Oil type for new rebuild 68 GTO 400 - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 05-20-2019, 06:10 PM Thread Starter
 
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Oil type for new rebuild 68 GTO 400

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
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post #2 of 10 (permalink) Old 05-21-2019, 07:43 AM
 
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Engine builder told you to run full synthetic on a fresh motor??

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #3 of 10 (permalink) Old 05-21-2019, 02:45 PM Thread Starter
 
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Is synthetic bad on fresh motor or something? I was more concerned with low viscosity
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post #4 of 10 (permalink) Old 05-21-2019, 03:58 PM
 
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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.
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post #5 of 10 (permalink) Old 05-21-2019, 05:08 PM
 
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Originally Posted by gtojoe68 View Post
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.

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #6 of 10 (permalink) Old 05-21-2019, 06:10 PM Thread Starter
 
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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.
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post #7 of 10 (permalink) Old 05-21-2019, 06:18 PM Thread Starter
 
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attached dyno and build sheet
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post #8 of 10 (permalink) Old 05-21-2019, 06:29 PM
 
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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.

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
GTO44 is online now  
post #9 of 10 (permalink) Old 05-21-2019, 07:01 PM Thread Starter
 
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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....
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post #10 of 10 (permalink) Old 05-21-2019, 08:23 PM
 
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Originally Posted by gtojoe68 View Post
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.
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