What Is Your Main Bearing Clearance???

[crownaviation]

Edit as the numbers were backwards lol My last setup MAINS were set at .0016-.0019. Looked pretty good and was surprised on those. Set the RODS to .0020 and those showed quite bit of wear but was expected as I was running "M" series Clevite bearings. Only a couple thousand miles on those bearings with new Kellogg crank. There was some wear on the edges of the front bearing but I likely got more life out of them than I should have. Was running Valvoline 10w30 racing oil with lots of zinc. My bearings were not made to last long tho. I am going with the same bearings and same clearance (Mains) this go also but will likely change up the ROD bearing clearances some. Color looked great tho.. no signs of any excessive heat or anything.

I rebuild every season anyway so there is that. I am going to switch to Joe Gibbs 5w30 and teardown at the same approximate mileage. I always beat it and will be running same power (1000hp) with the exception I will get there all on boost now instead of using the Nitrous as an additional power adder. Granted I only sprayed it that hard a couple times and pretty sure the wear accelerated from that and the higher rpm. I may be shifting at a little lower rpm now also so those all need to be accounted for. I suspect if I can still make the power at 6200-6500 vs 7k like before I will likely see less wear patterns like I did on this set of bearings.

Cams looked great. Had two followers (#3 and #6 exhaust side) starting to discolor tho and the bearings on those followers were loose (also new OEM at time of installation). Getting oil and oil pressure was never a concern. My VCT is locked out.

Will try to post a pic. Was not horrible but not as clean as the stock bearings look when those are removed (albeit they are a different material/purpose bearing)

 

[deebo05]

.0025 on the front and .0022 on the rest, because of a blower and 20+ psi i have scuffed several #1 top mains so i learned to open it up a bit.
on my turbo and n/a motors i run .021 across the board zero problems.
I do run 40w oil on blower motors.
turbo motors 30w works just fine for 1000+hp.
i think anything over .0025 and your going to need a 50w oil, and the 3v cam journals are too tight for that. these clearences are what i have found to work with mod motors and the Kellogg cranks. remember tighter clearances = more friction which = heat. that's not good for bearings. i like to have that cushion of oil there for lubrication and cooling this is from my experiences and preference so take it for what it is.

 

[justinsstang]

I wish I knew what the heck you guys are talking about lol. Looking at the oil etc though, I'm running 5w20 Mobil 1 on my m90 stock motor. Is that bad =X

 

[BruceH]

No. It's not bad at all. I ran various 5w-20 with the stock motor and a Whipple. The bearings looked new when the motor was torn down. So did the crank and cams. It protected the motor just fine and is thin enough to get into those tight clearances. If the oil can't get in very well you won't have a wedge, you will have less oil movement, and you will have more heat.

BTW a question like you just asked should go into the great oil debate that is stickied at the top.

I wish I knew what the heck you guys are talking about lol. Looking at the oil etc though, I'm running 5w20 Mobil 1 on my m90 stock motor. Is that bad =X

 

[05stroker]

I want to say mine are and have always been around .0025 I would have to check my notes next weekend when I am home but that sounds about right. I like it a little on the loose side though for my application. I run about twice the normal rod side clearance at .030 per pair to keep the bearings cooler but still run around .0025 bearing clearance. I run 10w40 in my motor also. I have been known to run the 5w50 in the summer time if I'm tracking the car a lot. I do have a lower oil psi at idle, about 25 psi. With a blip of the throttle though it is right up where I want it under load though. It really comes down to use and preference.

 

[BeachMonkey100]

I had my machine shop target .0015 on mains and rods. I haven't mic'd or plastigauged either yet. Right within Ford specs using 5W-20, shouldn't be a problem.

 

[AutoXRacer]

My builder builds more old pushrod and lsx motors than anything else, my motor was his 3rd 3v shortblock to build. He set mine right at .002, I told him I wanted to run ~18psi at some point during the motors life, and he recomended 10w30 and no thicker than 10w40 pending on operating temps. The motor itself has been solid and I have no complaints over it after 20,000 miles. It has seen 14psi noncooled and now 11psi with a2a.

0.002X...? What?

0.0021
0.0022
0.0025
0.0029

 

[AutoXRacer]

So I took the two bearing sets to my builder tonight. I also had a short conversation with him; I asked him to educate me on the clearances.

So, first of all he said, do not take those OEM specs in the service manual to heart. All the engines he's torn down, especially Honda engines are known to be looser (have greater clearances) than specified.

He also said, the whole 5W-20 thing was created to meet emissions regulations. Proof, performance and race cars do not use 20 weight oil.

So what drives clearances...? Basically the crank journal and crank diameter. Depending what bearings you use (taking into consideration material, bearing type, intended engine application) that will dictate your clearances. OEM bearings are typically aluminum and made of softer material which allow for tighter clearances. Performance bearings have a stronger metal for high loads thus requiring larger clearances. Its all speced out according to the bearing manufacturer, clearance between parts, and intended oil weight.

He told me he is shooting for 0.0022" but can go up to 0.0025". Slightly different numbers than what he originally told me. But at least we are firm now of where he is going with this. He told me off the bat that I will not be using OEM weight oil in this motor. He said we are far from a stock motor.

After our short conversation, I trust my builder and his decisions with my motor. He's been doing this for over 30 yrs and builds motorcycle, old school motors, and modern domestic and foreign engines. He supplies motors for various racing teams in motorcycle racing, automobile road racing and drag motors. So I guess I can trust what he is doing...

Anyway, that's all I got for now...

 

[BruceH]

That's true. Racing motors used to use straight 10 or 20 weight. Nascar uses 0w2.

So I took the two bearing sets to my builder tonight. I also had a short conversation with him; I asked him to educate me on the clearances.

So, first of all he said, do not take those OEM specs in the service manual to heart. All the engines he's torn down, especially Honda engines are known to be looser (have greater clearances) than specified.

He also said, the whole 5W-20 thing was created to meet emissions regulations. Proof, performance and race cars do not use 20 weight oil.

So what drives clearances...? Basically the crank journal and crank diameter. Depending what bearings you use (taking into consideration material, bearing type, intended engine application) that will dictate your clearances. OEM bearings are typically aluminum and made of softer material which allow for tighter clearances. Performance bearings have a stronger metal for high loads thus requiring larger clearances. Its all speced out according to the bearing manufacturer, clearance between parts, and intended oil weight.

He told me he is shooting for 0.0022" but can go up to 0.0025". Slightly different numbers than what he originally told me. But at least we are firm now of where he is going with this. He told me off the bat that I will not be using OEM weight oil in this motor. He said we are far from a stock motor.

After our short conversation, I trust my builder and his decisions with my motor. He's been doing this for over 30 yrs and builds motorcycle, old school motors, and modern domestic and foreign engines. He supplies motors for various racing teams in motorcycle racing, automobile road racing and drag motors. So I guess I can trust what he is doing...

Anyway, that's all I got for now...

 

[BeachMonkey100]

But also many of people use close to factory spec pushing 800-900+ so why change something that's proven and works.

My other question is, would oil weight and viscosity still play a factor in the VCT? If you decided to change clearances and run different oil?

 

[BruceH]

Gerald,
Here is what is going on with your lubrication system. I have a stiffer pressure relief spring for the oil pump if you want it.

 

[AutoXRacer]

But also many of people use close to factory spec pushing 800-900+ so why change something that's proven and works.

My other question is, would oil weight and viscosity still play a factor in the VCT? If you decided to change clearances and run different oil?

Frankly, I don't think these 800-900HP motors are running OEM clearances.

VCT will still work regardless of oil used. ROUSH P-51 engine is speced for 5W-50 oil. All they did was build the short block. Everything else is pure stock.

In my particular case, my VCT will be removed and blocking plates will be used in lieu of the VCT assembly.

 

[AutoXRacer]

Gerald,
Here is what is going on with your lubrication system. I have a stiffer pressure relief spring for the oil pump if you want it.

I am running JDMs high flow and volume SVT oil pump. 90psi cold, 60psi warm.

Regarding the NASCAR oil, I'm sure they are using oils not available to the regular Joe. Plus I thought they used that really thin oil for qualifying only.

Also, you can't compare race engines to street motors... NASCAR engines are built for one race...bearings are different; use and life expectancy of the motor is totally different from what you and me need. Not trying to argue with you Bruce and I agree with you. These NASCAR motors get torn down race after race...my motor, is hopefully not getting torn down until it reaches 100K-200K miles. lol

We just have to compare apples to apples.

I'm just glad the builder will be staying with the original JDM specs and typical 3V clearances.

 

[BeachMonkey100]

Frankly, I don't think these 800-900HP motors are running OEM clearances.

VCT will still work regardless of oil used. ROUSH P-51 engine is speced for 5W-50 oil. All they did was build the short block. Everything else is pure stock.

In my particular case, my VCT will be removed and blocking plates will be used in lieu of the VCT assembly.

I've seen with my own eyes the tear down of a 800 to the wheel car having .0019-.0020" clearance on the mains and .0016-.0019 on the rods.

okay, I have read somewhere where it might have been a theory or actually happened. I can't remember lol.

 

[BruceH]

I did with my Procharger D1. Is your builder going to clearance the rod bearings and side rod clearance too?

Frankly, I don't think these 800-900HP motors are running OEM clearances.

VCT will still work regardless of oil used. ROUSH P-51 engine is speced for 5W-50 oil. All they did was build the short block. Everything else is pure stock.

In my particular case, my VCT will be removed and blocking plates will be used in lieu of the VCT assembly.

 

[AutoXRacer]

I did with my Procharger D1. Is your builder going to clearance the rod bearings and side rod clearance too?

I'm sure he is... I didn't inquire about those clearances.

Unfortunately, I am not one to question a successful engine builder with 30+ yrs experience in the trade. lol

I'll post all the clearances once I get the build sheet. I should get the motor back next week!! Crossing my toes!! lol

 

[BruceH]

So he didn't talk about the pressure or flow requirements of a mod motor? Or specifically if the pump needs any kind of modification for the heavier oil and bypass valve?

You started this thread questioning your builder. Now you are all good with him, is that correct?

I'm sure he is... I didn't inquire about those clearances.

Unfortunately, I am not one to question a successful engine builder with 30+ yrs experience in the trade. lol

I'll post all the clearances once I get the build sheet. I should get the motor back next week!! Crossing my toes!! lol

 

[Redrocket06]

0.002X...? What?

0.0021
0.0022
0.0025
0.0029

He has no number after '2', so I assumed a '0' after that. Now I feel like an idiot.

 

[AutoXRacer]

So he didn't talk about the pressure or flow requirements of a mod motor? Or specifically if the pump needs any kind of modification for the heavier oil and bypass valve?

You started this thread questioning your builder. Now you are all good with him, is that correct?

When you say heavier oil...what oil weight are you referring to?

The oil he is going to spec I have a feeling will be in the 30 weight family.
Thats what I was running per JDM specs anyway; its also speced by OEM.

Yes, I would like to know what everyone else's main bearing clearances are just to see what other builders are setting these motors at. Then how the motor is running, oil pressures, oil weight, issues, etc...

This is my first time getting into the nitty gritty with these motors. My last build I put it all in JDM's hands and I just requested a sealed motor. This time, I'm getting involved in specs of clearances and such (not by choice).

I'm getting an education... lol

 

[Pentalab]

I don't understand something. The GT-500 uses oem GT narrow clearances... yet they spec motocraft 5W-50 oil ( which shears fast..down to a 40). Why are they using 5W-50 with way smaller clearances than autoXracer?? The oil pressure would be higher vs a 4.6L oem eng using 5W-20. I think the flow would be the same though.

What am I missing here ?

Is it possible to use 5W-20 or 5W-30 with the much bigger clearances ? It would flow easy enough.