Compression test, where to go from here?

[Marcohotrod]

I said pop the heads off cuz u mentioned changing valvesprings, and u do not know about checking heights and loads etc. The 1968 -70 340 was blueprint rated at 10.5 : 1 with the thin factory headgasket. 1971 at 10.2 : 1 - thicker factory headgsket. those plugs are for 1972+ , 1968-1971 n9yc or 53 or 63

 

[DentalDart]

I said pop the heads off cuz u mentioned changing valvesprings, and u do not know about checking heights and loads etc. The 1968 -70 340 was blueprint rated at 10.5 : 1 with the thin factory headgasket. 1971 at 10.2 : 1 - thicker factory headgsket. those plugs are for 1972+ , 1968-1971 n9yc or 53 or 63

These are the plugs going in it. When I went to the store we searched by year, make and model and then also these have been posted as good plugs here on FABO.

I'll be pulling stuff apart soon to check some of the things mentioned here.

 

[Wyrmrider]

but u are not blueprinted
more like 9.5:1
post a compression test
now listen up
those plugs yr and i mentioned were invented after your motor was built because they work better

 

[DentalDart]

but u are not blueprinted
more like 9.5:1
post a compression test
now listen up
those plugs yr and i mentioned were invented after your motor was built because they work better

The plugs I got are cross referenced with the Champions. Also I posted a comp test., heres a picture of when I did it and wrote the numbers down. I've been busy havent done a wet test but I did get some marvel mystery oil today that I will use to do the wet test with, hopefully in the morning. Today no working on the car, I cleaned up my tool box, garage, did the dishes then swept and mopped the floor.

 

[Wyrmrider]

u x rf obsoete pluh
garbage in garbage out
NGK ZFR5N

Lets visually compare a Champion RC12LYC, an NGK FR51, and an NGK ZFR5N which is the updated plug for the 99 and newer coil on plug ignition.
The ZFR5N is the OE Mopar specified plug for 99 and newer...

"
So I go to the local parts store, pick up 8 new spark plugs and swap them in.
Right away I notice it started up just a tiny bit quicker and the idle is noticeably smoother. A quick drive and the engine seems to have just a little bit more pep and all around just seems to run much smoother.
So now I wonder why. The only thing I can think of, is the longer electrode places the point of ignition closer to the center of the combustion chamber and the piston.

 

[DentalDart]

u x rf obsoete pluh
garbage in garbage out
NGK ZFR5N

Lets visually compare a Champion RC12LYC, an NGK FR51, and an NGK ZFR5N which is the updated plug for the 99 and newer coil on plug ignition.
The ZFR5N is the OE Mopar specified plug for 99 and newer...

"
So I go to the local parts store, pick up 8 new spark plugs and swap them in.
Right away I notice it started up just a tiny bit quicker and the idle is noticeably smoother. A quick drive and the engine seems to have just a little bit more pep and all around just seems to run much smoother.
So now I wonder why. The only thing I can think of, is the longer electrode places the point of ignition closer to the center of the combustion chamber and the piston.

The differences with the ZFR5N and the GR4 is the heat range ZFR5N is slightly cooler ( 11-12 vs 13-14 when cross referenced to champions) and the gap. The gap on the ZFR5N is .036 vs .040 in the GR4. I guess if the car isnt running as well with the GR4s maybe then I'll have to try out the ZFR5N plugs or go back to the champion plugs. let's hope the car just continues to run awesome or better with the GR4s though

 

[nm9stheham]

Today no working on the car, I cleaned up my tool box, garage, did the dishes then swept and mopped the floor.

Your priorities are obviously wrong LOL

BTW, with all this talk, your #3 numbers are not bad. I personally would continue to do simple tests like the leakdown, and wet compression test, to see if I could better ID what is going on, and continue to run the engine and do a a compression test every 100 miles or so to see the trend, before taking any action.

 

[missing linc]

Still within 15% from best to worst, so IMO no reason to fret.

 

[Cudafever]

Still within 15% from best to worst, so IMO no reason to fret.

Agree.
But with a new cam and Valve spring. i would be wanting to know if the head need to be pulled off to fix a burnt valve/seat.
If not, and it's just tolerance stacking up. run it.
But i would want too know before a did or changed AnyThing.

 

[yellow rose]

The differences with the ZFR5N and the GR4 is the heat range ZFR5N is slightly cooler ( 11-12 vs 13-14 when cross referenced to champions) and the gap. The gap on the ZFR5N is .036 vs .040 in the GR4. I guess if the car isnt running as well with the GR4s maybe then I'll have to try out the ZFR5N plugs or go back to the champion plugs. let's hope the car just continues to run awesome or better with the GR4s though

Using a cross reference to pick a plug is abusing the purpose of a cross reference chart.

If you are going to use an NGK plug, get the NGK catalog and look at what it calls out for a plug and buy that.

I don't use NGK plugs, partly because their numbering system is retarded and partly because their catalog is a joke.

On top of that, I can read a champion and make better tuning decisions than I can with an NGK. Even on blown alcohol stuff the NGK plug never looked happy and any tuning move never made sense by what the plug wanted.

 

[Wyrmrider]

problem with using the catalog is that both Chrysler and AMC upgraded the plugs as years went by
for low- mid compression motors the new plugs work better

 

[DentalDart]

Did a wet compression test today, I should have done a dry right before the wet one but it's to late now haha.

Since the time of the dry test I've adjusted the carb and the engine is getting much more fuel since, even after warming the engine I could smell a little gas on the plugs. I added about 1 qt of oil, 1 qt trans fluid, and all new coolant (I installed a new radiator, so I checked all the fluids)

First picture is dry test from what like a week or so ago? Second is wet test! As you can see all cylinders except for #'s 2/3 rose by 5-10psi. Cylinder # 2 and 3 rose by 20-30 which means the rings are sealing as well, that's good to know for the future though. Also added pictures of my spark plugs.

 

[Cudafever]

If you had a burnt valve, the compression wouldn't have came up.

Don't see any sign of oil on your spark plugs.........Time to move forward.

 

[DentalDart]

If you had a burnt valve, the compression wouldn't have came up.

Don't see any sign of oil on your spark plugs.........Time to move forward.

Thanks!

Going to take the engine apart starting tomorrow to have it ready to install the camshaft, lifters, seals, springs, and timing chain on Tuesday.

 

[Wyrmrider]

dental compression is looking better
U do not get that one plug has a much longer nose on it than the one u got
they burn clezner

 

[RustyRatRod]

I have a 72 340 in my duster with aftermarket KB 243 pistons, and stock "x" heads and have 8.98 compression, measured.
But with with careful camshaft selection I make 160 psi cranking, so it is decent on pump gas.

And you can make it run like STINK! Most of these guys will turn their noses up because it's not 10:1 at least, but low compression engines can be made to RUN with the right components.