I just felt I should share what I learned today from Randy at Randy Beyer Racing in Gretna, NE. This is the machinist that Dodger has used for a long time. Thanks to Dodger I have found him too.
I had been asked why I was coating the piston top in addition to the skirt. I really didn't know except I heard it was a good thing. This is what Randy said as well as I can remember:
A combustion engine creates power by the btu's from the burning fuel. This heat energy is diverted in 3 different ways. #1 to the radiator via the cooling system. #2 to the chamber area with the heat expansion. #3 out the exhaust.
The idea is to keep the energy within the chamber to maximize the usable power. The ceramic coating reflects the heat and bounces it around in the chamber to more fully contain it. It doesn't soak in as much for the cooling system to remove. Oft times the hardcore racers coat the cylinder head chamber and valves too. Randy has done this.
So that's the reason for ceramic coating the piston tops. The skirts are for reduced friction and to reduce clearances. According to Randy the theory of piston clearances and bearing clearances has changed greatly. He used to run .007-.008 piston clearance and heavy oil like 50wt race oil. Then as things progressed the clearances dropped to .004-.005 with 20-50wt racing oil. Then to .003" with a 5w30 synthetic oil. Now he is running .002" piston skirt clearance and (take note of this) 2wt Mobil One. Read this again, TWO weight Mobil One Syn oil. The reduced skirt clearance protects the skirts from slapping against the wall and damaging them. Not only has the piston clearance been reduced but also the main and rod bearing clearances. He says the reason for that is there is more area for support that way. He does drill the oil passages to the mains so there are 3 drilled passages in his race engine. He
does some upper end valley pan mods like he did to my engine for oil control.
Randy says he has gone from completely rebuilding and replacing every bearing, rods, pistons , etc to finding after the season that things are still OK. No trashed bearings and beat up piston skirts. His engine is started and warmed well about an hour before a run but he runs it cold and at the end of a run he's only showing around 130-140 degs. His engine stays 160 or below when fully warm. The old "more efficient at 180 deg" doesn't necessarily ring true anymore.
Randy runs his shop to support his racing habit as he's not a big bucks sponsored guy who can throw money at it constantly. He can't race every week-end as he's working on other people's stuff then too. He does have a day job but I'm not sure what it is. I'm thinking he's a diesel mechanic??? He's running a Mopar 312ci engine which spins at 9800rpm through the lights. I believe he said he runs about 7.80'sin the 1/4. The engine is a Mopar racing block that starts with a 3.91" bore and you can get different strokes to get the right cubes. He is using a 3.1" stroke offset ground crank with Honda journal size. He makes 750hp.
It was very interesting going over this with him today. I'll enclose a picture of his 312 Mopar and race car, a Daytona. Hope I got it all right and didn't bore you.
Rich Kinsley '64 Dodge Polara LeRoar 4dr 324 poly w/goodies
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