4.0 Valvetrain

[avid]

Is this difference in the height of the valve stems a problem?

 

[SenorNoob]

I'm gonna say no because you have hydraulic valve lash adjustment. As long as nothing is outside the range of that it should be fine.

 

[Uncle Gump]

Well being the 4.0L has no adjustment for valve lash... it certainly could be a problem.

 

[avid]

I've never had to dig into a valvetrain before so I have no idea. I just thought I'd ask before I spend a bunch of time trying to figure all this stuff out. The guy in this video (at 42-seconds in) says the valve tips need to align to a straightedge but I don't know if he knows what he's talking about or not. He sounds like he does, so... I'm sure some of the members here on the forum know the answer.

 

[Uncle Gump]

There should be a spec for valve stem installed height.

Did you measure the distance of the gap in your photo?

 

[avid]

There should be a spec for valve stem installed height.

Did you measure the distance of the gap in your photo?

I haven't measured yet but I will. We had a blizzard yesterday after 70s the day before. It's finally warming up to get back out there. I need to finish cleaing up those lifters too so I'll post a little later.

I have not been able to locate any specs yet for what the length of those valve stems should be, or anything official about whether they should line up or will be different.

 

[Uncle Gump]

Again.... because they're non adjustable... they have to be close.

You're allowed .022 inch variance on the spring height. I would think that's likely the allowed tolerance on tip height too.

The closer to exact the better...

 

[avid]

Thanks for the reply and info, @Uncle Gump. But isn't the spring variance there .031 rather than .022?

(You have to be a little careful with Google AI as I just asked it the valve order for a Ford 4.0 OHV and it told me there were two intake and two exhaust valves per cylinder. )



I measured the gaps with a straightedge and this is what I got.

Cylinder Head 1 (Passenger)

1 E: .031 low
1 I : .031 low
2 E: ———
2 I : .014 low
3 E: ———
3 I : ———

Cylinder Head 2 (Driver)

4 E: .022 low
4 I : ———
5 E: .006 low
5 I : ———
6 E: .007 low
6 I : .002 low

The photos with a straight edge wouldn't focus on all valve stems at the same time.



In case anyone is interested in looking at the other side of the cylinders where the valves function:

 

[avid]

Here's an interesting (and brief) read on Installed Valve Stem Height from some ASE certification practice test website: https://www.freeasestudyguides.com/valve-stem-installed-height.html

That page addresses the possible cause for a valve stem being higher than others, but not lower. (Higher could be due to the valve face or seat being worn).

 

[Mechrick]

In case anyone is interested in looking at the other side of the cylinders where the valves function:

I think you may be experiencing seat recession. The seats get pounded out and the valve stem will be a bit higher on that cylinder. Do you have a valve spring compressor to tear it down further?

 

[Uncle Gump]

You're right @avid ... I looked right past the .009

And for the AI... I get it. But by past experience with these sorts of things... it seemed close enough to give you an idea. It was also the first thing on my search.

Typically the exhaust valves and seats take a bigger thrashing then the intakes.

Why are the heads off in the first place?

I would be hard pressed to just reinstall them without freshening them up.

 

[avid]

I think you may be experiencing seat recession. The seats get pounded out and the valve stem will be a bit higher on that cylinder. Do you have a valve spring compressor to tear it down further?

I don't have a valve spring compressor but I wonder if auto parts stores have that as a "rental" tool. I suspect they would.

I read a couple reasons valve stems would be higher: 1) wear to the seat and 2) streching of the valve stem. And it's possible some of mine are higher, but it would be curious if 5 of them are higher by the same amount.

I don't know.

 

[avid]

You're right @avid ... I looked right past the .009

And for the AI... I get it. But by past experience with these sorts of things... it seemed close enough to give you an idea. It was also the first thing on my search.

Typically the exhaust valves and seats take a bigger thrashing then the intakes.

Why are the heads off in the first place?

I would be hard pressed to just reinstall them without freshening them up.

I've only recently been using google's AI to point me in the right direction. It's sorta like everything else online: it might be right but you can't really believe it without some official source. But it's ok for low-stakes questions.

The heads are off because I was inspecting the valvetrains while the engine is out and noticed several of the lifter cups were broken off. So I pulled the heads to replace some or maybe all of the lifters.