Suggested oil weight

[Nervouswreck]

Hey guys. Just curious on your guys thoughts on this. I’ve always ran the factory oil weight of 5W-20 . Now I’ve had my engine completely overhauled top to oil pan. I’ve put roughly 600 miles on it since build and have changed the oil twice so far. The first 100 miles i ran Joe Gibbs break in oil , then just regular Penzoil after. Both 5w-20 . The end of the summer into fall i noticed a very faint blue smoke that happens ONLY on start up, you really have to look for it but it’s there . Now remember i had my heads completely redone with new seats , and seals. My buddy who owns a shop, builds motors , and races says don’t worry about it , it’s common for some to smoke on startup after sitting for a while and it may even clear up . So that leads to my question, what oil weight do you guys suggest after a complete rebuild ? Maybe I’m running to thin an oil and that’s why it’s getting past valve seals ? Should i run a slightly heavier weight oil ? I’m ready to get new Amsoil ordered for my car . Should i switch to 10W-30 ? Thanks guys


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[Albatross]

I run Mobil 1 full synthetic 5w-30. Maybe try the amsoil in a 5w-30? I'm not an oil guru so I'm not even sure it would make that drastic of a difference. I just feel like 10w-30 is a tad too thick. I'm sure the slight smoke on startup isn't anything to worry about.

 

[me32]

Id run 5w-30, but if you live in high heat or humidity 10w-30 is a good option.

 

[gt347mustang]

What are your clearences and whats the cold and hot idle pressure?

Oil weight isnt going to clear up the smoke on startup.

 

[Nervouswreck]

What are your clearences and whats the cold and hot idle pressure?

Oil weight isnt going to clear up the smoke on startup.

I don’t know buddy. I’d like to tell you but i can’t give you those numbers . What i can tell you is we did Manly Pistons , all new pins , all new bearings , 5 way valve job , new valves , seats, seals, springs , ARP everything, stayed stock bore and stroke


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[gt347mustang]

I don’t know buddy. I’d like to tell you but i can’t give you those numbers . What i can tell you is we did Manly Pistons , all new pins , all new bearings , 5 way valve job , new valves , seats, seals, springs , ARP everything, stayed stock bore and stroke


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Well then we cant be much help, sorry.
Good luck!

 

[gt347mustang]

Is this the same engine that has high crankcase pressure?

 

[DocB]

In my cars, I run 5W-30 M1. If I used it more, I'd run the Amsoil.
Additionally, if you are planning on running the Amsoil full synthetic, you might consider waiting to switch until everything is good and seated and broken in.

 

[SID297]

Do you do a lot of winter driving?

 

[MalcolmV8]

Now remember i had my heads completely redone with new seats , and seals.

Having had plenty of heads rebuilt over the years I can tell you that means nothing. I can't tell you how many times I've had machine shops screw it all up. Fire up the car and it puffs smoke like you describe or sometimes the car just smokes like the rings were totally shot. I reached the point where I'll only send heads to Livernoise or Fox Lake and pay the extra premium. It's not worth pulling the heads again to redo.

Hopefully its not your heads but just FYI.

 

[Coz]

If they were not careful installing the new seals over the valve stem, they could have nicked the inside of the seals.

I used a soda straw over the end of the valve stem (making sure the straw goes down over the valve stem ridges) and crimped and folded the other end where the seal slipped on. Generously lubed with assembly lube and installed the seal.

Do you even know what brand of seals were installed?

 

[TerminatoRS]

I'm not an expert, but I have two cents to toss in the idea hat:
If it's definitely oil burning, then the motor is obviously consuming it which will be evident on the dipstick level eventually. Maybe try an oil stabilizer such as Lucas and see if anything happens before getting too drastic.
Is it possible that an injector has a slight leak and it's excess fuel burning off? The smoke would certainly dissipate very quickly after startup.
Again, not a pro engine builder here.