Engine: A knock that comes and goes???

[Never Enough Studebakers]

Have a 259 that has sat for a few years. I started it and it has run great. Oil pressure starts at 60 and after awhile it will go down to 25 psi @ idle. Now today I start it and i get a knock which sounds to be around the #1 cylinder. I can rev it up and the knock gets louder. Then after it runs for 5 minutes or so the knock is completely gone. I suspected some carbon on the head. So As it was running I dribbled some water down the carb. The knock went away. I shut it off for 5 minutes. Started it back up and the knock was back. I revved up the engine again and it went away. Any thoughts out there as to what it could be?

[Studebakercenteroforegon]

In a car with an automatic transmission? If so I suspect the torque converter drive plate. Even though at the rear of the engine the sound can be heard in the front. It also is a knock that comes and goes.
As a long time parts dealer, I can tell you I have sold a lot of replacement torque converter drive plates to cure such a knock sound.

[PackardV8]

I suspected some carbon on the head.

The 259" pistons are .070" down in the hole. It's not carbon.

Over fifty years, random noises have been hard to find and show up in strange places.

1. Check the front balance damper bolts. The rubber therein "perishes" as our Brit friends are wont to say.
2. Check the flywheel/flexplate bolts. They've been known to work loose.
3. Check the distributor timing. If it gets wonky, it can cause even a 259" to rattle.

jack vines

[Never Enough Studebakers]

This car has a 4 speed. The sound is from up front on the #1 cylinder side. I put a stethoscope to the engine and can not track the sound down. Once I get an edelbrock carb on it I'll check out the timing. Right now I have the AFB from my Avanti sitting on it. I would think if i had something going in the bottom end the knock would be constant.

[JoeHall]

I'd check the fuel pump. They tend to have a knock that comes and goes. Also, it is near #1 cylinder.

[studegary]

I'd check the fuel pump. They tend to have a knock that comes and goes. Also, it is near #1 cylinder.

I will second this. (I think that this is the second time today that I posted an agreement with Joe.)

[spokejr]

I'm with Joe. The first time I started the new engine, all was quiet. Then I installed the mechanical pump and clack, clack, clack (I had previously used a hang bottle). Took pump out and all's quiet. Tomorrow night the electric pump will be finished, can't wait.

[Never Enough Studebakers]

Well guys you could be on to something. I did not have this noise with the original pump. I did change it out with a newer one as I thought the old one wasn't pumping from a can that I had going to it. The noise started right after the new fuel pump was installed. This could be it. I was thinking maybe a water pump. There are no leaks but there is some wiggle. But this pump thing is something to dive into. I will let you know.

[altair]

Don't be fooled by good oil pressure that is only half of the programme you also need volume. I have a 259 that had excellent oil pressure however was seizing up when warm. The engine was torn down to find the main oil passages were fully clogged and the mains and throws were not getting any oil, but I still had 40 - 50 lbs of pressure. Fortunately the problem was diagnosed in time before any serious damage was done and I had to replace the mains and rod shells and have the crankshaft polished. All is well now.

[Never Enough Studebakers]

Problem Solved: It turned out to be the fuel pump. I switched it out witht the one that I had on there prior and the noise was gone. Strange, I compared both with each other and nothing looked out of the norm and they seemed to work in the same manner. Just wanted to post a follow up as it seems all to often that doesn't happen on forums. You would have swore it was a rod that was about to let loose.

[Never Enough Studebakers]

Problem Solved: It turned out to be the fuel pump. I switched it out witht the one that I had on there prior and the noise was gone. Strange, I compared both with each other and nothing looked out of the norm and they seemed to work in the same manner. Just wanted to post a follow up as it seems all to often that doesn't happen on forums. You would have swore it was a rod that was about to let loose. A huge Thanks goes out to all of you that responded. Awesome Work Guys!!!

[RadioRoy]

Thanks for posting the solution. That adds to the general knowledge base.

[studegary]

Problem Solved: It turned out to be the fuel pump. I switched it out witht the one that I had on there prior and the noise was gone. Strange, I compared both with each other and nothing looked out of the norm and they seemed to work in the same manner. Just wanted to post a follow up as it seems all to often that doesn't happen on forums. You would have swore it was a rod that was about to let loose.

Thanks for posting the follow-up.
YOU would have swore that it was a rod. I thought that it was the fuel pump.

[TWChamp]

Thanks for posting the follow-up.
YOU would have swore that it was a rod. I thought that it was the fuel pump.

Yep, noises can be tricky. In the mid 80's I bought a very nice loaded Cutlass that was only a few years old and had what I swore was a rod knock. I pulled all the rod bearings, and saw they were fine, but as long as I had them out I put in new ones. Next I checked all the plastic buttons holding the rockers in place, and replaced the broken ones. Then I drove to the auto parts store and bought a can of Sea Foam to put in the oil. Before I drove the 5 miles home, the stuck tappet was freed up, and the engine sounded like new. Lesson learned, try the cheap easy things first, if the exact cause is not known.

[T.J lavallee]

Just curious... but was the replacement pump an Airtec? I, along with others, have experienced problems with these units made in China. This is the first time I've heard a knocking problem from one but I'm not all that surprised.