Packard Forum Index » Pre-War (1899-1942)

Of all the engines I’ve rebuild including a couple 245s, I’ve always had the guides replaced professionally. That said, yes, I can be done in the car. As for the pop test, I’ve never done that and had even forgotten about it until now! I always did it by feel or by using a gauge but primarily by feel.

Yes, guides can be replaced with the block in the car, and the exhaust valves see more abuse.

I also recommend carefully measuring what you currently have before you do anything else.

On my '37 120, the exhaust valves were very loose in the guides. It turned out that at some point in the engine's past, the Packard exhaust valves were replaced with Pontiac exhaust valves. All of the head diameters were the same, so the engine ran, but the stems were .020" smaller in diameter! Once I sourced the correct valves, the clearance between valve and guide was perfect!

All that to say, a lot can happen in the 85 years since the car left the assembly line, so before you replace parts you may or may not need to, I recommend ensuring you understand what is in the car now! Best of luck!