Cold valve clearances - 1930 Marmon 8-79?

[Guest virgilmule]

Does anyone know what the valve clearances are for a 1930 Marmon Model 8-79? I know the HOT clearances are .007 for both inlet and exhaust valves, but would like to know COLD clearances if possible.

Thanks,

Jim

[DWR46]

I realize that setting cold clearances is a lot easier than working with a hot engine, but there are a number of reasons for doing that way. Most engines do not warm up evenly, with certain areas running hotter than other areas, so setting valves cold may not equate to consistent hot clearances throughout the motor. Also intake valves usually change clearance differently from exhausts as the engine warms, due to the hotter environment that the exhausts live in. On my Marmon Sixteen, the manual calls for .008" HOT for all valves. However, the hotter the engine, the greater the clearances (probably due to the aluminum construction). Also the exhaust clearances "grow" more than the intakes as stated above. When cold, my intake clearance is about .005" and the exhaust is about .0035", but they are both .008" at 175 degrees water temp. You can set your valves hot and then recheck them after the engine cools. This should give you a baseline to work from. However, be prepared to possibly find varying clearances from valve to valve.

[W_Higgins]

For most cars of the period, 0.010 intake and 0.012 exhaust is standard when cold. If you're setting-up a new engine, that will get you running and then you can tweak it after it's hot. You can probably go as high as about 0.015 - 0.017 if you're paranoid about burning them, but anything much over that is just going to contribute to it being noisy. Do the final set hot, though. There's a reason the manufacturer specified it that way.

[Guest virgilmule]

Walter -

Thank you. I'll take your advice. Your thoughts about what the manufacturer had in mind make lots of sense.

Jim

[Guest virgilmule]

DWR46 -

Thank you for your insight - especailly regarding the fact that different areas of the engine experience different heat ranges. My plan is to set all clearances at .010" to begin with, then recheck (probably more than once - why get lazy now after coming this far?) and set them at .008" once the beast is up and running again.

What has me spooked is the recommendation in the original "Information Book" (owner's manual) that after each 1,000 miles the valve clearances be adjusted "to .008 inch when hot and running." Hot and RUNNING? I'm not quite sure how that would be possible, but apparently the mechanics in 1930 could do it, so I'm sure I can find someone in this day and age to accomplish it.

I hope...

Jim

[DWR46]

Jim: When I was young and stupid, I used to set clearances with the engine running. As the old Chevrolet inline six called for "hot and running". You can do the valves by this method, but you will beat up a lot of feeler gauges. In my experience, the same practical results are obtained by just getting the engine good and hot (getting the oil hot is more important than just the water, as hot oil signals a more even distribution of heat throughout the motor), and then setting the clearances as rapidly as you can before you loose too much heat. On Vee type engines, many times I will set one bank, put the valve cover back on and warm the engine again before setting the other bank to keep heat in the motor. On the Sixteen, you really need to do this, as the combination of lots of cylinders and alloy construction defintely will change the effective clearance between the first valve you set and the last valve. Normally the first valve has closed up about .001" by the time you finish the last valve, so the last valve is efffectively .001" looser at operating temps.

[Guest virgilmule]

I'm learning (and spending!) a lot! We tried to reinstall the pistons: the rings were the wrong size! My fault: I had taken a spare piston (from a set I had purchased from a gentleman who told me they were from a car like mine) to the machine shop to ensure that the correct ones were ordered. Turns out the "spares" are 1/16" bigger than mine! New rings are being ordered.

Then the learning/expense curve took a huge upswing: babbitt bearings! It appears I need one or two bearings repaired/repoured. Fascinating process - I watched a "Youtube" video of how it is done. The parts are on their way to South Dakota for repairs.

The big picture: better to find/fix these problems now rather than later, because you KNOW that "later" would come at a MOST inconvenient time!

Restoration sure teaches one patience!

Jim

[Rusty_OToole]

So far as I know the last engine requiring valve adjustment when hot is the Dodge slant 6. This is not a problem as solid lifter engines do not throw oil around like a hydraulic lifter and the engine will idle down to where it is barely moving.

If you loosen the jam nuts and retighten barely tight you can adjust the valves easily while running and will not hammer the feeler gauge unless the adjustment is way loose. After doing the adjustment tighten the jam nuts. They do not need to be real tight just snug.

Do the adjustment correctly and the valve train will be dead quiet red hot or stone cold and stay that way for thousands of miles.

The only problem I had was with an engine that had been neglected to the point where the valve gear was loose and hammering. Once the rocker arms and valves get pounded and peened over adjusting will not get them dead quiet again, you will always have a slight rustling sound if you listen close.

Other than that solid lifters are better than hydraulics in every way except of course you have to adjust them once in a while.

[Guest virgilmule]

Thanks, Rusty. You make it sound fairly easy...and not nearly as messy as I pictured it might be. I was imagining hot oil splashing all over everything and everyone.

It will be a couple of weeks before the babbitt bearings are repaired, then I'll be back to work on the car. Maybe I'll get the courage up by then to adjust those valves the RIGHT way!

Jim

[Owen_Dyneto]

I've done my 34 Packard Eight lifters hot and running a few times; though it's hardly something I look forward to, it's not that difficult and made easier by the fact that these long-stroke engines can idle so slowly.

If you wanted to estimate the running temperature of the valves (lot's of info on that) and know the valve stem length, you could take a mathematical approach and find the coefficient of thermal expansion for similar alloys and just calculate the growth in stem length and get to a cold clearance from that calculation.

[Guest virgilmule]

Owen -

Holy cow! You GREATLY overestimate my mathematical ability! I have a better chance of success setting the valve clearances using ESP than doing those calculations!

Nonetheless, I do appreciate the advice!

Jim

[pacerman]

The only suggestion that I have is that if you are going to adjust the valves on a running engine, get a set of long feeler gauges. Joe

[Rusty_OToole]

They make heat proof sleeves for mechanics now. I am thinking about working around a hot exhaust manifold if you dont have asbestos arms lol.

[Guest virgilmule]

I'm still plugging away on my engine repairs! I've had to fix a burned valve, cracked exhaust manifold, seized heat riser, and chipped babbit bearing.

Finally, the pistons have been reinstalled, but I need advice regarding how tight to snug the nuts which hold the connecting rods to the crankshaft.

If I tighten them too much, the engine is VERY difficult to turn, but how loose do I leave them? There is a cotter pin which goes through each bolt, preventing them from ending up in my oil pan, but is there a preferred "looseness" for those nuts?

A friend mentioned that a shim can be used to help, but how thick of a shim do I use? Also, do I use the shim between the two halves of the babbit bearing, or between nut and rod?

Any help SURE would be appreciated!

[DavidAU]

Jim,

I would seriously suggest if you dont know how to check the bearing clearances and crankshaft torque settings that you get someone who has experience at this type of thing to do it for you or show you how to do it.

If you have new poured bearings they will probably require scraping to the correct clearance and that is really a job for an experienced person.

If the crank is not set up correctly it could turn out to be a very expensive problem.

[Guest virgilmule]

David -

Your advice is good. As you probably can tell, I am no mechanic. I have an amateur - albeit very knowledgable - mechanic with over 40 years experience helping with the work. I also rely heavily of the local machinist who has repaired many of the issues I've uncovered since opening up the engine.

My machinist recommended 40# of torque, based on the fact that there are 3/8" bolts holding the rod bearings together. Of course, there's also the issue of those pesky cotter pins, which will necessitate slightly over- or under-tightening the nuts so that the holes line up. His recommendation is to over-tighten if necessary.

I'm unsure about your warning regarding scraping the bearing. The one bearing I had repoured was done professionally to the correct specs. I believe these bearings have an internal oiling system, as there is a tiny hole in the upper half of the bearing leading up into the rod.

So, I'm FAIRLY confident that I'm not about to damage the crank - although as you say, if I'm wrong I have a huge expense awaiting me.

I appreciate your help. I will continue posting as the job continues to update you (and everyone else) on my progress.

Wish me luck!

Jim

[Ben Bruce aka First Born]

DO NOT leave the connecting rod bolts loose! Your friend has good advise. Shims between the connecting rod and the connecting rod cap. They should be availsble in several thicknesses starting at about .001. Then torque the bolts/nuts. 40 pounds sounds about right.

[Guest Backyardmechanic]

David -

Your advice is good. As you probably can tell, I am no mechanic. I have an amateur - albeit very knowledgable - mechanic with over 40 years experience helping with the work. I also rely heavily of the local machinist who has repaired many of the issues I've uncovered since opening up the engine.

My machinist recommended 40# of torque, based on the fact that there are 3/8" bolts holding the rod bearings together. Of course, there's also the issue of those pesky cotter pins, which will necessitate slightly over- or under-tightening the nuts so that the holes line up. His recommendation is to over-tighten if necessary.

I'm unsure about your warning regarding scraping the bearing. The one bearing I had repoured was done professionally to the correct specs. I believe these bearings have an internal oiling system, as there is a tiny hole in the upper half of the bearing leading up into the rod.

So, I'm FAIRLY confident that I'm not about to damage the crank - although as you say, if I'm wrong I have a huge expense awaiting me.

I appreciate your help. I will continue posting as the job continues to update you (and everyone else) on my progress.

Wish me luck!

Jim

Jim,

If the crankshaft was even .001 out of round when you install the repair rods uyou will have a tight rods on the crankshaft when the high spot comes up on the rtod jonual.

This Why one should remove the crank and have it true up before one temps to repair.

Vern

[Guest]

The proper way to tighten your connectiong rods is to use plastiguage to get the correct clearance and then if the nuts don't line up for the cotter pins you file the nut (bearing surface) until the correct torque has the pin and nut line up. At least this is the way Packard mechanics were taught to do it.