Curious, how do YOU check valve guides with the "wiggle" test?

Which way for you?

  • #1 - wiggle the stem valve shut

    Votes: 1 6.3%

  • #2 - wiggle the head valve open

    Votes: 15 93.8%

  • I'm afraid to attempt it myself :(

    Votes: 0 0.0%
  • Total voters
    16
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318willrun

318willrun

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#1 - valve closed and wiggle the end of the stem..... .002-.003 tolerance


#2 - valve open about 3/8 and wiggle the head.... keep it under .020 :D

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nm9stheham said:
Valve open.... but .020" is waaaaaaaaaaaaaaaay high for a good, reliable seal IMHO.

A useful question to ask, BTW.
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I've never went into depth about checking valve guides. I focused so much on home porting here at this site. I want to open up the can of "knowledge" that is in abundance here on FABO, and I don't want it to be just me.
  • So, how far out do you open the valve, and what do you find acceptable for valve "slop" moving the head side-to-side?
  • P.S. - I was vague in saying "under .020"
 
- Just open enough to grab reliably so that any wear on the stem is still in the guide.
- Around .006-.010" for a stem to guide clearance of .002", which is a stockish kind of clearance. But that is VERY general number, because it will vary from engine to engine depending on guide length and distance from bottom of guide to valve head, and how tight you want the clearance to be. Exhaust would typically be OK on the higher end of that.
 

mopowers said:
Here's what the FSM has to say. They use .017" as the service limit. I wonder how tall the official positioning tool is.

View attachment 1715089043
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And .017 is way too loose. If you think about it, with bronze guides I set the exhaust clearance at .003. That means .017 would be almost 6 times the clearance.

With cast guides you can use .0025 clearance.

Talking 3/8 stems.
 
I've always took the valve out and measured with a micrometer at multiple points on the good area and worn area.
Then took the valve and put it in "upside down" valve in the spring side and wiggled it then to see how much its worn. (unworn portion of the stem into the valve guide side)
That gives me the wear of the guides. Add the two up and a good backyard measurement is had.
 
mopowers said:
Here's what the FSM has to say. They use .017" as the service limit. I wonder how tall the official positioning tool is.

View attachment 1715089043
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I think I have that tool somewhere. IIRC, it was about 1/2" long. I'll see if I can't scare it up, and measure it. It was in a bunch of Chrysler tools, I bought at a swap meet, years ago.
 
yellow rose said:
And .017 is way too loose. If you think about it, with bronze guides I set the exhaust clearance at .003. That means .017 would be almost 6 times the clearance.

With cast guides you can use .0025 clearance.

Talking 3/8 stems.
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But.... follow me before you correct me :D ........ Your tolerances are to make "better than new". Your a machinist that cares and takes pride in your work, no expenses barred. So, this may be very difficult for one such as yourself. However, picture a guy at home, that pulls the heads off, shall we say, to install new exhaust valves and lap all valves, or perhaps some home porting, wouldn't .017 be "acceptable" for this type of build?
 
318willrun said:
But.... follow me before you correct me :D ........ Your tolerances are to make "better than new". Your a machinist that cares and takes pride in your work, no expenses barred. So, this may be very difficult for one such as yourself. However, picture a guy at home, that pulls the heads off, shall we say, to install new exhaust valves and lap all valves, or perhaps some home porting, wouldn't .017 be "acceptable" for this type of build?
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I agree, but what I've found is even the best valve stem seal struggles when the clearance is that loose. Other than that it would be ok.

Also, with the clearance it beats up the valve job quicker.
 
when you use the wiggle method, it will show up as the guide is tapered. not a very true method. we mike guides and valves then install bronze liners, now the guide is straight. the valve job will last a lot longer. also, wiggle method doesn't show stem wear. can have both. like anything else, you get what you pay for!
 
The .017" is for the valve up out of the hole about like we are talking (see the illustration posted by Mopowers). Valve to stem clearance will be somewhere around 1/2 of the total wiggle for most engines/heads of this era, so I would guess a wiggle at the valve head of .017" is about .008" valve to stem clearance.

Compare this to a stock new tolerance of .001-.003" for intakes and .001" more for exhaust and you can get some idea of how sloppy loose service limits can be.... Service limits for piston to bore clearance are often up in the .008" range, and service limits for a /6 chain give you about 5* of cam retard! So for any performance use, service limits are IMHO not at all appropriate.
As for overall performance, it it not a matter of professionalism; it is a very real detractor from performance and durability. Using wide valve-to-guide clearances do indeed result in erratic valve seating (acting similarly to worn rings and grooves) and fast seat wear, as YR indicates. It is just gonna get worse as you put in a bigger cam and struggle with idle vacuum, etc. I rank it just as important as a good ring seal if you are after performance.

I often have knurled guides to get a a tight guide for a while when I was cash limited, just to make things run better. So that is one alternative to the cost of new guides. Guys who runs shops for local circle track racers do this regularly in my experience; they are dealing with guys who race on limited budgets and need to get the engine as much up to snuff as as possible in a short time and for little $$ and for a few months of racing. It is a practical solution, albeit for a limited term.
 
One can wiggle them for an idea. But a modern valve job has to have perfect guides to be of any quality. So honestly, it's not even worth me checking. I just budget for guides or liners.
 
moper said:
One can wiggle them for an idea. But a modern valve job has to have perfect guides to be of any quality. So honestly, it's not even worth me checking. I just budget for guides or liners.
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I fully agree with Moper; part of properly redoing a head IS new guides. Years ago when I was Dealer ship wrench we would send heads out to be knurled to save $ and slow oil burning on used cars.
Now a days with Viton seals and bronze guides; you can have a tight valve shaft tolerances and valve seals that last! I like bringing iron heads to the machine shop- for an older auto machinist, these old Chrysler heads are a walk down memory lane. I've even asked them if they had any old Chrysler heads and have come home with more than one set of good heads cheap (beer money!) Ya just gotta ask.
 
Syleng1 said:
I fully agree with Moper; part of properly redoing a head IS new guides. Years ago when I was Dealer ship wrench we would send heads out to be knurled to save $ and slow oil burning on used cars.
Now a days with Viton seals and bronze guides; you can have a tight valve shaft tolerances and valve seals that last! I like bringing iron heads to the machine shop- for an older auto machinist, these old Chrysler heads are a walk down memory lane. I've even asked them if they had any old Chrysler heads and have come home with more than one set of good heads cheap (beer money!) Ya just gotta ask.
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Agree w/ the last two posts. My head guy is an 18 time national record holder, and lifelong friend. Does heads for himself and customers. He can wiggle a valve and tell weather it needs guides or not, I can too now, no secret to it. He uses a new bronze screw in quide that has to be reamed to fit, and comes out precise, and lasts very well/ they are usually tighter than what is mentioned here, and no taper to them. Machine work of any kind is only as good as the guy doing it.
 
The reason for fresh correctly sized guides as a precursor to the valve job is that the high end valve and seat machines need a straight guide to do their job properly. You can't get a good seat of angles cut if the pilot can't be centered because it's rattling around in a loose or tapered guide.
The key to power in any Mopar shaft type head is the quality and accuracy of the valve job.
 
Reviving this thread for some help. I have a pair of "new" EQ heads. Actually they had about 3 dyno runs on them. When I pulled the springs I found a badly bent exh valve. There were no contact marks on the valve. I chucked the rest of valves in my drill press and mic the valve face. I found 3 exh and 4 intake with very slight bend (.010 runout) even though they seat OK (no light shines through). I'll replace those. I have no idea what the cause was. On a recent post I have read that valve guide clearance should be checked for tightness on all new heads. Thinking this was the cause I tried a wobble test and I'm getting .005 on the intake and .006 on exhaust with the valves held about 1/2 inch off of the seat. This seems good to me as far as not being too tight. All valves slide freely in their guides. I'm tight on funds otherwise I would take another trip to the machine shop plus waiting a few more weeks. What do you guys think?
 
famous bob said:
Agree w/ the last two posts. My head guy is an 18 time national record holder, and lifelong friend. Does heads for himself and customers. He can wiggle a valve and tell weather it needs guides or not, I can too now, no secret to it. He uses a new bronze screw in quide that has to be reamed to fit, and comes out precise, and lasts very well/ they are usually tighter than what is mentioned here, and no taper to them. Machine work of any kind is only as good as the guy doing it.
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I've seen a couple of instances, where people had their seats cut with a Serdi type seat cutter machines, and the seats look trick, but don't seal against valve face, because the seats are not concentric with the guide centerline. I didn't do them so I can't tell you whether that was from the machine, tooling, and/or operator error. I just know I had to fix them with my old-school Sioux grinder. I have a vacuum tester I use to check the valve to seat seal. I used it to determine the problem initially, and confirmed that the problem was corrected afterward.
 
An older and wiser machinist showed me a trick he used on tear down after removing the spring and retainer put your finger over the top of the valve guide to seal it then pull the valve out if it pop's then it's good.
 
JoePole1 said:
Reviving this thread for some help. I have a pair of "new" EQ heads. Actually they had about 3 dyno runs on them. When I pulled the springs I found a badly bent exh valve. There were no contact marks on the valve. I chucked the rest of valves in my drill press and mic the valve face. I found 3 exh and 4 intake with very slight bend (.010 runout) even though they seat OK (no light shines through). I'll replace those. I have no idea what the cause was. On a recent post I have read that valve guide clearance should be checked for tightness on all new heads. Thinking this was the cause I tried a wobble test and I'm getting .005 on the intake and .006 on exhaust with the valves held about 1/2 inch off of the seat. This seems good to me as far as not being too tight. All valves slide freely in their guides. I'm tight on funds otherwise I would take another trip to the machine shop plus waiting a few more weeks. What do you guys think?
Click to expand...
I’d take them in as soon as cash allows and have the guides honed/sized properly, and replace any valves as needed. Do it right like your Grandpa would do (or have done) I never go wrong with that logic. I have EQ’s (the good ones) and added my own valves and even though the bare heads were marketed as ready for drop in valves, there were too many that were tight. To the machine shop they went for proper valve fitting and the required valve job. Why chance things when patience and a little extra time (and likely some new found funds) is all that’s needed:thumbsup:
 
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318willrun said:
#1 - valve closed and wiggle the end of the stem..... .002-.003 tolerance


#2 - valve open about 3/8 and wiggle the head.... keep it under .020 :D

View attachment 1715089026

View attachment 1715089027
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I use a Full Ball small hole gauge set and a micrometer and measure the guides (top, middle and bottom) and mic the length of the valves as well. Repeat a few times to verify. The tools can be had for not too much money, new or used, and the process works pretty good and is accurate enough once you get the feel of things. Half & Full Ball Small Hole Gage Sets | 419249 | Travers Tool Co., Inc.

EEDF8B75-1131-47CE-954E-184FABDA581B.jpeg
 
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318willrun said:
But.... follow me before you correct me :D ........ Your tolerances are to make "better than new". Your a machinist that cares and takes pride in your work, no expenses barred. So, this may be very difficult for one such as yourself. However, picture a guy at home, that pulls the heads off, shall we say, to install new exhaust valves and lap all valves, or perhaps some home porting, wouldn't .017 be "acceptable" for this type of build?
Click to expand...
Not for me. I have run up to .008 in my old broke days. It my buddies have run up towards .015. On the cheap side u could have the guides knurled. Ask ur head guy what he thinks. Kim
 
Forgot about this thread.... 4 yrs old. I got quoted and didn't recognize my own threads title LOL
 
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