[Skip Fix]

The factory TRW valve notches for my RAIV head-which has a very shallow chamber as it is more open than 72cc D port and E heads- was really tight on some bigger cams. Even extending the factory angle into the flat portion in the center(there is a shelf on the center part into the relief) helps by about 0.030-0./040. Having extra is probably helpful.

Like John said make sure the rods are correct direction, valve notches since already done at the top and put it together.

[67 455 Bird ragtop]

Ok here is a little visual for ya. The first pic is the stock L2359. The second is piston #1. The last is the problem child #5. The purple is the factory stamping. The orange is either the factory arrow or where it should be and pointing to the front of the engine. The green is the factory valve relief. And the red is the new expanded valve relief. So you can see if I flip #5 and put it in the proper orientation the new relief is useless. And leaving it alone is no good because like Half-inch said I don't want metallic gravy for oil. But it's looking more and more like these reliefs were actually necessary. Was given some bad advice many years ago. So in the next few days I'll flip the piston and reinstall it and check the clearance. If it works it works. If it doesn't so be it and I'll move on to another option.

[johnta1]

I still wouldn't worry about it.
That cylinder may have a very minute amount of HP more than the others.
You would never know or feel the difference.


The main thing is that the rod main journal be facing the right way.

[67 455 Bird ragtop]

Originally Posted by johnta1

The main thing is that the rod main journal be facing the right way.

Agreed.

[Skip Fix]

Intake runner length, exhaust runner length, fuel distribution all will probably cause more variance that the piston offset. Part of why teh Engine Masters guys tune with a wide band in every header tube!

[lust4speed]

FWIW I was taught that the offset was there to quiet down possible piston slap, and that there was a very small loss in horsepower; and installed backwards would result in slightly more efficiency but with a slight possibility of noise.

Only thing that would generate metallic particles in the oil would be a rod installed backwards.

[Skip Fix]

FWIW I was taught that the offset was there to quiet down possible piston slap, and that there was a very small loss in horsepower; and installed backwards would result in slightly more efficiency but with a slight possibility of noise

My old machinists said the same.

[77 TRASHCAN]

Smokey Yunick mentioned this often...He said he put the higher powered offset in every engine he built...

[Half-Inch Stud]

Per Post 22, maybe let it ride as-is. Only 1 CYL would have more sidewall loading, but itsa rear CYL where lots of oil rides up. Valve clearance cut is big enough to drive the decision.

Would be good to know the Rods are all properly facing each other, and Crank's Radius Journal.

[KEN CROCIE]

That piston is now a driver side piston if you keep the offset correct. Mentioned floating rods several times but no mention of pistons being machined for pin retainers?

[67 455 Bird ragtop]

Originally Posted by KEN CROCIE

That piston is now a driver side piston if you keep the offset correct. Mentioned floating rods several times but no mention of pistons being machined for pin retainers?

I figured that was a give. Yes they were machine for spiral locks.

Ken Crocie = H-O Racing Specialties ??? Looks like I may finally get to use the pistons I got from you 100 years ago ... .LOL

My timeline has changed. It will be Monday or Tuesday now before I can switch the piston around and check the valve clearance. All things seem to point to that not being an issue.

[439gto]

Take that piston out and measure the offset. Left bank should be offset to the intake side, right bank to the exhaust side. Number stamps are not always in the same orientation, you shouldn't use them as an indicator of the offset. You may be fine.....Just my thoughts.