Low compression on 2 cylinders

[SasaniFab]

Ahh good ole machine shops......finding a person you can trust. It's a wonderful thing isn't it? Before you pull the head and slap another one on id consider checking the Pistons or the condition of the block. Drag your finger nail across the cylinder walls, if your nail cAtches ....you probably need to pull the Pistons.

 

[jdm9221]

Will do. I'll run a leak down test tonight and probably start ripping it all apart again tomorrow. As long as there's no block damage should my compression numbers go up when putting on a new head

 

[SasaniFab]

If your block isn't damaged then yes. But I'd be very suspicious. Take some close up shots of the cylinder walls

 

[jdm9221]

Will do

 

[kmetiuk]

Will do. I'll run a leak down test tonight and probably start ripping it all apart again tomorrow. As long as there's no block damage should my compression numbers go up when putting on a new head

Tough to say TBH. Could go up could go down. Depends on too much to guess at this point.

I wouldn't buy a new head tho....unless you get a virgin one you could just be inheriting new problems. First determine the health of your current head. You know its dead flat which is a huge plus and everything might measure out to spec....you wont know until you measure and test it.

Personally I would pull the pistons (or with that shitty cylinder wall at the minimum) and check the rings for carbon build up or cracked lands and check the walls, tear down the head and check everything (guide to stem clearance, valve seat seal test, etc), I'd lap the valves back in cause "your in there anyways", and then reassemble if it all looks good (or you can live with the issues you find).

 

[SasaniFab]

Tough to say TBH. Could go up could go down. Depends on too much to guess at this point.

I wouldn't buy a new head tho....unless you get a virgin one you could just be inheriting new problems. First determine the health of your current head. You know its dead flat which is a huge plus and everything might measure out to spec....you wont know until you measure and test it.

Personally I would pull the pistons (or with that sh**ty cylinder wall at the minimum) and check the rings for carbon build up or cracked lands and check the walls, tear down the head and check everything (guide to stem clearance, valve seat seal test, etc), I'd lap the valves back in cause "your in there anyways", and then reassemble if it all looks good (or you can live with the issues you find).

This is an aging platform....every part needs to be scrutinized too the T.....never
Assume something is ok. You'll be sorry in the end.

 

[jdm9221]

If I fill cylinder #4 cylinder 3 leaks air from the spark plug hole

 

[SasaniFab]

If I fill cylinder #4 cylinder 3 leaks air from the spark plug hole

? Did u perform a leakdown? Are you just pressuring the cylinder with air. Is it holding pressure at all at tdc?

 

[jdm9221]

I don't think the leak tester is working right. On cylinder 1 it says 0 which I know isn't right but I know as soon as I fill cylinder 4 it leaks into #3

 

[jdm9221]

If I did something right cylinders 1,2,4 read 40 and cylinder 3 at 35%

 

[jdm9221]

At tdc when I fill it with air thru the leak down test they read about 40%

 

[SasaniFab]

you need to pull the head, i would stop wasting time. Those numbers if accurate are not good. Pull the head and inspect the block. I have a totally rebuilt 6 bolt head I might sell yah if you need one....Take some pics of those cylinder walls

 

[jdm9221]

I'll rip it all apart tomorrow. At the moment I'm almost completely broke since I've dumped all of my money into this car already so I'll come back with pictures tomorrow

 

[jdm9221]

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Well I'm getting good at thispulled the head off again today. The walls have marks but no scoring at all. Haven't leak tested the valves yet but they look to be seated fine

 

[boostdawd]

Did u drain your coolant before pulling the head? Why is there coolant/fluid on your block?

 

[jdm9221]

I drained most. There was a lot of oil and coolant on the block surface under the head gasket

 

[jdm9221]

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After the water test the valves are definitely leaking. Could this be my full problem? By the time I took the pictures some had already puddled so much it started running out

 

[kmetiuk]

@jdm9221 It's not helping that's for sure. That is quite the leak in the 10 seconds it took you to snap the pic so It's likely contributing a large amount to the compression problem.

I am literally doing the exact same thing right now. Hahaha. Leak test FTW!

I cut my own valve seats with some Neway cutters over the last few days and I have been chasing leaks this afternoon. I started with 5 of which 2 were big dribblers like you seem to have and now I'm down too the last 2 which are just kinda sweating....takes about 2-3 mins for it to build up enough for a drop to form. I'm doing my test the other way tho....filling up the runners with the runners pointing up and the HG surface out(instead of up). I was doing it this way before but I found 1 extra leaking doing it the other way. So I feel your pain for sure man.

TBH I am not sure how much they "can" leak. Did a lot of reading and some guys say it takes 1000 miles for new seats to really "seat" in....others say no leaks at all. I tend to be in the no leak at school of thought.

But that's for new seats and you did nothing to your seats correct? Just that knicked valve....

Anyways, I'd recommend puling the valve train apart and then just relapping the valves into the seats. I't's can be just carbon and some pitting from normal wear and tear that is causing them to not seal. OOOOORRR now that I think about it maybe its some chips from getting your head decked with the valves in. I'm kinda leaning towards that now...those chips can be tiny and if they got wedged in there before start up and then mashed in the seat after start up.

I dunno...either way you gotta dig deeper now that your valves are for sure leaking. Pull it apart and inspect the valve seats....might be an easy re-lap and your sealed up again.


That cylinder wall doesn't look as bad as It first did tho. It doesn't look like scratched at least. The super shiny wall is of concern tho I think....like to me it looks like the piston to wall clearance isn't quite enough there, or just less than the rest of the cylinder, b/c it seems to be rubbing and making the it super shiny. The cross hatching it mos def gone there too. I dunno tho....you've been good for 40K so ya.

 

[jdm9221]

I'm gonna pull the valve train apart and start trying to fix all of my leaks tomorrow. As of right now these results are better than scoring on the walls and needing a block rebuild. I'm gonna take care of all my leaks, pick up another headgasket and hopefully start throwing it back together again soon and do a first start on a tuned ecu, also not sure if it will make a difference but I was running without an ect sensor because I broke the pigtail but I just got a new one soldered on tonight

 

[pauleyman]

Lemme get this straight...you ran an evo ecu and no coolant temp sensor and expected it to start?

 

[jdm9221]

It did start,and ran, and neither of those would cause low compression. So you're correct yes I did. The ecu was setup for an evo 8 maf and 560s. I'm running evo 8 maf and 550s. It definitely started and ran. That's not my issue

 

[jdm9221]

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So all of the valves are ready to go back in tommorow when my new valve spring compressor comes in however I was looking at the head and found a 2 spots in concerned about, are these gonna be a problem?

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[boostdawd]

Are u going to be using a composite or mls? Those look a bit deep. I say slap a gasket and bolt it on.

 

[jdm9221]

Felpro permatourqe

 

[kmetiuk]

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So all of the valves are ready to go back in tommorow when my new valve spring compressor comes in however I was looking at the head and found a 2 spots in concerned about, are these gonna be a problem?

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In the pic of the seat in the head: what are those little silver bits? Are they metal chips from something else or little dents in the soot? Hard to tell but PLEASE answer...if they are little dents then you had something bouncing around inside the cylinder.

The dents in the headgasket surface:
- The first one doesn't look like its an issue. Super close to the edge and its just a head stud there so should be okay but keep an eye on the area during first startup.
- The second one is right where the combustion chamber seal or metal ring is in the headgasket (felpro). I think that might be causing some leackage. It looks like a gouge from the journal sleeves where the headstud holes are in the block. Kinda looks like it got set on them pretty roughly...and by the looks of it more than once.