Cylinder #7 down on compression

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Inertia said:
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There is still something funky about cyl #5 difference in appearance.
Maybe scrutinize the head gasket for coolant loss, not sure from here, lol.
Good luck.
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#5 the washed piston dome shows oil is getting past the rings....
 
those look like TRW's or 72~73 stock replacements

they *could* be badger P296's depending on when/if it was rebuilt

i think sealed power also had a similar piston.
 
I'd test #5 ring by moving the piston about 1/2ish way down, or in a position so another piston is about equal distance down, as best possible, then pour equal amounts of clean solvent/varsol/ diesel in each cyl .
Wait. . a coupla hours . It's not uncommon for the liquid to diss-appeared/drain relatively quickly in one, as compared to the other cyl.
Not uncommon for some cylinders to hold fluid overnight.
We do this on every valve grind, test ring seal.
Oil change mandatory. ! !
Cheers
 
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NITROUS.jpg
 
Whatever intake and head gasket issues I might have had will be replaced when the engine goes back together. Other head is coming off since I have it all apart to make sure all is well but will probably get it to a shop to have it looked at. It would be stupid to just fix the problem i know of and not fix future problems while its apart.
 
gtgto said:
Whatever intake and head gasket issues I might have had will be replaced when the engine goes back together. Other head is coming off since I have it all apart to make sure all is well but will probably get it to a shop to have it looked at. It would be stupid to just fix the problem i know of and not fix future problems while its apart.
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Trickflow makes some heads that will go right on there.... just sayin... :)
 
I got carbon off my pistons with seafoam spray and a scotchbrite scrub pad. Granted yours are a bit dirtier..
 
While they may be the 72-73 8.5:1 compression pistons, that doesn’t necessarily mean that’s what your compression will be. Those look like the pistons I have but my compression comes in at 9.0:1.
 
1971 CY Dodge Dart said:
While they may be the 72-73 8.5:1 compression pistons, that doesn’t necessarily mean that’s what your compression will be. Those look like the pistons I have but my compression comes in at 9.0:1.
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Ok, but you have to know how far the piston is down the hole (or how far out of the hole they are), chamber volume and head gasket thickness and bore diameter to know what he has compared to what you have.

At best, as yours appears to be a best case scenario the OP is still a long way away from 10.5:1 no matter what.
 
10.5:1 is way too high anyway.... stay low and run cheap gas! In all seriousness i was honestly curious at what CR can you get away with **** 87 octane?
 
Icetech said:
10.5:1 is way too high anyway.... stay low and run cheap gas! In all seriousness i was honestly curious at what CR can you get away with **** 87 octane?
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I’d keep it below 10:1. Not because that’s all 87 octane will take but because low and mid grade pump fuels are allowed many more fillers and other junk I can’t think of now that premium fuel can’t have.

If anyone wants to know how you can run 12:1 on pump premium they need to study the testing methods for octane rating.

Once that is learned it’s easy to see why needing all that octane isn’t always needed.

The tests have limits or better yet the testing is limited in scope because if it wasn’t it would be difficult to actually determine what the octane rating even means.

We just need to know what the test parameters are and what the limits of the testing shows.
 
James Clews said:
There is one thing for sure! I wouldn't do just one of the heads. Do both while it is down!
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Agree with this

While the other head is off, I strongly suggest you try that wet leak down test, fill all cyls to brim as possible, especially #5, then see which cyls are sealed. It's an inexpensive valid test.
You may be very surprised. ( Diesel is kinda on thick side, stay with solvent/paint thinner viscosity stuff)
The test is a comparison, to find the worst ring seal, and may convince you to go a little further, if #5 drains in an hour, and some of the rest hold fluid waaay longer, or overnight.
Something is funky . That spark plug is telling you a story .
 
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If it was mine, I would overhaul it. Never had a lot of luck myself putting a good top end over worn rings. I will leak down an engine everytime vs a compression test. Plug threads look a little cold, 2 threads? Maybe a little rich too. It's your engine and budget. Now everyone can say how wrong I am!
Best of luck.
 
It was normal to valve grind these things at 60 - 80k, and re-ring at 110k+ ish.
And your right, it's disappointing to put fresh heads on a worn out engine, hence the test.
Come-backs were never wanted
 
So a compression test is not a good test for overall condition of each cylinder? My compression test produced 7 holes of 140 or more and one of 105. With all the plugs out and the block stone cold. I don't consider that worn to the point that I need a complete rebuild. #5 was one at 140 PSI. Maybe I'm wrong but I'm an IT guy and not a mechanic.
 
One person banned for a month. You guys want to make it 2 or 3?
 
I'm just passing on 40 yrs experience working then owning a large auto repair center in our Capital city.
I had an outstanding mentor, and I trained 3 apprentices.
If one of my mechanics showed me that piston, compared to others, I'd want to know why, and certainly warn the customer that something was awry.
I come here to share my knowledge and experience, while "hunting" on a different site .

And miss the juicy stuff from those on ignore, rofl
 
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