Need help with this engine problem...lol

[Zack]

After 2500 miserable miles, I broke down and bought a leakdown tester.

Pretty sure I found the problem, but Ill let you guys insert your thoughts before I mention mine.
Results:

Bank
1 2
33 55
35 55
32 57
31 51

OMFG

a 60% leakage percentage between both banks???? I cant believe it runs as good as it does!

 

[Turbocharged400sbc]

did you make sure the rings were seated by moving the crank? cause even with a cold engine you shouldnt see more than 25% leakage way less than that with a hot engine.

looks like bank 2 is fucked either rings/bore or valve seat leakage...

where was the air leaking too? into the crankcase? intake? exhaust?

 

[Zack]

did you make sure the rings were seated by moving the crank? cause even with a cold engine you shouldnt see more than 25% leakage way less than that with a hot engine.

looks like bank 2 is fucked either rings/bore or valve seat leakage...

where was the air leaking too? into the crankcase? intake? exhaust?

Engine was hot and i did rock the crank with a breaker bar and socket.

Im positive its nothing of what you think it is.

Thing is I did not see bubbles in the coolant or hear air from anywhere. Its such a small volume of air going through its really hard to hear.

Ill just say it...there has to be a chain a tooth off.

 

[Turbocharged400sbc]

its gotta be more than a tooth off if any valves are hanging open for the compression stroke

only 5 points to leak bud, rings/bore, hg, intake, exhaust valves, plug

did you do the proper gauge cal/setup then connect it to the hose going to the cylinder? should be disconnected and the pressure set to the needle at 0% leakage, then connect to the cylinder.... cause shit man at 20% leakage i can hear it through the intake/exhaust pipe/crankcase at 30-60% you should hear it like a damned steam whistle

 

[Zack]

its gotta be more than a tooth off if any valves are hanging open for the compression stroke

only 5 points to leak bud, rings/bore, hg, intake, exhaust valves, plug

did you do the proper gauge cal/setup then connect it to the hose going to the cylinder? should be disconnected and the pressure set to the needle at 0% leakage, then connect to the cylinder.... cause shit man at 20% leakage i can hear it through the intake/exhaust pipe/crankcase at 30-60% you should hear it like a damned steam whistle

I conducted the test exactly as you described.
Only took 15psi to get the needle to 0% leakage.
I was outside and did listen for the leak but could not hear it.

It runs like its out of time, tests like its out of time..

If it looks like a duck and quacks like a duck....

Keep in mind this was a perfect running engine in my other car, then i had the heads done before installing it into the current car.

 

[Turbocharged400sbc]

i take it you did the usual shortcut and hung the cam gear/chains to keep em under tension as the heads were removed?
sounds like you know it has more than a slim chance at being mistimed, so ill defer to the guy with his grubby mits up 'er skirt

my leakdown tester is usually at 40ish psi at 0% needle under no flow conditions

 

[Zack]

i take it you did the usual shortcut and hung the cam gear/chains to keep em under tension as the heads were removed?
sounds like you know it has more than a slim chance at being mistimed, so ill defer to the guy with his grubby mits up 'er skirt

my leakdown tester is usually at 40ish psi at 0% needle under no flow conditions

The engine was on a stand when I had the heads done so everything was taken apart.

I have the leakdown tester from harbor freight. I even watched a video on youtube with one and it too reached 0% at 15psi.

The thing that doesn't make sense is:
The bank with the higher % is the side I just pulled and took back to the shop suspecting a loose valve seat after I pumped 40psi into cylinder 6 and heard it coming out the exhaust. WTF

 

[TERMINATED97]

Hope you get it squared away man.

 

[Turbocharged400sbc]

not 100% on those fuckers but any chance it had the valvetrain shimmed for reduced base circle cams? any chance the shims/hyd lash adjusters are holding the valves open? any chance the head cam bores were remachined? that would lower the cams in the head...

maybe retest the back cylinders with the cam bearing caps loose just to make sure something isnt hanging the valves open. ive had shitty valve jobs before with seats cut a hair off center, sealed ok when cold but when the valvestem grew when hot the guide no longer had enough slop to let it seat fully.

dunno man but you gotta find where that air's going.

i once had a customer with an earlier 4.6 that had a bad pcm injector driver circuit keeping the inj open, he didnt have the $ to fix it until a week or two later....car ran better but still ran like shit, cylinder/rings were completly shot to shit, cylinder had 50 or so psi compression.

fuel washdown will destroy ring seal in no time flat...find out where your air is going otherwise you might as well throw a dart at a fart in the wind

 

[Zack]

Ok ive been racking my brain over this....and come up with a theory.

Before i took this head off a few weeks ago thinking it was a valve seat, I did the following:
Compression test. All 175 with the exception of #6 which was 150. Then I brought it to TDC and pumped 40psi into the cylinder and heard it coming out the exhaust.

Head came off, #6 seats were fine, all new guides installed and everything checked. Put it back on and same shit.

The ONLY thing i can think of is....
The shop marked the small chain one tooth off the first time they re-assembled the head, thus causing the problem. Then, when re-assembling a second time, they used the same paint mark that was still there and the problem still exists.

It cant be bad seats or valves after 2 times lapping them in.

I will re-test tonight with straight air into the cylinders with the pistons at TDC. If I still hear air out the exhaust it has to be a mis-timed exhaust cam.....right?!!!

 

[Zack]

Duh, the exhaust cam cant be out of time.
It is connectod to the big chain and ultimately drives the intake cam.

Hmm. Wonder if the intake and exhaust cams got swapped. Now that would make some more sense.
Im driving myself nuts!

 

[Turbocharged400sbc]

ah so its a dohc
id say get out a degree wheel and start measuring intake and Ex opening and closing centerlines. or at the least redo the leakdown tests with the cams loosened up.

tdc compression it should be sealed, tdc exhaust/intake stroke the valves would still be open dep on cam profile and overlap.

part of diagnostics is whittling away at the possibilities.....besides i would think there's a stamping/paint splotch to identify the cam as I/E profile

 

[Zack]

Ok I did more testing.
At TDC on #4 cylinder I heard air pouring out the exhaust with 35psi in the cylinder.
Its apparent the is a cam or timing issue, but here is where the thinking cap needs to be put on...
The exhaust cam is the same cam that the big gear is bolted to. This means if the big gear is timed right, there is no way the exhaust cam could be off.
There is no way in hell I would have mis-timed the chain twice...just no way.
It has new valve guides and all the seats are intact. No valves burnt nor past the safe amount of material to resurface.

The only thing I can think of is the exhaust cams are swapped side to side. But it also begs the question how the other side could have leakdown readings that are great.
What else would cause this???!!!!

 

[Jon01]

Have you tried popping the retainer caps off of the cams?
That should in theory allow the valves to close if they're being held open out of time.

 

[Zack]

Have you tried popping the retainer caps off of the cams?
That should in theory allow the valves to close if they're being held open out of time.

Im taking it all apart on Saturday.
Checking time, cam part #'s etc.

 

[Turbocharged400sbc]

are the cam gears identical from L to the R banks? maybe cams aare fine but gears were swapped?

im just spitballin here, i hate them things so i never work on em

 

[massacre]

Have you tried popping the retainer caps off of the cams?
That should in theory allow the valves to close if they're being held open out of time.

Removing the followers would achieve the same goal, should keep all the valves closed and remove the cams as a suspect.

Zack, if you remove the followers and your leak is gone, that could point to a pumped up lash adjuster(s) that is hanging the valve(s) open.
If you remove the followers and the leak is still there, that could point to a bent valve(s) that is hanging open.

What baffles me, is if the exhaust cam was off that much, you wouldn't be seeing the same compression in every hole except one, I would think that they would all be off the same amount on that bank.

The fact that they are all the same except that one, to me says there's a problem with that particular cylinder.

Wow this one is really weird, I hope you get it figured out soon!

 

[Zack]

I am officially defeated.
Cams are in the proper spot.
All followers on the exhaust are off. In cylinders 5&6 with 40 psi in the cylinder it is pouring out the tail pipe.
This car has no x-pipe, so its all drivers side. I have no explanation for this....at all.
40psi in 7&8 and it holds air good. Can still hear it a small amount out the exhaust but just barely.
I swear im hearing it in the intake too, but I can't be sure since the upper lid is off. Checking now...

Edit....nothing coming out the intake.

 

[Zack]

Cracked valves? Head? How could neither of these be seen when doing a valve job? How could the engine run great before the valve job????????
WTF!

 

[massacre]

Could be cracked valve. Could be head too. Are you seeing bubbles in the coolant in the reservoir when you apply air? Maybe cylinders are bleeding into an adjacent cylinder?

I know you don't degree cams Zack but it kinda sounds like maybe cam lobes moved/got twisted, but air is getting by somehow if you can hear it. Could it be as simple as valve seals?

Just because all the marks line up doesn't mean that the valve timing events are happening when they are supposed to be, it takes a degree wheel and dial indicator to get that info.

What centerline are your exhaust cams currently at?

 

[Zack]

Could be cracked valve. Could be head too. Are you seeing bubbles in the coolant in the reservoir when you apply air? Maybe cylinders are bleeding into an adjacent cylinder?

I know you don't degree cams Zack but it kinda sounds like maybe cam lobes moved/got twisted, but air is getting by somehow if you can hear it. Could it be as simple as valve seals?

Just because all the marks line up doesn't mean that the valve timing events are happening when they are supposed to be, it takes a degree wheel and dial indicator to get that info.

What centerline are your exhaust cams currently at?

None of what you asked matters.....I had ALL 8 followers popped off the exhaust valves..

How can 2 cylinders have cracked valves and go un-noticed by me or the shop!
This makes no sense.

Snice this has made me a miserable man, I am going to swap the built engine i took out of the Blue. I hate cars

 

[wolfe]

Sorry to hear this has been such a pita. Hopefully you find out what it is even if you are putting in a different motor just so you know and it will quit driving you nuts.

 

[massacre]

None of what you asked matters.....I had ALL 8 followers popped off the exhaust valves

Then there's a leak with no pressure at all on the exhaust valvesprings and for all intents and purposes all of the valves are "relieved of their duties"?
Something is keeping something open.

Or there's a leak somewhere else and you can get that sorted out I'm sure

 

[massacre]

.....

Sorry double post duh

 

[Jon01]

Do you have a known good head you can just stick on there Zack?