1973 Newport 400 "engine knock"

[NWPT70]

Hello guys,

The new to me 1973 Newport with the 400 engine I recently bought runs amazingly well and smooth but I noticed when the engine is cold and a bit shaky (I still need to adjust the choke) there is an audible low tone knocking inconsistent sound coming from the lower engine bay. Once the idle smooths out and the engine is no longer shaky the "knocking sound" subdues. It still can be faintly heard but hardly notable. When engine RPM increases while revving the engine, the noise is not heard at all. The engine is quiet and runs very smooth.

I would like to get an idea what this knocking noise "could" be. I have heard it could be anything from a be a rode bearing knock to the torque converter bolts being loose. (I am hoping it is just the bolts!)

Any say would be much appreciated!

 

[Slantsix]

Get 40-50cm long hard wood or metal rod. Place 1 end near ear (dunno what is called, that nipple front of ear tunnel) and other end on engine and start listening where it comes. Or if trying find where exhaust leak, use piece of garden hose, but keep that 2-3cm from ear. Dont want too loud noise or hot exhaust gas into ear
Could be rod bearing, leaking exhaust etc..

 

[traintech55]

After you try the above tests, I would also do an oil pressure test cold and hot. Note what the pressure is cold, and then at operating temp. when the engine is warmed up you should have at least 30 P.S.I. at idle. 10 - 20 P.S.I. I would try a different oil pump. Under 10 P.S.I. on a warm engine start saving money as you are going to need major work.

 

[Carmine]

I once had a 318 with a main bearing knock. Lower tone and not as rythmic as a rod. It takes a long time for that one to cause trouble... sold the car many years ago.

 

[NWPT70]

I going to check all the above today,,

I have been hearing that loose torque converter bolts can cause the same symptoms. I crossing my fingers.

 

[superfragl]

I had similar situation on a big block - exhaust manifold was leaking... Took me a while to figure out.

 

[70bigblockdodge]

Tune it up, change the oil, drive

 

[1978 NYB]

Don't start the engine anymore until you check those bolts.

 

[65sporty]

Please don't take this wrong but do you know the difference between a lifter tick and a rod knock? The reason I ask is because a rod knock usually gets worse when the engine is warm. Lifter noise can be either way warm or cold.

 

[NWPT70]

Don't start the engine anymore until you check those bolts.

It turned out it was the bolts.

 

[Marian]

Don't start the engine anymore until you check those bolts.

If bolts are loose and engine starts, what can happen?

 

[commando1]

If bolts are loose and engine starts, what can happen?

Or so it would seem.

 

[Marian]

Or so it would seem.

Thanks Stan <sarcastic tone>. I was wondering because we had the Monaco's original transmission rebuilt in Austin and then installed by "that" shop in Tx. I was told this week that we will need new torque converter due to something with bolt...stripped...I don't remember why....I shut down after hearing it would cost another 800.00 for this. I know the trans shop in Austin totally rebuilt the 727 but I'm no wondering if the texas "shop" did install correctly and then Kansas shop started car. Not that it really matters much now...I'm still going to be out some more money. I just wanted to know how this could happen. BTW...that pic looks like something that would happen after eating jack n the box tacos. Hmmm.

 

[traintech55]

Thanks Stan <sarcastic tone>. I was wondering because we had the Monaco's original transmission rebuilt in Austin and then installed by "that" shop in Tx. I was told this week that we will need new torque converter due to something with bolt...stripped...I don't remember why....I shut down after hearing it would cost another 800.00 for this. I know the trans shop in Austin totally rebuilt the 727 but I'm no wondering if the texas "shop" did install correctly and then Kansas shop started car. Not that it really matters much now...I'm still going to be out some more money. I just wanted to know how this could happen. BTW...that pic looks like something that would happen after eating jack n the box tacos. Hmmm.

The bolts that hold the flex plate to the torque cònverter are easy to strip oùt. You might be able to use a heli coil to repair the threads, but if more than one is stripped I would replace the converter. You have to pull the trans anyway.

 

[traintech55]

Thanks Stan <sarcastic tone>. I was wondering because we had the Monaco's original transmission rebuilt in Austin and then installed by "that" shop in Tx. I was told this week that we will need new torque converter due to something with bolt...stripped...I don't remember why....I shut down after hearing it would cost another 800.00 for this. I know the trans shop in Austin totally rebuilt the 727 but I'm no wondering if the texas "shop" did install correctly and then Kansas shop started car. Not that it really matters much now...I'm still going to be out some more money. I just wanted to know how this could happen. BTW...that pic looks like something that would happen after eating jack n the box tacos. Hmmm.

Hey Marian, Sorry I did not completely answer this in my earlier post. Most of the Generic Motors Cretans do not know why Chrysler has 4 torque converter bolts instead of the 3 they are used to.
Chrysler has one bolt slightly offset on the flex plate and converter, (also the rear of the crankshaft), this is so when the converter is built for a particular engine it will balance up with the assembly. Certain engines are internally balanced and some are externally balanced. What they have not learned yet is you have to install all four bolts before you tighten them, if not trust me one will always be off. Also being very short, 5/16 in diameter, and a fine thread, equals very easy to strip out. Wish you could find the idiot that did this.

 

[Snotty]

I had a problem once where I thought I was losing a rod or two. Turned out to be a bad harmonic damper. Roids were fine but that thing sure hammered!

 

[78Brougham]

Welcome back Marian, we haven't heard from you in a long time!

 

[Marian]

I had a problem once where I thought I was losing a rod or two. Turned out to be a bad harmonic damper. Roids were fine but that thing sure hammered!

Roids got hammered? Ohhhhh my!!!!!

 

[Snotty]

Ha!!!

I can't type to save my life!!!

 

[traintech55]

Roids got hammered? Ohhhhh my!!!!!

"Roids got hammered", that really had to hurt.