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| Compression loss in 4 of the 6... https://www.slantsix.org/forum/viewtopic.php?t=65075 |
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| Author: | Joshie225 [ Mon Jul 06, 2020 9:40 am ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Have you checked the valve lash? |
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| Author: | nitro_rat [ Mon Jul 06, 2020 12:41 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Can we have a pic under the hood? Also one with the valve cover off if possible... Beautiful car BTW! I'm thinking pull, carefully clean without stripping the original paint. Check bottom end and likely reassemble with original bearings. Lightly hone the cylinders and fresh rings on original pistons. Reseal with a NOS steel shim head gasket. Should be good as new and still look original. If you just send the head out it will come back bare. I would clean and disassemble the head myself being careful to put all reusable components back in their original position. Have a discussion with the machinist and tell them not to hot tank it and that you'll clean it you're when they're done with the machine work. I would refurbish the original oil pump and replace the timing set at this time. Maybe a fresh water pump too. That's just me, I would rather see a 80k mile original car looking original than with a "rebuilt" and repainted engine... |
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| Author: | Dart270 [ Mon Jul 06, 2020 12:48 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Yes, you need to check valve lash before you do anything else, as Josh said. The super quick and dirty would be to pull the valve cover and turn each valve adjustment screw 1/2 turn and try to start it, if you don't want to measure a thing. If it starts, you will need to do a full valve adjustment, which is not hard. Lou |
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| Author: | SlantSixDan [ Mon Jul 06, 2020 1:46 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
That is: turn each lash adjuster counterclockwise half a turn and see if anything changes. If so, do a proper valve adjustment, pay attention to the tune-up parts and technique suggestions in this post, and be happily on your way. It may turn out you do need major engine work, in which case you're on the right track as far as the cylinder head goes (hardened exhaust seats, good guides, etc). Putting a nice, good-sealing head atop an old bottom end is a sure-fire recipe for an oil burner de luxe, so you're also on the right track pulling and going through the whole engine. This will involve the usual thorough cleaning (inside and out—there's probably quite a bit of rust and mud in the coolant passages) and extensive careful measurement to determine what-all is needed to bring it up to snuff, so ignore bad advice to just blindly reuse the original bearings and otherwise like that. Likewise, failure to hot-tank the head and the upper valvetrain components would be foolhardy. There is also no good reason to go chasing all over for a NOS shim steel head gasket—the current production composite types make it easier to get a good block-to-head seal for everything (combustion, oil, coolant), and if you wish to compensate for the minor increase in gasket thickness you can have the head and/or block surface skimmed. New timing chain and sprockets, yes, and you might want to take the opportunity to put in a № 2106R camshaft from Oregon Cam—that's the Dutra RV-10RDP, which breathes much better than the '63 stock cam for peppier performance and better economy while keeping smooth idle and driveability. Will the oil pump want refurbishing? Maybe or not; this is another area to measure, not blindly assume. Either way, though, it will be a good idea to service the oil pressure relief valve to make sure it's doing its job, as described in these two threads: thread 1, thread 2. It's your choice whether and how to paint the engine once it's all put back together. International-Harvester Red is an excellent match for the original color on a 1963 225; the Mopar red engine paint is not. There's any number of other ancillaries to pay attention to—if you still have the original bolt-together fuel pump, it's a fine idea to put a rebuild kit in it; those come from Then & Now Automotive. If you want or need a water pump, shop carefully because there's a lot of junk on the market, etc. One way or another you ought to be able to win the fight with that Stromberg carburetor unless it has been horribly abused; it's a very well-designed unit. Because it's a one-year-only item, rebuild kits are difficult to find, but not impossible; it's a kit № 233 from thecarburetorshop.com. |
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| Author: | GregCon [ Mon Jul 06, 2020 2:05 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
If your valves are out of adjustment, they're probably out because the valves are sinking. You can adjust them and it'll last a while. Then, it'll come back. |
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| Author: | plymouthcranbrook [ Mon Jul 06, 2020 8:55 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Are not the slant sixes of that era like most other Mopar engines and already have hardened valve seats? |
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| Author: | Joshie225 [ Mon Jul 06, 2020 9:52 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Quote: Are not the slant sixes of that era like most other Mopar engines and already have hardened valve seats?
Not the regular passenger car engine in 1963, no. The higher spec truck engines may have. The induction hardened seats came later.
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| Author: | SlantSixDan [ Mon Jul 06, 2020 11:16 pm ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
Quote: Are not the slant sixes of that era like most other Mopar engines and already have hardened valve seats?
The first year for hard exhaust seats from the factory on any Mopar roadgoing motor (car, truck, van, school bus…) was 1972, in V8s. Slant-6s got them the next year, in 1973. These were not separate seats, but just local induction hardening of the exhaust valve seat area to a depth of approximately 0.045".There might have been a few earlier low-volume exceptions for special-service engines (running on propane, for example), but no, a '63 225 does not have hardened exhaust valve seats. |
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| Author: | GregCon [ Tue Jul 07, 2020 5:47 am ] |
| Post subject: | Re: Compression loss in 4 of the 6... |
I doubt any engines of the 60's had hardened seats, again discounting some 'fringe' applications. The valves on my '68 225 were sunk plenty when I bought it. |
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| Author: | Matriks [ Sat Aug 29, 2020 1:36 am ] | |||
| Post subject: | Re: Compression loss in 4 of the 6... | |||
Is it ok when I follow up in this thread with my problem too? As said, I also have troubles with the compression on my /6... I was at a garage in my town, they made the measurements in the first pic. They also did a pressure test and said the pressure at no.6 goes out by the exhaust. I checked / adjusted the valve lash, tested the compression again (with another tester by myself), now i got the facts as shown in the second pic. Measurements in bar, not psi. 7 bar is around 100 psi. As you can see, no one is really that great. Number 6 is almost dead. What are your thoughts on this one? Burned valve seats? Bent valve on no. 6? PS: The idle rpm of the motor is noticeable higher since i adjusted the valves. I think I will now remove the cylinder head and see what I got.
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