61 galaxie 292 running cold on one side

[mbjones]

have a 61 galaxie with a 292 y block , one side exhaust is running cold , the passenger side .
about 1/5 the heat and pressure of the other side exhaust pipe ,
engine is running well and firing on all eight cylinders,
has 2 separate exhaust pipes from the manifolds to the rear . no crossover pipe
have checked the muffler for blockages , not blocked.
the heat riser valve on the passenger side has been removed as was leaking .
have checked valve clearances , all ok .
checked timing .
have done a compression test to check for blown head gasket , all cylinders between 115 and 125 .so assuming it is not blown between 2 cylinders ,
checked for inlet manifold leaks , no leakage found .
fitted new plugs , leads, cap and rotor .
anyone had any experience with this, or any advice on what else the problem could be .
thanks in advance

 

[Bob from Northport]

What temperatures are you recording?? Have the manifolds been changed or different??

 

[Bob from Northport]

I think you have a vacuum leak around the intake manifold on the passenger side.
With the engine idling, spray starter fluid around the intake ports. If the RPMs pick up, you've found the leak.

 

[mbjones]

done that , no vacuum leak , stock manifolds , have not got temp gauge.

 

[miker98038]

Break down and buy an infrared gun. Even the cheap Amazon ones are fine for auto use. Get the water temp at the front cross over and the rear of the heads at the temp sender, and the soft plug behind the distributor. Each exhaust port at the manifold flange. Warm after idle, and a mile or so drive.

Whatever it is, it is really odd, something I’ve never seen. You’ll spend more in parts and gaskets chasing it without some hard numbers. Besides, the gun let’s you get the perfect temp on the griddle for pancakes.

https://www.amazon.com/ThermoPro-TP...djustable/dp/B07VTPJXH9/?tag=atomicindus08-20