fastlane40

Okay let me start by saying it's driving me nuts.Just pulled a destroyed Gen IV 454 out.Purchased a factory rebuilt Gen V 502 because there are no new Gen VI 502's in the country.I connected oil cooler lines to the provided outlets.There was no threaded adapter to take a spin on filter so i pulled the one out of the remote filter pad from the old Gen IV.The reason i put that bit in is it could be the problem.With 10w- 40 oil at idle oil pressure is 90 psi.When i bump rev's to 1200 it blows the rubber oil filter gasket.Could the threaded adapter from the old remote pad be causing a problem with the bypass valve in the block oil pad?The internal thread length is about 15mm.I just can't think of anything else.I've done exactly the same install in my big boat with 2 new 502 Gen VI's 2 years ago with no problems.The new engines came with oil filters already installed.Is the oil pad bypass just inside the oil return tube?Any help greatly appreciated.Thanks

Linster

The Gen VI has a different oil system than the Gen IV. Here's some things to do. Looking at the oil pan rail on the Gen VI engine you will see the oil filter pad. Just forward on the block there are two 3/8 " plugs used for auto hook ups. Do not use them. Back to the filter area, in the center is a screw in location that will require a adapter to be screwed in. Just to the left will be a bypass valve pressed into the block still within the filter location. Look down into the screwed location. There should be another bypass plug about 1" down in there. Depending on who rebuilt the motor it might not be there. If the bypass valve is down in the hole, pull it out. It is a restrictive device if not used with the 3/8" plugs not to be used. They make two of these bypass valve. One is 11 psi and one is 30psi. You need to get the 30psi. GM Part #25161284 its about $2 so I would replace it if you are not sure. Do not install one down in the center hole 1" below.

Next you need Merc part #811681 screw in adapter, 27-91892 Gasket, 35-818400A1 Adapter, 26-42077 Seal, & 22-806121 Fitting. They will install on the oil filter area of the block. The center hole will be for oil return, the side hole will be for oil out to filter and cooler.

Hope this helps.

fastlane40

Would high oil pressure be the result if there is no bypass valve in the oil return where the spin on adapter fits?I'm trying to work out the problem of the high pressure,something must be missing.

Linster

If that bypass valve is missing next to the adapter the oil will short circut and not go through the filter or cooler. That might raise the pressure a little.

What kind of oil pump is used? A GM Gen VI works very good. All oil pumps have a sping to set the bypass pressure. If someone welded or brazed the pickup with the spring in it it could sieze the spring causing pressure. You need to get the oil pump out and look at the spring.

I do not like the Melling HV that costs about $25. The Melling 10666 as now being sold by Jeggs is good. You need to put the high pressure spring in it.

fastlane40

I just got it out.It's a GM pump.What do i look for in regards to the spring?To get it out do you remove the pin?

Wobble

Just a thought, if you connect oil filter lines backwards and you have oil filter with check valve, this could cause excess pressure.

Mark

fastlane40

Thanks for your help.It is the piston i can't get it out.I took the bottom off my mark IV pump,checked the piston and spring and put that on.Fair bit of rusty fluid in the bottom of the pump.Not real good for a GM factory rebuilt engine,shipped without oil and probably left to sit for a while in Australia awaiting purchase.I've learn't about oil pumps now though.Thanks again for your thoughts.

Wobble

Sounds like you have gotten the high oil pressure problem solved. Remember that the gen 4 oil cooler adapter you have also has a bypass that should be plugged when used on gen 5/6 block. Linster also mentioned the 30lb differential bypass spring that needs to be in the block. Neither one of these items will affect oil pressure much but they will allow too much oil to bypass the filter/cooler causing high oil temps and possible failure.

Mark

fastlane40

I got that.Thanks very much for your help.Wish i was in Texas,be a fantastic change,at least for a while.

Wobble

I spent some time in Perth in 83, wished I could have gotten over to your side. Looked up townsville on the web.. looks awesome. We don't see too much blue water around here, mostly brown of murky, a few lakes excepted. Good luck with your boat.

Mark