smoke blows out of the valve cover

[jiho2]

Ah, but have you?

Seriously, I've been thinking about starting a thread on this. I'm not sure if it should go here or in the general Engine Tech forum. It would be interesting to collect real world experiences, and maybe even useful.

We've all heard the NA crank is fine. NA pistons are less well known.

Looking at the pictures jimski posted here, this NA piston is actually a little better than the earliest Turbo piston, because this NA has a series of short holes in the oil ring groove where the earliest Turbo has transverse slots. Otherwise, it looks like it could pass for the same piston.

 

[jiho2]

Take a look in the 86/87 section and you'll find many people have used NA short block with success.

Actually I've looked and haven't found much about NA pistons. Block and crank yes, pistons no.

I've seen one post from several years ago where one guy said his friend put a lot of miles on a junkyard NA motor with a Turbo setup bolted onto it. Everything else I've seen was about breaking NA pistons with a Turbo conversion, usually due to ignition and overboosting. But not a lot of success stories.

 

[usetaboost]

I'm running an n/a block built to 82 turbo shortblock spec if that helps.

 

[b4black]

Yes, I have run them. Both my '82 GN's came with NA long blocks in them and they are still there. Years back, if you went get a remanufactured Buick V6, even from GM, they specified the part number for the NA and carb/turbos. That would be with a warranty.

If I were rebuilding a motor, I would use a turbo crank and pistons for sure. If I got a great deal on a good, solid NA short block, I would use it. (Of course, it would need to be a 4.1 )

 

[jiho2]

I'm running an n/a block built to 82 turbo shortblock spec if that helps.

Still has the NA pistons?

 

[jiho2]

Yes, I have run them. Both my '82 GN's came with NA long blocks in them and they are still there.

You converted those '82 GNs to Turbos, and they still have the original NA pistons?

 

[jiho2]

You converted those '82 GNs to Turbos, and they still have the original NA pistons?

Wait a minute, those are 4.1L motors, which undoubtedly have beefed up pistons that aren't really comparable to the NA 3.8L anyway.

 

[jimski]

jimski--

What car is your motor from?

Very recently I looked inside an '83 NA motor. Its pistons look EXACTLY like yours, in every detail (the design details, I mean, not the cracks).

At the time i thought it was an 84 regal with very low miles but it may have been an 85. My cutlass motor was a 307 that i yanked out.

 

[jimski]

Sorry, I just noticed this is an older thread, in a more recent one you say it's an NA block. With the 109 casting I assume it's the original motor in the '84 Olds.

In the past b4black has said it's ok to convert an NA block with NA pistons to a turbo, so long as you keep ignition and boost close to stock and run premium octane gas. But your pistons don't look too encouraging. What did you do to that thing, anyway?

For some reason when the car was cold under boost it would knock, i was trying to pass some a hole in the morning going to work and i guess i over did it. The engine did not have time to warm up. Thats how this crap started.

Plus i had no thermostat in the motor was too lazy to install one. On some days thou the car would reach about 160 degree before all this and under boost everytime the car was hot no knocks pings nothing at all, it was a true hot rod. This is all my fault i should have installed that dang thermostat.

 

[usetaboost]

yeah you don't wanna be getting on a turbo car when it's cold.

 

[jiho2]

Huh. I was assuming those pistons saw too much thermal expansion. You are saying they saw too little. People are always finding new ways.

 

[jiho2]

For some reason when the car was cold under boost it would knock.

That was probably piston slap. The pistons actually knocking against the cylinder walls due to too much clearance because they hadn't heated up enough. Based on what you've said, anyway, and the broken rings and cracked skirts.

 

[jiho2]

This is all my fault i should have installed that dang thermostat.

Don't berate yourself too much. We're all taught that you want to keep these things cool, that heat is your enemy. In addition to a 160* thermostat, a lot of people block off the bypass hose and drill a small bypass hole in the thermostat. Just to keep things a little cooler. So actually leaving the thermostat out entirely makes a certain amount of sense.

 

[jiho2]

usetaboost --

Ok, for lack of response , I'll assume your build DOES NOT have NA pistons, and you didn't quite catch my original point.

 

[b4black]

You converted those '82 GNs to Turbos, and they still have the original NA pistons?

No, they are factory turbo 3.8's. Both had the engines replaced by previous owners and both used NA engines. One was a remanufactured motor and the other is probably a junk yard motor. To most people, a 3.8 is a 3.8.

I don't think the 4.1 got special pistons, but it did get the rolled fillet crank.

 

[b4black]

For some reason when the car was cold under boost it would knock, i was trying to pass some a hole in the morning going to work and i guess i over did it. The engine did not have time to warm up. Thats how this crap started.

Plus i had no thermostat in the motor was too lazy to install one. On some days thou the car would reach about 160 degree before all this and under boost everytime the car was hot no knocks pings nothing at all, it was a true hot rod. This is all my fault i should have installed that dang thermostat.

When the engine is cold, it stays in "open loop" and disregards the oxygen sensor until it warms up. Without a thermostat, it may never warm up enough to get to closed loop. I'm not sure, but it open loop, the knock system may not function.

When the ESC (knock) system is working, you won't ever here any knocking. You will feel it pull out a lot of timing. I've had my knock gauge go full red - never heard a thing, but the car fell flat on it's face.

In other words, if you here knocking, something's very wrong.

 

[usetaboost]

usetaboost --

Ok, for lack of response , I'll assume your build DOES NOT have NA pistons, and you didn't quite catch my original point.

If I was you I'd just rebuild it and be done. If you need a block, just grab any 3.8. Just do a turbo rebuild kit for that year.

 

[jiho2]

No, they are factory turbo 3.8's. Both had the engines replaced by previous owners and both used NA engines. One was a remanufactured motor and the other is probably a junk yard motor.

You've looked inside and seen the NA pistons first hand? How did you ID that they are NA?

Please bear with me in my dogged determination.

 

[jiho2]

If I was you I'd just rebuild it and be done. If you need a block, just grab any 3.8. Just do a turbo rebuild kit for that year.

I tend to agree, but this issue has been around for years, and I want to flog it into the ground.

 

[jimski]

When the engine is cold, it stays in "open loop" and disregards the oxygen sensor until it warms up. Without a thermostat, it may never warm up enough to get to closed loop. I'm not sure, but it open loop, the knock system may not function.

When the ESC (knock) system is working, you won't ever here any knocking. You will feel it pull out a lot of timing. I've had my knock gauge go full red - never heard a thing, but the car fell flat on it's face.

In other words, if you here knocking, something's very wrong.

The open closed loop thing was exactly my theory also. The radiator was kinda plugged thats why on some warmer days it would reach temperature and run extremly well. I changed it too a pep boys aluminium rad and it never reached temp. I was just too lazy to put the thermostat in. Big Mistake