Compression Test Results

[crownvic97]

Finally got around to doing a compression test on my new Marauder. It’s been having a cylinder 8 misfire unchanged by plug or cop change. I pretty much knew what the test was going to say, but here are the results to back it up...

Cyl 1: 210
Cyl 2: 210
Cyl 3: 210
Cyl 4: 210
Cyl 5: 210
Cyl 6: 210
Cyl 7: 190
Cyl 8: 85

I put a little oil in 8 and retested, it was roughly the same, maybe reached 90 but that could just be gauge inconsistency.

So, correct me if I’m wrong, I have a valve/valve seat issue on 8 and the head needs to come off.

Question for all:

Do I just pull the D/S Head have it gone through and slap it back on? Do both heads? Pull the engine and do an entire rebuild?

I plan on checking/replacing the timing chain guides and tensioners when I pull the head. But at 166k miles, am I stupid to put all this work in to the top end and leave the bottom end alone?

Any advice is much appreciated.

[Logizyme]

Well you should probably finish your diagnosis by determining the actual failure.


A leak down test would help indicate where your compression is going - into the intake could indicate something wrong with the seat, or possibly the lifters/followers or spring.


Depends how much you want to spend, you could do as little as replace a seat and headgasket to replacing the engine.

[RubberCtyRauder]

Send a pm to A_D_A_M here..he had pretty much same issue a couple years ago on number 8 and just did the head..He can prolly tell you some info.

[crownvic97]

Well you should probably finish your diagnosis by determining the actual failure.


A leak down test would help indicate where your compression is going - into the intake could indicate something wrong with the seat, or possibly the lifters/followers or spring.


Depends how much you want to spend, you could do as little as replace a seat and headgasket to replacing the engine.

I’m not disagreeing, but given the numbers and that adding oil had no measurable change in the number, it is pretty likely the issue lies in the head and not the the bottom end/piston. That, and the history of the cylinder heads with #8 issues.

[crownvic97]

Send a pm to A_D_A_M here..he had pretty much same issue a couple years ago on number 8 and just did the head..He can prolly tell you some info.

Yes, that is a good idea, I did see his write up.

[Zack]

I would do both heads

[justbob]

I would do both heads



100% agree.

The fact that you are only 10 bolts and 8 exhaust studs away from doing it anyhow only makes sense. Sure it's another $225 or so in rebuild labor, but if you wait till next year or whenever it goes bad you'll certainly kick you own ass for having to dismantle the top and front of the engine again! If your on a tight budget though I totally understand that..

Here is a good price on a gasket and bolt kit.

https://fordracingpartsbydonwood.com/engine-parts/gaskets/head-changing-kit-4v-m-6067-t46/?gclid=EAIaIQobChMIxOjwmN2T1wI VDilpCh3mHgVjEAQYASABEgJWjfD_B wE

Might want to consider a rear cooling mod on the re assembly as well..




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[crownvic97]

I would do both heads


100% agree.

The fact that you are only 10 bolts and 8 exhaust studs away from doing it anyhow only makes sense. Sure it's another $225 or so in rebuild labor, but if you wait till next year or whenever it goes bad you'll certainly kick you own ass for having to dismantle the top and front of the engine again! If your on a tight budget though I totally understand that..

Here is a good price on a gasket and bolt kit.

https://fordracingpartsbydonwood.com/engine-parts/gaskets/head-changing-kit-4v-m-6067-t46/?gclid=EAIaIQobChMIxOjwmN2T1wI VDilpCh3mHgVjEAQYASABEgJWjfD_B wE

Might want to consider a rear cooling mod on the re assembly as well..




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That’s what I was thinking, it would be kind of crazy not to do both cylinder heads once it’s torn down. Thank you!

Budget isn’t tight really, I’ll spend what I need to get it done right, just wasn’t expecting to be doing major repair so soon.

Thank you for the link to that, and I will definitely be doing the rear cooling mod when I put it all back together.

If I can find some 96-98 Cobra intake cams I may try to swap and degree the cams. I hate to tear something apart without upgrading anything.

[a_d_a_m]

I only did the driver's side head, but I also only had 100k on my car and the inside looked fairly clean, plus I was pretty cash-strapped that year.

If you can swing it, yeah, doing both sounds like the better option.

[crownvic97]

I only did the driver's side head, but I also only had 100k on my car and the inside looked fairly clean, plus I was pretty cash-strapped that year.

If you can swing it, yeah, doing both sounds like the better option.

If I only had around 100k I probably wouldn’t do both, but at 166k it seems like the right thing to do.

[crownvic97]

Last question before tear down...should I do this with the engine in the car or pull it?

[BLACKMARAUDER04]

What is the approximate cost to fix this?
I have same problem in cylinder #7 on my new Marauder.
It has a miss at low speeds causing the engine light on.

[crownvic97]

I’m up over $5k in parts, but that’s because I went way over the top and am rebuilding the whole top end and adding a bunch of mods while it’s all apart. I suspect you could do the whole job for around $700 if you only do one head and put everything back together as is.

[FordNut]

Or just drive it.

[crownvic97]

Or just drive it.

Wouldn’t that cause further damage? I was wondering about that actually.

[justbob]

I’m up over $5k in parts, but that’s because I went way over the top and am rebuilding the whole top end and adding a bunch of mods while it’s all apart. I suspect you could do the whole job for around $700 if you only do one head and put everything back together as is.



Funny how things just add up isn’t it?

I bought my son a 2000 Ranger 4X4 with a cyl 6 misfire figuring worst case heads. At least the parts are stupid cheap on this truck. Owning and heavily modifying a Marauder I’m certainly NOT used to cheap..

Heads and gaskets led to-
Water pump and thermostat led to-
Oil pan gasket led to-
Simultaneously raising the engine and trans to max height, starter out, lowering the passenger side front axle, and repairing broken bolts from two different skid plates.. Had I known this POS 3.0 better and what to look for I would’ve yanked the engine and rebuilt it in full on a stand like a gentleman AND saved time!

Couldn’t just be a spark plug. That would be too easy...




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[crownvic97]

Funny how things just add up isn’t it?

I bought my son a 2000 Ranger 4X4 with a cyl 6 misfire figuring worst case heads. At least the parts are stupid cheap on this truck. Owning and heavily modifying a Marauder I’m certainly NOT used to cheap..

Heads and gaskets led to-
Water pump and thermostat led to-
Oil pan gasket led to-
Simultaneously raising the engine and trans to max height, starter out, lowering the passenger side front axle, and repairing broken bolts from two different skid plates.. Had I known this POS 3.0 better and what to look for I would’ve yanked the engine and rebuilt it in full on a stand like a gentleman AND saved time!

Couldn’t just be a spark plug. That would be too easy...




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It’s out of control! Started with 9 thread heads, then I figure I might as well get a 3 angle valve job and SS Manley valves, then 96-98 intake cams, then all new timing components might as well go in, and then I decided putting stock manifolds back on was a waste so I ordered up the SW headers and catted lead pipe. JLT CAI, ON3 COT delete, rear cooling mod. Then there’s the gaskets, ARP bolts, fluids, etc.

Now I am on the fence on just getting a shortblock built for all these new parts! Having a hard time drawing the line :D

“It’s probably a spark plug” yeah, that cost me 5 grand!!!

[FordNut]

Or just drive it.


Wouldn’t that cause further damage? I was wondering about that actually.

The high mileage one I'm driving now was diagnosed with weak cylinders on 7 & 8 about 4 or 5 years ago. Still no check engine light. Still has a slight miss/stumble/vibration at idle. Still runs fine when driving. Still averages 21 mpg. If it was bad enough to set the check engine light, I might feel differently.

[tbone]

I figure #8 on mine is a bit weak. Don't want to find out. Ignorance is bliss. Runs good.

Once the engine goes all will be forged and boost will rise significantly. Until then, I drive it like I stole it.

[crownvic97]

The high mileage one I'm driving now was diagnosed with weak cylinders on 7 & 8 about 4 or 5 years ago. Still no check engine light. Still has a slight miss/stumble/vibration at idle. Still runs fine when driving. Still averages 21 mpg. If it was bad enough to set the check engine light, I might feel differently.

I have a CEL, but the car runs pretty good other than the miss that’s most noticeable at idle.

[tbone]

Mine doesn't miss at idle but if I grab the throttle body and give it a little gas it vibrates just a bit. I figured its probably normal.

[BLACKMARAUDER04]

My engine light is on. I can not pass smog and the tags are expired.
Car is sitting in my backyard.

[tbone]

My engine light is on. I can not pass smog and the tags are expired.
Car is sitting in my backyard.

Kalifornia.....beautiful! :burnout:

[ARodmarauder]

My engine light is on. I can not pass smog and the tags are expired.
Car is sitting in my backyard.



When this started happening to my car, I was lucky to fine an engine for dirt cheap. Is yours the one for sale on Craigslist


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