3.4c mods?? Want lots of N/A power

[series8217]

I'm not saying the filter is a restriction. It will flow as much oil as the system can shove through it. It will handle, 70, 80, 90psi just fine, but the bypass will open long before that. Think about when this engine was made. Do you really think the oil filters made in 1990 are the same quality as the ones today? Filters today can handle higher pressures. The bypass was put there to protect the filter. If your filter doesn't need protection, you don't need the bypass.

You're missing the point of the bypass. It is not specifically intended to protect the filter (though it does this too); it's designed to ensure that your engine has full oil flow under all conditions. Dirty oil is better than none.
The bypass works by a pressure differential accross the filter. Therefore, if the filter flows enough to prevent a 15psi drop across the bypass, the bypass will never open. This is fine. The engine will operate as you intend it to: no bypass.
If the filter is a restriction, there will be a pressure drop across the filter. The pressure drop across the filter is proportional to the reduction in flow. If the pressure drop reaches ~15 psi, the bypass begins to divert oil around the filter to ensure that the filter does not prevent full oil flow to the engine oiling passages.
Therefore, if you block off the bypass doing so only has an effect if the filter was restricting flow, and therefore you are forcing restriction of flow by the filter by blocking it off. Leave the bypass alone! It only helps.

And consider this. The oil pressure sensor on the oil cooler comes AFTER the filter, not before.

Where did you get that idea? Look again at your oil cooler my friend.
You can also look at the factory service manual oiling diagrams I have attached to this post. The location of the oil pressure sender is clearly pre-filter. I have confirmed this by inspection of my own oil cooler. If anyone has one removed from their vehicle, they could take pics for you as well.
I may have some pics but I may have to look around for a bit.

If blocking the bypass restricts oil flow, like you claim, why do I have much better pressure than I did before I blocked it? My idle oil pressure has gone from 18psi to 33psi. If you think I'm crazy, fine. But how do you explain the results?

Well there you go. Your results directly disprove your claim, since the oil pressure sender is PRE-filter. You blocked the bypass and pre-filter pressure went up. This is direct evidence that the oil filter is restricting flow. I don't think you're crazy; I think you're just misunderstanding how the oiling system works (or misinterpreting your results since the oil pressure sender isn't where you thought it was).

If you still don't understand, I highly recommend checking out some of the following SAE publications:
SAE 2000-01-1988, which measured oil pressure in five different areas on the engine"

http://www.sae.org/technical/papers/2000-01-1988

SAE 2000-01-2921, which uses a computer model of an engine oiling system including modelling of flow restriction across the filter at various temperatures:

http://www.sae.org/technical/papers/2000-01-2921

[Emc209i]

...wow

Pretty cool argument actually. I think Steven has ya though. Nicely handled btw.

[OldSkoolGP]

Well I've just looked at this more carefully. It seems like you are correct. This explains why my lifters tick at high revs. Because of this, I now have a friend who I can no longer trust with my car, but he owes me a rod and a set of bearings. This just goes to show that one shouldn't trust everything they're told about engines. All my preconceptions about the bypass were based on what he told me. I had no reason to doubt since he's been working on cars about as long as I've been alive, but he got this one wrong. Way wrong. The one thing this doesn't completely explain though is the pressure gauge. The bypass has been blocked ever since I built up this motor up. Initially, the gauge would always show sub par oil pressure. Then when I had to replace the rod and bearings, and the dummy shaft bearings, the pressure shot up to where it is now. I think this year I'll be running without the bypass blocked and see what happens. Thanks for explaining this so thoroughly and professionally. I'm big enough to admit I may have this one wrong.

And to think. The car runs 14.32 with possibly low oil pressure. I wonder what it can run with full oil pressure...

[series8217]

Well I've just looked at this more carefully. It seems like you are correct. This explains why my lifters tick at high revs.

Do your lifters tick at high RPM immediately, or only after prolonged high RPM runs when the oil is getting really hot?

Because of this, I now have a friend who I can no longer trust with my car, but he owes me a rod and a set of bearings.

Did you wear out a set of bearings prematurely? How bad do they look?

Thanks for explaining this so thoroughly and professionally.

No problem!

The one thing this doesn't completely explain though is the pressure gauge. The bypass has been blocked ever since I built up this motor up. Initially, the gauge would always show sub par oil pressure. Then when I had to replace the rod and bearings, and the dummy shaft bearings, the pressure shot up to where it is now.

It makes sense that your pressure went up when you replaced the bearings. Worn bearings = big clearance. Since oil pressure goes up as flow is restricted, at the same RPM of the pump if you have more restriction you'll see higher pressure. Tighter bearing clearances reduce oil flow since there is less room for the oil to flow out of the bearings.. hence you measure higher pressure at the oil pressure sensor.
You do need pressure to keep things like hydraulic lifters pumped up, and bearing surfaces seperated by oil films. If the clearances are too large there isn't enough resistance to keep the oil film from being broken.
There's a lot of debate over what the ideal tradeoff between pressure and flow at the bearings is. You need flow to keep the surfaces cool and clean, but pressure also helps maintain film strength to keep metal surfaces such as your rod bearings and crankshaft journals seperated. Obviously doing something that restricts flow to ALL oiled surfaces in the motor is going to be a bad thing.
Keep in mind the oil pressure sensor is basically right after the pump.. so if you have a restriction between the sensor and the thing that needs to be oiled, you'll measure increased pressure at the sensor... but you'll actually have less pressure and less flow after the point of restriction. Ideally we'd have a pressure sensor at the end of each oil galley... then we could see what bearings are worn, where a passage might be getting clogged up from deposits, etc. There ARE a few oil galley plugs on our motors but I'm not sure how many are actually accessible externally. I know there's at least one in the bellhousing, and the heads have them behind the cam cogs. It would be cool to find some that are accessible and put some sensors in to see what the relative pressure is in places like the head vs the block. There are a LOT of oiling holes in the DOHC and who knows how good of a job GM did balancing flow. There has been some debate on this forum and others about the top end being over-oiled... but with the lifter tap problems a lot of people have had, maybe it needs MORE oil.
I hope that makes sense.. I've been sick for the past few days and my head isn't working as well as it usually does.

[OldSkoolGP]

Someone once made the observation to me that you could install an oil pressure sensor in the oil distribution valley cover by just removing one of the plugs in the V-shaped passage and putting a sensor in there. That may be a worthwhile investment. Regarding the lifter tick, they really only tick during prolonged high revs. They don't tick at all on a drag pass or top speed run.

[fermec]

One thing I learned in life is never loan your car or your wife.

[series8217]

Someone once made the observation to me that you could install an oil pressure sensor in the oil distribution valley cover by just removing one of the plugs in the V-shaped passage and putting a sensor in there. That may be a worthwhile investment. Regarding the lifter tick, they really only tick during prolonged high revs. They don't tick at all on a drag pass or top speed run.

Whoa. I never thought of that. You think it would clear the LIM and the cover? If there'es enough space I think I'm going to do that next time I have the LIM off.

I have the same ticking problem during prolonged high revs. The heads are probably under-oiled or the cam carriers aren't cooled well and get so hot that there clearances get all wonky.

[OldSkoolGP]

I'm going to try it. In my mind I'd rather know the oil pressure up there than down at the filter.

[series8217]

Same here. It'd help a lot with diagnosing the lifter oiling problem. Maybe we can come up with a solution.

[OldSkoolGP]

If it were warmer up here I'd be in my garage right now researching the matter. Unless it does warm up it will have to wait till I get my car back from the header shop.

[gpchris]

Update!: I'll be picking up my 97 Engine and PCM in a couple of days, I cant wait to start my build! L67 CRUSHING NA DOHC FTW!!

[pocket-rocket]

If it were warmer up here I'd be in my garage right now researching the matter. Unless it does warm up it will have to wait till I get my car back from the header shop.

If you haven't done this yet, Josh, I will be in my garage today working on that Jetta thats been an eyesore for the last week. I still have that engine I got from Ben and can take the intake off to find out. There may be snow outside, but that 65k btu salamander I got from Ben's dad does a great job of heating my garage This is also something I have been thinking of ever since I found out about the bad flow on the Frams. I plan on an aftermarket oil pressure gauge in an A-pillar pod, but didn't want to use the place where the stock sender is.

[gpchris]

Just checked. Behind the plugs is the main oil path right after the intermediate shaft and right before the heads/cam carriers.

[OldSkoolGP]

THe place I was talking about was on the oil distribution cover,which site in the galley under the lower intake. The L shaped piece cast into the cover has two removeable pipe plugs in it. If we could find a sensor that could fit into one of those, that would be the best place to get the most accurate pressure for the top of the engine.

[pocket-rocket]

THe place I was talking about was on the oil distribution cover,which site in the galley under the lower intake. The L shaped piece cast into the cover has two removeable pipe plugs in it. If we could find a sensor that could fit into one of those, that would be the best place to get the most accurate pressure for the top of the engine.

That's exactly where I was thinking of putting one. I think it would clear the LIM , but the way they point, it would take some handy work.