help with switching to 0-30w oil

[seth]

when switching from a 20-50w to a 0-30w oil do you need to tighten up the clearances. I have tried 0-30w oils in the past with limited sucess. if i run .001" per inch of dia. as my oil clearance do i need to tighten that up and how much as a rule.

amsoil racing oil 20-50w and switched to their 0-30w bearing life has been shortend drastically.

as of now i'm not sold on the 0-30w

[Darin Morgan]

when switching from a 20-50w to a 0-30w oil do you need to tighten up the clearances. I have tried 0-30w oils in the past with limited sucess. if i run .001" per inch of dia. as my oil clearance do i need to tighten that up and how much as a rule.

amsoil racing oil 20-50w and switched to their 0-30w bearing life has been shortend drastically.

as of now i'm not sold on the 0-30w

If your having bearing problems with 05-30W synthetic oils your problems are not with the oil as much as they are the clearances and the machine work. Bearing misalignment or worse yet, to tight a clearance will hurt you every time. A good line honed main and properly trued and honed rod housing bores seem like a given but they seldom are. They need to be addressed, checked out and honed by a professional that knows what he is doing. You need to have .003 on the rods and .0035 on the mains or your playing with fire. We run .003+ on the rods at all times never less than that, ever. We run .0035 to .00375 on the mains and never less than that, ever. On engines with higher loads the clearances go up never down. Pin bores can have up to .00225 for clearance on some engines with high vacuum in the crank case and good oil control in the pan. The better the oil control and vacuum in the pan, the less oil the wrist pins get! We run 0055 (not a misprint) weight and it about the thickness of water. we run .0035 on the rods and upwards to.004 on the mains in the PS engines and the mains last all year long. Our 1300 horsepower Super Series engines have .003 rods and .0035 mains and run for 600 runs down the track! The record so far is 675 runs by Scotty Richardson.

(1) Get a good, professional machinist to line hone the mains and hone the rods properly.
(2) Make sure you have proper oiling. If your pressure fluctuates during the run,, you have problems.
(3) .003 rods and .0035 mains for clearance
(4) Use a good synthetic 05-30w oil like Mobil-1 or Castrol syntec
(5) In my personal opinion you need to stop using any oil from Amsoil. That is not a racing oil even if they say it is.

[Joe Mendelis]

What I want to know is why 0 and 5 weight have the same kinematic viscosity in the Bosch handbook.

Darin, why can Cup engine's run so much tighter bearing clearances? Is it a function of peak cyl pressure being so much higher in a Pro Stock engine? Journal sizes? Something else?

[DavidHarsay]

That all sounds good except for this part....

(4) Use a good synthetic 05-30w oil like Mobil-1 or Castrol syntec

In the US, Castrol Syntec uses hydrocracked basestocks, no PAO base present... Castrol Syntec is a good oil... it's just not a synthetic oil despite the advertisemebts, and not in the same class as Mobil 1. (in Europe Syntec is a true PAO based synthetic similar to Mobil 1)

[Harbinger]

FWIW, my local AutoZone carries a "German" spec Castrol Syntec. Maybe this depends on your location?

Chuck

[SWR]

Darin,

How many inches of diameter are the mains and rods of the engines those 0.003" and 0.0035" clearances are run on?

[Darin Morgan]

First off, I don't know the EXACT clearances that the NASCAR engine builders use so I will have to check on that. I do know that there average operating temperature is way above what a drag race engine SHOULD see and in this case I can see the clearances tightening up a little but due to component expansion but I don't think its whole lot. I will have to call some of my engine building friends over there and ask. I also see why there oils wont/don't/cant make power in a drag racing engine. We have tested all there high dollar oils that where specially formulated for them. Some costing in the $30.00 a quart range. They all failed miserably in the power department. There oils are formulated for extreme temps above 200+F and have additive packages to withstand stresses for extended periods of time. Anyone who takes a Drag racing engine over 140F at launch needs to have there head examined! (personal opinion)

The main and rod diameters we use are stock BBC and SBC and the Pro Stock engines have a 1.880rod journal a little over .625" wide and a 283 SBC main about .750" wide. Total bearing surface area in a P/S engine is about 20% less than a stock SBC.
If your looking at some preconceived clearance derived from the bearing diameter and surface area your missing the point. You cant scale the clearances up and down from a simple equation based on surface area and bearing speed. Don't take me wrong here, you must take into account the bearings surface speed and area but they are not the major factor in determining clearance. Factors yes, primary factor, no. You need to consider Internal component deflection and distortion when determining bearing clearance as well. We still routinely hone rods oval. Wider at the parting line than top to bottom. Why, because the rods distort under dynamic conditions and the parting line pulls in and wipes the bearing. When the bearing parting line touches the journal, BOOM out the side of the block it goes. We have had to oval Titanium rods .0075 at the parting line in order to make them live! Titanium has a very high modulus of elasticity in comparison to steal so the deflection and contortions of the rods big end had to be compensated for.


Why people think that there is something in having tight clearances is something I just don't understand?????
What possible benefit could you derive from shrinking the clearance down that last little .001 close to where the bearing seizes?????

[SWR]

Darin,

Thanks. My reason for asking was that I've run 0.0007" per inch main (0.025mm on a 36mm crank main) and 0.00085" per inch (0.033mm on a 38mm big end) dia on my Suzuki GSX-R Turbo (the one in my avatar) putting out 330hp,it has run several hundred hard miles and the bearings look like new... Like you said,a "0.001 per inch dia" rule is no rule,just a rough approximation,it obviously comes down to diameter,deflection and heat expansion.

Why I did it? You know...sometimes you just have to check where the limits of "too tight" are... ...besides,I've seen bearings fail due to "race wide" clearances.

[seth]

Darin,

thanks for the reply. boss's choice on the amsoil but will share this with him. current clearances running 20-50w is around .002-.0023 rods and .0025-.0027 mains. this is engine sees 30-45min sprint races (scca club racing). as far as the machine work is concerned it's as accurate as i can get with the shops antiquated machines. oil temps normally run around 220-240 degrees. the Bill Daily pump draws about 6" of vaccum from 4500 rpm on. this is a really little engine in comparison to most on this board 2.4L 275hp due to a SIR rule.

thanks again yall for the responses

[hotrod]

We still routinely hone rods oval. Wider at the parting line than top to bottom.

Darin:

Is this because you can't get bearings with enough eccentricity taper at the parting line?

Just wondering how you go about putting an eccentric hone on a rod.
Lots of hand work, or honing it a bit oversize and then grinding the cap and rod a smidge to bring the top to bottom dimension into spec?

Larry

[Stevespeed]

Darin, I think everyone (myself included) is shocked at how loose you are running clearances with light oil. But after thinking about the differences between full load at cold temps vs. full load at say 240* oil temp, I can see where you are coming from. Compare 0 or 5 weight oil at 120 degrees with 10-40 or 20-50 at 240 degrees and they are probably pretty similar. The only thing that doesn't make any sense is the piston pin bore clearance at .002+. I'm sure you have a stout enough pin that it won't deform, does that mean your pistons are deflecting / bending over the pin that much? I've seen the Mahle style pistons fail by cracking through the deck parallel to the pin. I'm assuming not enough internal support? As always you are an amazing wealth of information. Thank you!

[Stevespeed]

Hotrod, you put shim stock between the cap and rod to produce the oval hole.

[Ed Wright]

Hotrod, you put shim stock between the cap and rod to produce the oval hole.

Or put a clamp across the parting line.

[maxracesoftware]

First off, I don't know the EXACT clearances that the NASCAR engine builders use so I will have to check on that. I do know that there average operating temperature is way above what a drag race engine SHOULD see and in this case I can see the clearances tightening up a little but due to component expansion but I don't think its whole lot. I will have to call some of my engine building friends over there and ask. I also see why there oils wont/don't/cant make power in a drag racing engine. We have tested all there high dollar oils that where specially formulated for them. Some costing in the $30.00 a quart range. They all failed miserably in the power department. There oils are formulated for extreme temps above 200+F and have additive packages to withstand stresses for extended periods of time. Anyone who takes a Drag racing engine over 140F at launch needs to have there head examined! (personal opinion)

The main and rod diameters we use are stock BBC and SBC and the Pro Stock engines have a 1.880rod journal a little over .625" wide and a 283 SBC main about .750" wide. Total bearing surface area in a P/S engine is about 20% less than a stock SBC.
If your looking at some preconceived clearance derived from the bearing diameter and surface area your missing the point. You cant scale the clearances up and down from a simple equation based on surface area and bearing speed. Don't take me wrong here, you must take into account the bearings surface speed and area but they are not the major factor in determining clearance. Factors yes, primary factor, no. You need to consider Internal component deflection and distortion when determining bearing clearance as well. We still routinely hone rods oval. Wider at the parting line than top to bottom. Why, because the rods distort under dynamic conditions and the parting line pulls in and wipes the bearing. When the bearing parting line touches the journal, BOOM out the side of the block it goes. We have had to oval Titanium rods .0075 at the parting line in order to make them live! Titanium has a very high modulus of elasticity in comparison to steal so the deflection and contortions of the rods big end had to be compensated for.


Why people think that there is something in having tight clearances is something I just don't understand?????
What possible benefit could you derive from shrinking the clearance down that last little .001 close to where the bearing seizes?????

Darin, all i can say is "I'm glad you Posted this first"

like your results , for the last 20+ years i've run nothing but
.0035" to .004" rod and main bearing clearances
on every Engine i've built, even my old Chevy Suburban Dragster Trailer Tow vehicle's SBC 406 cid has .0035"
never had 1 rod/main bearing failure yet in 20 years, not one !
Bearings look new -to- almost brand new after full season or more,
and most of time i never replace the main bearings, just new Rod Bearings instead on rebuilds.

all the Engine Builders i deal with run .003 to .004" Rod/Main clearances,
and most just tell Customers they have .002" to .0025"

(1) Get a good, professional machinist to line hone the mains and hone the rods properly.
(2) Make sure you have proper oiling. If your pressure fluctuates during the run,, you have problems.
(3) .003 rods and .0035 mains for clearance
(4) Use a good synthetic 05-30w oil like Mobil-1 or Castrol syntec
(5) In my personal opinion you need to stop using any oil from Amsoil. That is not a racing oil even if they say it is.

like you on the Amsoil,
i've never seen any HP/Torque gains.
Amsoil might be awesome "protecting" engine parts,
but as far as any gains in HP/TQ over other
similar weight oils, i've never seen any gains on my Dyno yet.

Mobil 1 and Castrol Syntec are very good oils as far as HP/TQ gains,
both are within 1 or so HP of each other on various engine Dyno testing i've done.

Royal Purple #9 is usually around 5 to as much as 12+ HP
more than Mobil 1 or Castrol Syntec
its been awhile since i last tested these Oils, formulations may change ??,
results may vary ?

[Joe Mendelis]

First off, I don't know the EXACT clearances that the NASCAR engine builders use so I will have to check on that.

Why people think that there is something in having tight clearances is something I just don't understand?????
What possible benefit could you derive from shrinking the clearance down that last little .001 close to where the bearing seizes?????

I know Cup guys are trying to tighten things up more and more. Running .0015 on rods on plate engines and .0018 on open stuff. Certain people are going from $3,000 Bryant's to $9,000 MCT's because of how straight and round everything is (tighter bearing clearance). I guess over the course of a 500 mile race the extra few hp is worth it.