well, i finally gave in and took my 89 iroc to the local dragstrip, and wouldnt you know it , i think i broke something. It now makes a strange noise. it seems ok at idle, but once it hits about 2k rpm, it makes kind of a hollow rattling noise, especially when i let off the gas. It sounds like its coming from under the valve covers near the back of the motor on both sides but its hard to tell. Also, after the run i noticed that i was quite low on oil and i filled it up that morning. It doesnt normally leak. I thank you in advance and appreciate any ideas on what i might have done to it or how to fix it.
thanks
Btw, its an 89 all stock iroc with 160k miles
auto tranny, 2.77 gears, tpi with maf.
I ran a 15.1 the first run and 15.2 the second time when something happened.

 

350 or 305?? Did your oil pressure drop??

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88 IROC-Z,L98 350 TPI, 700R-4 Tranny 2.77, K&N Filters, 126K Miles runs great. http://www.j-body.org/library/humor-...arearicer.html

 

it is possible with that many miles on your car you could have a rod knocking...which is not good..i would have it checked out now just to make sure

 

If you have a rod knok you can sometimes hear it through the exhaust during idele. The excess "piston slap" will make an un-eaven spitting sound.

 

uhmm wouldnt a wraped rod make noise at any rpm? my 4.3 did..

what about when you first get on the gas? does it make the noise thruout the rpm range?

 

Thanks for the info. My freind and I were poking around with a hose and he is convinced that it is rods knocking. We determined that it is coming from under both valve covers. It is a 350 and I was pretty low on oil when I checked it right after the noise started. My friend told me that it was blowing out of the pcv system and we fixed that. If it is bent pushrods, would that damage the valves or the cam? Is it safe to drive, and what would you guys recommend doing with it? I could replace the pushrods if i could just figure out how to get the passenger side valve cover off. Is there anything else I need to do?
Thanks

 

If you suspect rod knocking, don't even chance it! There are different sounds for different engine components. Usually a valve train noise will be a higher, almost ticking kind of sound whereas a rod knock would be low but sharp sound. Valve trains are tough ... I'm, unfortunately, leaning towards a rod knock. Hopefully, you caught it fast enough to where you can polish the crack and replace the rod and crank bearings and be on your way. I recommend pulling out the pistons/rods and have them inspected. A lot of work, yes, but you'll end up doing it anyway once it blows so at least now you have something to work with. If you end up throwing a rod, you decrease the chance of being able to use the block. A rod is under tremendous pressure, if it goes, it'll take a lot to stop it, sometimes resulting in a cracked block. Too many times I've seen thrown rods eject straight out the side of a cast iron block. Not good.

Enough lecturing ... I hope it works out for you. Hey, maybe a good excuse to bore her out to a 355.

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The Camaro Shrine
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'88 Camaro IROC-Z 350 TPI
'98 Grand Prix GTP 3.8L SC

"Yea, though I walk through the valley of rice,
I shall fear no Turbo; for Torque art with me."
- Cullan Hooley

 

I just learned that that my problem seems to be bent pushrods. We took the driver side vavle cover off and removed a couple of the pushrods to inspect them. Two of them, the rear two, are slightly bent. I am off to the parts store down the street right now to pick up a new set of melling pushrods. I just hope i can figure out how to get the passenger side valve cover off. There is a ton of stuff in the way over there. Is there anything else that i need to know when i change them? Thanks a lot for the info guys. Im so glad that this site here.

 

I have a rod knock and sounds like what you are describing. If you have the ability to fix it then go right ahead and do it as for me I will just have to wait till it lets go.

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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

the same thing happened to my iroc and i though it was push rods or valves but it turned out to be a rod knocing i hope it is just your push rods but i didnt get off that easy

 

Well, I replaced the pushrods and set the valve lash again and the knocking is still there. I guess its time so start thinking about a new motor. Anybody have and suggestions for a new motor? I live in CA so i have to live with the emissions stuff here and i want to get the strongest motor that i can get to pass smog checks. Thanks

 

I'd look into a ZZ4 and plan on swapping the TPI over. If you're looking to spend less, you can probably find a decent short block for a lot less cash, but as long as you're going to go through the work, look into ZZ4.

If you're ambitious and want to rebuild the motor yourself, you can save a bunch of cash.

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The IROC Homepage
<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
"I didn't know a bored out Ford could go so slow" -Shenandoah

 

Jim, I'm willing to bet his block is probably fine. He may have caught it in time. If he's a cheap *** like me, I'd stick with the same block and build it up a bit.

 

Take at look at the flexplate.
You might want to rule this $50 part out before digging into the motor.
Every flexplate I broke made a different noise. It only take a couple of minutes to check, and I fooled many people who thought it was a rod knocking.
Make sure all the bolts are present, and you'll need to look close for little hire line cracks around the hub.

Good Luck,

Ron C. Terry

BTW, the last time I spun a rod bearing the engine would not start easy at all, more or less idle ? and knocked like crazy at idle.



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'82 Trans Am
'81 Camaro Z-28
'94 Vette LT1 Coupe

 

ronterry, thats what i was hinting at when i asked what about when you first get on the gas hard, and it not being consistant at all rpms.. im thinking cracked flexplate, or possibly a couple sheered TC bolts.. id hate to tell this guy its a rod knock, and have him break into his engine to find its perfectally fine.. check that flexplate first before shotgunning to the next thing...

 

Wow, i never even thought about the flex plate. I will try to get in there and look at that. Thanks.

 

well any luck? let us know.. im curious to know what the problem was..

 

How bout checking the timing chain and cover too? In the most recent edition of Chevy high performance, they say that a rod knock can sound alot like the timing chain slapping against the cover.. Especially since this is the original motor and possibly timing chain??