Chevy Corvette Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
So, I got the vette out today and I noticed it was "knocking". After doing some investigating, I am still not sure where it is coming from! I am trying not to think the worst. It does not knock when you first start it up, so I don't think that it is internal. Is it? I was thinking along the lines of fan or fan clutch,water pump,harmonic balancer or maybe exhaust? Any advice? Speculation? Experiences? Thanks.

:479:
 

·
Registered
Joined
·
9,695 Posts
So, I got the vette out today and I noticed it was "knocking". After doing some investigating, I am still not sure where it is coming from! I am trying not to think the worst. It does not knock when you first start it up, so I don't think that it is internal. Is it? I was thinking along the lines of fan or fan clutch,water pump,harmonic balancer or maybe exhaust? Any advice? Speculation? Experiences? Thanks.

:479:

First of all you need to find out where the knock is coming from. How many miles to you have on your engine? Does it have good oil pressure? Is the knock loudest on the right or left side? A fuel pump makes a slight knocking noise as it's pumping. Bad lifters/rocker arms make a ticking noise, and an alternator makes a whining noise. How loud is the knock? Slight or real loud? Try jacking it up and put your ear against the bottom of the oil pan when the engine is running.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #3
Car is new to me and was represented as having 53,000 mi. Oil pressure is 20 @ idle & 40 at lower cruising speeds.It is not a tickor a whine.It,s a fairly significant knock. Initially,I thought it sounded like the exhaust knocking on the frame or something. It wouldn't be internal or a lubrication problem or it would knock at start up. Right?
 

·
Registered
Joined
·
20 Posts
Discussion Starter #7
I checked out some things today and I think that it is an engine related "knock". Something interesting was the oil pressure. Start up (fast idle)= above 40psi(no knocking). Several minutes after starting it up=20+psi(still no knock). Whenit gets to operating temp the oilpressure drops below 20psi and it begins knocking. Oil pump/sending unit?
 

·
Premium Member
Joined
·
9,048 Posts
boy, I hate to say this but... if it gets louder as the oil gets hot , and pressure drops off, sounds like a bearing to me..does the noise sound like it comes from down low ? If you pull one plug wire at a time while its running and knocking, you will hear a difference when you pull the cylinder thats making it.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #9
Iwas afraid of that! I just thought that if it did not knock upon start up, maybe it would not be a bearing. Doesn't make sense to me that the knock wouldn't develop until after several minutes of running. I think that I can see more "horses" in my future!
 

·
Registered
Joined
·
20 Posts
Discussion Starter #10 (Edited)
Oh,yeah. I do believe that it is down low. Oil pressure gauge is acting erratic also. When you are pulling plug wires, when you get to the one that's the problem it should quiet down or get louder?
 

·
Premium Member
Joined
·
9,048 Posts
well ,not completely, but you will hear the difference when you remove spark from that cylinder, if its a rod bearing.... it sure sounds like it ,tho. It s not loud cold because the oil is thick and the metal hasn t expanded yet.. Look at it positively, broken parts is a good excuse to "UPGRADE"!
 

·
Premium Member
Joined
·
9,048 Posts
good solid engine, reasonable price.. there are lots of options out there... can you swap an engine yourself or know someone who can help you , with basic skills?
 

·
Registered
Joined
·
20 Posts
Discussion Starter #14
Yeah,a swap would be no problem. I was thinking about this motor simply because I didn't want to do any other drive line changes. You know of any other crates that would be similar? Does anyone know what type of horsepower the Edelbrock intake and carb(or Holley carb) would add to the GM 350/290hp motor?
 

·
Registered
Joined
·
523 Posts
There are many options for engines without making any driveline changes- GM has several (along with others) that offer a warranty.
If staying original is not a big deal, a crate 383 or maybe a Vortec 350? There are so many options it's unreal.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #16
Thanks, everyone for taking the time to help me to sort out this issue. I am new to this site and I must say "SmokinVette Rocks!" Later.

:driving:
 
1 - 16 of 16 Posts
Top