Need some opinions on where to go from here...

[mshred]

I had to open and clearance mine quite a bit, and all I had were Hughes rockers and a shim. But that doesn't address the #4 issue unless the push rod bent.

Yea, I clearance mine to what I thought was enough but clearly it could have gone more. The valvetrain always seemed to move okay with the engine on the stand, but I guess it can't hurt to pull the rockers and check the pushrods.

Not sure if I should just pull the heads and start there with inspecting pushrods, cam lobes, lifters, and head gaskets along with the valves...or if my plan of attack should be something else to check before starting to disassemble it. My compression numbers, plug readings, and leakdown results all point to different things

 

[PRH]

If you have an infrared temp gun, I’d fire the engine up, warm it up a bit, set the engine speed to an rpm where the cam has started to smooth out, and see how even the ex temps are.

 

[mshred]

If you have an infrared temp gun, I’d fire the engine up, warm it up a bit, set the engine speed to an rpm where the cam has started to smooth out, and see how even the ex temps are.

That's actually how I found out cylinder 4 was dead in the first place. After doing that what am I looking for and how will it help to troubleshoot? Not questioning the idea, just want to know what it may help me determine

 

[dano]

Yea, I clearance mine to what I thought was enough but clearly it could have gone more. The valvetrain always seemed to move okay with the engine on the stand, but I guess it can't hurt to pull the rockers and check the pushrods.

Not sure if I should just pull the heads and start there with inspecting pushrods, cam lobes, lifters, and head gaskets along with the valves...or if my plan of attack should be something else to check before starting to disassemble it. My compression numbers, plug readings, and leakdown results all point to different things

Have you pulled the valve covers and looked things over? Did you replace the plug wires, you mentioned some melting issues.

 

[PRH]

That's actually how I found out cylinder 4 was dead in the first place. After doing that what am I looking for and how will it help to troubleshoot? Not questioning the idea, just want to know what it may help me determine

if there is a dead cylinder, it can be from a whole host of reasons.
Step one, find the dead one.
That’s what the temp gun is for.
Beyond that, you just have to start ruling things out.
I could be anything from a bad spark plug to a bad head gasket, and probably 50 things in between.

I’m surprised the cylinder with the bad leak down wasn’t showing cold.
Apparently as bad as it’s leaking…….. it’s still firing.

 

[mygasser]

too tight on the valve clearances on cyl 4? it'd fire but could be bleeding cylinder pressure past the valves not fully closed.
neil.

 

[SRT_DSTRHOLC]

Your best case is to make a list of the things you can do with the engine in the car and check them off 1 by one and then if nothing is resolved, pull the engine and check everything over 1 by one. I personally would look at the rockers, and do another compression test with putting some oil in and seeing what happens, you could have an issue with the rings if everything else is new and working "well"

 

[mshred]

Have you pulled the valve covers and looked things over? Did you replace the plug wires, you mentioned some melting issues.

Yes. Story is I released the valves a few weeks ago, and was planning to fire it up when I noticed transmission is locked up in one direction when in neutral. So I haven't fired it up because now I'm worried I damaged the converter. I did the leakdown yesterday with the valve covers off and all appears fine aside from pushrod clearance issues. I haven't ordered new wires yet- the boots were starting to melt, but nothing crazy...although I guess it wouldn't take much to screw things up there.

if there is a dead cylinder, it can be from a whole host of reasons.
Step one, find the dead one.
That’s what the temp gun is for.
Beyond that, you just have to start ruling things out.
I could be anything from a bad spark plug to a bad head gasket, and probably 50 things in between.

I’m surprised the cylinder with the bad leak down wasn’t showing cold.
Apparently as bad as it’s leaking…….. it’s still firing.

Yea I'm not sure, the compression test, leakdown, and how the plugs look are pretty well all over the place and hard to narrow down a direction of what's going on.

too tight on the valve clearances on cyl 4? it'd fire but could be bleeding cylinder pressure past the valves not fully closed.
neil.

Yes that was something I thought of, so I ran the valves a couple weeks back and they were all pretty close. Has me wondering if number 4 having the pushrods rubbing is possibly what is bleeding cylinder pressure there and not allowing the valves to fully close.

Your best case is to make a list of the things you can do with the engine in the car and check them off 1 by one and then if nothing is resolved, pull the engine and check everything over 1 by one. I personally would look at the rockers, and do another compression test with putting some oil in and seeing what happens, you could have an issue with the rings if everything else is new and working "well"

Is there any use in a COLD compression test? I was always under the impression that a leakdown is more telling than a compression test.

I do think you're right though, it's going to have to be a process of elimination. I've put together 4 or 5 small blocks, none gave me trouble like this one has..

 

[oldkimmer]

I can tell u that the only time I’ve seen clean plugs like that is when they weren’t firing or had a major vacuum leak. Kim

 

[SRT_DSTRHOLC]

I would do a cold again on all of them and then drop oil in them all and keep track of the sealing for them all to have a full test. A leak down is good yes, but it seems we are in the process of eliminating something that isn't as easily located as we hope.

And because you happened to reuse some parts, we are dealing with mix match stuff. You could have leaky valves or valve seals or something in regards to burning oil, my "assumption" is going to be those cylinders letting oil pass through. What did the plugs look like on those cylinders?


The spark plug issue, I have not even thought about. You have a basket of things going on, best to sort out the internal ones first, as to eliminate the need to disassemble the engine and then you can move on to spark related issues sooner. IMO

 

[Oldmanmopar]

Is it dual exhaust with no cross over H or X. I had a car here that the one side muffler was clogged partially and the engine was running bad through the cross over in the intake. Fought that until we did a head job and fired it up open headers. Ran great until we bolted the pipes up.

But I honestly thing you have a issue with the cap. 3 and 4 are neighbors only in the cap. Unless you tore up two lifters side by side exhaust on one and intake on the other.

 

[mshred]

I would do a cold again on all of them and then drop oil in them all and keep track of the sealing for them all to have a full test. A leak down is good yes, but it seems we are in the process of eliminating something that isn't as easily located as we hope.

And because you happened to reuse some parts, we are dealing with mix match stuff. You could have leaky valves or valve seals or something in regards to burning oil, my "assumption" is going to be those cylinders letting oil pass through. What did the plugs look like on those cylinders?


The spark plug issue, I have not even thought about. You have a basket of things going on, best to sort out the internal ones first, as to eliminate the need to disassemble the engine and then you can move on to spark related issues sooner. IMO

I guess even a cold test is worth something. The heads were brand new fully assembled, so the only thing I reused were the rings. If you check my original post I have pictures of the plugs from all the cylinders....all looking rich as hell, except for 3 and 4 which appear to be clean from not firing at all. Truly just hoping it's a spark issue, but the leakdown test is telling a different tale

Is it dual exhaust with no cross over H or X. I had a car here that the one side muffler was clogged partially and the engine was running bad through the cross over in the intake. Fought that until we did a head job and fired it up open headers. Ran great until we bolted the pipes up.

But I honestly thing you have a issue with the cap. 3 and 4 are neighbors only in the cap. Unless you tore up two lifters side by side exhaust on one and intake on the other.

It's a dual with no crossover, with brand new straight through mufflers, and I looked down both of them before install, just because- all clear lol

I'm going to check the cap tonight...I mean hell it would be GREAT if it was something that easy, but man knowing my luck it won't be an easy fix lol

 

[oldkimmer]

I’ve also had where the dual carb bolt pattern was getting air sucked thru either the inside bolt hole or the outside bolt hole. Kim

 

[mshred]

Well I found this upon taking a quick look at the cap

 

[oldkimmer]

Time for a new cap with brass contacts. Kim

 

[SRT_DSTRHOLC]

yup looks like it's it

 

[Bewy]

I do not see a problem with the cap.

 

[MOPAROFFICIAL]

Well I found this upon taking a quick look at the cap

View attachment 1716461692

View attachment 1716461693

Looks like bad rotor/cap phasing.
Also make sure the rotor is pushed down all the way.

Even your average good sealing cylinder will lend some leakage to the crankcase when doing a leak down test via ring gaps.
The air is going somewhere, be it head gasket or rings.. both will enter the crank case or neighboring cylinder.. so remove the rocker shaft and pull the plug on the cyl next to it and put your finger over the plug hole to feel for pressure build.

One thing is for sure is if it's not just a valve hung open due to maladjustment.. its gonna a need to come back apart.

The cylinders that are clean are burning the fuel well... while the others are not.
Bad needle and seat can wash out rings and flood cyls making them extremely rich and blackened plugs as well. You checked the lash and say it didn't really change, so bad lobe seems less likely

 

[RustyRatRod]

The reason I included the firing order wasn't doubting you wire install. It was to show that 3 & 4 are next to each other on the cap. I don't see the strap on the plug burnt back on 3 or 4 So those cylinders are getting washed with fuel and not firing,

Pull those wires 3 and 4 while its running one at a time. Hold your wife's hand while doing it and you won't get jolted. I always tell who ever is standing here to hold me back so I don't fall into the engine while its running. You know a safety reason, LOL works every time. After about 4 times my wife don't care if I fall in anymore.

 

[Oldmanmopar]

Well I found this upon taking a quick look at the cap

View attachment 1716461692

View attachment 1716461693

Well like I said several times above , I think you have a Bad cap issue. That's the only thing that ties 3 and 4. Find a matching cap and rotor with brass contacts. Make sure it has a vent to disperse condensation. It would be your quickest and cheapest try for process of elimination.

 

[mshred]

I do not see a problem with the cap.

I couldn't any cracks visible to the eye, but it does appear there is a rotor phasing issue to me.

Well I found this upon taking a quick look at the cap

Well like I said several times above , I think you have a Bad cap issue. That's the only thing that ties 3 and 4. Find a matching cap and rotor with brass contacts. Make sure it has a vent to disperse condensation. It would be your quickest and cheapest try for process of elimination.

Looks like bad rotor/cap phasing.
Also make sure the rotor is pushed down all the way.

Even your average good sealing cylinder will lend some leakage to the crankcase when doing a leak down test via ring gaps.
The air is going somewhere, be it head gasket or rings.. both will enter the crank case or neighboring cylinder.. so remove the rocker shaft and pull the plug on the cyl next to it and put your finger over the plug hole to feel for pressure build.

One thing is for sure is if it's not just a valve hung open due to maladjustment.. its gonna a need to come back apart.

The cylinders that are clean are burning the fuel well... while the others are not.
Bad needle and seat can wash out rings and flood cyls making them extremely rich and blackened plugs as well. You checked the lash and say it didn't really change, so bad lobe seems less likely

Going to try a new rotor and cap, but before I fire it up with that, I'm going run a compression test dry and with oil, as well as add water back to the cooling system (drained last year before the winter) and try a leakdown on cylinder 6 again and see if I get bubbles in the rad, which would point to a head gasket issue and something I didn't think of before. I did the leakdown tests with all the plugs removed, but rockers on, and when I struggled to find the issue with cyl 6, I could not feel air coming from neighboring cylinders as I did check for that. Carb was completely rebuilt with all new parts before first fireup, but anything is possible in there as well.

Went to go run the compression test last night but the battery was dead. Put the charger on and it showed 100% charged. It's only 3 years old so maybe it's gone bad, but I noticed the negative cable post was pretty corroded, so hoping that is my only problem to add to the list

 

[340sFastback]

I would be making sure that #4 spark plug is firing cause that seems suspect to me.

Did you try running starter with valve covers off watching all the rocker arms?

 

[SRT_DSTRHOLC]

Looks like bad rotor/cap phasing.
Also make sure the rotor is pushed down all the way.

Even your average good sealing cylinder will lend some leakage to the crankcase when doing a leak down test via ring gaps.
The air is going somewhere, be it head gasket or rings.. both will enter the crank case or neighboring cylinder.. so remove the rocker shaft and pull the plug on the cyl next to it and put your finger over the plug hole to feel for pressure build.

One thing is for sure is if it's not just a valve hung open due to maladjustment.. its gonna a need to come back apart.

The cylinders that are clean are burning the fuel well... while the others are not.
Bad needle and seat can wash out rings and flood cyls making them extremely rich and blackened plugs as well. You checked the lash and say it didn't really change, so bad lobe seems less likely

smelling the oil will help to see if theres any kind of gas there

 

[MOPAROFFICIAL]

I couldn't any cracks visible to the eye, but it does appear there is a rotor phasing issue to me.


Going to try a new rotor and cap, but before I fire it up with that, I'm going run a compression test dry and with oil, as well as add water back to the cooling system (drained last year before the winter) and try a leakdown on cylinder 6 again and see if I get bubbles in the rad, which would point to a head gasket issue and something I didn't think of before. I did the leakdown tests with all the plugs removed, but rockers on, and when I struggled to find the issue with cyl 6, I could not feel air coming from neighboring cylinders as I did check for that. Carb was completely rebuilt with all new parts before first fireup, but anything is possible in there as well.

Went to go run the compression test last night but the battery was dead. Put the charger on and it showed 100% charged. It's only 3 years old so maybe it's gone bad, but I noticed the negative cable post was pretty corroded, so hoping that is my only problem to add to the list

Connection issue. Clean the cables, posts, if they're clamp style ..loosen scrape and reclamp them and test again.

 

[MOPAROFFICIAL]

So far every response to questions returns an answer of "I've already done that". Deja vu. lol
I think op will figure it out on his own the answer we all know.
What would have been a really good idea... is to have bore gauged the cylinders. The tapper and oor could be huge , like .007+