427 LT5 Build 2 underway

[Scrrem]

Originally Posted by tpepmeie

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.

So what do you think the issue was with the ring seal on the first build? I just recently did a 380 build and only have about 800 miles on the motor but am getting a significant amount of blow-by as well. I was thinking my rings just haven't seated in yet but maybe it's something else. Starting to wonder now. Would be intersted to hear your thoughts.

[tpepmeie]

Originally Posted by Scrrem

So what do you think the issue was with the ring seal on the first build? I just recently did a 380 build and only have about 800 miles on the motor but am getting a significant amount of blow-by as well. I was thinking my rings just haven't seated in yet but maybe it's something else. Starting to wonder now. Would be intersted to hear your thoughts.

Well, I'm no expert, but I think it's a handful of things. The bore finish is obviously important. I don't know what hone finish was put on my first build, I will specify exactly what it is on the second one. A cylinder deck plate is a must, especially with open deck (mine is not open deck, and had a plate hone). The quality of the ring pack can't be overlooked either--I'm upgrading that too.

I also think piston stability in the bore hurts us as well. Especially with longer stroke/shorter rods. In the end, I have chosen a slightly heavier piston this time, with longer skirts. Still the box-bridge inboard pin boss design. My belief is that the piston starts rocking around in the bore, the ring seal gets disturbed, and the rings start to flutter at high rpm.

It was a well-built engine, and still had enough blow-by to push the dipstick up an inch under WOT. I never measured blow-by directly with a meter, but I wish I would have. It ran well and made a lot of power, so it couldn't have been too much of a problem.

Todd

PS- your rings should be seated by now. Did you break it in initially with a load? either on a dyno or hard street runs?

[tpepmeie]

Originally Posted by bradley

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

No. Mainly because I haven't got it all figured out yet. Will probably involve venting the crankcase directly to atmosphere, and possibly eliminating the PCV system. Or else figure out how to significantly increase the flow capacity of the PCV system.

[bradley]

you might want to call corey on this . he did his masters paper on trying to improve the lt5 pvc system

[Scrrem]

Originally Posted by tpepmeie

PS- your rings should be seated by now. Did you break it in initially with a load? either on a dyno or hard street runs?

Todd,
Yes, I did get some hard runs during breakin, nothing excessive though. I am getting a good deal of oil seeping out around the exhaust flange where my headers bolt up, no its no coming from the header stud. It's getting better the more I drive it, so by the time I return from BG, hopefully it will be to a minimum. The final hone on my liners was done with a really good honing machine and a deck plate was used. Hopefully this will resolve itself. Good luck with the build, can't wait to see the final product!! .
Rich

[XfireZ51]

Originally Posted by tpepmeie

No. Mainly because I haven't got it all figured out yet. Will probably involve venting the crankcase directly to atmosphere, and possibly eliminating the PCV system. Or else figure out how to significantly increase the flow capacity of the PCV system.

Todd,

Suggest you speak to Pete about venting to atmosphere. I believe they tried that with BobGs 427.

[ALZR1]

Hey Todd what is the length of the con-rods?

Al.

[tpepmeie]

Originally Posted by ALZR1

Hey Todd what is the length of the con-rods?

Al.

6" Carrillo's

[tpepmeie]

Heads are done... 41.5mm valves. "A lot" of airflow....

[Jagdpanzer]

Originally Posted by tpepmeie

Heads are done... 41.5mm valves. "A lot" of airflow....

How much did you gain?