Blowing Oil After Top End Rebuild

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C J Murray
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Re: Blowing Oil After Top End Rebuild

#76 Post by C J Murray » Fri Dec 28, 2018 1:54 pm

Zero leakdown is impressive.
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Re: Blowing Oil After Top End Rebuild

#77 Post by Craig Richter » Fri Dec 28, 2018 3:08 pm

Rusty, The 130 mains sound OK, but the 55 idle jets may be a bit weak. A/C jets? But this is fine tuning, not likely to be causing the main problems you're describing.
"Zero leak-down" is more than impressive....never seen with the old equipment I used. Best of luck, you'll find it .
 

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Ron LaDow
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Re: Blowing Oil After Top End Rebuild

#78 Post by Ron LaDow » Sat Dec 29, 2018 12:28 am

OK, I'll put on my black hat here.
There are no IC cylinder/piston/ring combos which yield 0% leak-down. None. Not possible. And I'm not gonna defend that statement with data and cites; suffice to say, it is an unobtainable ideal under the best possible/imaginable engine design, which does not include 616 engines.
If you get numbers which are not within the physical limits of the parts, you need to look at what might have given you faulty data.
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Vic Skirmants
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Re: Blowing Oil After Top End Rebuild

#79 Post by Vic Skirmants » Sat Dec 29, 2018 8:37 am

Ron LaDow wrote:OK, I'll put on my black hat here.
There are no IC cylinder/piston/ring combos which yield 0% leak-down. None. Not possible. And I'm not gonna defend that statement with data and cites; suffice to say, it is an unobtainable ideal under the best possible/imaginable engine design, which does not include 616 engines.
If you get numbers which are not within the physical limits of the parts, you need to look at what might have given you faulty data.
I totally agree that 0% leak-down is impossible. Best I have ever seen is 2%; that's 98 with 100 psi input.

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Re: Blowing Oil After Top End Rebuild

#80 Post by Rusty Ferrell » Sat Dec 29, 2018 11:49 am

Why is it that I don't disagree with Ron or Vic. Best I've had on a rebuild has been 3% out of the gate. I've used total seal rings in the past but don't recall ever doing a leakdown. The rings installed has a gapless 2nd ring. Others as the first set.
I ran the car this morning and running about 70 for 10 to 15 minutes, I smelled burned oil.
Brought it to the shop and pulled number 2 plug, it's easy and I'm old. Plug looks normal burn, but a little darker up the ceramic. I did increase main jet to 140 and idle to 60.
Did another leakdown on number 2. Same result as yesterday, ~0% leakage.
leakdown #2.jpg
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Re: Blowing Oil After Top End Rebuild

#81 Post by Rusty Ferrell » Sat Dec 29, 2018 12:35 pm

Compression pressure on #2 on a warm engine read just under 150psi. 140 yesterday on a cold engine.
Prior to reassemble as Greg stated, The ring gap was checked and set as per spec, cylinders were checked for taper and roundness, Heads pulled apart and spring installed length was checked as was the running clearance between stem and guide. Haven't found anything out of spec.
The engine runs strong with no ill effects under varying throttle positions and load, no smoke and no leaks. All that changes a steady state running on the interstate at constant 70mph after about 15 minutes.
Next checks: take my infared reader with me the next trip out and check exhaust temp when she acts up. Also considering removing the muffler and installing a Sebring type extractor.
I bought an engine dyno last year, but find it needs a bit of work to get it operational.
Need an Einstein moment as my neighbor just said to me.
Need some left coast help too. Thanks to Cliff and Vic from the eastern half.
Common Denominators?
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C J Murray
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Re: Blowing Oil After Top End Rebuild

#82 Post by C J Murray » Sat Dec 29, 2018 1:00 pm

150psi is starting to get up there a little. If you don't come up with a better idea you could pour in some octane booster and see if the highway problem goes away.
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Re: Blowing Oil After Top End Rebuild

#83 Post by Rusty Ferrell » Sat Dec 29, 2018 2:40 pm

Thanks Cliff. Will let you know how it works out.
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Re: Blowing Oil After Top End Rebuild

#84 Post by Rusty Ferrell » Mon Jan 07, 2019 5:28 pm

This baby is kicking my Ass and it's not getting a a virgin.
Drove the car fairly hard yesterday, Coke can wired to the breather. No event, Coke can had a little coke in the bottom but no oil. After checking the coke can wired it back up and took it for an interstate run at 70mph, about 7 miles out I got a smell of oil. Continued running to a return exit and continued at 70. Got smoke coming from the back of car, got back to the shop and the Coke can was full of oil. I theorized what happens is the oil is building up in the vent to the breather until the crankcase pressure can overcome the oil resistance then pushes the oil out of the breather (about 1/2 qt) in one instance then back to normal. It's like the engine breather is choked off the clears itself. Will go on a chassis dyno on Friday. Making a water manometer for crankcase press and wide band. Will put the original jets back in the Zeniths prior to run.
Also put a Wilhoit recurved distributor on it last Friday. Max advance is 36 degrees.
Anyone out there run into this kind of issue? Also, had anyone have any specifications or procedures for checking blowby, what is excessive. What's normal?
It is starting to look like a pretty interesting New Year. Appreciate any comments. Just think of it as a Bring A Trailer comment section. I won't be offended.
Thanks
Rusty

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Re: Blowing Oil After Top End Rebuild

#85 Post by Matthew Devereux » Mon Jan 07, 2019 5:48 pm

Blowby should be diagnosed with a leak down test which you have done. Although there was some debate on the numbers it doesn't sound like the engine has issues unless you are using one of those momentary type testers that doesn't apply air continuously but it didn't look like you had that type. If leak down is bad you should hear the compressed air moving past the rings. You can usually hear it at the oil filler lid. I can't come up with a scenario where an engine passes a leak down test yet still has serious blowby in operation. Is there any vapor flow through the oil canister at idle when hot? Can you post a pic of your breather set-up? The only other thing I can suggest is to check the exhaust valve guides. With excessive clearance you perhaps you could get some combustion gases back into the engine especially under long duration high rpm runs. Again, you should have seen issues on the leak down if this was the case.
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C J Murray
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Re: Blowing Oil After Top End Rebuild

#86 Post by C J Murray » Mon Jan 07, 2019 6:47 pm

The breather function will not change. It has a certain capacity and will only fail once the capacity is exceeded. The problem is happening when the engine conditions change. It only happens on the highway. 70mph is not much rpm but the rpm is continuous. Usually a healthy engine only has breathing problems when overfilled with oil(almost always), or at very high rpm(maybe), or when the displacement is substantially enlarged(maybe), or when it is detonating(always). Worn out engines overwhelm the breather continuously whereas detonating engines only overwhelm the breather when they detonate.
Last edited by C J Murray on Mon Jan 07, 2019 7:38 pm, edited 1 time in total.
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Re: Blowing Oil After Top End Rebuild

#87 Post by Alan Hall » Mon Jan 07, 2019 7:07 pm

Try pressurizing the cylinder directly with 100 psi air thru the spark plug hole, with the valves closed (using an "air hold" type fitting, or perhaps the fitting that comes with the leak down tester). Listen for air escaping thru the breather, or the carbs or the exhaust. Somehow I think you are being fooled by the leakdown tester which may be plugged somehow between the gage and the cylinder.

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Re: Blowing Oil After Top End Rebuild

#88 Post by Greg Carter » Mon Jan 07, 2019 10:15 pm

Mr. Murray,

Is it possible the engine is detonating under load due to the carbs being too small?

The engine is a 1720cc with an RO 200.5 cam (similar to an SC cam). It also has 9.2:1 compression but I am running Zenith carbs with 28mm venturis and one size larger main and idle jets to fix a slightly lean condition.

I know it's a shot in the dark but thought I'd throw it out there.

Greg

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Re: Blowing Oil After Top End Rebuild

#89 Post by Ron LaDow » Mon Jan 07, 2019 10:28 pm

Greg Carter wrote:Mr. Murray,
Is it possible the engine is detonating under load due to the carbs being too small?
Greg
Greg,
A smaller carb is going to admit less air/mixture, lessening the chance of detonation. And if detonation was a problem, the result would not be intermittent.
I repeat, time to quit guessing:
https://www.yellowpages.com/norfolk-va/dyno-tuning
30, count 'em 30 dyno facilities around Norfolk, VA.
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Re: Blowing Oil After Top End Rebuild

#90 Post by Greg Carter » Mon Jan 07, 2019 11:11 pm

Mr. LaDow,

We’re putting it on a dyno Friday.

Greg

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