First off the car is a 1988 Firebird Formula 305 Vin Letter E. I've
picked up a new oil pump but when I printed out the repair specs I've
decided to try and get some input from the web.
I'm having an issue where on startup cold I'm getting around 30 psi and
that stays pretty constant until engine warms up, then I start to lose
oil pressure and eventually at idle it completely drops to zero. When
I am driving I get about 15 - 25 psi but if I come to a complete stop
or slow down to a crawl I lose complete oil pressure and then I get a
knock that scares me. The only time it knocks is at idle or driving
really slow with no oil presure. I've decided to not drive it until I'm
sure what can be done to help the issue. I am running 10w30 and I
believe the oil type isn't the issue. I'm afraid the oil pump might be
going out. Is there any other options that might be the issue before I
have to start the long process of changing the Oil Pump. Like maybe a
faulty pressure relief valve or a sending unit?
Thank you for your input
Kind of sounds like worn bearings to me, too. Change your oil and put some
straight 30W in and see if your pressure goes up. Or try some a little
heavier. Do you have to pull the engine to change your oil pump? I would
have to on my '74. In any case, if you change the pump, you can always
plasti-gage your bearings to see where they're at.
yeah I have to pull the starter, exhaust, undo the engine mounts and
lift the engine about 6 to 8 inches. I'm really debating the oil pump
replacement because people are telling me that it might be the
bearings... In that case I might as well buy a rebuild kit and redo the
engine. I just do not want to waste my time putting in a pump if thats
not gonna help the issue.
I hope I get some more comments on this post.
Imagine that the oil pump is the most lubricated part in the entire
engine. Other than the relief spring stuck open (i have seen this &
results in No or little oil pressure even at startup) i suspect the
bearings are heavily worn. These can be replaced from underneath (seeing
as you have to lift the motor to get the sump off) just replace 1 at a
time & retorque the caps.
I did have a ford 351 Cleveland that ran several years at about 5-15 psi
idle. it actually died by the piston splitting & going through the
block.(so its a ford - who cares) :->
Take that back ! :-)
My 305 i had fitted in my '78 Camaro (replaced the 6 pot) was very sweet &
smooth. I replaced it with a crate 350 4 Bolt which just never did run
right. The 305 (stock cam) averaged about 28 MPG cruising at 90mph and ran
high 16's. I could drive all day on a tank of gas!
point of actually getting real performance out of it, properly taken
care of they get good economy, ok performance for the timeframe, and
last decently. That said, you have it on the nose, the bearings are
clearly gone on that puppy.
That's a no brainer since they will cost the same to rebuild. Take
the one with the better bore and stroke ratio and more potential. The
intake and peripherals will fit on the 327. The only thing you should
have to change is the valve covers and maybe elongate a couple of bolt
holes for the intake. Get a book on rebuilding the small block Chevy,
well worth the read even if you are going to farm out the work.
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