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Very high oil pressure causing leaks

9K views 58 replies 8 participants last post by  Pupsvette76 
#1 ·
OK guys need some help here, i have an issue with my 70 nova that makes it undriveable due to its smoking, it leaks oil out of the valve covers but not the gasket its coming out of the breather holes. my oil pressure is crazy high it reads 99psi at WOT but the digital gauge only goes to 99psi so it may be higher. At idle its 60-70psi and that with 5w-30. Last time i took it out i drove it hard and had to come back home because it was smoking so much. it has a SBC 355 roller cam with AFR heads professional products EFI and a GT45 turbo on it. I have an oil filter sandwich adapter on it that i have the two port plugs on and a oil restrictor on the feed line for the turbo... just wanted to mention that because they are in the oiling system. Thanks in advance guys
 
#6 ·
yep. if your having to high of pressure with that thin of an oil then your bypass is clogged. and excessive pressure can ruin seals and cause smoking in a heart beat. a restrictor may have prevented that but with super high pressure it may have still caused premature failure. Also, check your cam and distributor gear, they don't like running with that high of pressure.
 
#8 ·
What kind of exhaust system you you have? If the exhaust system is restrictive with excessive back pressure , it can cause oil to blow out the oil breathers on an open PCV system by over-pressurizing the crankcase . A open PCV system was used starting with the 1962 tri-power Pontiacs through all 1967 GM vehicles. Those engines were equipped with PCV but they also had open valve cover breathers. Restrictive exhaust system can cause oil blow by and will cause oil to blow out the breathers, especially on large displaacement engines with single exhaust. . The closed PCV system was introduced in 1968 with no valve cover breathers.

Example:
I put a 455 CI Pontiac engine in a 1963 Catalina that was originally equipped with a single exhaust system. The 455 CI engine was too large for a single exhaust system and it over-pressurized the crankcase and blew oil out of the valve cover breathers and all over the firewall. I installed a dual exhaust system on the car and the problem was solved.
 
#12 ·
IMHO, in spite of all the other "what-ifs" involved ... that overly-high oil pressure reading on the guage (if accurate) surely indicates that the oil pump relief spring is stuck. It's about the only thing that I know of that would cause this.

I'd hook up a manual o/p "master guage" to verify. (Not a fan of digital guages, either)

You'll have to drop the pan and probably just end up replacing the pump.
Replace the pickup tube at the same time as cheap insurance.

Do this NOW, before driving it any further, because if you push out a seal or rupture the oil filter ... a LOT of oil is going to dissapear in a big hurry at 90 PSI! :sweat: :eek:
 
#15 ·
because its only a journal bearing turbo , only ball bearing units have to have a restrictor , the only exception to this is if u have very high oil presure ,example would be my 3.1 camaro i run a 61mm turbo on it but the engine makes 55-60 psi hot and 105 psi at redline 8k rpms , on this setup i use a -4 feed line with a restrictor .

those ebay turbos when u have normal oil presure like a -4 feed and -10 return with no restrictor

a -3 feed line if u get a tiny bit of smoke out of the downpipe with the -4

journal bearing turbos need a good supply of oil to live happily

everyone of those ebay gt45's ive used/installed ive always used a -4 feed and -10 return with no issues its also what everyone on the turbo forums is running with them
 
#19 ·
depends on what spring you're running and to a lesser extent which oil. There's a chart floating around somewhere with all the different springs and their associated max pressure, search google for the sbc melling oil pump spring chart or something of that nature and you'll find it.

While you're there I would port the pump and rear cap, it reduces cavitation and can help things out a bit. Oil flow is so often overlooked and it means a LOT when it comes to durability.
 
#18 ·
SB Chevrolet by-pass pressure relief valve is rated at 21 PSI differential pressure with oil cooler and remote oil filter, p/n 25014612. A SB Chevy by-pass valve rated at 11 PSID is p/n 25014006 and is used in engines w/o oil cooler. Note: It is best to use the 21 PSID valve for all SB Chevy applications. A BB Chevy by-pass valve is p/n 25161284 and is rated at 30 PSID. The BB Chevy by-pass valve is not interchangable with the SB Chevy by-pass valve.

Differential pressure is the difference in PSI between the oil filter inlet pressure from the oil pump, compared to the oil filter outlet pressure to the engine. Example: On a SB Chevy, when the differential pressure reaches 21 PSID, the by-pass opens and prevents the oil pump from having a hydraulic lock that may be caused by a over restrictive oil filter or excessive oil pump pressure. Oil filters used on engine blocks equipped with a by-pass valve are not equipped with a by-pass valve.

A BB Chevy by-pass valve is p/n 25161284 and is rated at 30 PSID. Will not interchange with the SB Chevy by-pass valve..
 
#20 ·
The spring and check ball in the oil pump is a "oil pump pressure regulator " and is not inteneded to be used as a by-pass valve. The oil pressure regulator controls the oil pump outlett pressure. The valve in the block is the "oil filter by-pass valve" which is a by-pass valve for the oil filter. People who block the oil filter by-pass valve risk blowing the oil filter gasket or having a oil pump hydraulic lock if the oil voloume exceeds the flow capacity of the oil filter. If the oil filter by-pass valve is removed, the engine will be running on unfiltered oil. It is best to leave the by-pass valve in place but replace the stock 11 PSID valve with a 21 PSID valve especially when using a HV oil pump with a remote oil filter and oil cooler.
 
#23 ·
if you really do have too much pressure then yes that's the only cause, OR you really don't have too much pressure and you have a faulty gauge. I would also disconnect your "evac kit" first, running that with the turbo system you described just seems like a bad idea all around. It can pressurize the crank case if you really botched the installation, and really can't do any good with the system you described.
 
#24 ·
i will check it with a mechanical gauge to verify but im pretty sure its accurate because i have developed a few little leaks that are not normal wear and tear type leaks and i cant take it anymore the car is begging to be driven but i cant drive it like this without being embarrassed because its a smokey mess everytime i try its even more embarassing cuz my friend know how much money on this engine andfor that it def should not leak.... i have heard so many good things about the evac kit but i was def expecting it to pull some serious vacuum and was surprised when i ran it with my hand over the hole how little it actually porduced... and again i appreciate everyones input
 
#27 ·
I always plug the filter bypass in the filter adapter. The filter has a bypass to prevent deadheading the pump.
The only filter I have ever seen severely restrict flow was when used in conjunction with some kind of Slick 50 crap that caused the media in the filter to almost totally stop the flow which resulted in low oil pressure indicated on the gauge.
If you want a high tech solution

Chevy Billet Oil Filter Bypass Adapter - Speedway Motors, America's Oldest Speed Shop

 
#28 ·
If you run a good filter I cant see a problem with plugging the filter bypass, except that it would cause a greater loss in pressure/flow in the system. with a cheap filter plugging the bypass can lead to a lot of mentioned problems. I like filtered oil, but going with a higher rated bypass would essentially mean the bypass is closed except if the filter becomes really clogged. I did not know there is a higher rated pressure option and for $5 it seems like a way to keep a bypass but still have all your oil filtered under normal conditions (assuming less than 21psi dynamic pressure loss through the filter).

Happen to have a PN for it so I may be able to buy just one through an online outlet?
 
#29 ·
The part numbers for the oil filter by-pass valves are listed in my previous posting. It is a good idea to replace the 11 PSID valve with a 21 PSID by-pass valve in order to raise the oil filter in to out differential pressure. You do not want the oil filter by pass to open at low pressure. Be advised, oil filters designed to fit engines with block by-pass valve in the block do not have a by-pass valve in the filter. If you block the by-pass in the block, you do not have a by-pass valve at all. Dirty oil is better than no oil.

1988-up, GM, 21 PSID valve, GM-25014612
1988-up, GM, 11 PSID valve, GM-25014006

They cost $5 each but they come in a package of 100 valves if you purchase them from a GM dealership. My local Chevrolet dealership will not bust up a package of parts but you can order one valve from most local parts retailer.I got mine from Autozone.
 
#35 ·
Gen 2 (1986-2000) SB Chevrolet engines have a by-pass valve in the block directly above the oil filter mount. The oil filters for those engines do not have a by-pass valve because they do not not need one. Example: WIX 51036, AC Delco UPF-52, PF-52, etc. have no by-pass valve.

The 21 PSID by-pass valve (GM-25014612) was introduced in 1992. It was a service replacment retro-fit for the original 11 PSID by-pass valve (25014006) used in the 1986-1991 engines that came into the dealership with spun rod bearings. Especially those engines equipped with oil coolers. The 21 PSID by-pass valves began to be installed in the 1992-2000 engines at the factory to prevent warranty problems.
 
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