Possible damaged exhaust valves? on 258

[Tony and Nicki]

Hi guys,

It’s been a while since I made my last post concerning the ‘77 jeep engine that I installed in our ‘80 Concord. Anyway here are the facts:

1) Bought the jeep engine which was seen/heard running while parked. Engine sounded good, no smoke no knocks etc. Ran for about 15 minutes or more (in park). Did not make any checks (vacuum or compression)

2) During swap accidentally tipped jeep donor engine upside down while in engine stand and full of 5 qts of oil

3) Installed into Concord using carb, intake and distributor from concord which was previously running well with 18Hg” in P (@ 2,500ft above sea level) and steady until it overheated and threw a rod.

4) Concord only had exhaust system from manifold to cat.

5) Cat was then gutted and still only had exhaust system from manifold to cat.

6) Started up jeep donor engine now installed in concord. Ran very rough. 10 minutes after starting was smoking really really badly.

7) Tried severel attempts to correct timing and fuel mix etc. to no avail

Vacuum flickering rapidly between 12"Hg and 13"Hg at 600rpms in D (@ 2,500ft above sea level)

9) Compression:

                    1      2      3      4     5      6
Test #1 Dry   150   150   150   150   90   30
Test #2 Dry   150   150   150   151   0   60   
Test #3 Wet   150   150   150   160   30   0
                                 
10) No leak down test performed (don’t have compressor or leak down tester at this time)

11) Block test tested negative for presence of combustion gasses.

12) Pulling spark cables from #5 or #6 sparks makes no difference to how the engine runs even though spark is present to both plugs.

13) Engine does not overheat even @ 100+* ambient temps

14) There is no evidence of coolant in the oil or vice versa

15) Now has complete exhaust system = No change.

So there you have it. What are your conclusions? Here is mine:

I have cracked or burned exhaust valves on 5 and 6 possibly caused by running the engine with an incomplete exhaust system (with the now gutted cat) and therefore creating low/no back pressure causing the exhaust valves to run too cold. The smoking could either be due to the spilt oil and/or the bad exhaust valves although it has not improved from approx 5 hours of running.

Either that or a head gasket leak between cylinders 5 and 6 but since there was no combustion gasses detected I ruled that out.

Anyway either way I reckon I need to pull the cylinder head and have a look.At which point I could just replace the damaged Exhaust valves, (assuming there is no damage to the pistons) or a complete valve job. I also toyed with the idea of just swapping the head from the concord engine which would be more within my current capabilties and tools and most of all, money.

Any suggestions or help would be greatly appreciated as always.

Cheers!
Tony and Nicki
Tucson AZ

[AMCKen]

What do the plugs look like in 5 and 6? How long was it upside down? Pull the rocker cover and see that the valves on 5 and 6 are working correctly.

[txjeeptx]

May have bent pushrods on 5 and 6? Agree, time to pull the valvecover and have a look.

[Tony and Nicki]

Checking the compression on either 5 or 6 with thespark plug in the other would help eliminate a head gasket leak between them.

Mmmm thanks, I never thought of that

What do the plugs look like in 5 and 6? How long was it upside down? Pull the rocker cover and see that the valves on 5 and 6 are working correctly.

Plugs look OK but I will take a better look and let you know. The engine was upside down for about 10 minutes max. I'll pull the rocker cover and see if the valves are working.

May have bent pushrods on 5 and 6? Agree, time to pull the valvecover and have a look.

Hopefully I'll get a chance to take a look later if not, definitely tomorrow.

Thanks guys. Much appreciated.

tonyandnicki
tucson az

[mudkicker715]

Just remember a motor can and will run a cylinder short. I drove a amc 360 homeon 3 cylinders. After it was bought. Afteri got it I was trying to figure out how it even started.

[Tony and Nicki]

Just remember a motor can and will run a cylinder short. I drove a amc 360 homeon 3 cylinders. After it was bought. Afteri got it I was trying to figure out how it even started.

Actually it runs pretty good considering it's two cylinders short. The main problem is the smoking. There's no way it'll pass emissions not to mention the looks and comments I've had.

cheers!
tony and nicki

[AMCKen]

The smoke is white?

[Tony and Nicki]

The smoke is white?

No. The smoke is grey or some might say it's blue but it's definitely not white which is why I figured it's not a head gasket leak between the cylinder and the water jacket. It's also not overheating and has no signs of oil in the coolant or vice versa.
It only smokes once it's reached about 180* water temp so I'm not sure what that means unless it's a symptom of oil present in the combustion chamber from the oil spill.

Cheers!
tony and nicki

[Tony and Nicki]

May have bent pushrods on 5 and 6? Agree, time to pull the valvecover and have a look.

Yep sure enough. I have a bent pushrod on 6 and a 'disconnected' pushrod on 5.

Unfortunately I will have to lower the cross member to get the valve cover completely off 'cos of interference from the dash panel but I can see well enough to say that that is only damage visible (without taking the cylinder head off) as far as I can tell.

Not sure what would have bent the pushrod but it's been suggested that the valves are sticky from gas varnish 'cos the car sat for 7 months.

If anybody has any ideas please let me know.

Cheers!
tony and nicki

[txjeeptx]

Yup, stuck valves from sitting, probably. You could steal a couple of good pushrods from the old engine and hope that's all there is to it.

[Tony and Nicki]

Yup, stuck valves from sitting, probably. You could steal a couple of good pushrods from the old engine and hope that's all there is to it.

Thanks,

Actually now I think about it, it could have been like that before I installed it. Call it a combination of stupidity/ignorance, not paying attention and wanting to see what I wanted to see but I do recall seeing the bent pushrod and ignoring thinking it.

Anyway If that's the case it occurred to me that since it came out of a jeep that it could have gotten bent from over revving 'cos I know he used it for rock crawling.

In any case, later I will get the valve cover off and use some good rods from the Concord's old engine but I'm not sure the #5 (which didn't get bent) will stay in place. It looks like the push rods are just held in place with pressure from below (you'll have to forgive my ignorance) but what is it that pushes it up The lifter?

Thanks for the input
cheers!
tony and nicki

[txjeeptx]

You're learning a lot about how engines work, something few people know or care to. I agree that the possibility of overrevving might be a source of a bent pushrod.

They're held in place by spring pressure of the valvespring and hydraulic(& some spring) pressure from the lifter. You have to remove the rocker arm to replace a pushrod. Reinstalling the rocker arm is simple, since these engines have hydraulic lifters, you don't have to set the lash in the valvetrain - it is automatically handled by the hydraulic lifter.

If it had a solid lifter cam, which it doesn't, you would have to set the amount of "lash", or free play the valvetrain has in it. You'd have to do that for each valve, so be thankful some enginerd came up with the hydraulic lifter.

[Tony and Nicki]

Awesome thanks!

Well the way I've always worked on cars (which have been my '65 Falcon (my 1st car which I have driven daily for 24 years), '64 Falcon, '75 Mercury Bobcat engine swap, and now '80 Concord engine swap) Is that I only ever learned about what I needed as needed and so far I never needed to get inside the engine but I definitely want and need to learn more about that.

BTW I just had a closer look at the #5 push rod and it is bent but just slightly but probably enough that it wouldn't stay in place.

BTW what is the order from front to back of the valves in terms of intake and Exhaust? Is it IE EI IE EI IE EI.
If it is then my bent pushrods are both corresponding to exhaust valves.

cheers!
tony and nicki

[txjeeptx]

You can tell what valve is what by what manifold runner it lines up with. AMC inlines have exhausts at both ends, so they're EI IE EI IE EI IE.

Exhaust valves get hotter than the intake valves, so they can stick more easily, and are affected more when an engine is overworked, overrevved, or improperly fueled(too lean can heat em way up).

[AMCKen]

...and you shouldn't have to lower the engine to get the cover off. I've done several without lowering. Actually, a Pacer is easier for this than GHSCE cars.