I've got a couple questions for you seasoned guys out there......some guys with TPI's say they have the stock gears which are 2.73s.....but I did some research on my car and I was told I've got 3.23's. Does that sound right to anyone? or do I most likely have the 2.73's. Ok, on to my next question. I remember hearin the average voltage for an 85' 305 is 14.4 volts (i think?) she usually hovers around 13 on the gauge, is that doin ok? one last thing.......whats a decent oil pressure reading? thanks for your help, sorry if i ask too many questions

 

The best way to tell, assuming the rearend hasnt been changed is to check your RPO code. There is a RPO code checker on this site. But, it is possible that you do have 3.23's.
I have a 85 Trans AM with a 305 as well, and I can assure you that your gauges are not the most accurate thing on your car. If you are showing 13 volts, I'd say youre in the ballpark. If you dont trust that, you can go to almost any auto parts store and they can tell you exactly what your alternator is putting out.

Decent oil pressure on the Chevy small block should be no less than 10 psi per 1000 RPM's. If yours is shownig a bit low, try a thicker oil. If youre running 5w30, you should be shot. I would run 10w 40 in the winter, and 20w50 in the summer. Thats just me, its always worked, so I have stuck with it. If it stays warm where you are, stick with 20w50 year round. Any small block I have had will read anywhere from 10 to 30 psi at Idle, and top out at 50 to 60 psi.

 

thanks bud! she usually stays around 30 psi when shes warm, so i suppose thats just fine. i'm getting ready to drain it and clean out the system really well with some of that gunk engine flush that supposedly works really well. then we'll she how she does from there. oh and i dont suppose you would kno about any kinda metallic clanging in a stock exhaust system? usually only does it when shes cold though. doesnt seem to effect the car, shes still pretty fast, but it just bugs the he** outta me. and ideas on what it might be?

 

First of all DO NOT use the engine oil flush stuff they sell at the local auto parts stores. The stuff is NOTHING more than kerosene. If you have sludge built up inside your motor, this will almost certainly get some of it loose enough to collect in the oil pan and stop up your oil pump pickup screen. Way bad idea. The best you can do for any engine is just keep the oil changed and run a good name brand oil, and stick with the same brand. If you want to "clean" the oil system, change the oil, and run it for 500 miles and change it again, but unless you have recently opened up the motor, such as a rebuild, cam swap, etc., there is no need. Waste of money. If you flush out the motor every time you change your oil, you will not see any increase in your oil pressure. Keep the filter changed too. I have never heard a bad word about AC delco oil filters. I have used them all my life, and NEVER a complint here. If youre holding 30 psi, Youre alot better off than most. My 85 bird only has 64,000 miles on her, and thats what she holds at idle with 10w30 at running temp.

The rattling noise in your exhaust is almost certainly the heat shield above or on the catalitic converter. Chances is that the heat shield has rusted and come loose. You can remove it, or any exhaust shop can solve that problem. The other possibilty is the air tube going to your cat. Just in front of the cat is a clamp that holds the air tube in place. if it has broke, come loose, etc. it can cause the noise as well. Some other causes of exhaust rattles are the heat rise (on the passenger side manifold), or even the muffler. If the baffles inside of the muffler have rusted or come loose, they can drive you insane.

 

Just curious, you have any pictures of your car? I have a good friend that has an 85 Z28. Awesome ride. I helped him rebuild the motor in it about 6 or 7 years ago. He bought it back in 91 or 92 and he still drives that car every day. I think youll like it. Theres alot you can do to it to help it out performance wise that is pretty cheap, and most if the mods will pay for themselvs with better gas mileage.