Took a closer look today at my cylinder block under some much stronger lighting and saw something I hadnt noticed earlier. All the cylinders have very light marks, but none seem to catch a fingernail except this one, on cylinder #1. I am doing a budget rebuild and simply don't have the money for a new block or to have the block restored. My nail just baaaarely catches on it. Do you think I'll be ok to run it with new rings and leave it as is? This would be for turbo duty, 9.5:1 CR build. BTW I have not cleaned the bores out yet with anything except blue shop towels and PB blaster. Would running an oiled scotch brite pad in there help polish it up at all? (probably not, I'm aware how hard the silicone matrix is) I assume a scrotch brite pad would be the preferred way to remove varnish near the tops of the bores?

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Would you consider installing shorter pistons?

 

For what purpose?

 

If this block is not good to run "as is" Any chance I can get ahold of the AN30 paste and felt pads and hone the cylinders myself without overboring it? That would still allow me to run stock size pistons, yes?

 

hard for someone to answer that if they haven't done it before. i would say seek advice from someone who's done that before. possibly a shop that posts here often.

 

Fair enough. Would you say that's even necessary Paul? Do you think the block is ok as is? The scratch on #1 is by far the worst on the whole block and its still so shallow that I can't feel it with the pad of my fingertip. It just baaarely catches a nail ever so slightly. I'm wondering if I should just ignore it and run it.

 

You should use a bore gauge and see how out of round the cylinder walls are. Looks like they have a bit of wear at the bottom of the cylinder (that darker color in the cylinder). I would just put turbo Pistons back in it and not worry about having to retune to 9.5:1 comp ratio. Plus with an 8v head you'll see detonation real fast vs using a 16v head with 9.5:1 pistons due to the timing advance needed on the 8v head. My stock 86 944 engine is 9.6:1 I think and I wouldn't turbo charge it. But if that's what you want to do then you should just find a used engine and throw it in the car and see how long it lasts. Or if you need a set of turbo Pistons and rarest rods I could hook you up. There not in the best shape but neither is your block.

 

For the purpose of merely popping in some pistons that wouldn't even reach the affected area. Just a bolt in fix if you will... slap some 7.5:1s in.

 

Not worried about detonation or retuning, I run megasquirt and only run E85 also I'm 8v not 16v. Also, I can get some really cheap 9.5:1 compression 83 pistons so that's what I'm going with since I'm broke and they are forged like 951 pistons (and it wont be an issue because of MS) Not trying to build an engine to see how long it lasts, I'm replacing everything and rebuilding it completely so it'll go another 100k miles.

 

Some more pics of the bottom of the cylinders, the two cylinders that are concerning me. From the reading I've done, the 928 crowd seems much more willing to put an engine back together even if the bores have marks like mine, even in boosted applications. It seems they are much less likely to immediately shout "sent it off to be cleaned up at a shop" and generally hold the opinion that minor marks like that are a very small or completely ummeasureable detriment to performance and are not worth the time and expense the fix since its so common. I should add that the block this motor came from was a well running DD car till it was pulled apart.

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Bottom of #2

 

I realize your using an 8v head, that's why I mentioned detonation using 9.5:1 pistons with a turbo. Rennlister racerboy built a 16v 2.5 and has 9.5:1 comp ratio, but since it's a 16v the timing can be fired with about 4 degrees or more retarded timing then an 8v head. I understand your running E85 and that definetly helps until you drive somewhere they don't sell it. Then you would have to turn down the boost which is easy enough I suppose. And I didn't realize that 83 pistons were forged or any of the N/A pistons for that matter, learning all the time. However racerboy uses 944S Pistons with 1mm machined off the top, I believe, to achieve 9.5:1 ratio and pushy out a lot of HP! But again it's a 16v 2.5L beast. I'm aware your in collage and broke for the most part so funds are an issue as well. And again like I said if you would want to run turbo pistons but don't think you can afford them over 83 Pistons, I have a set of turbo pistons I can hook you up with at your buget level. Rarest rods too.

 

The real answer is partly what you want to hear, partly what you know will scare...
Yes, you can use the block as is.
It will always have that wear.
You'll probably never see the likes of it again but you'll always know it's there.
You'll wonder, how much power am I missing? Is there extra wear and tear?
How much better could it be?
How much are you willing to live with....or without?

It's just a small scratch, we've all seen a lot worse. On a budget that block is your way to go, plain and simple. With money to blow you would fix that scratch but I doubt the benefit would be much. You would have more peace of mind though.
I don't see that scratch making a big difference. Like humboldt said, you may want to check other specs.

I think the main issue is undue long-term wear, and how much something like this can cause.

 

Thanks for an honest answer...as you said, nothing I didn't know. Just needed to hear it from someone else. I have seen motors go back together with way worse scratches and run fine, and this motor will probably never see 100k miles ever since it won't be my DD. It will probably never see 50k. I'm already over it and moving on to other issues, which is deciding between goetze and LR rings. I've heard that the goetze rings are often too big on their gap, so weighing my options. I don't want to compound a scratched block with loose rings.

Probably won't bother checking out of round, at this point with this block the less I know, the better as I've already made the decision to run it and if its a little off, it'll still probably be ok. This block came from a decent running car that was a DD before being pulled apart for something that had nothing to do with the block. Didn't smoke or anything like that and had reasonable compression.

 

Your money saved might go farther if you spend it wisely elsewhere.

 

What are you suggesting? I'm all ears?