Reviving my GN. Syn or Dino???

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I finally got around to installing the new heads, intake, cam (flat tappet), and turbo. I have a few gallons of ACD that I'm going to use to break the cam in for 30minutes.

Using Superflo dino 20w-50, the engine still has the cross hatching at 20,000 miles at the highest power level and boost the car has ever seen.

As many know, I have had bad wear as shown by teardowns (even though UOAs were ok) with anything synthetic and anything less than a 20-50. This was my first run for this long on pure dino 20-50 and it's the best the cylinders have ever looked. The shortblock was left in the car so I don't know what the bearings look like but oil pressure is great. The new dual ball bearing turbo with it's oil restrictor has increased pressure a little also.

My dilema is I really really want to try a Redline straight weight. I know I should stick with what works but on the flip side, my 4.5L forged engine is nearing completion, the GN is just a toy, and I have less than $2,000 in the shortblock so if it did wear out quickly it's not the end of the world. If it lasted a while I would feel better about running syn in the new more expensive engine.

I was also thinking that since I know the engine is healthy (I will be performing a leakdown soon) my curiosity is getting the best of me. If it wears out quickly after installing synthetic then my mind is made up forever.
 
I would use Syn if it was my car, how much HP and torque will this bad boy make ?

I got a case of 'red cap'15w50 Mobil 1 that I would give you if you lived closer.
 
I appreciate it but that's the stuff I used to run when it would pound the bearings out and kill the rings/cylinders.

I'm not looking to make more hp on the stock bottom end, just looking for the same power with a little less boost.
 
I use Rsdline 10W/30 in my Grand National - while it is not making the power your's is - it has served me well.
 
Mobil 1 15W-50 is a little thin for a 50 grade oil. I have used it 100% for the last 19 years in engines that called for 20 and 30 grade, with fantastic results.

have you considered a 20W-50 synthetic motorcycle oil? Higher HTHS, higher 100C cSt, up to around 1600 ZDDP, more anit shear, antioxidant, anti foam. The downside, to me maybe not to you, is that motorcycle oil has no FM.
 
Originally Posted By: GMBoy
I use Rsdline 10W/30 in my Grand National - while it is not making the power your's is - it has served me well.


That's the other thing, my friend's stock longblock 11.60 GN is running the same oil as you with 90,000 miles on it and it runs great and passes smog easily.

I really want to get to the bottom of this before the StageII engine goes in.
 
FWIW,

A guy I know that owns a 87 GN that runs low 11's / high 10's, runs Redline oil.I dont know what weight etc, as he's in the Air Force now
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but runs the [censored] outta the car and had no problems.
 
If you are up to experimentation consider Red Line 10W-30, a straight 30 grade synthetic and for the next run use the 5W-20 if pressures allow for it.

aehaas
 
I'd take note of, and possibly be scared of full synthetic oil also, if my empirical evidence was like yours.

But with the heat of a turbo and other hot spots [like piston bottoms]a full synthetic is more suitable, as you well know.

Did your bearings pound out or wear? Wear is one thing, but if they are pounded out/distorted, it isn't the oil that is to blame.
 
I'd stick with what works. you have proof it works, so don't 'mess' with that. Shorter changes on 'sale' dio 20w-50 is probably cheaper than a longer run on full syn, anyway.
 
Originally Posted By: mechtech2
I'd take note of, and possibly be scared of full synthetic oil also, if my empirical evidence was like yours.



Seriously. Why, if synthetic in the past has produced more wear, would you then break in a new flat tappet cam with synthetic!
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I'd run Valvoline VR-1 straight 40, straight 50, or 20w-50. Extra zinc for the cam.
 
Originally Posted By: Drew99GT
Originally Posted By: mechtech2
I'd take note of, and possibly be scared of full synthetic oil also, if my empirical evidence was like yours.



Seriously. Why, if synthetic in the past has produced more wear, would you then break in a new flat tappet cam with synthetic!
54.gif


I'd run Valvoline VR-1 straight 40, straight 50, or 20w-50. Extra zinc for the cam.




The honest answer is to prove to myself that synthetic will hold up since that's what I plan on running the forged motor on.

As for the cam break-in, that consists of 30 minutes in neutral varying rpms. No load on the engine so all I need is a straight weight with lots of ZDDP. Oil gets changed immediately afterwards.
 
Originally Posted By: AEHaas
If you are up to experimentation consider Red Line 10W-30, a straight 30 grade synthetic and for the next run use the 5W-20 if pressures allow for it.

aehaas


LOL. This engine would not last a single 1/4 pass on 5w-20. Roughly 120hp per hole with even more torque all below 6,000rpm. It has a ton of cylinder pressure on a narrow bearing small journal crank.

I've run as light as a 10w-30 and ended up with excessive wear on all rod bearings, the thrust bearing, wrist pins were nearly siezed, and the cylinders were extremely worn with a giant wear ridge at the top.

I'm thinking with the pounding the bearings take I want a straight weight with no VIIs to sheer and one of Redline's straight weights would be just the ticket since they have decent cold flow.

I have nothing to gain with a lighter oil. I warm it up until oil hits a minimum of 160 degrees, gas mileage is a joke, and I've heard the Total Seal rings don't like the light stuff. On top of that, the forged JEs already make noise during the warm up process which I have a feeling a lighter oil will make worse.

Pressures won't allow for it anyway. The last time I broke in the cam on a 30wt, idle pressure fell to 6psi which is mostly due to the terrible factory oil pump design.
 
Originally Posted By: BuickGN
Originally Posted By: AEHaas
If you are up to experimentation consider Red Line 10W-30, a straight 30 grade synthetic and for the next run use the 5W-20 if pressures allow for it.

aehaas


LOL. This engine would not last a single 1/4 pass on 5w-20. Roughly 120hp per hole with even more torque all below 6,000rpm. It has a ton of cylinder pressure on a narrow bearing small journal crank.

I've run as light as a 10w-30 and ended up with excessive wear on all rod bearings, the thrust bearing, wrist pins were nearly siezed, and the cylinders were extremely worn with a giant wear ridge at the top.

I'm thinking with the pounding the bearings take I want a straight weight with no VIIs to sheer and one of Redline's straight weights would be just the ticket since they have decent cold flow.

I have nothing to gain with a lighter oil. I warm it up until oil hits a minimum of 160 degrees, gas mileage is a joke, and I've heard the Total Seal rings don't like the light stuff. On top of that, the forged JEs already make noise during the warm up process which I have a feeling a lighter oil will make worse.

Pressures won't allow for it anyway. The last time I broke in the cam on a 30wt, idle pressure fell to 6psi which is mostly due to the terrible factory oil pump design.



Yeah, the bottom-end on that engine is like that of a Ford 302.... Unlike the Modular and LSx engines with the bottom-ends from [censored]......
 
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