CALLING ENGINE GUYS/GALS

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CFD244

CFD244

"THE NEW OLDSMOBILES ARE IN EARLY THIS YEAR"
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Hi Folks

Started looking at the matching 340 that came with my '71 Demon (stock bore on a stand). Seller told me that it was freshened up but never ran. For ***** and Giggles I decided to do a leak down check on it. Yikes......I was at 70% leakdown with most of the pressure escaping into the block, with a little escaping out of the intake ports.

The test was done with the respective pistons at TDC and the push rods removed.

I pulled a head expecting to see total ****, but everything looked pretty good. The pistons and cylinders were cleaned up nice(ridge removed and de-glazed with cross hatch pattern). As well, the heads looked like they were freshened as well (clean combustion chambers, decent looking seats, knurled guides, and new seals).

So I guess my question is......Are my numbers indicative of what to expect after the engine is run for a bit, or does running it seat everything together. I assume that if the seller pulled it apart, new rigs would have went in, but you know what assuming gets you........

What are your thoughts folks???

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70% is bad. What are the last 2 pictures? I don't see knurled guides. You need a good valve job. Cylinders look worn, pistons are already oversized. Did you measure bores or pistons?
 
I see cross hatching in the cylinders so how could they be worn?
 
Pull a piston and measure bore concentricity and taper. Look at the rings closely. They may have the wrong size (too low of tension) rings in it. Are those rust pits in the cylinder wall?
 
So if it measured out all right and they honed it and installed new rings and never ran the engine the rings aren't seated, correct? You might ask him what "freshened up" means...
 
Looking up into the valve guide, you can see the (and feel) the knurling. There are no pits on the cylinder walls. I just noticed the "OS". I haven't measured the cyls yet. When I didn't see a number (.030, .020) I assumed that they were factory bore.
 
str12-340 said:
So if it measured out all right and they honed it and installed new rings and never ran the engine the rings aren't seated, correct? You might ask him what "freshened up" means...
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Seller is long gone.......I am planning on tearing it down before installing it. Correct, the engine has never been run so you are right they are not seated. I was wondering if the "unseated" condition would account for the crappy leakdown readings.
 
CFD244 said:
Seller is long gone.......I am planning on tearing it down before installing it. Correct, the engine has never been run so you are right they are not seated. I was wondering if the "unseated" condition would account for the crappy leakdown readings.
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It obviously has been less than run from the pics.

The re-vamp barely cross scratch's the up and downs from previous piston movement! IMO it was a quick ball hone and sale!
 
CFD244 said:
I was wondering if the "unseated" condition would account for the crappy leakdown readings.
Click to expand...

I couldn't say how much. but sure - that's the whole point of engine break in and why if the rings don't conform to the cylinders in break in you end up pulling it all apart and fixing it. But if this can account for all the leak down is another question. I personally would be leery of a re-ring job that didn't clean the pistons any better than what I see on the piston domes. Considering it's an an original block for your car, I wouldn't chance it.
 
CFD244 said:
Seller is long gone.......I am planning on tearing it down before installing it. Correct, the engine has never been run so you are right they are not seated. I was wondering if the "unseated" condition would account for the crappy leakdown readings.
Click to expand...
Nope. Bores look like rusted poop honed in the hopes of a dingleberry revival, valve seats wide as the Grand Canyon, piston crowns fairly crater-pitted, I haven't pulled out the Sunnen roller knurlers to "save" a guide in 25 yrs. Too many real guide restoration choices to excuse that these days.
Choice #1) drop it in, hook it up, light it, say it magically seals & You get lucky.
Choice #2) take it to a trusted shop & have it done right.
Choice #3) enjoy choices 1&2 and spend more quality time with Your ride.
 
I'm with taking it in for a proper rebuild. I see too oversights in the "cleaning" and other general details that make me suspicious of what else is lurking in there. I know when the person I take stuff to cleans blocks and heads, they probably look better than they did when they were in the factory. Bake cleaning and steel shot blasting.
 
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My 408 had some noticeable blowby when I first fired it up. It was all fine within the first few test drives.
Rings take time to seat and seal properly. Almost like they have to break in.....

I wouldn't be too worried about it. But I would tear it down and inspect it just for peace of mind and knowing what you've got.
 
pitted cylinder and cross hatch........dingleberry hone with pistons in. could be the picture but the cross hatch does'nt look like it goes all the way to the piston in the second pic of the cylinder IMO.
 
70* scares me. Pull the pistons and mike the cylinders. Measure ring gap and pistons. Check crank.
 
Killer6 said:
Nope. Bores look like rusted poop honed in the hopes of a dingleberry revival, valve seats wide as the Grand Canyon, piston crowns fairly crater-pitted, I haven't pulled out the Sunnen roller knurlers to "save" a guide in 25 yrs. Too many real guide restoration choices to excuse that these days.
Choice #1) drop it in, hook it up, light it, say it magically seals & You get lucky.
Choice #2) take it to a trusted shop & have it done right.
Choice #3) enjoy choices 1&2 and spend more quality time with Your ride.
Click to expand...
The hone work looks poor to me. Even with just doing a rering, there's nothing like having a machine shop hone the bores for you. I've honed plenty of blocks in my time and you can't beat a machine shop honing job. If it's something that you are just re ringing till you have a complete rebuild then a garage style hone will work
 
A lot of inexperienced BS answers in this thread. How in the WORLD can you measure leak down when the rings have never been broken in? They can't produce a proper seal unless the engine has been run in and the rings broken in. It's absolutely hilarious anyone would think the rings could even be sealing at all. Of course it has 70% leak down. Get it running, break the rings in and it will probably be just fine.
 
Fix it right so you can enjoy cruising instead of working in it.

Prior
Preperation
Prevents
Piss
Poor
Performance
 
Treblig said:
I see cross hatching in the cylinders so how could they be worn?
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If you look at picture #5 it appears the hone did not clean up the cylinder. The typical max wear when the rings "rock" on compression to power stroke.
 
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I’d go forwards on rebuilding it. .020 over maybe.
 
Garrett Ellison said:
I'm with taking it in for a proper rebuild. I see too oversights in the "cleaning" and other general details that make me suspicious of what else is lurking in there. I know when the person I take stuff to cleans blocks and heads, they probably look better than they did when they were in the factory. Bake cleaning and steel shot blasting.
Click to expand...

70% is all I need to see. Either take on the project yourself or find a reputable shop (I wish you luck) and get back to square one. IMO trying to fire this off is a waste of time and if you think that leakdown is a problem imagine a major clearance issue with the Crankshaft and really making a mess.....

On the bright side you have the numbers matching motor to the car which is a big deal to some....

JW
 
Guys, what would you expect a engine that hasn't been ran after an overhaul to leak down? I don't think a leak down test would have any relevance to it's health at this point.
 
justinp61 said:
Guys, what would you expect a engine that hasn't been ran after an overhaul to leak down? I don't think a leak down test would have any relevance to it's health at this point.
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Exactly.
 
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