[1972 Riviera GS 455 knocking when hot?]

Just now, NTX5467 said:

How new is the fan clutch?

Fan clutch is also new.

[1972 Riviera GS 455 knocking when hot?]

Just now, arnulfo de l.a. said:

 If the block was  machined to address poor quench ( poor quench causes detonation issues) which 430 and 455 engines are known for and too much was taken off the deck,  then when it warms up and everything expands the piston kisses the head. If thats the case its a relatively easy fix. A thicker head gasket. Good luck.

Block's cylinder head planes are not machined.

[1972 Riviera GS 455 knocking when hot?]

Just now, NTX5467 said:

( "Mechanical" sound is "irregular"?  Variable happening frequency at same engine speed? )

 

Heat riser valve, if equipped?

Frequency has no relation to engine speed.

[1972 Riviera GS 455 knocking when hot?]

Thank you for your great tips,

 

I have not yet connected extrrnal oil gauge but I do not think the sound is caused by low oil pressure, since the sound is so irregular. But you never know... No oil leaks anywhere. Oli level is fine as the oil.

 

The radiator is new 4 row model and cooling system flushed. Radiator cap is new and works, since expansion tank fills after drive and and declines after cooling down.

 

 

[1972 Riviera GS 455 knocking when hot?]

16 hours ago, 60FlatTop said:

Something looks fishy about that vacuum advance hose and the fitting near the temperature sensor. Got a closer shot?

 

Most of my experience is with Nailheads, but looking at the window in the distributor cap makes me have all kinds of bad thought about adjusting the points while it is running.

 

I would double check the advance hoses and watch the timing from cold to hot.

 

Thanks for your thoughts!

 

On the video & pic the vacuum hose fitting has one open nipple, which is normally connected to air cleaner snorkel valve sensor. Since air cleaner is removed nipple is open but it makes no difference to knocking sound if it is plugged or not.  Distributor has been converted to Pertronix ignition. Timing has been checked.

 

I corrected the video link. In video you hear irregular sound that i call "knocking". It is mechanical sound. In the video it might sound like some wire is loose and hits somewhere but that is not the case. To me it sounds like thermostat spring bangs but I have changed thermostat twice.

[1972 Riviera GS 455 knocking when hot?]

Hi thrusted community,

 

Case: Buick Riviera GS 1972 ie. 455 stage 1

 

I need your expertise  What might be the cause of the knocking sound that you can hear on the video? Symptoms:

- comes only when engine is really hot and running idle. Never even during during highway driving - but appears when slowed down and stopped to traffic lights.

- Same time upper radiator hose occasionally sucks flat but after few seconds expands to normal

- might or might not be related: When engine is warm (never when cold) reading on vacuum gauge unevenly jumps a little bit down. Like it is missing spark some times.

 

I have replace thermostat two times and checked it in a pot on a stove. Opens at right temp. Water pump is new. All valve rockers are in tact.

I'm suspecting sticking valve guides and planning to do head job.

 

Any ideas? Thanks in advance!

- Markku

 

PS. below only pic, video link embedded to text above

 

[Are standard interior seat covers available for boat tail?]

I wanted to post this follow-up since I started the whole thread. Finally I had my 72 GS seats with custom covers replaced by standard covers. Because there isn't company who makes them (as custom covers), a very skilled upholster made the new seats just by looking the reference pictures (the same at the beginning of this thread). I'm very happy. Below are pictures before and after. Cheers, Markku

[Are standard interior seat covers available for boat tail?]

Hi,

 

Is there any vendor that sells so called standard seat covers for 1971...73 Riv?

I know OPGI sells custom seat covers but the do not have standard. Below are two reference pics of standard seats.

 

BR, Markku