408 tear down after high blowby issue

[RedHeartbeat]

Well, finally decided to tear the 408 down and see why it had the incredible amount of oil blowby in the crankcase. The prognosis isn't good. Number 7 piston had a lot of deformation to the point that the piston rings looks like a big smile, obviously caused by excessive heat. Pistons 1, 3 and 5 also had deformation in between the top and middle ring causing a loose fitting top ring on one side. I suppose there had been a fueling issue on the LH side of the engine. I think the bores are fine on that side. I need to have number 7 bore checked to see if there is any out of round that might cause future issues on a new set of pistons/rings.

My next decision is to figure out how to build it up for the turbo. I have the option of -32cc, -28cc, -8cc (what came out of it) and many others. I also have my 64cc P&P Patriot heads and a set of stock 71cc LQ4 317 heads with dual Patriot springs already installed. I'm trying to decide if I should go very low CR using the -32 or -28 cc piston and install the 317s or go for the higher flowing heads and sacrifice a few lbs of boost.

I have a Bosch fuel pump I'm going to install before the 408 goes back in so the fuel supply will not be an issue. I am also going to bypass the variable speed fuel pump wiring and run a 1/2" fuel line to the intake along with my billet fuel rails from my old truck. I'd love to be able to push a solid 15 psi of boost on pump gas.

Suggestions? Am I nuts? (most likely)

[farmtruc]

If you're looking to run only 15psi through the engine, keep the compression at a high 9cr.
Use somewhat flattop pistons and 317 heads. If you ever decide to remove the turbo, install the 64cc's and have a decent NA engine.

One fuel pump will handle about 550hp to the wheels, i'm sure your setup will make more than that. The larger fuel line will help, but so will better fuel rails.
Meth will supplement the fuel system as well.

Are you still gonna run the rear mount setup? Larger turbo?

[408.Luke]

i have a set of diamond custom -28cc pistons lmk if you want them

and how many 408's have you gone through now?

[RedHeartbeat]

Gonna stay with the rear mount since its paid for and cash has proven they can make some serious power if done correctly.

[RedHeartbeat]

i have a set of diamond custom -28cc pistons lmk if you want them

and how many 408's have you gone through now?

Still on the same one. fourth iteration.

[IXLR8]

I'm trying to decide if I should go very low CR using the -32 or -28 cc piston and install the 317s or go for the higher flowing heads and sacrifice a few lbs of boost.

Food for thought...Since you're talking about forced induction, a bit higher flowing head has less of an impact than when naturally aspirated, and IMO valve size and cam selection becomes more important. A good blower cam with nice sized valves will make boost go down and power go up.

A small cam with small valves acts like a dam raising boost psi and can make less power with more boost. Comrpressing air makes heat no matter how it's done. Higher boost psi means hotter air. Heat means less dense air and less power with more detonation which equals carnage. More power with less boost is a very good thing. A good blower cam with big valves and reasonably good heads usually works well.

Just my .02

[keniff]

so....where's the build thread on this Redheartbeat? lol id like to see this happen. i dont know anything about the pistons to help you sorry so ill just be lurking and watching out for a build thread so i hope.

good luck with the build, and i hope you get the numbers you want

[ducky]

Are you going to rely on meth at all? If you decide to just use pump gas only, what are you looking to do for your fuel system?

[SCIV]

Pics of the motor damage?

[RedHeartbeat]

This is the only visible carnage. Everything else looks good. Other damage is just slight deformation of the lands between the rings. Oh, the top ring on all 8 cylinders obviously got hot because there is hardly a gap in them unlike the 2nd ring which has about a 1/2" gap after removing them from the cylinders.