I have a rebuilt engine with low hot oil pressure. I have seen the mod to install a slug in place of the spring in the lifter oil gallery between cyls 1&2. The GC blocks eliminated this valve completely. Anyone know the dimensions? Thanks, Brad p914ltd@yahoo.com

What!? I have rebuilt several GC engines. I have never seen a case without an oil pressure relief valve. Do you have some pics? I have never heard of the slug you talk about either. Can you elaborate please?

..........You don't need to go to that much trouble......USE A CUT PIECE OF COAT HANGER WIRE......if cut just a little too long it will bend nicely as you screw in the plug...holding the relief plunger in the closed position and under tension....I have also used a non factory VERY stiff spring to accomplish the same result....AFTER this fix is performed you will see very high cold oil,starting, pressure.(something around 70 psi at idle)...As I always allow the engine to warm up some before using... the oil pressure drops during this brief warm up. The up -side is that hot Idle oil pressure will be more than 10-20 psi. than before, and operating(rpm/vs) pressure is approximately 20 psi higher.

The GC cases are in fact blocked off.

I wouldn't use some backyard repair that could possibly fail unexpectedly on a 800 mile trip to Moab for the RRC (or something like that).

I would slide the relief valve into the case (not the spring of the plug) and use a vernier caliper to measure from the edge of the case to the top of the relief valve. Then measure the plug height from the top of the spring seat to the sealing flange. Subtract the plug height from the bore depth and you have the length you need.

i'd ask why does a new engine have low pressure, this bandaid is not the way to go. if the oil pressure is too low, and if the relief valve is working right, it wont even come into play, and the bulk of oil will be heading too the cooler. by blocking he relief valve, you will be by passing the cooler.

do you have an idea what your oil temp is? if not find out, you warm running oil pressure probelm may be a temp issue. or you may have a faulty oil pump, or bad bearings.

if your running too hot, your oil pressure will be way too low, you need to figure what is causing this, if it is heat, then you not going to fix it this way.

Id only mness with the relief spring and plunger is I knew they was bad, else look for the probelm elsewhere
get some oil temp data to use, and let us knwo what your pressures are verrse rpm, what are they cold, what are they when warmed up?



what wieght oil you use?


good luck

.............IN my OPINION...that particular oil pressure blow-off valve is a complete disaster....This is a case of over engineering for a non existant problem....this blow-off valve is a P R I M E contributor of Low oil pressure in the type IV engine.(if assembled the factory way.).....I think the engineers had the belief that the factory oil pump , housing and gears, were working just great......If you lived in freezing temperatures, and your oil was really thick and stiff...maybe the system could have some value....I believe, in the very last production, crankcase design this blowoff-valve was eliminated. (I have a crankcase with the blow-off eliminated)....Well , while the suggestion I made may be a "backyard solution."( it,s ok if you use red neck racer solution).....It works just great, its inexpensive, and follows my beloved principals of KISS....keep it simple stupid......(.I revised my previous post for added info. so go back)...

Dave, you're thinking of the wrong oil relief. We're talking about the one under cylinder #1.

Hmm, I guess I assumed the wrong vlave also. My bad!

ok, the other valve, but I'd still question why a new motor has low pressure before modifing the valve (if he has one) cuase that may not be the problem, oil pressure can drastically drop with a small increase in temp.

straight 30 W oil:
example, 2000 rpm 180F, oil is at 40 psi
example, 2000 rpm, 200F, oil is at 30 psi
example, 2000 rpm, 225F, oil is at 20 psi

these are real world numbers from an engine that was running a bit hot.

if we just go ahead and change teh oil valves, without understanding temps or oil wieght then we might be doing the wrong thing.

we need to know the temperatures values


thats my advice,

Could be as simple as a worn out spring on that valve.

Thanks for all the tips! I'll let you know the outcome. Brad