Breaking in New Engine, Leaks...crankcase pressure? |
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Breaking in New Engine, Leaks...crankcase pressure? |
BeatNavy |
Sep 6 2019, 03:06 PM
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#1
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
The last week or so I've been breaking in a new engine I built last winter and finally manage to install a couple of weeks ago. I'm pretty happy with how it pulls, and after a LOT of fiddling with the MPS and timing I think I've got it where it will start right up, idle cold (barely), idle nicely when warm, and run with nice cool head temps. I do seem to have a slight bit of ping/detonation under load around 2800 to 3000 RPM, so I guess I need to play with timing a bit more.
I am much less happy with the oil leaks. I know building a leak-free Type IV is a challenge, and given this is my first effort, I didn't expect perfection. But right now it's leaking pretty badly in a couple of places: out of the transmission weep hole (probably RMS, I guess), somewhere around oil filter console and/or pressure relief valve, and, surprisingly, what seems to be sort of spraying out and around oil filler neck. Here I need help from the World; I see a combination of three possible causes for this many leaks (when I otherwise took my time and tried to follow guidelines, using Jake's recommended sealants): 1. My own inexperience 2. Too much crankcase pressure from rings not seating yet 3. Too much crankcase pressure from no head venting. Here are some details on build: 2056 with 9950 Cam using D-Jet Brand new AA Heads built by HAM, and Len sealed up the vents 96mm KB Pistons with Hastings Rings 8.6 CR A couple of notes: I didn't gap the rings per Jake's philosophy that crankcase pressure is what causes oil leaks, and the rings come properly gapped. Also, Len (and Jake) don't like head venting for oil flow (so my heads had vent plugged). If I understand him correctly, Len told me the stock PCV vale should provide enough crankcase pressure relief on a street car. RMS is the Sabo brand (the "good" one). Any thoughts on 1, 2 or 3 above? I'm willing to pull the engine and reseal, but I wanted to see if 2 or 3 are possibilities that I need to address. Is the stock PCV valve (which I am sure is not clogged) enough pressure relief? Thanks for any help. |
Superhawk996 |
Sep 6 2019, 03:17 PM
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#2
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914 Guru Group: Members Posts: 5,824 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Sounds an awful lot like too much crank case pressure. How many miles are on it? Even if only a few miles, I've never seen that much crank pressure even before break in to have oil coming out the fill neck / breather assembly.
When you say you didn't gap the rings, I'm assuming you mean ring end gaps. Do you at least know what the end gaps were when you built it? Likewise, did you stagger the ring gaps between top, middle, and oil scraper rings? If all of those ring gaps are lined up, that could be a source of too much blow by. Likewise you could potentially do a leakdown test and see if you have cylinders that aren't sealed and blowing into the case. |
BeatNavy |
Sep 6 2019, 03:50 PM
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#3
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Certified Professional Scapegoat Group: Members Posts: 2,924 Joined: 26-February 14 From: Easton, MD Member No.: 17,042 Region Association: MidAtlantic Region |
Thanks for the ideas.
How many miles are on it? Even if only a few miles, I've never seen that much crank pressure even before break in to have oil coming out the fill neck / breather assembly. Right now I've got only about 65 miles on it. When you say you didn't gap the rings, I'm assuming you mean ring end gaps. Do you at least know what the end gaps were when you built it? Correct, ring end gaps. I don't have it written down in my notes but I seem to recall gaps being roughly 15 thousandths or thereabouts. I really debated whether to gap them further, but deferred to Jake's philosophy. Likewise, did you stagger the ring gaps between top, middle, and oil scraper rings? If all of those ring gaps are lined up, that could be a source of too much blow by. Yes, definitely tried to stagger the gaps. Likewise you could potentially do a leakdown test and see if you have cylinders that aren't sealed and blowing into the case. Good point. I don't have a leakdown tester, but that may change. |
Superhawk996 |
Sep 6 2019, 04:54 PM
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#4
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914 Guru Group: Members Posts: 5,824 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
0.015 ring end gap is great. Factory manual is 0.014" - 0.022". I definitely wouldn't have gapped them further either. Buy (or make) a leakdown tester. probably your best bet to ID where it is blowing by. By 65 miles you should have enough break in to not be seeing these types of crank pressure issues. On the rear main seal leak. Did you use a new flywheel? I've had issues in the past with the flywheel being worn such that a new seal still can't seal properly due to groove/taper wear in the sealing surface. The other possibility is a cocked installation of RMS or folded seal lip. When you say leaking at the filler neck. Is that at the base of the breather? You do have the case to breather gasket in there right? I'm so sorry you're going through this. Are the head vents welded or plugged? I just bought a set of Len's AA 2.0L heads and they are threaded. if just plugged with a tapped plug, you could pull the plugs, install barbed fittings, route hoses to an EMPI breather and see if the situation improves. However, I would fear that is just a band aid even if it did improve. |
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