Yes,
All the piston pin concerns are noted and in principle, I agree.

In application, the rods I am using in Twiggy are "recycled" from a different race engine. These rods were set-up the way they are now and then pulled from that engine after about 100 passes and some street use. The rods looked fine with no signs of scuffing / wear and they measure-out correctly... so they are being put back into service.

Does this engine (Twiggy) need full floating pins... no, especially with the "good" 1.7 rod ratio it has. Is a "steel on steel" pin to con rod interface surface ideal... no but the other options are limited and somewhat expensive. (use a different set of 198 rods, bush or specially plate and re-size the small end)

One good thing about having floating pins is that it makes piston disassembly easy but there is not much advantage beond that.
Oh... the floater pin is shorter and therefore, lighter in weight
DD

I am running floating steel on steel pins in Eileen.
My builder told a story about a circle track motor they couldn't get to turn more than 7500rpm. All he did was float the pins and it would now turn into the 8000 range. I was surprized to learn that there was that much friction in the rod-pin connection. He also said it only made a big difference on really high RPM motors.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I was kinda worrying because I run steel on steel floating pins... now I do feel better.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Sorry, went back and re-read my post and it seemed kind of harsh. It was just a quick post with my opinion, didn't mean it to sound judgemental.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Isn't there a coating that can be applied to the pins that will help reduce wear or galling?

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Slant Cecil

Doc, I have a question about your coated pistons. Wont the coating on the pistons side, between the top of the piston and the top ring land, cause you clearance problems? If I remember right, the coating is supposed to be about .003 thick and the piston to bore clearance with a hypereutectic piston should be about .0025. I've never measured a piston there. Is it actually smaller up there at the top? I'm wanting to coat mine too and thought I would use a ring compressor as masking while I applied the coating but it sure would be nice to apply it down to the top ring. Earlier in this post you said you were wondering about a coating for your piston pins. Techline makes a dry film lubricant that can be burnished into metal that helps retain oil. If applied correctly it does not change the dimensions of what it's applied to. Techline says its for crankshafts but I would think it would help pins too.

When we did mine Blaine had the pins coated. I think the name of the place was Thermadyn or something like that. When I tore the motor apart there was none of it left anywhere.

When we assembled the 632 at the race shop they had everything coated at a place up in Rockford here. It kinda looked like gun bluing when they were done. Supposed to be a big friction reducer. I know it was a pretty good wallet reducer. The Camaro is the quickest and fastest all motor car in the class. Maybe it does work?

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Official Cookie and Mater Tormentor.

What about hard chroming the wrist pins to prevent galling?

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Excuse me, does this smell like chloroform to you?

Busy work week... not much engine build-up progress but I did make some calls about special pin coatings, I checked into hard chrome, copper strike, DLC and TiNi.
Hard chrome is expensive and thick for my situation, I would have to grind the pins undersize, build them back-up oversize and then regrind them to finish size. I think hard chrome is done more as a repair process.

DLC (diamond like coating) is a vacuum chamber, vapor deposited coating, it can be applied thin seeing some of the carbon material gets absorbed into the steel's surface... tough and slippery stuff but $$$.

TiNi (titanium nitride) is also a vacuum chamber, vapor deposited coating, it can be applied in a thin layer, it's tough and slippery. I see this stuff all the time as that gold colored coating on cutting tools and drill bits.

Copper strike (also called copper flash) is electroplating, usually done as a base coat for other electroplate materials such as nickel, chrome, etc. it goes on a little thick (.0001 to .00025) so it would be applied to the eye of the con rod and then re-sized... think of it as electroplating-in a real thin pin bushing.

I have local contacts that do the TiNi and the copper strike process so I need to go visit these guys 'face to face' and see if I can 'pull-in a favor' out of one of them.

In the meantime, I do have all the pistons / rods / rings assembled, with the top ring gaps set at .025



I will install the number 1 piston and degree-in the cam this weekend. (cross check with #6)

...Need to make a decision to "coat or not to coat" pins / con rod eyes early next week, cost and lead time will be the main consideration.
Here is what the piston / rod assembly looks like.
DD

Good questions.
The largest diameter on the piston is appx 1/2 way down on the skirt, the ring land area is usually .020-.030 smaller. Pistons are precision machined items, good ones, new, right out of the box are actually machined oval by a few thousands. Measure a piston when you get a chance, there is more to them then meets the eye.

We set piston clearance on Twiggy at .003 and yes, the anti-friction coating added .0015-.0025 of thickness but the piston skirt also has deep oil retention turning marks that fill-in with the coating. After coating, the pistons still fit into the bores, (I've already tried one) and I expect that the skirt coating will quickly get worn-off of the highest points, right at start-up. The maker of the coating states that over time, the coating gets "burnished' into the surface so time will tell on that.

Up on the piston crown, the thermal barrier coating can extend down the side of the piston to the first ring land and it has lots of clearance. In operation, this area expands and it is common to see contact in this region of the piston. Once that coated surface touches a cylinder wall, the .001 - .002 thick layer of coating is history.
DD

Aluminum block SL6 engines use an expansion plug to cap-off the front of the oil gallery. I needed to drill a small hole into the plug and used a slide hammer to remove it for oil passage cleaning and porting work.
A tube is now brazed into that hole and positioned so it squirts a stream of oil onto the timing chain and gears.

Another oil squirter was made to spray oil onto the oil pump to cam drive gear.
DD

That sounds similar to the old babbited rod process except the bearing material is electroplated on instead of poured.

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Slant Cecil

Here is a photo of the installed front oil gallery "plug oiler".


Pressed-in, glued and then staked... it better not come out.

I had to decide which way to point the nozzle's hole, so I choose straight up. (with the engine slanted 30 degrees)
The stream of oil is directed at the the back-side of the gear / chain, any splash or deflected oil should drip back down onto the spinning assembly.

Also note the large oil pressure relief channel cut across the top timing gear's thrust surface. This groove keeps oil pressure from building up behind the top gear which will push the cam forward. The groove is a smaller cut circle on some cast iron SL6 blocks and should be enlarged.
DD

Hey Doc, I've heard about doing a simalar thing with the gallery plug on iron blocks (with out the tube) what size hole would you drill in the plug ? Also, where does the other oiler go ? (for the cam/oil pump gear) I'm sure you'll show it, I'm just getting ahead of you.

Watching and learning....thanks!

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A .025 hole is what I drilled, you can also use a 1/32 (.031) and crush it down a bit to fan-out the spray and restrict the flow so you don't reduce the engine's hot idle oil pressure.

The other oiler goes into the unused pocket of the oil pump mounting pad and sprays oil onto the drive gear.
DD