Don Terrill’s Speed-Talk

Let me know how that abradable coating makes you bearings look after a while. I'm not against coatings but if it wears off of the piston , it falls in the pan and goes through the pump. Does the filter catch it? Does some get by in bypass mode? Am I just being too cautious?

piston guy wrote:Let me know how that abradable coating makes you bearings look after a while. I'm not against coatings but if it wears off of the piston , it falls in the pan and goes through the pump. Does the filter catch it? Does some get by in bypass mode? Am I just being too cautious?

L2L says the abraded particles are soft, mostly very small and just harmlessly discolour the oil. The few larger ones are caught in the filter. When the oil stops turning dark, the bedding process is complete.

MadBill,
I heard the same thing at the PRI show from them. I would like to hear from someone who has used it. I'm just old and hard to convince I guess.

If no one else pipes up, the glacial-paced build of my L2L-coated BBC should be completed in a few months and I'll post my results.

Many people with high hp street cars pretend longevity but resistance to track day/race abuse,
so the choice for the 2618 are the anti-friction coatings and round design and that's it?
What about rings thickness and skirt lenght?

Gear heads, racers and engine builders tend to be close in genealogy to dinosaurs and fossils. They tend to remember 25-30 year old methods and materials as if they were only released a year or so ago. We've heard from a few of those in the "know" and they make it clear that when properly spec'd and used that there are few if any negatives for using a correctly designed and manufactured 2618 piston for a long lived street mileage use. Today's materials technology, computer controlled machining operations and innovation developed methods in pistons have taken the piston driven engine into a new millennium.

Hey Bill, as you've probably read lately, those glaciers are now melting and moving even faster than your build! I really don't want to post with your grand kids and find out how that beauty ran!! Speed it up Dude!

Newold1 wrote: We've heard from a few of those in the "know" and they make it clear that when properly spec'd and used that there are few if any negatives for using a correctly designed and manufactured 2618 piston for a long lived street mileage use. Today's materials technology, computer controlled machining operations and innovation developed methods in pistons have taken the piston driven engine into a new millennium.

Ok, but what about ptw clearance varying so much based on how the owner is driving?
Talking about the same car, I'd imagine the (aluminum) piston to wall (iron) clearance when driving in traffic should really be way different than after a 30 minutes track session: so isn't that going to make any difference talking about wear?
I've seen some WRC pistons and they have a lot of taper to compensate piston top expansion at ultra high and sustained temperature in the chamber: wouldn't normally street driving those pistons (so lot of dome to wall gap) take to fuel wash of rings and wall?

Modern CNC lathes can produce very complex shapes onto piston skirts. Some piston companies have 30 or more of these different shapes at their disposal. The variations can accommodate long or short skirt lengths and still minimize skirt "drag". Others are very specific to narrow skirt "box" design forgings. Piston designers routinely create parts with operating temperatures and conditions in mind so that piston to wall clearance is correct when running and the piston is as stable as possible for maximum endurance and ring seal. "IF" a 2618 alloy part were vulnerable , it would be that time when it is not up to temperature. "Warm up" time is all that is necessary and 2618 will perform well for a long time in most cases. Nitromethane and other power adders can obviously shorten any piston's life down to seconds as we see on TV all the time.

piston guy wrote:Modern CNC lathes can produce very complex shapes onto piston skirts. Some piston companies have 30 or more of these different shapes at their disposal. The variations can accommodate long or short skirt lengths and still minimize skirt "drag". Others are very specific to narrow skirt "box" design forgings. Piston designers routinely create parts with operating temperatures and conditions in mind so that piston to wall clearance is correct when running and the piston is as stable as possible for maximum endurance and ring seal. "IF" a 2618 alloy part were vulnerable , it would be that time when it is not up to temperature. "Warm up" time is all that is necessary and 2618 will perform well for a long time in most cases. Nitromethane and other power adders can obviously shorten any piston's life down to seconds as we see on TV all the time.

Thanks piston guy, have you got any advice on skirt lenght and piston structure/design to minimize wear during warm up and not-racing conditions?
I suppose round design, skirt as long as possible and maximum lenght pins?

I was told piston anodization makes a difference in 2618 absolute expansion, thus reducing ptw needed: do you agree?

Good info. So what is the more durable design on street the narrow x forging or a wide round skirt?

If it is primarily a street engine with not "over the top" HP and RPM's my thought is to keep the compression height on the piston reasonably long and make sure there is as little skirt as possible hanging out of the bottom of the bore at BDC and don't get carried away with super long strokes and longer rods. Most all of us love Rock and Roll, but pistons and rings hate that music!

Matt80 wrote:I was told piston anodization makes a difference in 2618 absolute expansion, thus reducing ptw needed: do you agree?

No I do not agree. Anodizing a piston does not allow reduced ptw. It should be used for extreme situations only .( big boost , nitro , for example)

MELWAY wrote:Good info. So what is the more durable design on street the narrow x forging or a wide round skirt?

"I" would stay away from an X forging for the street. I don't see any benefit. Race engine yes on the x forging. I am only one person and one opinion. Others may have a different opinion and that is fine.

piston guy wrote:

Matt80 wrote:I was told piston anodization makes a difference in 2618 absolute expansion, thus reducing ptw needed: do you agree?

No I do not agree. Anodizing a piston does not allow reduced ptw. It should be used for extreme situations only .( big boost , nitro , for example)

2X. Anodizing is a process that converts the surface layer, (less than 0.001", often much less) of the aluminum to aluminum oxide, therefore it can't affect thermal expansion.