FI and bearing clearances, oil pumps

[Catmaigne]

Trying to figure out what sort of clearances I want to run on my motor. I've heard everything from 15/20 rods/mains to 25/30, both with looser clearance on the rearmost main. I was thinking around .0021-22/.0025-26 with the rear @ .0029-30 but I'm not sure if this is loose enough for what I'm doing. I'm also not sure if these clearances would be any good with the oil pump I already have (Melling 10554, std vol, high pressure). Last thing I want is low oil pressure in a car that will see more street duty than anything. Not sure if I want to swap this for a 10552 (+10% volume, high pressure) pump to keep the pressure up a bit down low. I will be retaining the stock oil pan but there's a 100% chance I'll be running an accusump with the 10552 HV pump just in case. This would make me less weary about adding an oil cooler too (something I'd want anyway).

Brief summary of the build:
383, supercharged, 224/236 or slightly bigger cam (w/order swap), shooting for a little over ~600whp.
That cam in a 383 with the LE ported TFS 195s should give me a peak under 6k. 6500 RPM is probably the max the motor will see.

Right now Erson can grind me a 4/7 swap cam for fairly cheap but if the billet LSM doesn't cost an arm and a leg I'll go with the full monty aka 4/7 & 2/3 swap. I saw a vendor that claimed they could get me one for not much more... Both of the order swaps should reduce crank deflection (LSM moreso than Erson) which means the main clearance can be a little tighter (theoretically). Not sure how wide everything has to be to account for things like block flex, blower drag on the snout, etc.

Other factors to consider --
Crank is cross-drilled (factory "V" style, not "T") which probably means more flow out of the rods at low RPM
Bearings will be 1/2 grooved with the chamfer (the fillet radius is big on the crank)

So... guys making big power with boost/juice and aren't spinning to the moon...
What are your clearances like?
What oil pump are you running?
What oil viscosity are you running?
What's your oil pressure look like @ hot idle and cruising?

[shownomercy]

.0025-.003 clearance
Melling high volume
15w40 rottella
pegs gauge at WOT, and is ~40psi hot idle.

If you have time, start perusing the Karl Ellwein builds, he details a lot of bearing clearances and setups.

[Catmaigne]

Is your pump +25% or +10% volume? Seems like most guys with the HV pumps are running the super-overkill 25% increase pumps which have the relief open nearly all the time. I'm guessing cavitation from maxing it out constantly is what causes pressure loss in a stock pan.

I've been looking through Ellwein's stuff but it varies. Generally seeing rods around 25 and the mains a few ten thou more. I did stumble upon a build of his using a stock pan and 10552 +10% vol pump so I'm starting to think this is the way to go if I can't find a bigger pan. Probably would be a good idea to increase the rods a hair and do some minor drainback mods.

It just seems like the clearances entailed by a boosted motor are probably too much for a std volume pump, especially one that's pushing extra oil to the rods at lower RPMs because of the cross drilling (in theory). Low psi in a stick car with a very very aggressive clutch will leave no margin for error and it would take much for the pressure to dive completely off idle. Driving with the Spec 3+ is already a handful.

Accusump is definitely a bandaid... I'd still want one for priming but it's more of a remedy than a real fix. A 242T popped up on the classifieds a while ago but it was long gone before I even asked.

[firebird_1995]

My engine was built with . 001 extra clearance bearing for (what I'm assuming is) the high volume pump. Melling hv155 I believe

[shownomercy]

I am not sure what my pump is % wise, I will try and grab a PN off it. I do run the large canton pan and usually overfill it due to the extra volume of turbo plumbing to fill etc. Why the accusump though? Usually they are used if you plan on turning hard enough to uncover the pickup, or sustained high RPM where all your oil is stuck up top.

Not to confuse you, but, a lot of people on the bullet will claim too large bearing clearances are a thing of the past and to embrace a more efficient, more detail oriented motor. I know callies has done a study that agrees.
http://www.superchevy.com/how-to/eng...learance-info/

Granted the study was most likely an NA motor, but, since you have no motor yet, something to think about. My motor will be getting the large clearances again cause a few lost HP can be easily gained back by more boost.

[firebird_1995]

Without reading the article, my take on the extended clearances is to all that extra volume somewhere to go as opposed to causing increased pressure. But that's just a guess

[Catmaigne]

I do like the idea of being able to prime my motor before startup with the accusump, but also I think it will provide a much better safety margin in the event that the pickup becomes uncovered from lack of oil or cavitation occurs. The pressure drop would be more gradual and it's probably possible to rig up some sort of sensor that'll let me know exactly when the accusump starts to drain. That way I can let off before things get catastrophic.

I don't think people are really "sucking the pan dry" with HV pumps... I mean 70psi from a STD volume pump is flowing the same amount of fluid out of the mains/rods/lifters/etc. as a HV pump @ 70psi, the difference is that a HV pump will be turning larger gears and creating a larger pressure gradient in the body of the pump. If you don't have larger clearances for the oil to escape then the 70psi relief opens much sooner and cavitation happens as the RPMs build causing pressure to drop like a lead balloon. What I'm not sure is how much volume is too much or too little for rods < 25 and mains > 25. If I can get away with my 10554 an still have 30+ psi at a hot idle I'd be happy but it seems like STD volume pumps are a small minority in FI builds.

This is all assuming that I keep windage under control but it's going to be extremely hard to prevent oil from climbing the back of the stock pan (if I keep it). Starting to think that after the power adder goes on a larger capacity pan with baffles will become a necessity. But I see Ellwein using the stock pan all the time... what gives?

[Catmaigne]

There's the school of thought that only wants to see .001" for every inch of journal diameter which means .21/.25. But everyone seems to be running the rods looser than that with FI and higher cylinder pressures.

[noice]

I can't recommend high volume or high pressure oil pumps. Especially not when a standard volume pump is more than enough to supply any drag racing LT1. Some guys are even running lower volume pumps in the super stock classes.

As for the 4/7 swap for the money you will spend, there is no advantage. If you want to reduce crank deflection, use a crankshaft with properly designed counterweights, balance it properly, don't spin it to the moon.

If you are super concerned about losing oil pressure, get a good pan. NOT a Canton pan, a Stef's, Milodon, or Moroso will work. Another option is Dry Sump, the pan will cost ~$300, the pump ~$1000, the tank and lines ~$500. Coupled with a ~$1000 vacuum pump and you got something that WILL show you gains in HP. Then you get into trouble with having to run a ATI Balancer and a mandrel/pulley system.

Or the cheapest route is just a electric accusump. When the ignition is on, the solenoid opens and pushes pressurized oil into the engine. accusumps are great for cars that lose oil pressure when they get on the brakes at the end of the drag strip.

[firebird_1995]

That's good info. I recall reading something that a well known builder (for race engines) that said more than 25psi at wot was leaving power on the table due to the frictional losses from the pump pressurizing the hell out of the system. A high volume pump wouldn't be my first choice but it was on the engine when I got it.