Oil by pass valve GenVI
 

After having the motor rebuilt a while back I have had a high oil temp problem that I haven't been able to solve. Larger cooler, larger lines with no sharp turns, syn-blend oil etc! No Better!!
Had initially ruled out the bypass valve after questioning the machine shop that did the short block. Oh no , we didn't change that..
After reading more and more about this on OSO lately I said the heck with it and ordered a 30psi bypass valve.
Decided to try to change it without pulling the motor, success!!
I was able to change the valve in my motor with very little problem.
Discovered that the machine shop had in fact replaced the original 30psi bypass valve with an 11psi one! There is a very obvious difference just by opening it in your hand with a screw driver.
Fortunately I haven't put a lot of hours on the motor and have changed oil often because i knew something wasn't right!!
There also appears to a by-pass valve up in the block in the return side, was that one ther from the factory or did the machine shop install that one as well?? This was a marine motor from the start. Should I leave it or just take it out and leave it open?? My understanding is that the one in the middle (return) is to divert oil to the oil cooler when the tapped holes in the block are utilized. Looking for an opinion from someone that has dealt with this issue successfully!

Re: Oil by pass valve GenVI
 

You're correct Tom. Remove that middle valve. You should not have that in a marine engine. It just restricts oil flow.

Re: Oil by pass valve GenVI
 

Tom,
I'm having a similar problem. Let us know if replacing the bypass with the 30 lb. one helps.

Bill

Re: Oil by pass valve GenVI
 

How do you remove the bypass valve? Does it destroy it? Will the machine shop or NAPA have a 30# avail or is this marine stuff? I'm building a gen6 and just about to put it together,seems the spring is really weak in the bypass,,must be the 11# one you are talking about.

Re: Oil by pass valve GenVI
 

Is the valve in the remote adaptor??

Re: Oil by pass valve GenVI
 

The valve is in the block.The 30 psi unit is available from G.M.

Re: Oil by pass valve GenVI
 

What happens if you plug it off to make all the oil filtered???

Like in the 350 and the 454 gen 4 oil filter adapters I drilled out and plugged to have no bypass.

Re: Oil by pass valve GenVI
 

The valve pops out with a little persuasion from a screw driver!
You will more than likely destroy it doing so!!
You can get the 30lb bypass valve from Jim Pace Parts. Call them and explain what you need, they have them in stock!

Re: Oil by pass valve GenVI
 

You can get them ( 30lb. Bypass Valves) or order them from any Chevy dealer. They are used in the 6.5L Diesel engines. They only cost about 5 bucks.

Re: Oil by pass valve GenVI
 

Thanks, I have removed the one in the center where the filter screws on and will replace the one flush with the block to the side with a 30#.Does this mean oil won't bypass the filter unless the restriction is 30# or ???

Re: Oil by pass valve GenVI
 

yes

Re: Oil by pass valve GenVI
 

I run mine plugged. Works great, no problems. Might be hard to do with the engine in the boat though. My mech. tapped and pipe plugged it at rebuild time. I was afraid it might not flow well through the oil filter when the oil was cold but I have 75 lbs at cold startup.

Re: Oil by pass valve GenVI
 

i have burned 2 motors up this year and i think it is oil related i have a gen 6 block with the center valve out and the other on plugged i would like some help

Re: Oil by pass valve GenVI
 

I feel your pain. I fried the bearings in my 2 worn gen 4's and am building the 2nd gen6. I am starting to think it was mostly due to the Fram ph5 oil filter.Oil was clean and after running 4900 for a minute or 2 max then slowing to 4000rpm I starting losing power and overheating. The first time I seezed it completely. The second time I started losing powr,killed that eng and limped home, pulled the filter and shavings came out. After reading some of the hundreds of post about filters I realise for the first time that I have chosen possibly the WORST filter available. The Walmart brand would have outflowed it 2:1. Also built my other gen6 without knowing about the bypass system being set up for an auto. there is a post close to this one about bypass setup. Sounds like yours is according to that recommendation. My new mtr is doing fine but I'm changing filters and going to try to fish out the center bypass and increase the other one to a 30#.

Re: Oil by pass valve GenVI
 

Hey guess what? That thread is VEEEERY close. It's not my day :(

Re: Oil by pass valve GenVI
 

If you run with the bypass plugged you should moniter pressure before and after the filter to monitor a restictive filter(dirty).With the stock setup you get oil all the time,it just might not be filtered.I would rather have dirty oil than no oil.

Re: Oil by pass valve GenVI
 

I decided to remove the bypass in the center(return) and leave the 11psi bypass on the supply side to filter as is. I talked to the machine shop today and they told of several race motors smoking cranks due to plugged bypasses. Also said they are hearing from the local GM dealer newer BBCs are having problems with low oil presure. I don't know about that last one and my other rebuilt Gen6 has great pressure even at warm idle BUT, I am afraid that in the future I may still want flow if the pressure dips below 30psi so I'm sticking with stock. I would like to know for sure that the bypass I'm removing is only good to divert oil to the cooler holes on the block and won't hurt me in some other way.

Re: Oil by pass valve GenVI
 

The way mine is set up oil goes from the pump to the filter to the thermostat to the cooler then to the block. My oil pressure sender is at the front of the block, as far from the pump as it can be. After 25 hours, oil change time, there is no drop in pressure. I'm not worried about running it this way and with all the horror stories I feel safer.

Re: Oil by pass valve GenVI
 

Just built 2 motors gen 6,I re used the remote filter adapter (spin on)from my stock 502 mpis the adapter has 2 1/2 inch flare lines coming from it and 1 line goes to cooler and the other to the filter bracket on the front head then returning back to the block adapter.Are we talking the same type of bypass?Just blew the motor bottom end sunday>Does any one have a diagram?

Re: Oil by pass valve GenVI
 

Cooltoys,

You can safely remove the center bypass as it does nothing but reroute the return oil through the unused passages of the stock oil cooler system. It is an unwanted restriction in the oil circuit. It will definitely NOT cause any problem. I would advise you to install a 30 psi bypass valve in the filter pad. It will only open if there is a restriction to flow that is greater than 30 lbs. versus an 11 lb restriction. It will help force more oil through the oil cooler since at higher RPMs the restriction is greater due to the increased flow.

Re: Oil by pass valve GenVI
 

Why would need a 30 psi bypass? If the oil pressure is above 30 psi it will bypassing right??

Would you not want all the oil going thru the oil filter?

If there is restriction I would think it would be the oil filter [dirty] which should NEVER happen unless there is a failure fixing to happen. If this is happing ,you want know it because its bypassing with all the metal going thru it.

Re: Oil by pass valve GenVI
 

Even the 30 lb valve, if you push on it it takes way less than 30 lbs to open it. Those valves work off of differential pressure. The valve has oil filter inlet pressure on one side and oil filter outlet pressure on the other.
Regardless.
I block them off by threading the hole for a 1/2 NPT plug. Never had any problems.

Re: Oil by pass valve GenVI
 

When the difference in pressure is greater then 30 psi is when the bypass opens. As long as filter is flowing oil you would be hard pressed to have a difference of 30 psi between the filter in & out.

The main reason for the 30 psi bypass is when you are using an oil cooler and/or remote filter. The oil cooler, fittings & hose will have a restriction & it is not hard to get a restriction of 11 psi, thus the reason for the 30 psi bypass. If the 30 psi opens you have some serious problems with your filter or oil cooler but at least your motor will be getting oil, just not clean and cool

Re: Oil by pass valve GenVI
 

I did not add. I use a good quality Wix oil filter with a bypass built in when blocking off the engine mounted bypass. .

Re: Oil by pass valve GenVI
 

Cooltoys- Listen to Macdad & Turbojack....use the 30psi valve or plug! I found this out the hard way.

Re: Oil by pass valve GenVI
 

Dang!! I knew if I kept at this thread I'd get some good responses. So the downside of using the 11# bypass is poor filtration but really good flow no matter what? Not being sarcastic, just fried 2 GenIV motors and trying to get to the bottom of this. If I keep my oil changed reg. it seems better to have terrible filtration?? What do I know. OK, both would be better but I need to KNOW I'm getting both. You guys ROCK, That's why I'm here. Thanks

Re: Oil by pass valve GenVI
 

cooltoys, I've been fighting this myself this season. The downside of the 11 lb valve is not only possible poor filtration. The 11 pounder could also limit oil flow to the cooler, which may result in higher oil temps {got oil temp gauges??}. I've posted on this same subject on OSO and on S/W. And the consensus is, change the side bypass valve to the 30 lb, and remove the center one.

Re: Oil by pass valve GenVI
 

I see. Gonna look at the routing tommorow and consider what you're saying. Thanks.

Re: Oil by pass valve GenVI
 

I have a temp gauge for oil,, but it never moved much until after I fried my bearings.

Re: Oil by pass valve GenVI
 

I removed the center valve which had been installed when the motor was rebuilt and replaced the one in the pad with the 30psi valve. I'm going to install a oil temp gage to determine if I need to get a larger cooler.
It did seem to show a slight drop in operating temp and a slight increase in oil pressure after a hard run, but I still need to install a oil temp gage to be sure of whereI'm at!

Re: Oil by pass valve GenVI
 

Not argueing here but some of your oil will still be getting filtered even if the bypass is open unless your filter is plugged. It may just make a couple of loops without hitting the filter??

Re: Oil by pass valve GenVI
 

Yup.

Not to argue here either cooltoys, but the more oil running through the filter {and cooler} the better.

Also, replacing with a 30 lb. valve may not even help, if your oil is already flowing well. It only helps if the pressure being put to the filter, cooler and oil lines is greater than the psi of the bypass valve {11 lb. or 30 lb.}. I'm hoping that is my problem. And hoping that changing to the 30 lb valve will force more oil into the filter/cooler system, therefore providing better oil cooling. Better filtering would be icing on the cake. Not too worried about filtration as I change the oil and filter at less than 20 hr. intervals.

Re: Oil by pass valve GenVI
 

Still pretty sure I blew both my Gen IV's by running Fram ph5 filters. Test show they flow 4 gal/min compared to the 8 or 10 on a merc filter. My new Gen 6's will have the purolater prem at 17gal/min. Not sure about these units sinse they were quoated as oz./min?? can be right. When I put the 1st gen 6 in my other gen 4 was running and I didn't know about the bypass in the center. Got lucky. I didn't plumb my remote by the new adapter directions, just followed the flow from the old setup,,BECAUSE IT WAS BACKWARDS!!!Unbelievable!
Anyway my oil never got hot and although I'm trying to figure a way to get to it I don't think it's worth pulling the motor. I have removed the one from the motor I'm putting in now. Hopefully we'll both have good luck.

Re: Oil by pass valve GenVI
 

Billy,

Where are the pictures from Monday?? BTW, I meant to mention to you to go to www.abirdseyeview.net to check out the pictures from the RI Poker Run. There are some nice shots of your boat. I was very pleased with a few of the shots of both my Scarab and the Pantera!

The motor I've been talking about here is the the one in my Scarab.

The race motor which is a GenVI also, has the bypass plugged. We just installed an oil temp gage in that and found 230-240 cruising 270 running hard! We have the stock HP500 setup, so I think we will go to a larger cooler and better plumbing this winter.

Re: Oil by pass valve GenVI
 

Cool!! When you blow them up they look pretty good.
BTW, Are you planning on being on the Cape next weekend??
Call me (508)237-3326

Re: Oil by pass valve GenVI
 

Ok, 11 lb valve out, 30 lb valve in. Ran the bajeebers out of her at WOT for around 15 minutes or so. Did that 3 times over the couse of the day. Oil temp down from just over 270 to just over 260. Only 10* drop. But better than what it was. Engine guy says he did not check to see if there was a valve in the center {return....pizz me off}. So I'll see if I can get that out myself, if one is in there.

Re: Oil by pass valve GenVI
 

I Have Purchased 2 502 Service Based Mag Engines From Acompany Called Marine Engines. They Also Sold Me Par #mpo520-000oil Adapter .the Contact There Is Jk Very Knowlegable Person.ph.800-786-7639

Re: Oil by pass valve GenVI
 

While my port mtr was out I took a screwdriver that I bent into a flat hook on the end and sized (using the 11# bypass I took out) and clamped it at a 90deg with vise grips , shoved that baby up the center hole, cocked it at an angle to grab the inside with the hook and whacked the vice grips with a hammer. It came out on the sec blow :).
I was very happy not to have to pull that motor,,AGAIN.

Re: Oil by pass valve GenVI
 

Talking about the starboard.

Re: Oil by pass valve GenVI
 

Where is the middle bypass located? I am familiar with the bypass in the filter pad, but not the middle one?