I'm looking at buying a used 350 tpi. Ad says it has about 65000 miles, and that it runs good, but needs main bearings work. slight tick/knock sometimes.

What would it take to fix this?? Or could it be something else more simple to fix?

Thanks for any advice

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Gunmetal 89GTA T-Tops L98
700R4 with 3.27 gears, street tires
Best 60 ft: 1.996
Best 1/8th mile: 9.02 @ 76.5mph with 60' time of 2.14
With these mods: air filter, hypertech chip, 3" exhaust (no cat.)

 

Main bearings don't just "go bad". Something kills them. And when they've been killed, usually plenty of other stuff is damaged too. About the only ways to kill main bearings are: run low of oil; fail to change the oil; let antifreeze get in the oil; or over-rev the motor. Which one of these would you prefer to have happened to your motor before you get it?

If it's real cheap it might be worth the risk. But IMHO a motor that knocks isn't a running motor, it's a blown-up junk core; and you shouldn't pay running motor price, or anywhere near it.

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"So many Mustangs, so little time..."
ICON Motorsports

 

How do you tell if your main bearings are bad? I am good about my oil..I always change it at 2500 miles. I do hear a ticking though..It goes away at idle..but I can hear it at like 2000 RPM. My oil pressure isn't very predicatble either. Most of the times it's perfect..Right about 30psi at idle..but other times I have seen it pretty low..

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• Red '88 IROC 5 Speed 305 TPI w/3.08
• Dual Friction Stage III Centerforce Clutch
• Accel 300+ Racing Ignition
• Accel 300+ Pro Sleeve Plug Wires
• AC Delco Rapid Fire Plugs
• Flowmaster Force II 3 Chamber Cat Back Exhaust
• Hypertech Chip
• Hypertech Airfoil
• Gutted Air Box
• Best Maryland (40 degrees) E/T 14.686, 60' 2.205, 1/8th mile 9.461, 1/4 mile MPH 93.91
• Best Florida (80 degrees) E/T 14.88, 60' 2.163, 1/8th mile 9.540, 1/4 mile MPH 92.74
• Best 60' 2.163(Florida)
• TPiS AFPR set to 42psi using Accel Fuel Pressure Gauge (Installed after Maryland run)
• Aluminum Driveshaft (Installed after Maryland run)

 

The heads would still be good, right? and all of the tpi induction? That could be used for something?

 

Could be rod bearings too...I've seen plenty of bearings spun, and a good way to tell is to drain the oil and check for metal on the plug and with a magnet...if theres more than a little bit, figure a crank job. The tapping could be a rod bearing because the journal now has play and the piston can over-travel, smacking the top of the head. Get's worse with time. REAL bad with aluminum heads. Also tends to be noisy. Use a stethoscope and listen when it makes the noise at eack individual cylinder. to get an idea. I havent seen many main bearings go bad unless the damper's shot or the bearing was a POS to begin with

 

It could be as simple as a loose rocker arm. You need to investigate what it is causing the noise. I have a hard time believing it's the mains.

 

Try disconnecting one spark plug at a time. This relieves the explosion off each cylinder. If the noise goes away when you remove one spark plug, then that is the cylinder with the bad rod bearing.

If that does not work then rev the engine to 2000 rpm's, if the noise goes away then it is in the valvetrain (ie. lifter or loose rocker arm).

Last put a stethoscope up to the bottom of the oil pan and then the side of the block. If the noise is louder at the oil pan then it is the main bearings, if it is louder on the side of the block then it is rod bearings.

Also, check the injectors with the stethoscope, they can sound like a bad lifter sometimes.

Paul

 

i recently(today) took oput my 355 to find that the machine shop guy didnt do to great of work on the block... i told him to bore it, hot tank it, cam bearing and freeze plug it. well he did that and no more... he didnt even finish hone the block!!! most reputable shops bore the lock to about 25 ths. and then finish hone the other 5 ths. the 30 thats need to complete the boring process!! this shop..didnt!! the pistons wore right into the block and the particles of metal from the wall of the block got chewed right into the mains and rods(bearings!) they were completely trashed..literally!!the crank was ****ed!! it had already went .10 .20ths!! so i had to buy a new crank! and the new rings and a gasket set for the enigne!! taking off heads tommorow~~!! oh not to mention all the block work ..again! this will now be done by completely reputable shop!! im thinking about that 400 i talked about in my mods!!..anyway the bearing will cause overheating oil pressure loss and horrible driveablity!! dont get the engine!!

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89 firebird formula

356 10.5:1compression
comp cams xe262 cam
performer rpm intake
#1405 edlebrock 600
sportsman 2 heads 64cc 2.02/1.60 valves 200cc intake runner
msd 6al
h.e.i. proform 50,000 volt vac. advance ditributor
700r-4 with 3.08 first gear and 3.23 posi 7 5/8 rear end.
b trans shift kit(will kill shifts...suck dong!!)
shorty heddman hedders with custom 3" pipe y-pipe back(no damn cat!) with 40 series flowmaster!


future mods: 406 roller REALLY REALLY REALLY RADICAL!!!!!

 

Well it sounds like they did exactly what you told them to. They can't really put a hone to the bores without knowing what type of rings you were going to use (although 400 stones are pretty universal). And you're supposed to clean the bores with detergent and a plastic bristle brush and then wipe them with AT fluid until the rag is clean. And you're supposed to check ring end gaps and mic the cylinder to make sure it's in spec and plastiguage all the mains/rods.

Sounds like you were in too much of a hurry. Not getting sore on ya or flaming or anything, but check everything... even oil pump clearances and make sure the oil galleys arn't filled with crap.