Two Questions: Re- Piston slap and oil press. mod.

[Dr. Freeze]

My '86 GN with 38k miles exhibits piston slap upon startup; it only last for two, maybe three seconds and is quite similar to what I hear from forged piston small and big blocks (that I'm more used to). It doesn't really alarm me unless there's reason to be...Is this a frequent/common thing with TR's?

Second question is regarding the oil pressure on 3.8 turbos... I know they don't oil very well and have heard there is a modification to the oiling system to improve in somewhat. I think it may involve the timing cover/oil pump assembly but am not sure. Point me in the right direction as it's something I intend to undertake before any mods take place.
-Jeb

 

[Reggie West]

If this is a stock motor and never been touched I would say you are hearing the lifters at start up..

No big deal

 

[Dr. Freeze]

Mmkay... Now what about the oil pressure "mod?"
-Jeb

 

[geno]

Are you sure its not dry fire knock?
Does it go away at the same time the oil lite goes off
Also does it only happen after the car sits for a long time or does it do it when its cold after sitting a few hours? Do you have a filter with a anti drain back? The best thing to do on the oil pump is to check the end play and keep it .001 or tighter if you can. You can get all different thickness gaskets to get were you want to be. Sometimes i glue the gasket to the oil pump cover and keep it dry so you can sand it thinner using a piece of glass and some 600 grit sand paper

 

[Nick Micale]

Originally posted by Dr. Freeze
My '86 GN with 38k miles exhibits piston slap upon startup; it only last for two, maybe three seconds and is quite similar to what I hear from forged piston.........Is this a frequent/common thing with TR's?

Second question is regarding the oil pressure on 3.8 turbos... I know they don't oil very well and have heard there is a modification to the oiling system to improve in somewhat. I think it may involve the timing cover/oil pump assembly but am not sure. Point me in the right direction as it's something I intend to undertake before any mods take place.
-Jeb

First, like Geno said, probably is not piston slap but bottom end noise. Some oil filters allow this to happen.

As far as what you have heard about Buick oil pressure not oiling well, is this from experienced builders or just hearsay? A 38k mile turbo motor should not have any oil pump issues. What pressures is yours running?

Lots of owners [and some engine builders] have decided to do mods to the cover and pump, only to end up with a bad situation even though it was fine to begin with.

We use un-modified factory pumps/covers on many race motors with good success. There are other factors for good oiling in these motors besides the pump itself.

 

[1ARUNEM]

Try a different brand of oil filter.. (Drainback valve)..

 

[Dr. Freeze]

I've "heard" the 3.8 Buicks don't have a very good oiling system; but as you state, probably heresy...

As for the rattle I would be more apt to think it IS something like a bottom-end noise; it sounds like piston slap but could certainly be lower. It occurs just about every time I start it but last maybe a second or two only... Could be dry main bearings or rod bearing; didn't really consider that. Which leads back to the oiling question of there being any improvements. I'm using a Mobil 1 filter which I don't remember whether it has the drainback or not. As for oil pressure, the gauge is still sitting in its Auto Meter box along with the boost, EGT, and fuel pressure gauges in the trunk of the car. I'm rarely driving it and am too busy currently to install them but will do so in the very near future.
-Jeb

 

[geno]

Next time you start the car watch the oil lite to see if it goes out at the same time the noise goes away The other way is to disconect the ecm at the battery and crank it until the oil lite goes out and plug it back in and start the car. See if that makes it stop

 

[Dr. Freeze]

I will try that...You're referring to the start-up oil light (idiot light), correct? I suspect that may be what it is... I'm so used to SBC's and BBC's (I'm an ex-machinist) and other 8cyl's the Buick is new to me. I built several of them when I had the shop but I've slept many times over since then... I know I set all the bearing clearances a lot tighter on the Buicks than I did on any other motor...
-Jeb