3rz valve lash job and cracked manifold

It goes to a trusted mechanic tomorrow am. 210k miles 3rz manual. Lumpy idle , exhaust manifold Is cracked clear in half at the half way point. I don’t think the valves have ever been set , previous owner didn’t know much. Was told cyl one has low compression. Is there any point in doing a compression test to confirm before a valve job or will setting the valves identify which cyl if any is indeed suspect?

 

It’s been a long slog to get here so sorry if that’s a dumb question , compression test or not , maybe the mechanic will do one as a process of elimination? With the manifold cracked in half so badly I figure it must have a lot to do with the rough running , smells like it’s running rich too? When it warms up and get up on some revs it really seems to boot along quite well so there is something to shoot for.

I’ve done a lot of work on this particularly underneath patching the frame in one location with a good friend and his welder and have since put at least 10 cans of fluid film in the frame and crossmembers then gone over that with a wax and oil based coating. I’m talking months of hammering shit of the frame and working bugs out of this. Btw the dent on the drivers side is from a moose. It adds character.

Just the usual first gen money pit in the heart of rust country... admire all the work of others on here but damn I get jealous of non rusty Tacoma’s in Texas and NM etc. Drilling out broken bolts sucks!!

 

Resetting the valve lash won't tell you anything about the compression. I compression check may be a good idea so you know what you have. If the compression is low due to a valve being too tight you will likely have a burnt valve and the head will have to come off for a complete valve job. But that is getting way ahead of where you are today. Have them check the valves and replace he manifold. They can also quickly check for blow by to see if your rings are excessively worn.

 

Valve lash only affects the compression if there isn't any clearance (which is rare) and the valve isn't closing. Otherwise its for noise, and proper timing of combustion.

I tend to inspect compression first, then decide on a leak down.

EGR maybe leaking, a valve may be burnt, a headgasket may be failing etc.

 

Thanks for your thoughts. Really hope it doesn’t turn into a fishing expedition with eventual head tear down. I had hoped the new OEM header I ordered would at lest partially help. Btw no engine codes shown. I bought this as a side by side or sorts not my daily but still would like it trusty and functional. I bought it at parts price but have put hours and hours into it so far.

 

All exhaust valves are tight , mechanic doesn’t know if he can shim it, as in no clearance left. The valve stems stretch o guess. I’m gonna run it.

 

After reading a bunch of other threads on this common issue 3rz exh valves tightening / burning ... with the extreme little or no lash clearance left it seems I’m driving a ticking time bomb in that I’m just asking for the head to crack. At some point when the weather gets better in spring time I guess we will pull the head like most everyone else and weigh options like overhauling vs China head

 

Going through the same thing on my buddy's 98 3RZFE. Going to pull the head tomorrow and verify cyl #1 and #2 exhaust valves are burnt after finding a cracked manifold and doing a leak-down. We're likely going to slap a remanufactured head on it but are trying to find the right company.

Good luck with yours and keep us posted!

 

hot seats get bashed into the soft aluminum head. Machine shop trims top of valve tip to shorten it, valve job to reseat.

 

Did he measure your existing shim and record it? I had some exhaust at .002 or. 003, just order the correct thinner or thicker shim.
Done deal

Also if you get a new or rebuilt head you'll still have to check your clearances, don't assume they'll be right.

 

This might be a very dumb question but, if the valves have never been set from factory , then what is the standard or default shim thickness? Or is that impossible as every head setup and valve combo is unique and needs a unique shim size?

 

https://www.yotatech.com/forums/f128/5vz-fe-3rz-fe-2rz-fe-valve-adjustment-tech-226997/

Here's some reading for you on basic valve setting overview. There's a bunch of post's on this inside the forum if you know how to search for them, I suck at it, I posted one myself a few years back.
I'm gonna go out on a limb and say yes, the valves are/should be correct from the factory from the get go, but after that time period, all bets are off,,,, my truck when I bought it had a rebuilt head that had been recently installed, just about all the exhaust valves were off if I remember right. Number 4 exhaust was the tightest, about .002" or .003", I can't remember. This was after a rebuild job.....

So I did a go through on all the valves, pulled the valve cover checked clearances and recorded them and pulled the shim, miked it, recorded and then went to the shim chart in the OEM manual and ordered my new shims, some I was able to swap around to get the right clearance.

Some guys pull the cam to get to the bucket because of the "difficulty" of getting to the shim, I didn't, I used and made some special tools to do it in place, it really wasn't that hard to me.

Do the search on setting the valves, there's a pretty good video of a guy doing it that'll help you.

 

Buggy, the valves are precision set from the factory, as in they are all slightly different and they install a test shim across all of them (usually a safe thickness), then take measurements, and then isntall the final shims (using the difference) that bring it in to the desired gap, and then they reinstall cams and recheck clearances till its perfect. Assuming no valves get burned up etc.. they should not change much over the life of the engine.

Sometimes when doing head swaps or headgaskets, people mix up the shims then you have to restart the process. I have done it quite a few times and it isn't difficult, just need the right feeler gauges and time.
.002 is way too close especially on the exhaust, you can probably remove the exhaust cam and measure and order the new shims for those cylinders to bring them back into range, but not sure if it will help as the valve is likely burned up.
when the valve is burned up it isn't just the gap but the valve and valve seat itself can be damaged. If you can get any feeler in there (even a .002) without forcing it in, then the valve is closed and it is likely bad.
If there were no gap to where you couldn't get a feeler in, the valve might be cracked open some and I would say you might be able to save it by shimming.

You can pull the cams and do a leakdown test on that cylinder, then you will hear what the problem is. IF you have the exhaust manifold out, stick a finger in the port and see if you can feel it wooshing out.
really at this point, I would do a leakdown test but since its a common problem, like other people said valve job or remanufactured head are decent options time and labor wise a remanufactured head might be better.

 

Really good input here

 

Get the 4runner mini header instead of the normal cast manifold. It seems all the cast manifolds crack eventually.

 

This is opposite though. If you CAN NOT get in a gauge of any thickness, the valve has been held open (that's how they burn, valve never closing completely on compression stroke) and chances of being burned are up.
A small opening gives hope you caught in time.

Remember, a small gap cold closes up when hot, making problem worse.


edit: To Op question though, yes correct that no same shim fits every valve from factory. I can't believe we still haven't got a floating shim kit. Every motorcycle forum I've been on made that one of it's main points of existence. Saves soo much time to do valves when you have a nice selection on hand and Toyo. crosses over to many models that fit.

edit 2: That 'less than .002' on #1 and the fact that he got a low compression reading doesn't sound too good. How much 'less' is going to have bearing.

 

Chances are up, and get larger as time increases. IF it just started to happen, it might not be burned up just yet.
A small gap and low compression means the valve is closed and re-shimming would not help. The problem has to be the valve or seat or both.

If it is a little cracked open that could alone explain the low compression, and would lead to burning up in time but it takes a while as the valves are stupid hard steel, but if you were to reshim it in time the seat and valve might still seal... emphasis on "might".
likely it could still be messed up, which is why I said might be able to. if you do not reshim it and keep running it, it will fully burn up and never seal right again.
If op caught this as soon as the misfires/loss of power occured, it is probably salvageable with a reshim. you would need a leakdown with the cams out to be sure.

If that .002 gap was when cold, you should get normal compression readings if the valve is ok.
When warmed up likely that gap will close and you get low compression and probably misfires.
really, the gap isn't that far off from some of the highest valve gaps on the chart, so I think OP caught it early and might be able to save it.

So a very cold compression test might tell you if that valve is beyond saving, who knows when the mechanic did the compression test (could have been on a warm or hot motor) and then by the time they removed everything to check clearances the motor could have been cold. I am not a mind reader so I don't know.
Usually at that point, you pop off the cam and do the leakdown test, so the valve gaps don't come into play, but that takes more dissasembly.

If you have a good leakdown on cylinder 1 at the same time you have a small gap (when cold in this case) or if the cams are out, then you can just reshim it.

If you have good compression at the same time you have even a small gap on cyl 1 (when cold in this case), then you can just reshim it.

If you have bad compression at the same time you have a small gap (cold) or a bad leakdown with the cams out, you need valve/head work.