Jump to content

Compression readings for 1929 standard engine


jps
 Share

Recommended Posts

The shop manual says 90 lbs compresion for the standard engine. But I assume that is for a warm engine? I just took readings on a cold engine (because I can't get it started) and got 50 - 60 psi on each cylinder except #3, which was only 40 psi. Adding a little oil brought it up to 45 psi. Do these numbers sound about right for a cold engine?

Thanks.

Link to comment
Share on other sites

That's a fairly significant variance between the #3 cylinder and the rest, I know for modern engines you normally want less than 10% difference across all the cylinders - if adding oil is bringing up the the PSI that would tend to suggest something is worn in #3

Link to comment
Share on other sites

Traditionally, if adding oil ups the compression, rings are the problem. If not, then it is valves.

However, getting the engine running may well improve things.

Even at that low compression, if carburation and ignetion, the engine should start and run.

Link to comment
Share on other sites

I am using SAE 30 weight in the engine, and for the drops I added to cylinder #3 during the compression test I used either SAE30 or 10W-30 (not certain which one is currently in my oil can.)

I guess at this point I am most interested in figuring out why the car won't start. It sounds like I have sufficient compression for starting (but maybe not for good power while running). I already verified spark at each plug, so I think that leaves carburetion as the only potential problem left. I know that I am getting gas to the carb because it floods after several starting attempts. So I am guessing that fuel isn't getting past the carb (plugs don't seem very wet when I remove them after flooding.)

Thanks for all the comments so far.

Link to comment
Share on other sites

Mark,

You are right, but what is weird is that the car was running OK one day, and then a few days later when I tried to start again it wouldn't do so. And I did nothing to the car in between. After several more days of attempting to start w/o success, I replaced wires and plugs, and then checked spark, but no improvement. Before replacing these electrical items I tried drying off the original plugs and that is when I noticed that they did not seem very wet considering that the carb was flooded. I am 100% positive that the new wires were routed the same as the original ones. The original wires were very bad.

Maybe the original timing was off and just barely allowed the car to start. A mechanic checked the timing before I bought the car in May. Could it change that much in 4 months? I do adjust the timing between retard & advance via the steering wheel adjustment on each start - could that screw up the timing after awhile so that it needs re-adjustment?

Thanks for your help.

Link to comment
Share on other sites

John,

I suggest you crank or bump the engine to get #1 at top dead center (compression stroke with both valves closed). Then, just take a look at the rotor on the distributor to see if it is pointing to #1 wire to verify it is close. Then look for the timing mark on the flywheel to see how far advanced or retarded it is & adjust according to the manual.

You do have a manual don't you?

Link to comment
Share on other sites

A few people have told me that a common problem is to have rust holes in the riser tube. I knew this would effect running performance but wasn't sure if it would prevent the car from starting or not. But if Don had that happen to him, then that answers my question.

I am trying to get replacement parts for the heat riser but so far no luck. However, the bolts for the heat riser to the manifold are very rusted and I am not sure I can get them loose without breaking something, so I may need an entire assembly.

I do have the manuals and am working through things as I am able.

Link to comment
Share on other sites

The first time i had this happen was on my '31-67 . The riser casting was a real mess and I ended up having to machine the tube remains out and making custom tubes to put back in!

Strangely, when it happened on my. '32-56, it was a piece of cake. Good luck!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...