Slant Six Forum
https://slantsix.org/forum/

Leak down test tips please
https://slantsix.org/forum/viewtopic.php?t=50115		 Page 1 of 1
Author:  Hewy [ Thu Oct 18, 2012 9:47 am ]
Post subject:  Leak down test tips please
I have a 1964 D100 with a 225.
When I got it I had to replace the cracked exhaust manifold and
drain out some very dirty oil. After reassembly with new gaskets I replaced the oil with a straight 30 and a quart of MM. Smoked very badly for several starts and warm ups.
Drained that out and added new filter and 10-30 oil, now less smoke but is now the telltale blue color. Valves were adjusted hot .10 and .20
Timing by vacuum gauge and timing marks steady about 2 + % btdc.
When idle the engine produces a slight amount of smoke, but revving up 1k
RPM or so the fumigation begins and neighbors start coughing. :(
Rings vales or both.
Want to find verify source before disassembly.
Never performed a leak down test before and don't have tools, but a
compression tester. Compression is low about 95 psi one at 100.
????? Help
Author:  CNC-Dude [ Thu Oct 18, 2012 10:42 am ]
Post subject: 
On an engine this old with unknown mileage, its rare that this problem is only one or the other...its likely both. It also should give you an indication as to the condition of the rest of the engine parts like the timing chain, rod and main bearings, crankshaft, cam and lifters, etc....So, just be prepared.
Author:  Hewy [ Thu Oct 18, 2012 2:03 pm ]
Post subject: 
Quote:
On an engine this old with unknown mileage, its rare that this problem is only one or the other...its likely both. It also should give you an indication as to the condition of the rest of the engine parts like the timing chain, rod and main bearings, crankshaft, cam and lifters, etc....So, just be prepared.
Ageed, but I want to have an idea if indications point to both then I can plan ahead.
Author:  SlantSixDan [ Thu Oct 18, 2012 2:28 pm ]
Post subject: 
Put a few teaspoons of engine oil in each cylinder thru the spark plug hole, one at a time before you retest its compression. If you see a large jump in compression on that cylinder, the rings are the bigger problem. If not, it's valves. This is "lost motion"; your engine is a tired pony that needs a rebuild. Halfway measures will make you sad, not happy (think you will save some time and money doing only the valves...put a good-sealing nice new head on top of a bottom end teetering on the edge between "worn out" and "whipped"...finish off the bottom end in a hurry).
Author:  slantfin [ Thu Oct 18, 2012 4:50 pm ]
Post subject: 
Having observed various played-out engines, I've found that the ones with bad valves smoke on start-up in the morning and then smoke less. Bad rings smoke more when you increase RPM, and usually cause a rough idle. If you want to keep this engine, plan on doing both rings and valves, with cylinder bore and deck plane. While you're at it why not add a cam and plane the head to increase compression? It's only money. :|
Or you could go to the Mopar forums and get a lower-mileage engine from someone swapping in a V8.
Then again, you might run it with some detergents for a couple of months, change the oil, and have it miracle itself back to life; it's a slant!
Author:  SlantSixDan [ Thu Oct 18, 2012 5:27 pm ]
Post subject: 
If you're going for broke, use soup.
Author:  Hewy [ Thu Oct 18, 2012 7:16 pm ]
Post subject: 
Ya I know just rebuild the whole thing, easier for some to say.
All I wanted to do is verify the source of the leak, rather than look in the rear view mirror to what fog is laid down :( :lol:
Missed a point in my description. When I first got the truck it did not smoke.
Author:  WagonsRcool [ Fri Oct 19, 2012 5:24 pm ]
Post subject: 
Well, there isn't any definitive means to determine cause of oil smoking without disassembly & inspection. (Oil can get into the cylinders via the pcv system- ie - missing valve cover baffle, but that's pretty rare). You can "look" for missing or damaged valve stem seals, but you need to take things apart to check for worn stems & guides. Unless you're at high altitude- or timing chain is very worn/loose- then compression pressures are low. Do Dan's test with oil to see if it improves. If it does- low comp + oil smoke = worn rings (& likely worn bores). Something (MM?) hastened the onset of (obvious) oil smoking.

You may not like to hear everyones' opinion- "just" rebuild it, but that's the LIKELY the best way to correct your problem.

A leakdown tester ($60-100+ on Amazon) can QUANTIFY how well a cylinder seals (or doesn't) & where it's leaking. One thing is that you can have worn or stuck/carboned up oil control rings while having good comp-leakdown numbers. The eng can run well but use lots of oil (it sounds like you have more problems than that.)
Author:  Hewy [ Fri Oct 19, 2012 9:52 pm ]
Post subject: 
MM is Marvel Mystery Oil, one of the ingredients is Dan's soup.
The fact that the engine did not smoke before I changed the oil, leads me
question dislodging gunk maybe in the oil ring,
or could it possibly have excessive valve stem clearance.
Author:  WagonsRcool [ Sat Oct 20, 2012 8:56 pm ]
Post subject: 
The only idea that comes to mind is if "cleaning" the engine might have improved oil flow/splash inside- which now overwhelms worn oil control parts. Or maybe there was a "magic- goo" buildup of varnish/sludge on the cylinder walls & rings- & the MM stripped that away.

Point is, the only "cheap" repair to attempt is (on the car) valve stem seal replacement- I certainly wouldn't hold my breath that this would help your engine at all. By the same token, pulling the head for a rebuild alone probably won't fix it either. The wet-dry compression test (& leakdown test) are likely going to confirm that you'll need rings/ overbore/ bearings etc.

Let me know if you get a leakdown tester (you need a decent air compressor & tank as well)
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/