Crank hard to turn with just 3 pistons installed

[arrowhead]

My FSM states .004" - .0098" and limit is .0154". In the manual it shows using feeler gauges to check this spec of connecting rod big end to crankshaft. They call it connecting rod big end thrust clearance. This was out of the 90-91' FSM for the 2.0L DOHC, I assume its the same for 93'. My 93-96' FSM's are incomplete

I believe on my Eagle rods, I set them to .007". Not really a reason why I set it to that spec though. Hopefully JacksonAuto can give a more educated recommendation for the ideal clearance

Could you expand on "I set them to .007", since these clearances are not set to but machine to.

One thing that has been left out is depending on wear also on the trust sides of the journals this clearance will vary, or how the crank was cut and how much radius was given to the journal, even if this would not change the side clearance much, stock rebuilds will be fine with factory specs, for anything else especially on these motors that are not going to be used as 200 hp motors those clearances have to be altered, by how much, it varies.
As stated before, experience and sometimes trial and error, the machinists that said, too much oil would be thrown around he is not very clear on max or min specs or he is trying to cover himself.
Usually 3 to 5 thou. extra will bring all the rods to acceptable clearance.

Please do not attempt to do this at home with your bench grinder and a ruler.
Also the extreme is bad as too much clearance will reduced your oil pressure,

 

[JacksonAuto]

What does "too tight" mean on an engine meant to have higher power? I wanted to ask because I could not find much info on this until now, or it was conflicting info across other forums. My machinist recommended not to be too loose otherwise it may turn into an "oil burner" by slinging too much oil on the cylinder walls, so we went with the middle of the factory specs, .007". This engine will make decent power by next summer, upwards of 400, so would I need to open up the gaps before that?

So even though rod bearing clearance is much tighter than thrust side clearance, I will still run into elevated oil temps? Is that due to the resistance of exiting oil fast enough?

Oil control and windage are a completely different conversation. I will try to stay on topic and describe why side clearance is so important and also why the clearances need to be adjusted on a modified engine.

In the bottom end, the rods are the last thing to get oil. It escapes the rod bearing by flowing out between the sides of the rod and the journal. If the side clearance is too tight the oil will not flow out properly and will back up. This will cause it to absorb a tremendous amount of heat and inhibit its ability to properly lubricate the bearings. The goal of increasing the side clearance is to allow the oil to escape more rapidly and make room for fresh, cool oil. A side effect of increasing the HP output of any engine is heat. We want to alter the clearances internally to deal with this heat. Also keep in mind that the increased temperatures will cause all of the components to expand more than normal. If you were to set the engine up to factory specs, this extra expansion will close up those clearances and cause a failure. For example when I wash a crank it comes out of the machine at around 90*f. If I measure a journal at that time and then again after it's cooled to room temperature the two reading will vary by up to .001". Combine that with the rod that has also expanded and your clearance is nearly cut in half. Now imagine how tight it will get when it reaches an operating temperature of 200-240*f! Things get tight, quick.

 

[NHerron]

Thanks for the good info everyone. I had a feeling it is just as important

However, I thought actual bearing clearance was the factor in lowering oil pressure, not side clearance. As long as the bearing clearance is in spec, the side clearance could be triple and not effect oil pressure. I'm no machinst obviously but have read to grasp most concepts. Is that not true?

When does too much side clearance loose it's benefits I suppose is the better question

 

[EagleTalonTim]

I contacted my machine shop and they said they could mill down the rods to be within range for less than $100. I will be attempting to load my engine up this weekend and taking it over to have the rods milled. Is there anything else I should have them look at while it is over there?

 

[arrowhead]

Thanks for the good info everyone. I had a feeling it is just as important

However, I thought actual bearing clearance was the factor in lowering oil pressure, not side clearance. As long as the bearing clearance is in spec, the side clearance could be triple and not effect oil pressure. I'm no machinst obviously but have read to grasp most concepts. Is that not true?

When does too much side clearance loose it's benefits I suppose is the better question

NO, excessive side clearance will also affect your oil pressure.

You state too much, too much will never have benefits.

As a guesstimate not more than .018, but again it would also depend on other factors, and the use the engine will see.
A marine engine is a total different animal from a drag or road racing engines.

 

[NHerron]

Do you have any additional information to back this up?

Even though I'm not a machinst, I can take a peek around other forums and I cannot find more than a couple saying it does affect oil pressure. Maybe I'm not seeing something and our application is different here but more than 10 places I can find show otherwise.

The main concern was oil being slung onto the cylinder walls in excessive amounts and the scraper rings cannot handle the task. Then you get oil in the combustion chamber, which is not good.

Just looking for clarification and a little more info other than a "Yes, it will affect". So I'm not arguing for no reason

OP, Do you have ARP's on the mains? That might qualify for a line hone if the measurement is out of specs. Did you check the crank for balance? How about balancing the whole rotating assembly?

 

[EagleTalonTim]

I do have ARP's on the rods. What is line hone? I have not checked the crank for balance nor did i check the whole assembly for balance. I did balance the pistons and rods to ensure the same weight was being moved up and down per stroke (1 & 4, 2 & 3)

 

[NHerron]

Sometimes when installing ARP's on the main crankshaft caps, it can make the main crankshaft bores distort in an oval fashion due to the increased clamp load of ARP's. From what I gather you would measure the consistency of the bore with the caps installed and if out of spec, you would get a line hone done to bring it back true. Line honing is similar to cylinder honing, in that it takes out much less metal than boring would and also leaves a better/smoother finish. The out-of-roundness is not much so line honing can usually take care of it

OEM cranks from what I hear are balanced very well from the factory so it may not be needed. I balanced mine though because I'm running no balance shafts and appreciate a smoother ride. I believe they would balance the crank by itself first then add on components and balance each componet. They ended up taking some weight out of my crank as well as the harmonic balancer and flywheel. It cost me about $120 and from what I hear that's a pretty standard price.

If anything is incorrect please let me know but this is my experience thus far.

Hope that helped, good luck

 

[huafist]

Do you have any additional information to back this up?

Even though I'm not a machinst, I can take a peek around other forums and I cannot find more than a couple saying it does affect oil pressure. Maybe I'm not seeing something and our application is different here but more than 10 places I can find show otherwise.

The main concern was oil being slung onto the cylinder walls in excessive amounts and the scraper rings cannot handle the task. Then you get oil in the combustion chamber, which is not good.

Just looking for clarification and a little more info other than a "Yes, it will affect". So I'm not arguing for no reason

OP, Do you have ARP's on the mains? That might qualify for a line hone if the measurement is out of specs. Did you check the crank for balance? How about balancing the whole rotating assembly?

Look at the oiling system like you would your intake tract ; any restriction will make a difference. Yes, bearing clearance is the primary determining factor on oil pressure at the rod bearings, but it has to get out of the rod bearing area somehow, and if the side clearance is too tight, it can't - thus, it backs up, causing oil pressure in that area to be higher (and as JAM stated, not carrying away the heat in the process.

If all other things are equal and side clearance is adequate, then the bearing clearance will be the determining factor.

And I'd also add that if you're slinging enough oil to cause the oil control rings to not be able to handle it, you've got worse problems than a little side clearance on a rod.