Valve lapping.. your take?

DandDMachine said:

Are you putting in new valve stem seals while you are in there? That maybe why they are so carboned up. The seats look pretty good. Those dual cam subarus with the non adjustable buckets are an expensive valve job. If You did have a valve job done you would have to either re-shim the buckets or mock up the valves and cams and adjust the clearance by grinding the valve stem end or the valve face itself. If you don't want to stick a lot of money into them just lap them as you have done poor some water or solvent into the ports, if you don't see any water seeping out after 10 seconds or so you should be good. Just be sure to clean all the lapping compound out from under the seats and especially the guide area. Valve guides get destroyed very quickly if that grit is not all cleaned out.
Might not be a bad idea also to check them with a straight edge to be sure they are not warped. We see a lot of warped Subaru heads. While resurfacing the heads may not be in the budget doing the whole job over again (including new gaskets)isn't worth the money you will save.

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Long story short I have the same heads on my car now, however about 2 weeks ago I had to stop quick to avoid hitting a jaywalking walking in front of a large box truck.. she and her child must of thought no traffic was coming in the other lane.. lucky for me I was moving slow as the light was red, I had no time to clutch in and i slam on the brakes.. meanwhile the light changed to green and the engine pretty much died (loss compression) as soon as I pushed it off to the side and saw the passenger side cam was 11 teeth off I knew the valves got bent.. still after lining it up it had a hard time idling, it would but you can tell I was dealing with a huge compression loss, from the look and knowing the cam profile cylinder 1 took the hit. Seems the belt stretched but it was interesting that the drivers side timing was still spot on.

2 years ago when I did the head gaskets on my car I had the heads resurfaced which was no big deal and I plan on doing it again

Gort the giant robot said:

Finding a Subaru cylinder head without bent valves is the hard part. If a Subaru loses a timing belt it bends the valves.

Gort.

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It's not that hard

MikeF2316 said:

I think you'd be crazy not to lap them while you have the heads off. And you'd be crazy not to change the valve seals too! And of course, as you've done, a thorough cleaning of everything.

Obviously while you're doing that you'd make sure the valve guides aren't worn, or you're just wasting your time. From your pics it looks like you've done a successful job.

I had the head off my 4 cylinder '76 Volvo back in the day. I lapped the valves before I put it back on, I remember being thankful there were only 8 total!

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And yes I ordered a valve keeper tool and 16 new valve seals, it's not that common for them to leak past the seal, my car has 265K and the seal is still good.. but since I'm this far might as well do it anyways since you never know how long the heads have been sitting for.

Long story short I have the same heads on my car now, however about 2 weeks ago I had to stop quick to avoid hitting a jaywalking walking in front of a large box truck.. she and her child must of thought no traffic was coming in the other lane.. lucky for me I was moving slow as the light was red, I had no time to clutch in and i slam on the brakes.. meanwhile the light changed to green and the engine pretty much died (loss compression) as soon as I pushed it off to the side and saw the passenger side cam was 11 teeth off I knew the valves got bent.. still after lining it up it had a hard time idling, it would but you can tell I was dealing with a huge compression loss, from the look and knowing the cam profile cylinder 1 took the hit. Seems the belt stretched but it was interesting that the drivers side timing was still spot on.2 years ago when I did the head gaskets on my car I had the heads resurfaced which was no big deal and I plan on doing it againIt's not that hardAnd yes I ordered a valve keeper tool and 16 new valve seals, it's not that common for them to leak past the seal, my car has 265K and the seal is still good.. but since I'm this far might as well do it anyways since you never know how long the heads have been sitting for.

There are valve jobs, screw jobs, and put in any other adjective jobs: Which do you want? If you need a valve job for a big block, high HP 454, I would recommend use the right tools.

I have in the past, out of desperation done valve jobs on heads that had the valve seats in pristine condition, by putting valve grinding compound on the unground valves and handlapping the seats and valves vigorously until I was sure they mated perfectly. Which they did, because none of the valves were burnt, needed major dressing or showed signs of wear. Indeed, the heads didn't need a valve job. Don't forget that the valve guides get worn and are a good place for the engine to suck oil; oh, don't overlook the valve guides for restoration during your "valve job," or you might be tearing your hair out before you start doing your valve job over.

If your heads need a valve job, instead of minor dressing, you might regret cheaping out on grinding the valves and the seats with the correct angles. The seats have to keep cool(less than red hot) and the correct valve angle helps, the seats have to avoid causing turbulence in the intake and exhaust stream and the correct valve seat angle is engineered to help keep the got gasses coming and going in perfect time, the valve seats have to shed heat so they don't glow red and cause detonation (dreaded valve knock). The valves must seat perfectly for the thousandth of a second they contact the seat during the power stroke, correct valve grind will accomplish this. Don't forget, for every power stroke, there are three other strokes that have to be coordinated by the valves and pistons. Intake, compression, power, and exhaust. These valves are busy.

There are valve grinding tricks, changing the factory valve seat size, lightening the valves, narrowing the valve faces, grinding the width of the valve seat to a smaller width, and many more HP increasing tricks to increase gas flow over the valves while working to prevent pre-ignition. Such HP increasing tricks are bypassed when cheaping out on a basic head rebuild. The poor way to rebuild will accept a clear and present danger of F'ing up a basic valve job or engine rebuild.

While on my soapbox; doing a valve job to a tired and worn out engine will: increase compression and suction such that any blow by on the old cylinder rings will cause smoking, oil consumption, knocking, and other bad things, while the extra HP from a valve job will stress the tired and worn out connecting rod bearings, rattle the crank bearings which might contribute to a catastrophic engine failure, thrown rod, etc. Valve jobs are like prescribing Viagra to an inmate at the local nursing home, short lived fun. WFO until the bottom drops out, through the bottom of the boat.

All comments are based upon my past experience in engine rebuilding. I left the trade and stopped working for a living years ago. Now I am just an attorney, not good for much. Except when I am needed to extricate someone's tit or dick from being mangled in the wringer.

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