05-17-2018, 11:36 AM | #1 |
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LS3 vs L99 block help and oil pressure issues.
Hello, I've spent some time researching this and still can't come up with an answer.
I hydrolocked my LS3 engine two weeks ago, so I picked up an L99 to swap the blocks as a replacement. I looked up the differences and the only 3 things I found were +3cc valve reliefs on the pistons which lowers compression from 10.7 to 10.4. LS3 crank is part #12597569, which says "LS3" when I look it up, L99 crank is part #12588612, which says LS2 when I look it up. Is there a difference between the two? They seem to have the same specs. Last one I found is the oil pump, LS3 says "Standard Volume (.96 c.i. per rev. @ 33 psi)", L99 says "High Volume (1.25 c.i. per rev. @ 33 psi)". Since the swap, my oil pressure has lowered significantly. I installed a brand new GM LS3 pump on it, should I have stayed with the high volume? Are the bearing clearances different between the two? I'm kind of worried about it. The old pump was a Melling M365, cold oil was almost 60 psi, hot would be at ~37psi. Now cold pressure is at ~40 and hot is at ~22-24psi. |
05-17-2018, 11:53 AM | #2 |
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i think those are pretty normal pressures for an LS3, but maybe someone else with a little more experience will chime in.
i'm going off of info from a few datalogs and looking at the factory oil pressure gauge while driving around
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05-17-2018, 11:59 AM | #3 |
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My new LSA Forged idles with ~24 PSI hot. As long as you have the LS3 valley cover, you should be good. I believe the going measurement is ~10 PSI per 1k rpm.
L99/VVT run a higher pressure pump and you don’t want to use that in you LS3... -Don
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05-17-2018, 02:34 PM | #4 |
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I have swapped everything over from my old block except it has a new cam. I actually thought the loss of pressure was because I didn't change the valley cover o-rings, but I swapped them last night and there's no difference.
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05-17-2018, 10:41 PM | #5 |
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Your pressures seem in the ball park. My cold start is a bit higher, around 50lbs, but my hot idle is around 1.5 bar at the lowest (@ 22-24lbs).
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05-17-2018, 11:41 PM | #6 |
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Not sure what the bars equal but on hot mine will show 1.6 - 1.8, and cold will be at 3.6 idle.
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05-18-2018, 02:17 AM | #7 |
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I run a Melling HV for the past 70k+ miles. warm idle is 22-25psi
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05-20-2018, 10:48 PM | #8 |
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I personally don’t favor the quality of the factory pump. Melling for me is built much better and performs outstanding. There are 3 versions; the 295-optional 10% pressure increase, 296-18% volume increase optional 10% pressure increase, 355- 33% volume increase. If you do not have external oil cooler or higher capacity oil cooling system I would stick with the 295. If you have oil system modifications and do not run at continuous high RPMs the 296 might be the ticket. The 355 was designed more for the L99 if you were to use it you might suck the pan dry at high RPM.
If you are interested in increasing your idle pressure high volume would be the ticket. High pressure is more for the top end. With all that said your pressures are pretty much in tolerance. The guys here have pretty much given sound advice.
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05-21-2018, 11:32 AM | #9 |
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1 bar = 14.7 lbs. The DIC reads in bar, so it's good to know how to convert it.
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06-18-2018, 04:03 PM | #10 |
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So, I've concluded that the "low" idle oil pressure is normal.
I did a few track days with it now and it's running strong, as soon as the revs go over 2,000, the pressure goes to over 50psi and stays good. Now I wish I knew why the old block oil pressure was so high. |
06-18-2018, 04:56 PM | #11 |
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your low oil pressure is fine, that is what my ls3 was before i put in a cam and turned up the idle.
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06-18-2018, 08:51 PM | #12 | |
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Quote:
L99 pump is higher pressure unit due to AFM lifters. Get rid of them and L99 valley cover for LS3 units and you're good to go with either pump really. But I fail to drink the koolaid of people who think more volume/pressure must always be better for every engine and every cam swap. But then again I've run my pan dry. |
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06-18-2018, 08:53 PM | #13 |
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A good article on it.
http://www.hotrod.com/articles/simpl...el-management/ |
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