I did a search and didn't find the answer I was looking for.

I was using Quaker State dino 10W40 oil with a high volume oil pump on my previous engine builder's recommendation but my engine didn't fair very well with it. Scuff marks and wear on bearings.

I just rebuilt the motor and I'm thinking of using Mobil 1 Synthtic with a normal psi oil pump now. What weight oil would I use? 10W30? 20W50?

Callie Dragon Slayer crank, Eagle H rods, SRP pistons. Naturally aspirated.

 

You running a oil cooler?
What are the bearing clearances on the rods and mains?
How much HP are we talking here?

All of those are going to lead you toward the right oil weight. As for synthetic vs. dino, that's a very easy choice. Synthetic and a full one at that, Mobil1 or German grade Syntec.

Bret

 

Thoughts:

1) 20W50 in Manitoba? Wouldn't you have to spoon it out of the can this time of year?

2) Ask your new engine builder. He probably has oil and viscosity he recommends for the clearances he built and the use of the engine.

3) If you built it, what are the clearances in mains and rods? What outside temps do you drive in?

4) Personally, I'd use Mobil 1 after a breakin with dino oil. 5W30 would be close.

5) Consider 10 psi per 100 fwhp at peak rpm if the clearances are right on. That would be 50 psi for a good 500 fwhp @ 6000 383.

 

It should be around 420rwhp.

And yes its damn cold up here but I don't drive the car in winter.

I don't know the clearances but this engine builder is recommending I stick with Quaker State 10W40 which, for reasons I stated above, I don't want to do.

Another shop that does LT1s (more expensive) recommend Mobil 1 10W30 and some of them have tried the Mobil 1 0W30 and liked it.

 

Find out the clearances and the weight of the oil will be easier to tell you. For your setup .0020-.0025 on the front 4 mains is going to be perfect and .0025-.0030 on the rear.

Bret

 

Thanx dude.

I'll post the clearances he uses in a couple of weeks.

 

Whats the theory behind the extra .0005" on the rear?

Steve

 

Come on guys......... Just because this is advanced tech, doesn't mean you need to make things harder than necessary.

Finding the proper weight of oil is super easy. First make your best guess and ask the engine builder what he recommends. Then check to see what your psi is at idle at normal operating temps and see what your oil pressure is running through a couple of gears at higher rpm.

If you’re over 25 or so at idle....... great. If you’re over 50-60 psi at higher rpm you’re probably OK, especially using the newer better oils which offer better protection.

If the idle pressure is lower, then make the oil thicker. If you’re idle pressure is higher and your psi at higher rpm’s is higher than 60psi, you will pick up hp by using a thinner oil.

Ain’t no harder than that.

 

Rear cap is twice as wide as the rest of the bearings. It's not just me who says this, Reher Morrison, Vizard, Smokey, Lingenfelter etc....



The 10 psi per 100hp is a good rule.

25psi at idle is low for me, I like about 35 psi HOT HOT and 40psi normally.

The problem with 25psi is that you can starve the lifters at idle.

I've seen 700hp motors with 55 psi max that worked awesome so sometimes the 10 psi per 100hp rule is a heavy rule.

The bearing clearance should be set to oil temp and viscosity. Higher the oil temp or the thinner the oil the tighter the clearance. A loose clearance and a thin oil will not make power.

Idle pressure should be set by the bearing clearance and the max pressure by the spring. Oil weight should be set to match this and the oil temps the motor sees. Today weight doesn't mean as much since a 0W-30 can take 300deg oil temps easy so it's more about clearances.

Bret

 

This falls into "do as I say" don't "do as I do".

I personally prefer 35-40psi at idle, but all the books I’ve read say 25 is OK. Your 10 psi for every 100 hp is interesting. Never thought of it in at way.

 

so, 30 psi in a stock z at wot is good? doesnt sound too good to me...

 

Well, yeah, there's probably a bottom end on that: a 120 hp s**t-box engine probably needs more than 12 psi.

The idea came from folks making well upwards of 500 fwhp on a 350+ cube V8, and applies to aftermarket engines with well controlled bearing clearances.

One old, but safe, rule of thumb was 10 psi per 1000 rpm. When 6500 was a high number, 65 psi sounded pretty good. Today's 9500+ Cup engines with 800+ hp would probably not have 95 psi, and maybe not even 80 at max rpm.

 

so, i wonder what a good answer would be?

 

So 35-40 psi at idle and 50-60 psi at 6500 rpm?

 

Not to sound like a smartass but that rule of thumb seems to have limited use. Does that mean a little 100hp civic only needs 10psi at 7500 rpms?