So what are you guys running for clearance? Seems like a lot of people run the .035 supertech says, but there are others (trackdayhooky, savington) that seem to run more clearance.

Lets hear some opinions. What should I run for an engine that will see a lot of track time and lots of HP...

 

Open it up, but be warned that the motor will not last as long and break-in procedure is absolutely critical to ward off excessive blowby. My clearances are right around .004".

 

How long are we talking here for engine longevity? And what kind of break in procedure would you reccomend? .004?

What I will most likely do is run the car N/A for break in. And have it trailered to the dyno from my place. Basically just turn it on at my place to make sure the car runs.

 

You say "open it up", but .004" < .035" ?!
What's your break in procedure?
What about piston slap on cold starts? How bad is that?

 

UMY enginee builder lauged when I said to go .004. He said there is no reason to and the engine will not last. It's currently with him and he is building it to .0025

 

I went with a loose bore on mine at the advice of my builder. I have no piston slap when cold, minimal blow-by, and I just ran 2-days at 5-hours of seat time with 250-280* oil temps and never once added oil.

My machinist told me to break-in by driving it to the track. He does a finish on the cylinder walls that supposedly minimized the need for break-in. I cruised up to 60-mph then hit over-run about 10-times and that's it. I ran 200whp for a week then up to 260whp and its stayed there for a while.

I hope you don't plan to track that car with .025" of wall clearance...but the builder probably knows more than me, Savingaids, my engine builder, and probably just about anyone tracking a turbo Miata.

 

0.0025" is tight, real tight. I'd run that on a NA motor but not something FI.

 

uHH

 

This dude's friend is smarter than you.

 

FWIW the alloy that Supertech uses in their piston has a different coefficient of thermal expansion (CTE) than the alloy that Wiseco uses in theirs (at least for Miatas).

 

As in Wiseco expands more, or less?

 

Uhhh. I think he meant .0035"

 

Wiseco expands more IIRC.

 

It's being built as a track car. And he knows that. I'm not too concerned because he warranties his work. If anything happens in regards to piston scoring, I can always be like "hey... see I said we should have gone with a larger bore"... And break in with him consists of like 5000kms of driving with a 4500RPM limit and 1000km check ups with a borescope to make sure everything is doing it's job. Or something along those lines... he went over it briefly with me.

 

I guess you're done asking questions and now you're telling us what you're doing? How much more reliable and stronger will your motor be than Savington's, thesnowboarder's, and mine? I guess this machinist knows something most don't since he insists on cutting the manufacturer's spec in half. What does he plan on checking with the bore scope? Lol @ oldschool break-in.

 

He sounds exactly like you did Hustler. You went from asking questions for 2...no 3 years about everything. To being an utmost expert on all things FI overnight with the only thing on your resume being installing a BEGI turbo kit.

So you and him should be able to see things eye to eye.

 

do not **** me off.

 

Oh noes, I'm shaking in my boots....

 

Lol @ Virginians in boots.

Claiming to be an expert on precision machine work and making fun of someone for cutting the tolerance spec in half are two different things.

 

THREEEEEETHOUGHSANDFUCKINGMILESUNDER4500RPM??????? ?

That is the longest break in i have ever heard of.

what the ******* ****???


i have never even heard of an oem break in close to that long. Ridiculous.