knock when at temp
Thread Starter
3rd Gear
Joined: Dec 2018
Posts: 3
Likes: 0
From: Kansas
knock when at temp
Greetings all. I am new to this forum stuff, but could really use a direction. Bought a 87 C4 130000 miles on it. Took a new fuel pump to get it running. Car runs great smooth and quiet from cold. Right about the 195 degree mark a knock begins and gets louder as it warms up. When at running temp it is loud and revs with the engine. If i pull number 2 plug wire it goes away. You can actually feel this knock if you lay your hand on the engine. Now I know this leads you to a bad rod bearing like it did me, however I checked and replaced the rod bearings and this made no difference at all. I have grown up working on small blocks and have never come across something I could not identify.
Can this be valve train?
Oil pressure is high 60s cold and around 25 when hot.
No obvious miss to speak of.
Ideas?
Can this be valve train?
Oil pressure is high 60s cold and around 25 when hot.
No obvious miss to speak of.
Ideas?
Le Mans Master
Joined: Aug 2017
Posts: 6,941
Likes: 1,490
From: New Jersey
2 things, first is it a manual? the throw out bearings make all sorts of wonderful noises when they go out...
second, it could be a wrist pin, but that is somewhat unusual for sbc's. That's generally a ford thing. Ask me how I know.
second, it could be a wrist pin, but that is somewhat unusual for sbc's. That's generally a ford thing. Ask me how I know.
Thread Starter
3rd Gear
Joined: Dec 2018
Posts: 3
Likes: 0
From: Kansas
Its an automatic. I thought of the wrist pin theory but it really doesn't feel like that also the relationship to the engine temp seems odd. From above the engine it almost sounds like a popping noise which is why I was going down the valve train road .....so confused
Heel & Toe
Joined: Dec 2018
Posts: 16
Likes: 1
From: Hendersonville TN
An old trick to find what’s causing the knock sencor to pull timing is to take a wood dowel and place it on where the noise is coming from and place the other end to your ear to hone in on where it’s coming from. If nothing is mechanically wrong than you mite want to check the connections to your mass airflow sencor, knock sencor and make sure everything is at least plugged in. Mine had similar issues years ago and it ended up being a bad maf sensor. Could also be fuel that’s set too long, any time mine sets for a long period of time it bucks pings and knocks till I get some new fuel in it. I don’t know how helpful that was but that’s where I would start.
Melting Slicks
Joined: May 2013
Posts: 2,692
Likes: 349
From: Sacramento California
With 130k do you think it could be something with the timing chain/gear set? *shrug*
That is what came to mind when you mentioned the knock feeling stronger above the throttle body
That is what came to mind when you mentioned the knock feeling stronger above the throttle body
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Intermediate
Joined: Jul 2018
Posts: 46
Likes: 2
From: statesville,north carolina
make sure ur getting spark to that cylinder? and the valves are adjusted right?
do a full tune up if that don't work sounds like cam is gone !
do a full tune up if that don't work sounds like cam is gone !
Last edited by skinnyt; Dec 27, 2018 at 08:48 PM.
