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  #16 (permalink)  
Old 04-29-2014, 10:58 PM
How fast is fast enough?
 
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Quote:
Originally Posted by ericnova72 View Post
An awful lot of engines have been run up over 7000-7500+ rpm over the years with nothing more than the stock 5/8" pick-up...and no failures.

I definitely don't see the need for 3/4" if this isn't a full-out solid roller cam race type engine.
Well gm saw a need for it in stock engines... I wouldn't aim to make something worse than stock.

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Old 04-29-2014, 11:42 PM
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Well gm saw a need for it in stock engines... I wouldn't aim to make something worse than stock.
Reason being, why did GM go to 3/4" pick-ups, after 40-45 years with 5/8"??

Story I heard was only because of oil coolers and remote filters adding to restriction...but I don't know if that is true...made sense to me when I thought about it. 3/4" pick-ups and those oil system coolers/remote filters with less than optimal lines all showed up around the same time in production vehicles.
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Old 04-30-2014, 06:59 AM
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Quote:
Originally Posted by ericnova72 View Post
Reason being, why did GM go to 3/4" pick-ups, after 40-45 years with 5/8"??

Story I heard was only because of oil coolers and remote filters adding to restriction...but I don't know if that is true...made sense to me when I thought about it. 3/4" pick-ups and those oil system coolers/remote filters with less than optimal lines all showed up around the same time in production vehicles.
except the oil coolers aren't on the suction side, so it really doesn't seem related at all.

the larger diameter pickup tubes reduce cavitation and aeration. For a street car a very cheap upgrade is to run a HV pump with a 3/4" pickup, check the tolerances and port the pump housing, while you're building the engine also take the time to improve the oil return.

For an endurance type of race engine I'd switch to a high pressure pump, prep the pump the same, but also drill out the oil passages in the block, still with the 3/4" pick up but add a windage tray and a higher volume pan.
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Old 04-30-2014, 07:21 AM
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Originally Posted by ap72 View Post
except the oil coolers aren't on the suction side, so it really doesn't seem related at all.

Actually it relates to it entirely. While true that it's on the pressure side not on the suction side. You're adding additional demand downstream more so than just bearing clearance. So naturally the total volume being pumped GPH needs to go up otherwise it won't build any pressure.
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  #20 (permalink)  
Old 04-30-2014, 08:08 AM
How fast is fast enough?
 
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Actually it relates to it entirely. While true that it's on the pressure side not on the suction side. You're adding additional demand downstream more so than just bearing clearance. So naturally the total volume being pumped GPH needs to go up otherwise it won't build any pressure.
you're not building any additional demand since your pressure relief valve is still ahead of it. The only difference is that your pressure relief valve will open at a slightly lower flow- actually going against your line of reasoning.
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Old 04-30-2014, 08:31 AM
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So if you have a static running system building 60psi with all the clearances and cavities full of oil. You then open add an additional demand. For arguments sake a 3/8 hole downstream at the end of the system. What happens to the oil pressure?

It drops until the volume increases to a point that it can begin building pressure again. Without adequate volume the pressure won't build enough to allow the bypass to open.
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Old 04-30-2014, 08:45 AM
How fast is fast enough?
 
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So if you have a static running system building 60psi with all the clearances and cavities full of oil. You then open add an additional demand. For arguments sake a 3/8 hole downstream at the end of the system. What happens to the oil pressure?

It drops until the volume increases to a point that it can begin building pressure again. Without adequate volume the pressure won't build enough to allow the bypass to open.
that's correct.

however an oil cooler or remote filter RESTRICTS the system and adds to the dynamic loss- it doesn't reduce it.
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Old 04-30-2014, 10:20 AM
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Depends on the design of the system.

Closed loop vs open loop
Length of lines
Diameter of lines
Number of elbows/fittings
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Old 04-30-2014, 12:25 PM
How fast is fast enough?
 
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Quote:
Originally Posted by engineczar View Post
Closed loop vs open loop
Length of lines
Diameter of lines
Number of elbows/fittings
The magnitude will vary with these parameters but the type of effect will not- basically for this discussion these parameters are meaningless and can remain unitless so as to not muddy the waters. No matter what, an inline oil cooler placed after the pressure regulator is going to reduce flow- that's the key element to notice.
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Old 04-30-2014, 02:19 PM
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So fill us in as to why GM went to 3/4 as you seem to know.
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Old 04-30-2014, 02:22 PM
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It reduces cavitation and aeration.
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Old 04-30-2014, 02:42 PM
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All my years of running SBC's of 3.48" and 3.75" strokes up to and over 7500 rpm...and I've only ever used 5/8" pick-up M55S or M55HV pumps...and I've never had an oiling issue.

I've broke or burnt pistons, burnt up rocker balls with too close to max spring pressures, pulled rods in half part way up the beam...but I've never lost a bearing.

I just guess I must be the luckiest SOB alive, AP.

I deburr and port the pump and rear main cap, but that's it....sometimes windage tray and rear cap baffle, depending on what the pan already has for features and depth/capacity.

GM did most of the work when they designed a good oiling system for the SBC.

The OP certainly isn't pushing the performance envelope so hard that he needs to worry about pick-up diameter, as far as I'm concerned. If what he has built will have a problem with 5/8", 3/4" wouldn't make a bit of difference.
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Old 04-30-2014, 02:53 PM
How fast is fast enough?
 
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Quote:
Originally Posted by ericnova72 View Post
All my years of running SBC's of 3.48" and 3.75" strokes up to and over 7500 rpm...and I've only ever used 5/8" pick-up M55S or M55HV pumps...and I've never had an oiling issue.

I've broke or burnt pistons, burnt up rocker balls with too close to max spring pressures, pulled rods in half part way up the beam...but I've never lost a bearing.

I just guess I must be the luckiest SOB alive, AP.

I deburr and port the pump and rear main cap, but that's it....sometimes windage tray and rear cap baffle, depending on what the pan already has for features and depth/capacity.

GM did most of the work when they designed a good oiling system for the SBC.

The OP certainly isn't pushing the performance envelope so hard that he needs to worry about pick-up diameter, as far as I'm concerned. If what he has built will have a problem with 5/8", 3/4" wouldn't make a bit of difference.

And reasoning like this would have kept us riding around in model T's.

Why run a part that is inferior to something GM started installing in the 90's? There's nothing to be afraid of when it comes to a better oiling system.

That being said- porting the pump will do more good than running a larger diameter pickup- but that takes time and tools, something not everyone has access to.
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Old 04-30-2014, 03:09 PM
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I know I have no race motor but just want to get the best I can with money involved of couse . With all that's been said, I agree could use 5/8" pickup I think and be fine, just figured 3/4 might be better but now trying to get pump and all to work. I still don't know if I should go hv or not and that depends on able to get one cheaper then select series if possible. Still don't know if the m155 is or had the thin casting issue as others did? Now with that said I have cleaned up main cap inlet but not pump yet until I decide on one. With all the talk about braking cover bolts or them coming lose how do u install pickups properly when the mount to cover with the bolts. Plus how do u check pump clearances. Sorry for long post
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Old 04-30-2014, 03:13 PM
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If casting issues are an issue with melling still, maybe I should get a milodon like a 18740($55) vs $100 select?
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