427 LT5 Build 2 underway

[tpepmeie]

Here we go, guys. Thought I would make a new thread to document build 2. The target is 800 bhp, @ 7400 rpm. Some upgrades from the previous version (700 bhp/6900):

• New larger inlet valves (41.5mm v. 39.5mm)
• Higher compression ratio
• Billet aluminum mono blade throttle body
• New cams...maybe

Here are two links to other discussions about Build II.
http://www.zr1.net/forum/showthread.php?t=23894
http://www.zr1.net/forum/showthread.php?t=23537

I was never really happy with the ring seal on the first build, both from a blow-by and oil control perspective. So, we're now using new pistons, a different bore finish, and new rings. These pistons (430g) are a bit heavier than the featherweight CP forgings I used in build 1, so the crankshaft will need rebalanced. The intention is to get better stability of the piston in the bore.

Ross Custom billet pistons. 14:1 / Flat Top / .140" deep valve pockets made from a mold of my combustion chamber. These valve pockets will accommodate more than .550" valve lift if I decide to go there...

.043/.043/3mm Total Seal rings

[XfireZ51]

Groundbreaking stuff Todd. You're one of the people we should celebrate for advancing the ball!

[FU]

Gas ported pistons nice option.

[Blue Flame Restorations]

What bore finish are you planning to use?

[A26B]

I've seen the groove between the compression rings on Mahle LT5 pistons before. Can you elaborate on yours?

[tpepmeie]

Originally Posted by Blue Flame Restorations

What bore finish are you planning to use?

Whatever Total Seal recommends . Seriously, though, I think the finish hone is 280-320, with a specific cross hatch angle. Keith Jones at Total Seal is the guy.

[tpepmeie]

Originally Posted by A26B

I've seen the groove between the compression rings on Mahle LT5 pistons before. Can you elaborate on yours?

Jerry,
most all of the high end pistons have this. I believe the theory is to provide more volume for the gas pressure that escapes past the top ring. The groove helps relieve that instead of compromising the ring seal in the land. At least that's the way I understand it.

[tpepmeie]

I added a couple of links to the original post, just to keep it all together.

Some other upgrades for Build II:

• Custom main bearing studs
• ARP head studs
• Cometic MLS head gasket
• Custom heavy duty secondary cam chains ()
• improved crankcase ventilation
• upsized fuel delivery system, incl. new rails & adj regulator
• alpha-n fuel calibration, fully mapped on engine dyno
• RAM dual disc clutch

That's all I can think of right now. This should be fun.

[USAFPILOT]

Is this a second engine or a rebuild of the 1st 427?

[bradley]

could you share what your doing to improve the crankcase vent system ??????