Kidnova

Hello all. I have a ZZ502/502 crate motor. I installed an oil temp guage this summer and found that oil temps are way too high. I've tried a larger oil cooler. After trying that, along with a bunch of other stuff, nothing seems to help much. So through the process of elimination, along with research and asking lots of questions, I've come to the conclusion that the 11 lb. relief valve in the block needs to be changed.

I've been told that there are two bypass, or relief valves in the oil filter location {on the block}. My question is, do both of those valves get changed, or just one of them. If just one, which gets changed, the center valve, or the one on the side of the pad.

Thanks in advance.

Cignificant

Been a while since I did mine, but here's more info...

Excerpt from Speed Reading written by Wade Hajek of GM Performance Parts

Gen V and Gen VI big-block crate engines come with two oil pressure bypass valves installed in the engine blocks. Both of these valves are rated at 11 psi pressure differential. One valve is for the oil filter and the other is for the production oil cooler. If you install an aftermarket oil cooler or remote oil filter that attaches to the oil filter pad on the engine block, you should be aware that you need to change the oil filter bypass valve in the engine block. The aftermarket oil lines add resistance which will cause the bypass valve to bypass the aftermarket oil cooler and/or oil filter all the time. Obviously, if the cooler and filter are bypassed the oil will be dirty and hot. Your engine could run hotter and could be damaged by dirt in the oil. If you choose to use an aftermarket cooler or remote oil filter that attaches to the pad, you should change the bypass valve to one with a higher differential pressure rating.
A good choice would be GM# 25161284 which is rated at 30 psi. Remove the valve that is closest to the crankshaft and replace it with the new valve. Press the new valve into the engine block and stake it in three places. You should note that the bypass valves don't need to be changed if you use a production oil cooler which uses the production holes in the engine block and you don't use a remote oil filter. Also, if you use an adapter that just angles the filter for clearance you don't need to change the bypass valves.

Kidnova

So don't change the one in the center, just the one that is off to the side?? I ask because I was told that I needed two valves.

US1 Fountain

My Gen V 502 only had the valve in the off center location. None in the center.

Turbojack

Plug the oil cooler ports on the block. Unless you have the special GM adapter that goes in there you will be bypassing your cooler.

Install 30psi bypass on side one. You will not need any in the middle if you use a oil filter adapter to plumb out of.

Kidnova

Thanks for the responses.

The way I read the GM text that Cignificant posted, there's a valve in the side of the oil filter location. And the 2nd valve must be located in one of the two ports that {I believe} are just in front of the oil pad. There are no oil lines comming from those ports. They are plugged.

We took a Merc 7.4 out of the boat and dropped in the ZZ502. All the marine bolt ons were taken off the 7.4 and put on the ZZ, including the remote filter pad. But the 11 lb. bypass valve in the block/oil filter location was not changed. I'm pretty sure that's the problem.

Thanks again for the information.

Bill

Turbojack

If you look at oil filter pad on block you will have hole in middle, an oblong hole where oil comes from the oil pump & another hole (round) close to the side. That is the one that needs to be pluggd or the 30lbs bypass installed in. I think the center one is only needed if you are using the cooler holes on the side of the block

MACDAD260

If you remove the center valve the oil can return directly back to the engine. With the center valve installed the oil has to go through the passages to where the production cooler would be if one was installed. Removing the center valve removes an additional restriction in the system which will improve oil flow to the remote filter and cooler by a slight amount. In this case every little bit helps. I went through all of this myself when I swapped a 7.4 for a 502. I ended up with a 3" x 12" cooler and increased the oil line sizes to 10AN. I would recommend an even larger cooler if you have a ZZ502. More horsepower makes more heat. Good luck.

Kidnova

MACDAD, I think you and I have kicked the oil cooler thing around before. How are your oil temps with the 3 x 12? I tried a 454 mag cooler, no good. I then went to a Hardin Marine 3 x 22 cooler with a tstat. It cools engine oil and power steering. Actually, about 3 x 15 or so is dedicated to the engine oil. It's supposed to be good up to 700 hp. I fugured with my hp at around 500, the Hardin would solve my problem. It's better than the mag cooler, but still not good enough. Process of elimination tells me it's likely the bypass in the block causing the oil temp problem. BTW, I think you mentioned before that the tstat in the oil cooler didn't seem to do much good. After taking a look at mine, I agree. I don't see where it would be of much use. Pretty poor design/fit. Lets lots of oil through open or closed.

Ok, leave the center hole empty, and put the 30 psi valve in the side hole.

I have a pic of what you guys are describing. The pic is on page 10 of Dennis Moore's book; BB Chevy Marine performance. Text under the pic notes the location of the valve.

I'll let you know how things go after valve replacement. Probably a week or two.

Thanks again!

HARRISONMIRAGE

Just remember that the oil enters the filter on the outside and re enters the block up the center so if the filter was pluged it would re enter through the offset port,therefor it is the bypass port.With the added restiction of the remote filter/cooler this bypass valve needs to be a greater pressure.The bypass in the center is to direct oil over to the cooler port on the block,out to the cooler then back into the block above the valve.Since your ports are plugged the valve is in bypass mode(open) all the time so you might as well turf it.With the stock cooler/fiter being on the same circuit I think there is a fair amount of bypass at start up due to cold thick oil.I would like to try running the filter on the block and using the stock cooler line ports on the block.This would eliminate a lot of external plumbing.You could run a selenoid to stop the flow of oil to the cooler to aid warm up.Your filter would not go into bypass as easy because the oil would be hot at the filter and non restricted by the cooler.Once in the cooler circuit if its getting too thick it would just bypass the cooler only.The stock GM system is excelent as it separates the cooler and filter bypass circuits.The only thing that would improove it is larger cooler ports in the block,but if you increased the cooler capacity knowing only a percentage of the oil is going to the cooler it should still work.The stock marine setup realy is a downgrade on the stock setup.Some times you can't outsmart the general.I have a modified zz 502 that is plumbed in the original remote filter cooler fashion with the heavier bypass and I had to inrease my cooler size due to oil temp problems(270 plus).I have an Edie 3"x18" combo cooler and I never hit more than 240 with 30 wt.dino oil.The problem is it takes a long time to warm up the oil,and if I don't run it hard enough I wont hit 212.Even with the stock undersized cooler I was suprised how long it took for the oil to get warm.I am checking the temps at the filter pad so the oil going into the block will be cooler.The setup works OK if you warm it up slowly(get it on plane but don't bag on it).I would be carfull withh that zz motor if your not using dry exhaust as they suffer from bad reversion if precautions are not taken.I can expand on that if you like.