40 LaSalle firing order

[csearider]

My Thompson Manual states firing order for 40 LaSalle 322 cu in v8 is 1,8,7,3,6,5,4,2. I assume #1 is front right (closest to radiator)...from there how are they numbered..... consecutively down right side towarf firewall and then down from radiator  (or up from firewall ) on the left side??? or across alternatively? Doing compression check on Sunday and want to verify firing order is set correctly....what is satisfactory compression pressure and I assume they should be within 15% of each other??

[Wayne Womble 12210]

Odd numbers down the left bank 1,3,5,7 starting in the front, and even down the right bank 2,4,6,8

[markl]

Dennis,
Taking up the second part of your question; the compression pressure.  Of course to be meaningful, the engine should be brought to normal operating temperature, so I think you'll know if you got the firing order correct!  And what Wayne is saying plus the firing order you got from the Manual should get you there if any corrections are indicated.  Unfortunately, I can't quote the expected compression pressure, but I would think it could be derived from the compression ratio for the 1940 LaSalle 322 which was 6.25 to 1.  Unfortunately, I've been out of school too long to figure that out!  But that being said, yes I agree that the variance between cylinders is actually the more critical issue, and 15% is fairly generous as I recall a desired maximum as being 10%, but again that is just from a vague recollection.

With the orientation of the valves in the flathead being up-slope from the piston, the method of adding a tablespoon or so of oil and then re-checking should give fairly definitive results.  If the reading goes up appreciably, the problem is rings, if not, then most likely the valves.  Of course w/ the flathead configuration, either one is rather bad news given that you don't get the valves to work on just by removing the heads!

Good luck, and hopefully someone can respond w/ the expected compression pressures either from a Manual, or by computing it.

Mark Lowery, CLC#25216

[markl]

Dennis,
So tomorrow is the day you do the compression check.  Well I think I have figured out how to derive the maximum expected compression gauge reading, but it would still be helpful if someone could reply w/ the figures usually obtained from "real world" readings.  Assuming no losses from an imperfect seal, and ignoring variations in atmospheric pressure, I believe the gauge should read 6.25 x 14.7 (average normal atmospheric pressure at sea level) minus 14.7.  That gives me a final figure of 77 psi.  This would be "gauge" pressure as opposed to absolute pressure (psig vs. psia).  Since the gauge will register zero before the test begins, it isn't reading the pressure we are subjected to on a daily basis.  Hence the subtraction of 14.7 after multiplying the compression ratio times the atmospheric pressure.

All that said, still like to hear from someone who has run compression checks on this or a similar low compression engine.  And once you have completed your test, let us know what sort of readings you get!

Mark Lowery CLC #25216

[Wayne Womble 12210]

Motors manual of the period list it at 155 @ 1000 RPM.   Sounds a little high for that low compression ratio engine, but thats what it says.

[harry s]

I have done compression tests a number of times on these engines and if memory serves the readings are somewhere between 90 and 105 psi with all spark plugs out and engine warmed. The variation between cylinders should not be more than 10%. Let us know what you came up with.  Harry

[csearider]

Sorry for the delay in responding but as it turns out standard compression gauges are 14/18 mm. I had to special order a 10mm adapter of a 322 cu in flathead v-8. Readings were as follows:1) 0 2)70 3) 70 4) 0 5) 70 6) 55 7) 69 60. #1 and #4 completely dead. Diagnosis cracked rings, holes in cylinders or stuck valves or combination of all. However, when engine is running (starts and runs fine) it sounds like there is an exhaust leak around the upper engine left side, but no sign of any leaking exhaust ( (no smoke anywhere even none out of exhaust, burns clean), . Where to go from here?: First I will fill cylinders with Marvel Mystery oil and let sit for a few hours, pump them out and re-do compression check as the noise indicates maybe stuck valves in open position from sitting up for too long (barn find), if that does not work will pull heads and inspect valves for proper functioning, If any improvement in valves in dead cylinders will re-do heads and install new head gaskets and redo compression check. 4) If valves functioning properlly and still have dead cylinders will proceed for complete engine overhaul. I really do not want to replace cam and crank bearings as I just do not think I will be able to find new ones with same structural steel strength as those made in 40's (same for rear wheel bearings as originals were in fine shape 70 years later). How does this sound to you folks??? I am not squeamish for advice as all is welcome as I consider myself to be a member of the original old-car club as my early years were spent driving "clunkers" of the day ('50 Pontiac straight eight sedan was first car and paid $50 for it even though my brother told my Dad $35 as Dad said $50 was too much to spend!

[markl]

Dennis,
I agree w/ your idea of introducing some Marvel Mystery oil and giving it a few days to do its magic if indeed you have stuck valves.  If the valve guides are at all worn (likely) some of the oil will end up in the crankcase.  Probably okay, but just wondering if a major dose might knock loose some of the accumulated sludge.  Most of these engines were not fitted w/ oil filters (is your's?) so anything that comes loose will circulate through the engine, and specifically into the bearings.  So maybe another member can comment on that issue.

I wouldn't let reservations about engine bearings influence your decisions.  Modern bearings are just fine. 

As to the exhaust leak issue, a quick way to find that is w/ the engine warmed up and running at fast idle, pour a fine stream of diesel into the throat of the carb.  Not so much that you kill the engine, but just enough to create some smoke.  If at all possible, before attempting this "not-so-scientific" test, attach a tube or pipe to the exhaust to get the discharge point as far as possible from where you are working.  You might also want to alert your neighbors so they don't think your house is burning down!  If there is a leak in or about the engine proper, you'll see it.

In the dead holes, if you still have low readings after trying to free up the valves, try introducing some heavy weight motor oil (40 wt. straight grade) in each cylinder that is suspect.  Turn the engine over a few times to distribute the oil, and then do the compression test again.  If the reading jumps up considerably, that would indicate a problem w/ the rings.

Mark Lowery, CLC#25216

[csearider]

Thanks Markl.....good advice on Marvel in oil as I have not changed original old crankcase oil just in case I needed to dump pan ....so not to waste fresh oil. I will take special note to not run engine until compression check test is complete and a decision is made