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

Greetings,
We noticed on our 1936 Business Coupe 8 cylinder that in two of the cylinders the gap on the spark plugs are completely closed due to making contact with the intake valves. After pulling the plugs we can see the contact points on the valves and plugs.
Any thoughts or suggestions?

Are you using the right plugs? Perhaps they are too long of a reach.

This not too unusual if the head has been heavily milled in the past. If your plugs are correct then the simplest expedient is to use an extra copper washer under each plug to lift them up a bit.

Could be weak valve springs... wrong valves.... thin head... wrong plugs or old plug gaskets.

All sounds logical and like great advice.
I have a shop manual for 1937-38. I assume the 8cyl. would be the same in the 36.
The manual calls for champion Y-4’s, there are currently J-8’s in the engine. I know the numbers pertains to the heat range,
What does the letter refer to?
Thanks

Have used nothing but 10mm AC M8 sparkplugs in my Packards since the late '70s. Luckily for us, they seem to be the right heat range. They're probably still available at NAPA, etc. because so many old Chevy cars and pick ups in Mexico, Latin and South America. They also fit 1936-on Cadillac, '37-on LaSalle, Buicks.

Nearly all the shop manuals are in the Literature Archive here on the website.

J8 is a 14mm plug which tells me you have a later head. No drama, shouldn't be an issue. Had same on my 998...try doubling up in the spark plug washers and see if that resolves??.

To continue the discussion on the 36 business coupe.
We took the push rod covers off today expecting to find a broken spring or keeper missing. But no, everything looks fine.
The valve lash is fine and nothing looks out of place.
We think the problem might be weak valve springs. Is this a common item with Packard flat head 8 engines?

To add to the discussion and give you a bit of history, we completed a compression test on the engine. Cold engine - each cylinder had 70psi with only slight variation between cylinders.
We started the engine and it ran fine for about 4 or 5 minutes then started to be rough and then engine died.
We ran compression test again on hot engine and got 0 for cylinders 2 and 3, all others 70 psi.
Let it cool and run compression test - 70 psi in all.
The intake valves have a very slight shiny spot on them from where they have been contacting the electrode of the spark plug. After correctly gapping each plug and running the engine, we find that the spark plug gap for cylinder 2 and 3 is totally closing. Something is causing the valve to contact the electrode.
Weak springs and valve flutter is our guess.
Your thoughts?

thanks very much,

Bill

Maybe the wrong plug? One that’s too long?