Broken pistons in a hot-air 4.1, why?

[Billy6point6]

Hello. My bro-in law bought a rough running '85 regal T-Type.
It has a .040 over 4.1 under the stock '85 T-Type turbo stuff.

It failed a compression test badly, holes 3 and 5 blew only 25psi.

Upon removing the oil pan, there were pieces of piston ring in the bottom of the pan. Further teardown revieled broken ring lands on pistons 3 and 5.

Previous owner had thrown rebuilds at it, ending up with a 4.1 block, under the 8445 heads and turbo stuff. He claims he ruined two turbos, so it was on it's third turbo, and third engine rebuild.

Lots of debris flying around in there, all engine bearings were shot, lifters sticking because they were full of crap, etc....

So I rebuilt the 4.1, new pistons, rings, bearings, lifters,etc...

The current turbo seems smooth and after flushing it well, spins nice and quiet, end play seems OK, we'll likely re-use the turbo.

The big question has to do with the wastegate.

It looks like the previous owner installed an adjustable wastegate actuator, and it's stiff, really stiff, I cannot open the gate with my fingers, it takes grabbing the lever with a pair of pliers.

Could this have overboosted the engine causing this piston ring land damage?

I have not re-installed the engine yet, but I do have an Autometer vacuume/boost gauge to monitor it with. It will be installed before we even test fire the engine.

Any advice on the wastegate actuator?

The bro-in-law is looking to just get it running well, not looking to improve HP or 1/4 mile, just wants it running and reliable.

Thanks ahead of time, Bill

 

[it's just a six]

Take the actuator arm off & see if the wastegate opens & closes easy.
Too stiff will cause a high boost pressure. Or sticky wastegate valve.

Internal wastegate, correct?

 

[LOT]

check

put regulated air to the pressure port (assuming it still has an 85 wastegate), that will be the port connected to intake. The other port connects to vacumn block on throttle body. I believe 9 psi should start to open. The more pressure it takes the higher boost will be.

 

[Billy6point6]

Thanks guys. Yeah it has the wastegate right in the cast iron exhuast side of the turbo, with a vacuume diaphram linked to the butterflies' lever. The link is adjustable, and probabaly cranked to the peanuts by previous owner. We'll see how much it takes to open it.

The test procudure you describe should be easy enough.
One of those, "why didn't I think of that" moments.

This car makes me feel like a real newbie sometimes. Embarassing, but I'd rather ask questions than learn the hard way.

I'm not new to cars, just new to the turbos.
Back in the '80s, I saw so many guys banging their heads against a wall (not to mention, emptying their wallets) over these things, it kinda turned me off to them. That, or they were swapping in small block Chevys or big block Buicks.

Now that I'm working on one, I like it. Maybe cause it's not my money? hahaha


Thanks again, Bill

 

[LOT]

It's not brain surgery

You can do it--helps to know how the wastegate functions--much easier to trouble shoot. All things being stock---with the wastegate rod disconnected--it should have to be pulled 1/8 in. more outward to hook. The farther away from hooking the more boost you will have. Best of luck.--lee

 

[Turbo-Archie]

Did it have turbo pistons??

What pistons did you use??


..

 

[RegalT-type85]

Did it have turbo pistons??

What pistons did you use??


..

x2 What else does the car have, fuel system upgrades, exhaust, good cat (or no cat) What fuel you burning, what chip does it have, injectors size(read the part number if not sure, all that will help.

 

[ZNix]

Why not just buy another wastegate and forget about it?

 

[Just a Six??]

Do some reading at Vortex Buicks & Turbo Regal Web Site for a wealth of info explained very well.

 

[Billy6point6]

Thanks for chiming in guys.
I'll try and answer your questions in order of your replies.

Archie, it had .040 over stock replacements with a deep dish, and oil return slots in the back of the oil control rings lands, that's the same type of pistons that Nate bought for me to use. Although the slot is smaller, it's still there.

I know, I know, we should be building it for it's intended use, it's really just common sense.
Also, from reading the GM manuals that we bought, the Turbo cars DID use a different style piston, but these are all we could find for the 4.1.

RegalT-type85, as far as I can tell, everything besides the 4.1 block is stock.
It's common sense I suppose, bigger motor = more air. More air needs more fuel, so I'll talk with Nate about injectors and whatever other mods you guys think the 4.1 needs before we fire it up.

According to previous owner, he replaced the turbo twice. ?????? And he rebuilt this 4.1 twice also. He reports the valves hit pistons, cracked a head, bent a rod, etc....

When we opened it up, previous owner used Felpro gaskets, and most of the pistons had little "history marks" where the valves contacted the pistons.
I am using thicker MLS head gaskets to prevent contact this time around.

ZNix, it looks like he replaced the wastegate controller with an adjustable one, and he cranked it full boost. We plan on tweaking it down to a level this 4.1 will live at. Basically, if it's adjustable, and working properly, we'll re-use it.

Thanks for the links, I've done some reading, I'll talk with Nate, and it looks like decision time. Do we open it back up and change out the pistons? Or do we try and make it live the way it is.

Thanks again guys, Bill

 

[charlief1]

If it's a .040 now and you're using regular cast pistons I'd honestly say tear it down and order some forged pistons. You'll have to have them custom made, which sucks, but they will at least live and keep you from having to tear it down because of a burned piston.