RustInPeace

Have an oil pressure question for everyone. Recently picked up a 99 FRC with 164k bone stock ls1, highway miles and appears to have been babied its whole life. Oil pressure is about 40 on a cold start and about 20 with oil temp 190-200. Yesterday it was about 70 degrees here in nj and I was doing some spirited driving and got the oil temp up to 225 where I noticed pressure was at 16 psi. Didn't think much of it cause I'm used to LT1s and this would be considered fine on them. After doing a little reading I learned this is pretty low for an ls1. I'm not sure the gauge is accurate though cause the motor runs smooth as silk and makes no valve train noise at all cold or hot even when the pressure is at 16, pressure climbs like normal with rpm and will see about 40 at 3k+ rpm with oil at 225+ degrees. I did notice the gauge is very slow to respond there is maybe a 3-5 sec delay where as my lt1 and l98 gauges are both pretty much instant with rpm increase, if a rev the ls1 the gauge doesn't move until after the rpm is back down to idle. I noticed it is wet around the oil pressure sending unit so it appears to be leaking back there but it is very hard to see. I ordered a new one anyway hoping that may correct a possibly inaccurate gauge. Thoughts? Pressure sender? Oil pump? Stuck relief valve?

Bill Curlee

Wellllllll,,,,, If its leaking its suspect and we cant really say every thing is FINE or YOU HAVE AN ISSUE until you get a new sensor in there.

After the new sensor, see what happens. In all reality, LS1 oil pressure can be normal on the lower side of the gage.

While you have the intake manifold off, If you can find a good used 2001-2004 LS1 intake OR an LS6 intake manifold, its a one for one easy swap and direct bolt on up-grade. You will get a few extra HP out of the swap.

Bill

RustInPeace

Thanks for the reply, will post an update once the sensor comes in and I get it installed. Was hoping to try and do it without removing the intake like some of the videos on YouTube

Jumper11

Take if from someone who learned it the hard way. I replace my OPS without removing the intake and it was a PITA!!! removing the intake is not difficult, you can install a OPS extension because the stock OPS will fail again. Besides, pulling the intake will give you the opportunity to clean under the intake and where it was leaking.

RustInPeace

Yea I may end up pulling the intake was looking under the car yesterday and there is a good amount of oil running down the back of the motor and onto the exhaust pretty sure its all coming from that sensor so I have some cleaning to do

jackthelad

If you don't want to dismantle the manifold, you can always go in through the HVAC duct at the base of the windshield. Plenty of info online as to how to do it.

And BTW, on early C5's the LS6 intake upgrade is not plug and play - you will need other parts as well.

Bill Curlee

What is NOT plug and play?????

If you are going to say the steam vent cross over pipe, That would NOT be an issue as I have proven it on the last THREE swaps that I have accomplished.

All you need to do is carefully bend the tubing down below the valley cover fastener heads and the manifold fits over the tubing like it was made to.

IF,, you are scaired it will contact the intake manifold, you can shave down the small ribs that are located over the piping. I have made them fit WITHOUT doing ANY manifold or vent line mods other than pressing them down below the bolts. The KNOCK Sensor cable was routed UNDER the pipe near cyl 7 (not in pic)


If you decide to shafe the RIBS, you can see how its done on this example. It not complete but, thats all there is to it:




On the later model C5s,, I ADDED the rear steam vent line to help improve the cooling of cyls 7 & 8.

I ordered a late model front steam vent, flipped it and installed it on the rear ports. I used a rubber line and a Stainless Steel "T" to pipe it into the front vent line!!!

02 ZO6 with rear steam vent crossover pipe installed:






Any other questions??


Bill

jackthelad

People who sell LS6 intake manifolds all say an installation kit is needed, including water pipes, etc.

Bill Curlee

Some people are reluctant to MAKE things work with what they have. Its easier to spend cash than to think things through.

Hey,, You can purchase the LS6/2001+ front cross over pipe and the rear block off plugs if you think thats easier.

Hell, I like the EXTRA steam vent capability especially when my car is heavily modified. Thats why I did the mod to my ZO6

BC

RustInPeace

Update: finally installed the new pressure sensor, ended up pulling the intake couldn't do it the other way with my big hands, seemed to have picked up about 4-5 psi cold and hot, still a little lower than what most people see but with 164k I guess that's to be expected. Runs good and valve train is quiet so I'm not too worried. Still have to do an oil change, have no idea what the last owner has in there, going to run amsoil 5w30 maybe I'll get lucky and pick up a few more psi with a quality oil

martysauto

Let us know what you get with fresh oil. I suggest using an AC delco or wix oil filter.

Jcrankshaw

Hello - I have similar issue where oil pressure is slow to build up on startup, it is intermittent. Curious if the sensor being replaced built pressure faster?

73Corvette

Not sure you noticed this is a pretty old thread... might want to start your own thread