today i pulled the 350 c.i. engine out of my 89 iroc 28 and removed the oil pan because the bottom of the engine was making a knocking nose. i saw that the pan had a big dent. could that restrict oil pressure. i noticed the engine had 2 bolt main caps not 4. i thought hi-perf chevy iroc z28s had 4 bolt mains. the casting number of the block is 14088548 and the cyl head is 14101083. are these two casting appropiate for this car. i am the third owner and have no history. the engine has hyd lifters and not the roller hyd and there is no spider assembly cast on the mainifold valley.

 

im pretty sure most of the gen 1 blocks out there are 2 bolt mains. thats why the 4 bolt is desireable to some folks. you shouldnt really have a need for a 4 bolt unless your pumping some serious hp...and if its really stressing you out, you could always get the block machined for 4 bolt mains. i think super chevy did it a few years back

http://www.dvorakmachine.com/4boltconversion.shtml

 

thanks, i am happy with the engine,head combo, what about that knocking noise, have any ideas what could cause it.

 

You might want to see if a rod was hitting the pan on the inside where that big dent is.
If that doesn't pan out (pun intended) start looking for a loose rod on the crank with a bad bearing.
It could also be a main bearing,either way the crank will need to be turned and new bearings installed at the minimum.
Other possibility's......bad wrist pin,cracked piston,collapsed lifter,bad cam bearings.
How was your oil pressure? did you pull the valve covers and check the heads for broken valve springs or rocker arms,maybe bent pushrods first?

 

thanks Y2K, i did check the pan, main/rod bolts, pushrods, rocker arms, valve springs, and everything checked o.k. now the collapsed lifter sounds like the problem because when the engine was running, the noise was coming from the lifters and the oil presure was fluxing or no output. i just might replace the cam and lifters while the engine is out.

 

lifters do occasionally get stuck especially on older engines.If i was you i would go ahead and get some 1.6rr with hardened or chromoly push rods as well as new springs.

 

o.k. thanks, i probably will invest in the new rocker arms and new pushrods and i will check the valve train at my local speed shop.

 

Sounds like your problem is with low oil pressure. Things can start to make noise when the oil pressure drops that low, but the components making the noise aren't necessarily the cause. Extremely low oil pressure is either from excessively worn main and/or rod bearings, or a bad oil pump. Your oil sending unit could be bad giving you a false reading, but that isn't going to cause your engine to make noise.

 

On my stock iroc motor that I pulled and gave away to a nieghbor when I put a ho crate in after but did notice the motor should have roller hyd lifters stock u might want to pull lifters and look for blueing or scuffing on cam that old block had low oil also very black inside to but after full breakdown of block found perfect cam with roller hyd lifters perfect crank and block jus a lil glazing of bores but mainly rod and main bearings were 60 to 70% thru and timing chain had excesive play as low oil issues.

 

were u running the correct weight motor oil? running to think of oil can actually cause a lifter to collapse and it would explain the low oil pressure.