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So am I running to high of psi, if so should I put relief valve back in oil pan, or put a different pump on at this point to drop it
I don't know, have the flu and brain has been foggy.
 

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My 2000 5.3 always ran about 60 psi cold and 45+ hot idle. If it was my truck, I'd leave things alone and just drive it they way it is.
 

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Ok so update time, after reading all the comments made me think about going through my order from summit. And they sent me standard main bearings instead of 10 over so after an hour on the phone with them I got them to send new bearings and m365 pump. Installed and started last night now I’m a lil concerned it may be to high of pressure first start went right to 60 psi and after it warmed up a lil dropped to roughly just under 50psi but taking idle up to around 2-2500 it gets up to like 70psi debating on if I should put relief valve back in to the pan or possibly look at shimming pump relief. Opinions
Hey Dale37time did you ever get a concrete answer to this? What did you end up doing? I have been running the Melling 10355 in my 5.3 LC9 and I put that pump in at rebuild because I was still using VVT. Now I have VVT (and of course AFM/DOD, needed to say) deleted and I like my pressure at cold idle (59psi) but it seems to me that I’m getting internal loss at me bypass relief valve in the pan. Because my pressure does not increase with rpm, but instead at operation temp stays around 41-46 depending if I’m sitting still or driving at cruising speed. It never goes above that 46ish mark. I was thinking of dropping the pan and plugging the bypass this weekend and putting the lower pressure spring in pump (I put the highest pressure spring in at rebuild). But I want to know what you ended up doing with your relief valve.
 

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Hey Dale37time did you ever get a concrete answer to this? What did you end up doing? I have been running the Melling 10355 in my 5.3 LC9 and I put that pump in at rebuild because I was still using VVT. Now I have VVT (and of course AFM/DOD, needed to say) deleted and I like my pressure at cold idle (59psi) but it seems to me that I’m getting internal loss at me bypass relief valve in the pan. Because my pressure does not increase with rpm, but instead at operation temp stays around 41-46 depending if I’m sitting still or driving at cruising speed. It never goes above that 46ish mark. I was thinking of dropping the pan and plugging the bypass this weekend and putting the lower pressure spring in pump (I put the highest pressure spring in at rebuild). But I want to know what you ended up doing with your relief valve.
You are supposed to have the M365 pump, its has thicker gerotor and pumps 1/3 more oil per revolution at lower pressures because of the looser tolerances of aluminum.
 

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You are supposed to have the M365 pump, its has thicker gerotor and pumps 1/3 more oil per revolution at lower pressures because of the looser tolerances of aluminum.
Per Melling and their website I’m supposed to have the 10355 pump. It is a high volume pump with thicker geroters than standard volume. I’m privy to what pump my engine needs. Perhaps that is what the m365 is as well. I don’t know about that P/N personally. Just wanted to know if the OP kept his relief bypass in the pan blocked off with these high volume pumps.
 

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Per Melling and their website I’m supposed to have the 10355 pump. It is a high volume pump with thicker geroters than standard volume. I’m privy to what pump my engine needs. Perhaps that is what the m365 is as well. I don’t know about that P/N personally. Just wanted to know if the OP kept his relief bypass in the pan blocked off with these high volume pumps.
Well, it does appear to have the same size gerotors in the photos and runs at a higher pressure than the M365 which is not necessary on a street motor IMO. It's not stock, the M365 is which is 12710304 last time I checked. The 10355 is a performance upgrade according to Melling's website. That's a good pump! Apparently, I was getting the 10355 confused with the M295 for the iron block motors.
 

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Well, it does appear to have the same size gerotors in the photos and runs at a higher pressure than the M365 which is not necessary on a street motor IMO. It's not stock, the M365 is which is 12710304 last time I checked. The 10355 is a performance upgrade according to Melling's website. That's a good pump! Apparently, I was getting the 10355 confused with the M295 for the iron block motors.
Yeah I looked it up after I posted too lol the 10355 is the performance option with hard cost anodized body and higher spring options. Comes with 8-10# lower than stock spring (yellow), stock pressure spring (orange), and 8-10# higher than stock spring (green). But they’re both standard volume pumps designed for the aluminum Gen 4 AFM/DOD and/or VVT blocks. I just am wondering if anyone is running these on their 5.3’s with the bypass relief valve in the pan blocked off.
 

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Yeah I looked it up after I posted too lol the 10355 is the performance option with hard cost anodized body and higher spring options. Comes with 8-10# lower than stock spring (yellow), stock pressure spring (orange), and 8-10# higher than stock spring (green). But they’re both standard volume pumps designed for the aluminum Gen 4 AFM/DOD and/or VVT blocks. I just am wondering if anyone is running these on their 5.3’s with the bypass relief valve in the pan blocked off.
Just to update in the event it may help someone else who is seeking the answer I was searching for:
I dropped the pan and removed the bypass relief valve and plugged the hole with a m14x1.5 plug in my 5.3 LC9 with VVT and AFM/DOD deleted with stock spec bearing clearances and put the 60# yellow spring in my 10355 Melling oil pump and my oil pressure is outstanding once the oil/engine is up to temp. While still cold I am making the effort not to rev too high as the pressure will raise to 75# pretty quickly at around 3500 rpm, but 10-15 mins once heated, my oil pressure tops at about 60-65# under heavy acceleration and idles right at 41#. Cold idle is good as well at around 57#.
 
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