable symptoms like excessive smoking. but with how deep the scouring is don't know why?

just got the motor out. intend to pull that #2 piston to see if/how bad it is damaged.

looking at options.

1. send block to Lindsey Racing, over bore and drop in new pistons. $2,000 + ?

2. get a used short block. found a couple in the $1,000 - $1500 range. unless I then rebuild that, a bit of a crap shoot.

3. saw a bare block that is tolerance group 0. my motor is tolerance group 1.

so my crazy idea is IF the pistons are good, get the bare block and have it honed/bored for my tolerance group 1 pistons and a new set of rings. or find a bare block tolerance group 1.

according to the PO, this engine had been rebuilt just before I got it. so I'd move everything from it to the new block.

suggestions for those who may have gone down one of these roads in the past.

[9FF]

...or you could just fit an Alusil dry sleeve in your damaged bore, hone it to tolerance group 1 and reuse your existing piston.

Also how deep are those marks? If you weren’t having issues before then it’s likely they’ll be fine. Possibly caused by a damaged ring, replace ring and leave it at that is another option.

[v2rocket_aka944]

good luck actually sourcing one of those sleeves though, 9FF.

[9FF]

Originally Posted by v2rocket_aka944

good luck actually sourcing one of those sleeves though, 9FF.

I’ve heard they are hard to find from two people now yet a shop near me did a friends car with these sleeves only last year. Are you saying KS don’t supply them anymore as I see they still list them in their catalogue. Also I’m absolutely certain 944Online offered a sleeve that was compatible with our pistons, they even offered a service to fit them and I saw a completed block at their shop. So, have all these sleeving options dried up now?

[curtisr]

928motorsports appears to have some. https://928motorsports.com/parts/dry_liners.php ~$2000.00 ...

[9FF]

Originally Posted by curtisr

928motorsports appears to have some. https://928motorsports.com/parts/dry_liners.php ~$2000.00 ...

Nope, those are steel and require different pistons and rings.

[jhowell371]

You need a can of special honing goo. I will go the garage and take picture of the can when the rain eases. Remove the piston and using a hone with the stones carefully wrapped in cloth hone the cylinder with this stuff. You will be surprised. I suspect most of that is deposited by the piston. This was the case with my S2 block. Do search on Rennlist, this subject has been well discussed, probably here too.

[jhowell371]

Follow this thread and links.
https://rennlist.com/forums/924-931-944-951-968-forum/932627-bore-cleaned-with-sunnen-an30.html

[v2rocket_aka944]

Originally Posted by 9FF

I’ve heard they are hard to find from two people now yet a shop near me did a friends car with these sleeves only last year. Are you saying KS don’t supply them anymore as I see they still list them in their catalogue. Also I’m absolutely certain 944Online offered a sleeve that was compatible with our pistons, they even offered a service to fit them and I saw a completed block at their shop. So, have all these sleeving options dried up now?

when i checked with 944 online, they were steel sleeving blocks and using steel-compatible rings on stock pistons - the alusil pistons don't care if the bores are steel or silicon

[jhowell371]

Don't know why photo is sideways. I rotated picture 90 degrees right and still posted this way.

[IdahoDoug]

Honestly those don't look bad and that you did not have any untoward operating issues is confirmation you could just deal with the head gasket. If you wonder (as do I) what caused it and suspect a ring issue (ditto) you might pull that piston and see if there's a bunch of carbon in the ring or something similar. If you do, be sure you mark the rings and place them EXACTLY as you found them in orientation and which surface is up. At that point you could also consider the honing suggestion if the cylinder measures within spec to hone.

Personally, I'd just do the head stuff and run it unless you're planning to race it or you tend to push the car hard. If it's a fair weather hobby car - run it. If you're a teenager and redline it often, fix it so it can handle frequent operation near the mechanical limits of its design.

[9FF]

Originally Posted by v2rocket_aka944

when i checked with 944 online, they were steel sleeving blocks and using steel-compatible rings on stock pistons - the alusil pistons don't care if the bores are steel or silicon

You are absolutely correct, I knew that, just didn’t put two and two together. Iirc the 944 pistons have a ferrous coating on them anyway.

So it seems there still are at least to options to sleeve a damaged bore and use existing pistons just with different rings, that’s good to know.

[v2rocket_aka944]

911tracker, i don't think you saw my post in your other thread.

i have a 64,000 mile 951 short block for sale and i am going to be moving to Tennessee in the next few months.
perhaps i could just bring it to you, depending on how quickly you need it?

[911tracker85]

unless you're planning to race it

it is my DE/track car that is street legal, so yea I run it pretty hard on the track.

V2
I did see your post. got the engine on the stand and will be pulling the oil pan to pull that piston. then we'll see where this goes.

on one level I would like to find a good bare block. found one but waiting for reply on condition and tolerance group.

will post when I have news, but this week preping for a big mother's day family gathering at our home.

[IdahoDoug]

Well, borrow or rent an inside micrometer or get a set of the adjustable measuring "T"s and be sure you have a micrometer large enough to measure these tools. 3" is a pretty large micrometer. Check the bores and see what you have. I do feel like a lot of folks needlessly fret over bore surface having to be near perfect. Even race engines are run with wall marks and the like.

Looking forward to seeing details and curious what you find in/on the rings...