# Oil type for new rebuild 68 GTO 400



## gtojoe68 (Jan 4, 2019)

I have brand new rebuild on numbers matching 400 WT code, manual shift motor. My builder has me using Quaker State 5W-20 Full Synthetic. It's running 10:1 comp. so I can run pump 92 octane gas. .030 over forged pistons and rods. Mild Crower Cam 0.455 int./0.470 exh. I've yet to adjust the rocker arms to address some valvetrain clicking at idle and a bit of chatter through the RPM; however, is this due to adjustment needed or is this oil too thin? I get great oil pressure running a SD Mellings pump. When warm, I get at least 50lb pressure at 3,000 RPM and 80lbs plus when cold. 

Other question involves adjustment of said rocker arms for noise. I remember factory is torque to 20lbs. No more. With the rebuild, and heads milled .010 ( and probably more on earlier rebuild before my time in 1987) should I be adjusting the rocker arms like other GM V-8? thanks, Joe


----------



## GTO44 (Apr 11, 2016)

Engine builder told you to run full synthetic on a fresh motor??


----------



## gtojoe68 (Jan 4, 2019)

Is synthetic bad on fresh motor or something? I was more concerned with low viscosity


----------



## Tflorek (Apr 21, 2019)

I had asked the same question a few weeks ago. I have a rebuild with 700 miles. Lots of guys said nothing synthetic till 2-3 miles but do what you want. But everyone agrees to use a ZDDP additive. And some guys run 15w40. I found that Lucas makes a oil for hot rod and classic cars in 10w30 that has high zinc properties from my understanding that’s what a guy wants. But it’s your car, and I choose to go with Lucas oil. Here’s a picture of the jug.


----------



## GTO44 (Apr 11, 2016)

gtojoe68 said:


> Is synthetic bad on fresh motor or something? I was more concerned with low viscosity


Assuming you got new rings with a fresh hone... The rings need to seal. Synthetic is too slippery to allow the rings to seal properly with the cylinder bore. It wont blow up or anything with synthetic... you may just end up with blow by... or a lot of blow by lol. 

And i always add a bottle of Comp ZDDP additive to help protect the cam. (If flat tappet i would add at every oil change. If roller cam just using a bottle at break in is good enough).

If you havent broke it in yet, use the cheapest 10w30 you can get with a bottle of the Comp ZDDP or an equivalent. If its a new flat tappet cam fire it up and go right to 2000rpm and vary up to 2,500 for 30mins. If roller cam or flat tappet is already broken in with the lifters... skip the cam break in and go right to engine break in... fire it up and let it get up to temp. Usually rev it up a few times and make sure there are no leaks and set timing. Let it cool down. Then bring it up to temp and cool down 2 more times for a total of 3. Change oil and oil filter. Use your better oil now... typicall weights i see are 10w40... 15w40... 20w50... ect. Here in florida you can use a straight 40 or 50 weight. If the engine builder setup tight tolerances like the factory you can run a 30 weight but typically its 40 or 50 for rebuilds. 

Usually i would go straight to the track or dyno at that point... but if its a daily driver or weekend cruiser and longevity is the goal... go easy for the first 500 to 1000 miles. Put it in varying loads, speeds, rpm ect. For the first couple miles you can do some engine braking to help seal the rings better. Put it in first, speed up to 4500 or so and let off. Let the engine slow you down. You can do this while driving in D as well. As you’re coming up to a light instead of braking pull the shifter down to 3rd them 2nd ect again letting ur engine slow you down. 

After the first 500 - 1000 miles change the oil and oil filter again. After 2-3k miles then you can switch to synthetic if you like. 

Ive never heard of an engine builder telling someone to use full synthetic on a rebuild. The only case i could see is if they used the same rings with no new hone on the cylinders (which usually is not the case)

Also ONLY use Wix or K&N oil filters... they are the best (smallest micron) filtering compared to the other off the shelf brands like STP or the absolute worst... Fram. There’s a local engine builder that has the best reputation in Central Florida and they won’t warrantee your motor if you use a fram filter for break in lol.


----------



## gtojoe68 (Jan 4, 2019)

Motor was already broke in - then placed on dyno. it is flat tappet cam. I've got less than 150 miles on it so far. It has new rings, and honed. I'm sure he used different oil on break in. I wouldn't even be worried about it except for the clicking rockers/lifters.


----------



## gtojoe68 (Jan 4, 2019)

attached dyno and build sheet


----------



## GTO44 (Apr 11, 2016)

Build looks good! Great torque. I just went back and re-read your first post. He had to of set up the bearing clearances pretty tight if he is recommending 20 weight. Nothing wrong with that. Just a little weird he wants full synthetic so soon. As far as the valves, it doesnt sound like anything wrong with the oil. Just go in and re-adjust now that its had some heat cycles. Also a good idea to re-torque your head bolts while you’re in there. If you want ALL the chatter out of the valve train you would need to adjust them with the engine running. You can take old valve covers, cut the center top part out which will give you access to the rocker nuts while keeping in the oil. Or just re adjust them the normal way to verify non of them have loosened up. Its not uncommon for them to send like a sewing machine and be just fine.


----------



## gtojoe68 (Jan 4, 2019)

cool. thanks for second opinion. I'll just adjust with it off, making sure each at TDC. I don't want that mess - I've done before on a small block chev with valve cover cut out. Yuk. Make sure they are all at 20lbs right? Or do I need to do the finger twist method.....I found this online....
Pontiac Rocker Arm Adjustment'

thanks again....


----------



## PontiacJim (Dec 29, 2012)

gtojoe68 said:


> cool. thanks for second opinion. I'll just adjust with it off, making sure each at TDC. I don't want that mess - I've done before on a small block chev with valve cover cut out. Yuk. Make sure they are all at 20lbs right? Or do I need to do the finger twist method.....I found this online....
> Pontiac Rocker Arm Adjustment'
> 
> thanks again....



If you have factory Pontiac rocker arm 3/8" bottle neck studs, *there is no adjustment* - torque to 20-25 ft pounds of torque.

If you want to adjust for "zero lash", then you will need a set of poly lock rocker arm nuts and adjust accordingly.

In either case, when the engine is running, you should see the pushrods spinning which indicates the lifters are rotating on the cam as they should. If not, then you can wipe out a cam lobe. No spin typically means too tight on the adjustment nut on the rocker arm. Too loose, and you get a lot of noise and worse case scenario could be a rocker arm falling off sideways and causing damage.


----------



## gtojoe68 (Jan 4, 2019)

So I am back to the original part of this post....oil type. I did install 7/16" BB Chev studs and new 1.5 to 1 ratio Elgin roller rocker arms w/ the poly locks BTW - did each one separately and have no more issues. thank you all - 

BUT - now wth with the oil? I simply can't wrap my arms around 5W-20 synthetic. After reading more than a few of the old posts on oil - my thought is now to go back to regular and use Lucas 10W-30 oil with all the extra Zinc goodies. I've attached the build sheet for my motor here - again - so see if anyone has any better advice or thoughts. 

Now if I can just get traction on those damn radial TA's when dumping the clutch at 2800...... lol It really has been fun getting this goat out with all the newly rebuilt items and interior.


----------



## PontiacJim (Dec 29, 2012)

gtojoe68 said:


> So I am back to the original part of this post....oil type. I did install 7/16" BB Chev studs and new 1.5 to 1 ratio Elgin roller rocker arms w/ the poly locks BTW - did each one separately and have no more issues. thank you all -
> 
> BUT - now wth with the oil? I simply can't wrap my arms around 5W-20 synthetic. After reading more than a few of the old posts on oil - my thought is now to go back to regular and use Lucas 10W-30 oil with all the extra Zinc goodies. I've attached the build sheet for my motor here - again - so see if anyone has any better advice or thoughts.
> 
> Now if I can just get traction on those damn radial TA's when dumping the clutch at 2800...... lol It really has been fun getting this goat out with all the newly rebuilt items and interior.


Nice. The Lucas seems to be a good choice as another forum member is going with it. The other popular choice is the Rotella T-4 15W-40 which is said to have the ZDDP. Several forum members use it with no issues. The Rotella may be easier to source.

I would be skeptical on a 5W-20 synthetic as that just seems too thin and is what modern cars use. My 2015 Hyundai calls for 5W-20 and I run a conventional Havoline 10W-30 in it. I just did an "experiment" and tried a 10W-30 synthetic and did not get the same mileage from a quart of oil as compared to the conventional oil. Not saying it isn't better, but I burned more oil using the synthetic. For me, I will continue to run the 10W-30 conventional oil in it on the next oil/filter change.

I would use a 10W-30 or 15W-40. Would not use a 20W-50 unless you had the clearances for it or raced the car and ran the engine hot.

Did you ever question your engine builder as to why he recommended 5w-20 synthetic and not a conventional oil?


----------



## geeteeohguy (Feb 2, 2008)

From your spec sheet, you have engine clearances on the loose side.....I would run Rotella 15/40 in that engine. Your piston to cylinder clearance, at .008" is beyond specifications..... .004" is the usual preferred amount. .008" is pretty sloppy, IMO. Also, the pistons are .021" in the hole....the engine would run better with a zero deck.....or no more than .010" or so in the hole. But, I'm not a machinist. You may want to look into this a bit. Running a 5w20 synthetic oil in this engine would be a mistake....The Brad Penn 10/30 with all the goodies or the Rotella and you'll be fine.


----------



## gtojoe68 (Jan 4, 2019)

So - I did inquire. I have a link to a blog here. It is ridonkulous how long it is but presents a very compelling argument for oils....and our misconceptions. but to answer PontiacJim - this is undoubtedly why he suggested the particular oil. Ranked #7 or something close to that for thermal wear protection.

https://automotiveamerican.com/2018...ts-not-myths-motor-oil-engineering-test-data/

the link to the blog is lower down..... it's right here: https://540ratblog.wordpress.com/ for easier access. 


thanks Joe


----------



## PontiacJim (Dec 29, 2012)

gtojoe68 said:


> So - I did inquire. I have a link to a blog here. It is ridonkulous how long it is but presents a very compelling argument for oils....and our misconceptions. but to answer PontiacJim - this is undoubtedly why he suggested the particular oil. Ranked #7 or something close to that for thermal wear protection.
> 
> https://automotiveamerican.com/2018...ts-not-myths-motor-oil-engineering-test-data/
> 
> ...



Yep, I knew of that website and read the whole thing. I can't confirm or deny any of his methods or results. I can understand what is being said, but my take away is that the oils are based on "shear" testing and almost dismiss the assorted additives. I have to question why they used ZDDP in the earlier oils for wear protection when I take awy from the discussion that the wear protection qualities of the additives are not as important as the "shear" ratings of the oils.

Next, does his means of oil testing comply with the API form of oil testing/rating? Here is a load test used on oils based on a method Timken bearings use and the results: http://www.animegame.com/cars/Oil Tests.pdf

Then, his analysis of using a thinner oil can be better seems to be contridicted by this statement, " *Viscosity and Wear Prevention
* - This same molecular friction prevents the oil from escaping too quickly when two engine surfaces in relative motion are brought closely together under pressure. This inability of the intervening oil to escape quickly and its level of incompressibility hold the two surfaces apart and prevent wear, a process that is termed hydrodynamic lubrication. The higher the viscosity, the greater the attraction of the oil molecules and the greater the wear protection."

So in my mind, and my choice, is a _thicker oil_, not thinner - like 10W30 or my choice of 15W-40.

The above info, and more, is found here: https://www.machinerylubrication.com/Read/30329/engine-oil-quality


The article sited also seems to indicate that there can be no metal-to-metal contact due in part of the incompressibilty of the oil film - so as long as an oil film is present. That may be great in a closed system, but that is not the reality of an engine - with oil leaks all over, ie the flow of oil out the bearings, out from under hydraulic lifters/cam lobes, etc.. That's were ZDDP can come into play -

"Zinc dialkyldithiophosphates (ZDDPs) have been used as a multi-functional additive in engine oil for over 50 years [9]. ZDDPs mainly function as an anti-wear additive; however, they also impart oxidative and corrosion resistance to the base oil. ZDDPs also exhibit mild EP (Extreme Pressure) characteristics. As an anti-wear agent, ZDDPs react with surface asperities (surface roughness) to reduce metal-on-metal contact. _When applied loads are high enough to collapse the thin-film on the surface, ZDDPs react with the entire metal surface to reduce wear._ In a general sense, the anti-wear film can be said to be composed of ZDDP degradation products; the thickness and composition of the products are directly influenced by temperature [9]. The nature of the ZDDP film has been extensively studied; however, no analysis provides a concise description of the film within automotive lubrication regimes." 

This info above is found here: https://www.ilma.org/PDF/ILMANews/2017/AAAreport.pdf
along with a wealth of other info _to include oil test methods. 
_

My conclusion? Who do you trust/believe - an independent home scientist and his methods, or the actual American Society for Testing and Materials (ASTM) standardized tests that meet the American Petroleum Institute (API) and International Lubricant Standardization and Approval Committee (ILSAC) specifications.

Of course you could also use the real world suggestions of other "old car" owners who have experienced no issues with their choice of oils and/or additives.

Which is the best oil to use? I don't think there will ever be a single answer to such a question. :thumbsup:


----------



## gtojoe68 (Jan 4, 2019)

I think I will change it out to the Lucas 10W-30 oil. Feel strange running that Rotella diesel oil but WTH? I guess a lot of folks like it. I'm in the PacNW so cold temps aren't really a problem. thanks again for your advice as always. J


----------



## gtojoe68 (Jan 4, 2019)

Finally got around the changing the oil. Went with the T-4 Rotella 15W-40. Valvetrain quieted down and oil pressure is up higher - like 75lbs at 2700rpm and 160 deg. I think this will be just what the Dr. ordered.
thanks all -


----------



## HiVolts (Jan 27, 2020)

AMSOIL a great Oil. I roll the Z rod 20W 50.


----------



## Dcur (Apr 5, 2021)

gtojoe68 said:


> I have brand new rebuild on numbers matching 400 WT code, manual shift motor. My builder has me using Quaker State 5W-20 Full Synthetic. It's running 10:1 comp. so I can run pump 92 octane gas. .030 over forged pistons and rods. Mild Crower Cam 0.455 int./0.470 exh. I've yet to adjust the rocker arms to address some valvetrain clicking at idle and a bit of chatter through the RPM; however, is this due to adjustment needed or is this oil too thin? I get great oil pressure running a SD Mellings pump. When warm, I get at least 50lb pressure at 3,000 RPM and 80lbs plus when cold.
> 
> Other question involves adjustment of said rocker arms for noise. I remember factory is torque to 20lbs. No more. With the rebuild, and heads milled .010 ( and probably more on earlier rebuild before my time in 1987) should I be adjusting the rocker arms like other GM V-8? thanks, Joe


My advice is if you’ve installed a hydraulic flat tappet camshaft use motor oil with high levels of ZINK and definitely not synthetic oils.Add Lucas tb zink-plus at every oil change.


----------



## Scott06 (May 6, 2020)

Definitely the rotella is a great value in oil, comes reccomened for many marine applications as well. 

The driven oil by Joe Gibbs racing also has high ZDDP levels and seems to be a little chaeper than the Lucas. I think youll be fine with any of these


----------



## Sick467 (Oct 29, 2019)

I've been happy with the Rotella 15w40 in a 17K 289 motor, a 200 mile pontiac 400 motor, and changed over to the 15w40 on a 135K 350 Chevy motor 30K ago. And, for some strange reason...it smells good!

I think you will be happy with your decision.


----------

