Does anyone know what specific clearances Supertech recommends? I have a block I bought used with supertech pistons and rods in them in my garage and the walls have vertical marks (no scoring) and have lost 90% of their crosshatching. I doubt this is a problem with the supertechs. I don't think that the previous machinist took care when working on this motor.

I assume I will need to re-ring and maybe rehone. I want my machinist to do this right.

Its on the supertech paper-work that I don't have. Your problem sounds like ring failure (scary) and not the piston touching the walls.

how do you feel about a Swain type thermal barrier coating on the piston tops to reduce piston temperatures?

About $100 poorer, I expect.

Why do you say that?

You would need to take out the pistons to be sure. If the pistons have no scoring on the skirts then Hustler is correct. If they do then he is wrong.

The sleeves in the block are steel, they will scratch the Al pistons if the oil film is broken and metal on metal contact is made.

There are other companies that do coatings as well for cheaper prices that do the same thing.

The coatings are not miraculous fairy dust, they don't shrink the piston or anything. The piston will still come up to temp and will still expand the same amount when doing so. What they DO do though is reflect the heat of combustion back into the chamber so that the pistons do not continue to expand during prolonged boost periods. The top coating does this.

Then there are side coatings that help suspend the oil film on the skirt to provide better lubrication. This can save your motor in the instant that you do in fact break through the oil film and you have piston to wall contact.

Lastly there is the oil shedding bottom coating that help when you have oil squirters like us. By shedding the oil cooling the bottom of the crown you maintain a greater temperature differential, which as you smart guys know causes the piston to cool faster.

As an example of price I had a local company in Richmond, VA do all three coatings on the set of pistons in Tom's motor for a total of $150. The $50 more than Swain charges for just the top. The place uses Techline Coatings. I also had them do the Chamber and Exhaust ports in the head.

because when pistons touch cylinder walls, its more than obvious and usually involves loud noises.
More Piston Scuffing

Joe..I am in the same situation as you. Looking to build my 1.6L with m-tuned rods and supertech pistons. Can't decide what bore/compression that I should go with. I thought about 1.8L, but I already forked out money for a 1.6L Rebello race head.

I recently got an email from Chris Swearingen who just got done tearing his engine down (again) and he sent me some pictures of the Wisecos that came out. He wasn't happy.

http://img31.picoodle.com/img/img31/...1m_5edc693.jpg

http://img15.imagefra.me/img/img15/2...2m_6631d82.jpg

Apart from the fact that Chris needs to stop taking close-ups with his iPhone, I can see his point. Note that the coating has come off not just on the skirts, but in the recessed area adjacent to the pin, where there has been no contact with the cylinder walls. I need to find out what clearance he was running, but this bodes not well for the Wisecos in my book. Looking like Supertech right now.

On a related note, I'll probably be going 1.8. I've decided I'd rather be able to take my time and build a new engine rather than do a quickie rebuild of the one in the car, and since I need a new turbo anyway, another manifold isn't going to kill me. Ideally, I'd like a '96-'00 motor so I can use the factory crank wheel, as mine isn't going to clear the swaybar with the extra length of the bigger motor. A '99-'00 would be idea, but I'm not married to the concept.

Joe one option is to take a 1.8 block with good ring seal, then swap just the rods, and re-using the rings - no honing. A few have done that with good results. I plan to do this on a VVT motor I have.

Another option is to take a block with bores in good condition and ring seal a bit less than perfect, do a re-ring with DIY hone. New stock pistons optional.

I'd like to know his clearance as well. Wisecos are some of the best. I had the machine shop hone to 0.0045" on the motor I built that Tom now has.

If you run too much clearance no one will know, if you don't run enough everyone will.

Unfortunately (from a financial standpoint) the whole reason I'm building this engine is not so much that I need a faster car as that I'm planning to do some proof-of-concept experimentation with "extreme" WI and I intend to push the boundaries a bit.

I'm not so much afraid of detonation (though it's always a concern) as I am that if I am successful at reaching my power goals, I'll destroy stock pistons in the process. Success, in this case, will mean having to sweep up pieces of my transmission off the dyno floor. In the interest of fudge factor, I've decided to build the motor as strong as is practical.

If you're gonna push hard you should get low c/r slugs.

btw, don't do coatings inside the exhaust parts pre-turbo for obvious reasons. I emphatically agree with the low compression idea too. It makes everything exponentially safer and you'll make tons of torque.

Go back and re-read post #1 in this thread. :D

I wouldn't blame that on the Weiscos. If he's been through multiple motors, he needs to find a new builder. Damage on the skirts like that suggests that the builder just fucked up his clearances. You have to look at any secondary failures, like the coating chipping away, as a possible result of the primary failure.

BTW - Supertech recommends some insanely low clearances, like .0027". I built my motor much looser than that, the .006" range, after talking with the machinist who did the bore/hone on the block about what it was going to be used for.



:fawk:

No replacement for displacement, though. Faster spool, more power.

Help me to decide on which piston CR.

After reading this thread, and many others along the way. It appears that going the low CR (8.6 supertechs) is the way to go for predominate track use. The increased torque is appealing, but the sluggishness outside of boost is not appealing. My car is a DD that will see a DE event one to two times a year. I am starting to lean towards the 9.5:1 pistons. If the MS uses these, then I figure I can use them as well for my build. It should take care of the sluggishness associated with the low CR pistons outside of boost. The lower torque will be missed, but it might help keep my transmission in one piece. I know that tuning will be much more critical with the higher CR pistons. i.e. less timing, lower boost. I'm shooting for ~300 whp. I little more or a little less won't bother me, and I am building the motor to withstand much more than my desired hp level. i.e.(forged internals, arp hardware, billet oil pmp gear, etc)

My goal is to steadily move this car to a track car that I drive on the street. If I ever decide to sell the car I would market it to a person that wanted a race car. Keeping that in mind, there are a lot of people who don't want a turboed race car. (Primarily the Dr's I work for that are into racing and have shown an interest in buying my car) Hence putting in higher CR pistons now would enable me to remove the turbo later, and not make the car a complete dog.

Please chime in, I have to get my part number in to the group buy.

they make a 9:1

I believe the site lists the 9.0:1 for the 85.5mm. I'm not overboring that much