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Old 12-19-2010, 04:25 PM
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Cross drilled mains???

Ok the crank in question is a cast steel scat crank. The mains are cross qdrilled. Dont know about the rod journals (never heard of cross drilled rod journals, so guessing not). With the bearing clearances all around 0.0025 would a high volume pump be in order? Also if some work was done to the oil returns, (ie. enlarging and smoothing) would a 5 quart oil pan be sufficient with the hv oil pump? This is a truck motor, That won't see more than 5000-5500 rpm. Thanks again guys!

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Old 12-19-2010, 05:18 PM
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Cross drilling is old school and does little on a street motor. .0025 clearance won't require a high volume pump. In most cases. What engine is this. ???
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Old 12-19-2010, 05:51 PM
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It will be a chevy 383 with vortec fuel injection. The crank came cross drilled. If I use a hv pump would a 5 quart pan be adequate with the return modifications described? I only ask because that is what I have on hand.
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Old 12-19-2010, 07:14 PM
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You don't need an HV pump. If you want more pressure, you can use a higher pressure spring or a z-28 style pump. Your 5 qt pan will be fine.

As BOB says, the cross-drilling is of no real advantage, with some methods of cross-drilling being better than others. Think of it this way. Cross-drilling was developed to provide more oil to the rods of slow-running, highly loaded industrial-type engines. If your engine fits that description.............

Don's sweat it either way. I'd be more worried about how that Eagle crank mics out................

tom
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Old 12-19-2010, 07:38 PM
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I don`t recommend the use of a HV pump, you`d be surprised how much power they required to drive.
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Old 12-19-2010, 10:38 PM
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Do you actually have this crank in hand to see the cross drilling?? I ask because Summit lists this crank as cross drilled in their online catalog, but it is a misprint, Scat DOES NOT cross drill ANY of their cranks and does not recommend cross drilling as it will do more harm than good in a high rpm engine.

If it is cross drilled and you have it in hand to verify this, either someone has had it cross drilled(who isn't up on current practice and modern info) or it isn't a real Scat crank.
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Old 12-20-2010, 08:40 AM
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Well the engine is going into my 3/4 ton truck. It does see a lot of towing with my gooseneck and pulling tractor, and is my main plow truck. It is a scat crank, I will check it out this afternoon and report back weather it is cross drilled or not. Maybe I can sell the HV pump, and get a regular pump. Does anyone have a part number for the high pressure spring handy? What kind of pressure can I expect? Thanks for all your help and suggestions, sure do appreciate it!
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Old 12-20-2010, 08:55 AM
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Good article here in CHP "July 2010" issue about Cranks, has a section on Cross drilling.
http://www.chevyhiperformance.com/te...fts/index.html
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Old 12-20-2010, 09:23 AM
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Sorry for my mis-interpretation.

Cast steel Scat cranks are not cross-drilled. You still have to check out the sizing, although Scat cranks are generally better in that department.

tom
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Old 12-20-2010, 09:38 AM
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cross drill cranks

Quote:
Originally Posted by SSedan64
Good article here in CHP "July 2010" issue about Cranks, has a section on Cross drilling.
http://www.chevyhiperformance.com/te...fts/index.html
very interesting articles,when i worked for cat dealer we rebuilt many 3208 diesels,used by ford and other lite duty applications.some used nitrited cranks,a very high #broke, those that survived could not be ground. the heat treated ones could be ground to a max of .050 under.the bearing failures where a issue on early 1160s ,resolved when3208s cam out,main difference being 40% increase in oil pump volume. my point is more volume is good,the relief valvdumps excess oil so power loss would be minuscule,diesel engines have far more stress than gas on bottom end so my exp. may be irrelevant to the post,but was surprised to read that nitrited cranks being recommended. cliff
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Old 12-20-2010, 11:46 AM
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Quote:
Originally Posted by CJ_1080
Well the engine is going into my 3/4 ton truck. It does see a lot of towing with my gooseneck and pulling tractor, and is my main plow truck. It is a scat crank, I will check it out this afternoon and report back weather it is cross drilled or not. Maybe I can sell the HV pump, and get a regular pump. Does anyone have a part number for the high pressure spring handy? What kind of pressure can I expect? Thanks for all your help and suggestions, sure do appreciate it!
I would say that this is the perfect application for a cross drilled crank and a high volume pump. This is a case of where the loading through the rod into the crank pin is high but the rotation speed is low. This is a situation where the load will want to blow the oil wedge out of the clearance especially when the RPMs aren?t so high that a really stout wedge is forming. This means that the clearance will need more oil feed to prevent metal to metal contact.

Cross drilling is a method to keep an oil hole on the main journal always open to the feed groove of the upper main bearing. This provides full revolution oiling to the rod journal and bearing. Where a conventional single point oil hole in the main journal is only open for ? the rotation of the crank as that hole passes over the slot in the upper main bearing. This was a replacement solution for using fully grooved mains; either journal or bearing, to feed the rods full time lubrication which had the problem of not being able to sustain the oil wedge in the main bearings due to the reduced load carrying surface area of the bearing. Damned if you do; damned if you don?t kind of thing. Cross drilling appeared to be a solution to full time oiling the pin while returning back to an un-grooved lower main.

The issue created with cross drilling is one of high sustained RPM, at revs getting over 6000 and staying there centrifugal force tends to pick up the oil in the crank passage and bleed it out the clearance faster than the oil pump can replace that oil. This drives to a high volume pump with takes more power to spin. Attempts have been tried to put a jet in the cross passage to reduce its size and thus the oil looses, this works. Other people changed the location of the feed holes to get control and others still just do away with the cross drilling. All of these are compromise solutions that sole one problem or another while creating new ones.

This is all a "game" to find what works that provides maximum bearing and journal life under race conditions using the least amount of power to supply just enough oil for the situation. One needs to keep in mind that what works in a racing engine does not translate to a street engine or one that is used in a more industrial type situation where the engine is working at the top of its power output at a lower RPM. A full throttle low RPM situation exposes all the components to long duration loads with a low frequency, this is startling hard on these parts for different reasons than are seen in a high power, high RPM situation.

Your situation of pushing snow cries for a cross drilled crank, a high volume pump and in reference to your earlier blog, better rods than what GM puts in the L31 and better pistons especially if your building from an 880 Vortec block which reduces the cylinder wall length which reduces support to the piston skirt as it goes around BDC.

Bogie
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Old 12-20-2010, 12:08 PM
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You guys are awesome! I am learning every day! Ok so I am running JE SRP forged pistons so they should be plenty strong, right? Is cross drilling the mains something that can be done by any fairly competant Joe? Or is it one of those send it to a shop jobs? I know you have to chamfer the oil holes after they are drilled! I have tri-metal bearings and a half groove main set. And back to my first question, would the stock 5 quart pan be sufficient?
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Old 12-20-2010, 02:00 PM
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Low rpm with a high volume pump is an engraved invitation to excessive wear at the cam gear to distributor gear interface as well as at the cam gear to block interface.

High-volume pumps (in the SBC) are designed for high rpms with maximum clearances.

Long dissertations rationalizing the use of cross-drilled mains in the SBC don't change facts.

tom
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Old 12-20-2010, 02:05 PM
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Quote:
Originally Posted by CJ_1080
You guys are awesome! I am learning every day! Ok so I am running JE SRP forged pistons so they should be plenty strong, right? Is cross drilling the mains something that can be done by any fairly competant Joe? Or is it one of those send it to a shop jobs? I know you have to chamfer the oil holes after they are drilled! I have tri-metal bearings and a half groove main set. And back to my first question, would the stock 5 quart pan be sufficient?
Don't bother cross-drilling your crank. The main oiling holes are not 180 degrees apart, so the drilled passage will miss one of the holes. Strictly a cobble job for no reason. Your SRP pistons will be fine. Don't run them too loose, they seem to end up collapsing when run at the max piston-to-wall clearance.

Your stock pan will be sufficient with a stock pump. Using an HV pump may cause some pan interference.

Use a stock pump and sell your HV pump to somebody that is uninformed.

tom
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Old 12-20-2010, 03:34 PM
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Quote:
Originally Posted by CJ_1080
You guys are awesome! I am learning every day! Ok so I am running JE SRP forged pistons so they should be plenty strong, right? Is cross drilling the mains something that can be done by any fairly competant Joe? Or is it one of those send it to a shop jobs? I know you have to chamfer the oil holes after they are drilled! I have tri-metal bearings and a half groove main set. And back to my first question, would the stock 5 quart pan be sufficient?
5 quarts is probably adequate but again the high power extraction you're proposing is going to get the oil hot, therefore, a cooler is a good idea. Living were you do the cooler should have a thermostatic bypass to route the oil around the cooler when it isn't hot enough to require some temperature removal.

I rather think that paying attention to where the oil feed holes in the block line up to the upper main bearing insert will be more useful than chamfering oil holes in the crank or cross-drilling them if they aren't.

If you go the high volume oil pump route, I much prefer the big block pump with its 12 teeth gearing over the small block configuration of 7 teeth. This is a smoother flow into the galleys and is easier on the gear teeth of the distributor and camshaft.

Bogie
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