valve stem height - need some help

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halfafish

halfafish

Damn those rabbits, and their holes!
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I bought a set of SpeedMaster BB heads, the fully assembled, non-cnc, hydraulic flat tappet version. I'm waiting another day or two till my valve spring tool gets here to disassemble them for a check, but so far they look good with one exception - all the exhaust valve stems are a fair bit shorter than the intakes. The intakes are all the same height but of the 8 exhausts, 6 are .039 short, one is .033 short, and the last one is .048 short.

I got some good advice on using adjustable pushrods or rockers to fix the mismatch (thanks @PRH), but either of those is a several hundred dollar fix and I'm trying not to bleed cash on this project. I intended to re-use the stock pushrods, and rockers. This is not going to be a beast of an engine, just a nicely spunky and fun street car so a hydraulic cam is fine with me.

Then while snooping around for adjustable arms or rockers and getting sticker shock, I saw some very old posts from @pishta on moparchat, suggesting the use of valve stem lash caps to solve a similar situation (pishta, feel free to weigh in on this!).

If I can find the right size caps that are .040 thick to add to the exhaust valves, would that solve the problem? That would put the six stems right on, one would be .007 short and one would be .008 long. I'm assuming with hydraulic lifters, being within .007-.008 is plenty close.

Has anyone tried this and if so, how did it work? It looks like it would turn out good on paper, but getting an informed opinion is better than guessing.
 
halfafish said:
I bought a set of SpeedMaster BB heads, the fully assembled, non-cnc, hydraulic flat tappet version. I'm waiting another day or two till my valve spring tool gets here to disassemble them for a check, but so far they look good with one exception - all the exhaust valve stems are a fair bit shorter than the intakes. The intakes are all the same height but of the 8 exhausts, 6 are .039 short, one is .033 short, and the last one is .048 short.

I got some good advice on using adjustable pushrods or rockers to fix the mismatch (thanks @PRH), but either of those is a several hundred dollar fix and I'm trying not to bleed cash on this project. I intended to re-use the stock pushrods, and rockers. This is not going to be a beast of an engine, just a nicely spunky and fun street car so a hydraulic cam is fine with me.

Then while snooping around for adjustable arms or rockers and getting sticker shock, I saw some very old posts from @pishta on moparchat, suggesting the use of valve stem lash caps to solve a similar situation (pishta, feel free to weigh in on this!).

If I can find the right size caps that are .040 thick to add to the exhaust valves, would that solve the problem? That would put the six stems right on, one would be .007 short and one would be .008 long. I'm assuming with hydraulic lifters, being within .007-.008 is plenty close.

Has anyone tried this and if so, how did it work? It looks like it would turn out good on paper, but getting an informed opinion is better than guessing.
Click to expand...




Lash caps are not worth the effort. Figure out why the valves are different heights. Either the valves themselves have different thickness of margins or the valve job is junk.

Either way, the fix is not lash caps.
 
You either have valves that are different lengths or a junk valve job as mentioned. Or both. Those are pretty big numbers for valve stem height differences.
 
Mike, if u have different stem heights u obviously have different spring heights all things being equal. Unless they put a different thickness shim under each spring which I think is unlikely. Or they missed a shim or two. The seats may be installed to deep into the head or not deep enough. Or as mentioned the valves may be the problem. Also the retainer and locks may be the problem. Kim
 
Its not a crutch for a short valve but its used to correct valve geometry on large lift cams. A short valve means all the other have sunk (gotten taller) or you got some carbon in the seat or even a bent valve. Id pull the spring and rotate it and see if it binds or doesnt have a solid thud when pulled shut. 'Lash caps' is not a good name for these, should be called "hardened valve caps"
 
In for a dime in for a dollar if you're putting performance heads on there why not a set of adjustable rockers? Then you can run solid lifters...
Screenshot_20191226-210755.png

A couple hundred bucks ain't much for a set of rockers...
 
I’m sure those millions of factory heads that were run without valve adjustment all had the tip heights perfectly matched.

Uh huh........ because the factory blueprinting on everything was spot on.
 
PRH said:
I’m sure those millions of factory heads that were run without valve adjustment all had the tip heights perfectly matched.

Uh huh........ because the factory blueprinting on everything was spot on.
Click to expand...

LOL
 
When you’re reworking heads for improved flow, many times there is no consideration made for the valve tip heights.
You position the valve depth in the chamber that flows best, and the tip height is what it is.

I just assembled a set of fairly expensive CNC ported Dart heads, that came from a very well respected porting service.
The intake/exhaust tip heights were off about .040-.050 from each other.
The intake seats were sunk a bit to gain more top angle length so there would be a better transition into the chamber, which results in the tips being higher.
That’s just how it is.

From another head porting service:
“The intake stem heights are equalized and the exhaust valve stem heights are equalized. ”

Notice they don’t say the intake and exhaust are equal height...... to each other.
 
I LOL'd you because I was in agreement that valve stem heights (among lots of other things) were far from perfect from the factory.

I still think I would rather have the valve stems all the correct and same heights than reposition the seats for optimal flow. That just doesn't sound right to me, regardless of how respected a porting service might be. "IF" I ever build one in that high end a category, I want valve train geometry to be dead on, even at the expense of additional flow.
 
RustyRatRod said:
I LOL'd you because I was in agreement that valve stem heights (among lots of other things) were far from perfect from the factory.

I still think I would rather have the valve stems all the correct and same heights than reposition the seats for optimal flow. That just doesn't sound right to me, regardless of how respected a porting service might be. "IF" I ever build one in that high end a category, I want valve train geometry to be dead on, even at the expense of additional flow.
Click to expand...
That is the way I've always done it on Chrysler heads. So far the air flow has been pretty good.
 
Many thanks for the input so far. I was hoping my valve spring tool would arrive today, but alas, it's in UPS purgatory at the moment. Perhaps it will get here on Monday. Once it arrives, I will get the heads disassembled for a better look and more measurements. My original intent was to go hydraulic, but it appears I will going solid lifters now. More on this to come...
 
halfafish said:
Many thanks for the input so far. I was hoping my valve spring tool would arrive today, but alas, it's in UPS purgatory at the moment. Perhaps it will get here on Monday. Once it arrives, I will get the heads disassembled for a better look and more measurements. My original intent was to go hydraulic, but it appears I will going solid lifters now. More on this to come...
Click to expand...

I pretty much agree w/ rrr and yellow rose------
In some instances tho ,lash caps are required , we used them on a s/s hemi engine quite succesfully w/ a hi 785 lift cam.
I think the heighth diff, is because of the depth of the hardedned valve seats and their machining in the chambers .
The springs are not the problem , a 300# spring will not be any diff. than a 400# spring as far as valve length .
 
The valve spring compressor just showed up, I'm off to the shop to see what I can figure out on these things.
 
Why would you go solid? If it's to keep from correcting stem heights, I don't recommend it. The whole purpose of hot rodding is to get more power. In doing that, tolerances and clearances are changed and usually tightened to more stringent specifications from what the factory allowed. Unless you correct the stem heights and get them all even and in spec, you're backing up, especially after purchasing aluminum heads. It's just not "that" difficult to do. If they were mine, I would verify what it likely is.......the seats or valves or both need touching just a bit more. Then take my findings to the machine shop and let them correct it. Won't cost much and your heads will be correct, instead of not correct. Then you can run hydraulic.......even though I still would recommend solid. LOL
 
This one from Amazon. I can get an item number later if you want it. Nicely made and about $30 IIRC.
20191228_131841.jpg
 
440 Mike said:
Thanks, let me know how you like it.
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I would give it an OK rating. It functions fine, but the amount of force needed to compress the springs required me to use a 24" cheater bar. It's decently made and perhaps for someone not on the downhill-slide side of life, it would get a rave review. Search Amazon for the below, it was $35.

WINTOOLS 16.7" Universal Adjustable Valve Spring Compressor Automotive Engine Repair Tool
 
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I have a new Pro-form Valve spring tool coming this week...I needed one that would handle 400+ springs.

I plan on copying it to make it better...
 
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Krooser said:
I have a new Pro-form Vale spring tool.coming this week...I needed one that would handle 400+ springs.

I plan on copying it to make it better...
Click to expand...

If you're talkin about the ProForm pneumatic one, it won't handle it.
 
I have a friend who has the LSM sc-2000. That's a bad beeotch.
 
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