fatpride111

my car was giving me problems, so i pulled the head, sprayed PB Blaster in the intake, and exhaust ports, and like half the valves leaked that stuff out...

so i dismantle the head, re-seat the valves, and valve seats, assemble it back together, and still leaked... i take it a machine shop to cut the valves, and re-cut the valve seats perfectly, so everything is practically brand new.

i re-seat the valves using 180 grit valve lapping compound, and keep going till theres a solid grey line accross both the seats, and valves (took about 2 hours). i just assembled it, and re-sprayed PB in it, and its leaking WORSE now! well, from about 3 intake ports. the exhaust seems to be sealing fine... unless its a SLOW leak.

wtf is going on?? this is the 3rd re-build on this head... im using buddyclub springs, and retainers but i highly doubt that'll cause any of this.

4g hatch

did you try the seats right after they were cut? who ever did the valve job is not gonna warranty the job after you laped them,with the modern valve cutting machines[serdi's,newmans] you shouldnt have to lap the valves

fatpride111

not sure what you mean, but right after they were cut, i seated them and tried to make sure they were done correctly since this is the 3rd time, so i kept going till the valves and the seats are 100% grey.

Combustion Contraption

2 questions, although the first may seem stupid, I have seen people do this

1. Did you reinstall valve springs and then do your liquid test?

2. Who cut the seats?

It is my experience that most high performance VJ's will leak on the bench with the liquid test when brand new. The valves need a heat cycle, and some spring pressure to get them to seat.

fatpride111

1. yeah, the valve springs have about 1,200 miles. installed them when i rebuilt my motor just very recently. car over heated on me for some reason, and began to mistfire BADLY, so head was pulled, only this time i just re-seated the valves with out getting cut, or nothing, and did the same thing, so pulled the head again.

2. this local machine shop. they specialize in short block assembling, head-rebuilding, and theyve been in business for ever. this is kinda their specialty

i have the springs, and retainers assembled on it right now, which is why im kinda pissed that its STILL leaking...

im thinking it might just be easier to buy a used head that was pulled out of a healthy running motor.. oh, and i also dont think this matters, but the valve stems were shaved down 5mm...

Combustion Contraption

They shortened the valves by .200"? Thats alot. Its done to correct tip height, wouldnt have an effect on valve sealing though.

Most "healthy running engines" have valves that leak, especially OEM ones with some miles on them.

fatpride111

thats exactly what i said, but they said thats whats 'recomended' since the ports have been cut about 2-3 times.

well, i filled the ports up about half way with PB blaster, and it leaked it ALL out in a few seconds... i just saw it dripping like if there was no valve there at all. im checking the Exhaust valves atm. took out the Intake, and they all look like they'd have no problem sealing... im gonna try to re-seat them again with 120grit compound, and re-test them again.

which, btw, whats the best way to seat them? we have this suction cup stick that you suck onto the top of the valve, and using your palm you swirl it around, and then lift up the valve slightly, and beat it down towards the seat repeatedly, and swirl it around some more. atleast thats the way i've been doin' it

ruffrhyder

iTrader: (1)

Tim Radley

You can get a false reading looking for a gray line with lapping paste due to the thickness of the grit. Also if you push the lapping stick hard and have quite a lot of valve stem float you can rock the valve and not get concentric lap.
If the seats were cut on a proper machine and the shop know what they are doing then there is no need to lap them in.
Also if the seats have been sunk in far enough to need 5mm grinding off the stem then you are way low on seat pressure. I've had plenty of heads come in where some idiot has sunk a seat and not shimmed the springs and then the valve burns out.

Combustion Contraption

What sort of machine was the VJ done on?

fatpride111

ah, he edited his post. didnt see that part im not too sure what all has been done to it, i just took it to the machine shop, and they cut it for us... they do alot of our machine work, so im assuming they came out pretty damn good... atleast i hope.

so you think the grey line COULD be just the 120 grit being too thick? i used 180 the first time, just a really quick pass, and it leaked anyway, so i went ahead and used 120... hope i didnt mess it up

im not sure... i didnt see the machine shop do it. it was just returned to me all shiny-like, and i seated the valves my self.

small update: re-seated the intake valves a bit more, and re-assembled them, put the head in the parts washer, and filled all the intake ports with liquid. i went to the bathroom, washed my hands, and walked around a bit, and the ports were still full. last time i did that you noticed it leaking down, so i THINK i either slowed down the leak, or eliminated it.

im thinking after i seated the valves this last time, i installed them backwards from cyld:1-2-3-4 to 4-3-2-1... possibility??

ruffrhyder

iTrader: (1)

I've been told that if the valve job is done properly it shouldn't matter what valves go to what cylinder.

fatpride111

even after they've been seated in?

i mean i know if theyre freshly cut it doesnt matter, but each valve/seat get grinded differently after they get swirled around with 120 grit compound.

anyway, the valves arent leaking the parts washing fluid, so i think theyre sealing right now... ill try the PB Blaster tommorrow since that always ends up dissapointing me. My GSR cam cracked while i was assembling everything just now, so i gotta look around for a set of those...

non-VTEC

why are you lapping the valves after a fresh valve job?

if they leak after the valve job was done on a proper machine you should have brought it back to the place and have them check it out. possible worn guides and the machine is not lining up perfectly to the seats??

lapping compounds are a thing of the past......past 90 years or so......im surprised they still sell that crap.

Combustion Contraption

No, no, no. Some valve jobs take time to seat. Trust me. If it is a 60, 45, 30 with a .060" 45 , it should seal on the bench with lapping compound and no run time. If it is something that actually makes power, it needs a heat cycle or two.

BuildOff

Also depends on the valveseat material. Ampco 45 and Berylium Copper definitely take a seating during the initial run-in. Ampco seats are really soft, but work harden on run-in. Berylium Copper seats are a bit harder, but don't work harden as much as they just get beat in... I like a .030"-.040" 45 (intake) for street engines using Ampco seats. That will end up around a .050"- .060" margin once they are run-in. I had one head that came from a Pro-Stock Bike guy that had a .020" 45 on the Ampco seats.

fatpride111

are those the only symptoms to worn guides? at first i thought they were worn because first time i installed the valves back in after taking them out, it was pretty hard to press them in... but i sprayed some WD-40, and it slid right in, so im thinking it was dirty, or something.

someone just told me to lap them anyway, so i did.

it was a clear 3 angle valve job (looked cool)

Combustion Contraption

Unfortunately, this means, and counts for, absolutely nothing.

fatpride111

how so?

4g hatch

you can put any angle you want on a 3 angle vj. cc said a stockish vj will seal with no run time,but performance vj's/angles need to be ran and heated

fatpride111

ah, ok then, i have no idea what angle it is

NAH2B

this may be a stupid question, but did they check the valves to see if any were slightly bent?

also i have seen machine shops use the wrong size cutter in the past and crosscut the valveseat which will also cause the problem you are describing.

if the valves are good and the seats were cut properly you should have no problem getting them to seal by hand lapping them in.

you can also check them w/ light rather than liquid, its a much cleaner process

fatpride111

well i checked them numorously for bent stems via straight-edge, laying them on a flat surface and running a .001" feeler guage on it, so theyre straight.

but i got it to seal (atleast it looks like it), so problem is solved now

i just kept seating them and seating them till they finally sealed. oh, and we have a parts washer... so just throw the head in there, fill up the ports, and check for leaks.... to clean it, just spray it down with clean water. pretty easy, and worth the mess to clean up the head a bit more

NAH2B

if i were you i would take the valves to the machine shop and have them checked. they will turn them against a stone which will show if they are slightly bent or not. not to mention it will give you a nice fresh surface to start with. i cant believe they didnt do that before the vj

fatpride111

true, but they wouldnt have a reason to be bent... well, my timing jumped twice, but it was only a tooth each time, and the car hasnt been on for over 2 minutes since it couldnt even idle.

and, yeah, i know, "it jumped = possible bendage " but i did my best to check, and they slid right in, so... maybe