kx3g

This is my first post. Been lurking for a while. I'm currently looking for my first third gen car. I've had 3 second gen cars in the past (1 camaro, 2 trans ams).

I'm looking at an 89 Formula with a 350. Motor has supposedly been rebuilt with a small cam and a high flow oil pump (that's all I know about the rebuild). Supposedly runs good with no obivious problems other than the oil pressure, based on the stock gauge, is running low. The rebuild has less than 100 miles on it and is outside the 3 mos, 3k mile warranty. Builder suspects the oil pump is bad and that it would be about a $400 expense to replace.

My question is, does this sound like the most likely cause of the low oil pressure? If it is the oil pump, how big of a deal is it to replace? I'm not super mechanical, but I can do some things.

I'm supposed to check this car out this coming weekend. Supposedly, the car has 124k on it. Engine, tranny, and rearend were rebuilt although it was running fine before the rebuild. Has new paint, tires, wheels, brakes, interior, and rubber gaskets. The owner basically did a complete restore and has 15k in receipts. Price is reasonable and negotiable. I just don't want to buy this thing and then get into a ton of issues (risk you take I guess).

Let me know what you think.

TIA,

Chris

fervernt

The oil pan can be a pain to get off. Other then that its pretty straightforward. Also, a lot of times, when oil pressure is out of spec it turns out to just be the sending unit for the gauge. Obviously can't guarantee that, but if the engine was rebuilt I think that's a good possibility.

sofakingdom

iTrader: (1)

The oil pump basically doesn't go bad.

IF (big IF right there) there's really an oil pressure problem, you can change the oil pump every day from now til Doomsday, and TWICE every Sunday just for good measure, and it will STILL never have good oil pressure.

Reason being, the reasons for ACTUAL low oil pressure almost invariably are, bearing clearance problems.

As stated above though, if you're relying on the factory trim package (aka "gauge") for your pressure readings, they are immediately suspect, especially if the motor isn't in any obvious low oil pressure distress. (noise, ticking, oil turns black within minutes after a change, smells burnt, etc.) Replace the sending unit first.

But even if the motor is garbage (a non-zero possibility, but let's hope not) the cost and difficulty of a successful rebuild isn't that great. But don't worry about how you're going to burn that bridge until you have no choice but to get there.

kx3g

Thanks for the input. I think I'm going to go check it out this weekend. Who knows, I might end up with it.

tzim350HO

Ive actually gone through this with my car and the oil pump pick up tube had fallen off. With this being a recent build it wouldnt suprise me. The press fit tubes are VERY prone to falling off. As for costing $400 to fix?? Not even close if you know how to do it yourself! There can be bearing clearance problems but i really dont think its very likely. Most sbc engines build alot of their oil pressure from the cam bearings, cam bearings get worn out and they lose oil pressure. If it was a bottom end bearing issue you would most definately hear some type of knock or tap that would get worse over time! I wouldnt automatically assume catastrophic failure of a bearing going down. Just inspect it as carefully as you can. You should be able to notice any metal shavings in the oil like glitter if you pull the dipstick and shine some light on it if there was indeed a bearing going down. Hope this helps.

TTOP350

iTrader: (8)

And also, what is considered low psi? These cars pumps have a low psi spring in them.

tzim350HO

Ive seen people run as low as 15 psi. it shouldnt hurt it as long as when you hit the throttle it spikes back up a little maybe to 30 psi or so. my car holds a steady 45-50lbs hot and about 70 on the gas.

kx3g

Thanks all. Talked to the owner last night and he had the engine builder check it out. The builder said it "sounded" like it wasn't moving/pumping enough oil. I'm not sure what that sounds like other than maybe it was knocking. Guess I will find out tomorrow morning when I go check it out.

kx3g

I'm a 3G owner! Bought the car. I'm not much of a mechanic, but I don't really think there is an oil pressure issue. By the stock guage, it was holding 15lbs at about an 8 - 900 rpm idle. I think the timing is off and maybe theres some other "tuning" issues. The engine has not been touched since the rebuild and driven less than 50 miles. Going to try to get it over to my mechanics place (via AAA membership free towing) in the next several days. Hopefully, he will tell me there no serious issues.

I'll post the specs on the rebuild later and maybe you guys can give me your experiences with a rebuild like mine and what is all involved in getting the engine dialed in.

Chris

fervernt

gotta say, 15 lbs sounds awfully low at that rpm... when mine is fully heated and after being driven on the highway, it idles at about 500 at a light and has 18-21, and my idle is too low. I know if it was right it would be 27-30 at 650. but I'm pretty sure 15 lbs at 900rpms is low. also dont think it should be idling that high? I'm willing to put money on it being in the red zone if it was idling where it should be. also, is that 15lbs while car is cold or hot? there's going to be more pressure til it warms up.

kx3g

Life sucks! My mechanic says 0 oil pressure on mechanical gauge (stock gauge shows 15) and lots of metal in the oil pan. It's a 350. Guess I'm going to go with a crate engine.

Tranny supposedly has a 2000 stall. Looking for something in the 300 - 350hp range. Any suggestions? Would like to keep the tpi and all the bolt ons.

fervernt

Price range?

kx3g

Was thinking somewhere in $2000 - $2500 range. Would like to have about 350 lbs of torque. Looking for something very reliable and streetable.

TTOP350

iTrader: (8)

Thats crappy, 100 miles and the motor falls apart? I think the builder needs to take care of that mess 4 you.
I would just look into the GM 350 shortblocks for a 96ish 3/4ton truck. I paid 1,200 for mine several years ago. I'm sure they have gone up in price. Then just reuse your heads and everything else after a good cleaning.

kx3g

Story goes the engine was rebuilt and the car sat for 6 mos which then put it out of warranty. Regarless, going back to the the builder is not an option. I bought it right with the knowledge that I would have to put some $$ into the engine. Just didn't expect a catastrophic failure.

That's water under the bridge. Now got to get it up and running. What about this engine:

http://www.gmpartsdirect.com/results...umber=12499529

says it's not for fuel injected engines and for cars 1985 and prior. My mechanic says the TPI will bolt right up as will everything else. Anybody had any experience with it?

ibmtech

iTrader: (1)

A 0 PSI the oil pressure sending unit should off the engine through the computer. That was a safety feature built into GM motors. The sensor is on the back of the block right behind the distrib and the other sensor is located above the Oil Filter housing..

Have another guage put on and recheck before you invest.. It might be as simple as the oil pump shaft or Distrib Gear problem or the Oil pump might be bad or the pickup tube is plugged.. I found a guy that used excessive RTV on his base pan and it came off inside the pan and plugged his pickup tube on the pump.

TTOP350

iTrader: (8)

I think those are older 2piece rear mains, flat tappet cam and smog era heads. you'll need different valvecovers, flexplate and mod the center 2 intake bolt holes.
It wont make that power it says in your car. you'd be giving up the roller cam and better heads that your motor has.

Here is more info on the cheap shortblock I have used many times. Its all new stuff. The shortblock number for a 96 truck is 12556121

Apeiron

There is no feature to shut off the engine under low oil pressure.

kx3g

Thanks for the replies so far.

Ibmtech, Mechanic put a mechanical oil pressure gauge on it. Tested, retested, confirmed gauge was working on had no pressure.

Ttop, done some more surfing and am seeing that this crate engine is probably not the best choice for tpi. Something about the cam not being that compatible with fuel injection.

Picked the car up today and got my first look at the oil and the cut open filter. The oil was gray due to the amount of metal in it. The K&N filter was gray and you could see metal all through it. There was a hunk of "goo" that was pulled from the bottom of the oil pan. Mechanic said it was a combination of some heavy weight oil and metal. I'm know engine mechanic, but even I know that it is bad.

I'm also considering a remanufactured engine. Maybe I can get an L98 that has some performance mods that will work with all the salvageable parts from my engine. Any suggestions would be appreciated. I'm starting to do some research on remans.

ibmtech

iTrader: (1)

I was mistaken. There is a safety switch though. It is called a oil / fuel pump pressure switch.. If it detects low oil, It shuts off the fuel...

TTOP350

iTrader: (8)

See my post #17 above.

ibmtech

iTrader: (1)

Sorry, to hear about the engine.. Took me almost 15 minutes to find the wiring diagram for your car.. I knew their was a safety switch but the Moderator was correct, Kinda, because it doesn't shut off the engine. The switch is located on the block above the filter housing and if it doesn't detect oil pressure, it switches off the fuel pump relay which in turn doesn't provide your engine with fuel. So, I was also right, that is why I attached the diagram for my proof..

kx3g

Going to start a new thread call "Pick My New Engine". Opening up to other possibilities. Follow me there with your advice

Tks,

Chris

Apeiron

No, it doesn't. It powers the fuel pump if the FP relay fails.

If the oil pressure drops, the fuel pump will be powered through the relay as normal.

ibmtech

iTrader: (1)

Now I am really confused as in this diagram what is the purpose of B2 on the ECM (Tan/White) Does that just receive a 12V signal then? Because the MAF relay also receives it power from the same source. I admit when I am wrong and I believe you are right.. I was wrong, I just don't understand the B2 connector now.

Apeiron

B2 is an input. If no voltage is seen there, a "low fuel pump voltage" code will be thrown.

Likethosecars

My Haynes guide doesn't have the best information sometimes. Can anyone recommend a better resource that covers the 1990 Formula Firebird 350's electrical and...well everything?