Valve clearance inspection results

[perk]

First of all, thanks to all who have helped me get to this point.

I very carefully and methodically checked and double-checked all of the clearances. I could see how easy it would be to make a mistake if one lost concentration.

I do have a few that are out of specs, fortunately not either of the rear #6 valves.
rear exhaust #1: .356mm
front intake #3: .254
front exhaust #3: .330
front exhaust #4: .356
front exhaust #5: .356
rear exhaust #5: .356
front exhaust #6: .356

Factory intake specs: 0.15-0.25mm
Factory exhaust specs: 0.25-0.35

A barage of ????'s
(Feel free to answer one...all...none )
I plan on adjusting these...it is necessary to adjust even though they are only slightly off right...? Should I expect the valves that are barely within specs to be out in the near future and therefore adjust them now while I'm in there?
Is the optimal clearance right in the middle of the range? Is there any noticeable difference in how the engine runs from the bottom to the top of the specified range? Should I expect to notice a difference after adjusting? Should compression increase?

I guess I am on hold until next week when I can get SST's and shims. I'm hoping Dan can send me the SST's. My local Toyota parts dept. won't sell them. Hopefully they aren't too expensive, as I probably will only use them this one time. Sure wish I could go borrow them from Toyota...yah right

Thanks
Perk

 

[Riley]

I'd be interested in what Robbie thinks but your clearances are so close to spec, I wouldn't mess with it. I always thought being a little wide is better than being too tight.

But I'm certainly no expert.

 

[IdahoDoug]

Perk,

I'd want Robbie's/Christo's/CDan's take as well, but as far as I know the valve clearances tighten with wear. If this is so, yours are all at the tight end, so will move toward the center of the tolerance over time. Which means if you like the way it is running now, it will be slightly smoother in another 100,000 miles.

DougM

 

[sleeoffroad]

What are the other readings. I assume you have only posted the ones you consider out of spec. They are on the open side, so I would not bother. It will tighten as they wear, so you should be ok. If they were on the close end, you should asjust them looser or closer to the middel/upper end of the spec.

 

[cruiserdan]

I echo Christo's observations. What are the other readings?

 

[John E Davies]

as far as I know the valve clearances tighten with wear. If this is so, yours are all at the tight end, so will move toward the center of the tolerance over time. DougM

If the valves get tighter, the clearances will lessen with miles.

However, I don't agree that this will happen. Neither does the experienced machine shop guy who rebuilt my head. He has done loads of Toyota twin cam heads (he does a lot of dealer work) and he recommends setting the clearances toward the minimum side, since _in his experience_ they LOOSEN with miles. I had him set up my clearances right near the lower limit.

This has been debated endlessly here..... I am interested to see that Christo recommends exactly the opposite. .

I just completed rechecking my clearances after 17,000 miles and I found that NONE had tightened. Six had loosened very slightly (none more than 0.001 inch). The total increase in clearance for all 24 valves was 0.006 inches, which is essentially within the margin of error for measuring correctly.

Since it's such a PITA to set clearances, I don't want to do it often, and recommend that anyone with out-of tolerance valves set them back to the tight end of the specs. It depends on how many miles you drive.... if you put only 10K miles per year on your truck your next valve check could be so far in the future that it doesn't matter!

Tighter clearances mean quieter operation and longer duration - the valves stay open longer. Tighter clearances also increase the risk of burning a valve since they have less time to dissipate heat into the seats.

My 2 cents. Run 'em (slightly) tight. Flip a coin and decide.

John

 

[e9999]

this is a very interesting topic.
Keep on bringing (not conflicting) info!

 

[IdahoDoug]

What's the logic behind this debate (looser vs tighter over the miles?). I'm guessing the 4.5's shim design has something to do with the difference vs the typical screw adjusters? If the shims are hardened it would force wear to occur elsewhere, for instance.

DougM

 

[cruiserman]

You need to pull the camshaft to do the shims on #6, so no need to wait for the SST. I would figure out what shims you have in there, and mix and max before deciding what shims you need to order. If it were my truck, I would get the clearances in the middle of the range and do whatever other maintenance you need at the same time (PHH, clean injectors, etc.).

 

[perk]

Thanks alot for your responses, I am sure glad you guys take the time.

Here is the complete list of clearances along with cylinder compression:

Intake Exhaust
front#1: .203 front#1: .305
rear#1: .178 rear#1: .356*

front#2: .178 front#2: .330
rear#2: .203 rear#2: .330

front#3: .254* front#3: .330
rear#3: .178 rear#3: .330

front#4: .203 front#4: .356*
rear#4: .229 rear#4: .330

front#5: .229 front#5: .356*
rear#5: .229 rear#5: .356*

front#6: .203 front#6: .356*
rear#6: .203 rear#6: .305
* out of spec

Compression
1-165 2-155 3-160 4-155 5-160 6-165

It's interesting there are differing opinions regarding valves loosening or tightening with wear. Intuitively, it seems that they would loosen with time, unless something is expanding??? I'm a little confused by Doug's reply, aren't my out of spec readings on the loose side? If they do tighten over time, should I adjust the .178's on intake, since I'm in there?
I drive between 7500 and 10000 miles/year.

Thanks again,
Perk

 

[perk]

You need to pull the camshaft to do the shims on #6, so no need to wait for the SST.

According to the FSM, only the rear valves on #6 require pulling the cam??

 

[Rich]

Wear occurs at different interfaces in the valve train at varying rates, due to differences in the materials, environment, and the forces involved.

Wear on the valve face and valve seat causes the clearance to tighten. Wear elsewhere in the valve train causes the clearance to increase.

The net difference in wear between the valve seat / valve face and everywhere else in the valve train determines if the net result is tighter or looser valve clearance.

 

[LukeO]

This is the first I've heard of wear causing things to tighten.

With engine wear I've always pictured less metal in between parts as mileage increases.

I always thought valves became loose and rattled with time and needed to be adjusted to tighten things back up again?

But I'm no expert.

 

[Rich]

You may wish to find a cutaway picture of a cylinder head / valve train. If you do, you will see how valve seat/face wear will reduce the clearance in the valve train when the valve is fully seated.

 

[RavenTai]

Pert did you find a metric feeler gage set? Just wondering why you are working in MM

I checked mine last summer one of them was .001" out on the high side, the rest were close to the high side, plan to get around to adjusting them at some point just not in a hurry to get to it. When I do I'll set them to the center of the range like the FSM tells me to.

 

[robbie]

The two different machinest we have used seem to side on that the twin cam stuff tightens over time. Back when I was on the80 cool list the ozies made the statement that the valve tightens. I have not had too many repeat valve clearence check that we could verify the statement. But if we look at the wear patterns of different materials in the valve train of a 1FZ then it may give us a clue. The cam is softer than the shim and bucket, the valve and seat wear due to heat, both are hard. The valve stem to bucket is both hard. So the true wear areas are the Valve to seat interface and the cam to shim. I believe that the area that gets the most wear is the valve to seat interface. I typically do not worry if the clearence is a little over specs, but do worry if the clearence is too tight. The statment by John is right in that you get at little more performance out of the tighter valve, but too tight may lead to a burned valve. Unless the cam is wearing faster then the valve to seat interface then not much else wears(loosen up) except the valve steam to bucket (very slight intial wear). Most of the stuff I have replaced is due to tightening of the valves.
In doing valve checks I have come to fined I can measure a set of readings turn the engine over and some times one will read some thing different. It can be flustrating at best. So If you want the experence of changing the shims then Have at it, The price of the shims are costly and as are the tools if you do not own a Micrometer and the tool for removing the shims. later robbie

 

[perk]

Thanks for the info...alot to weigh. I think if I decide to adjust I'll put them in the middle. Robbie...I take it you would not adjust any of those over specs. Would you adjust the ones (.178's) barely within on the tighter side?
With the SST's, is adjusting a difficult procedure?
Still wondering if I should notice an improvement in performance and compression if I did tighten up those out of specs. Is it true that a looser clearance will equal a lower compression?

Perk

 

[robbie]

First i do not think in metric when it comes to valve clearences. But to look at what you have even in metric You are close and I would ask if you would want me to spend your money(could only take a 1 maybe 2 do get it close to where you want and new shims at 8-9 dollars a piece) on this endevor for what I think is close enough for this time.
My sugestion is to use this for a base line and if you have the truck in 60k miles more then make a decision on what you would like to do with the next set of measurement.
One thought is that maybe your feeler guage set is not as accurate as you would like to think. have you taken a mic to it to see how off it may be? it could be thicker or thinner than you think.
any how just my thoughts. later robbie

 

[Tools R Us]

I haven't done an 80, but lots of VW's and other Toy's, with those numbers I would run it. Three digits right of the decimal is a very small number in metric! If they were .37+ then start worrying about it? To loose = tapping noise, to tight = possibly holding the valve open, leading to reduced compression and burned valve.

 

[John E Davies]

OK, here's a thought (a conjecture, not based on anything I have read).

If increased cam wear results in looser clearance, and increased valve recession causes tighter clearance, can we relate this to oil change frequency and engine abuse?

I would expect that an engine that runs a premium lubricant (synthetic esp) and gets frequent oil and filter changes would not see as much cam wear as one that has been neglected.

If you really flog your engine (eg: you tow a heavy trailer and run a non-intercooled supercharger), we could expect much faster valve seat wear (recession) and tighter clearances.

So a pampered truck that gets driven easy ought to see the clearances remain the same or perhaps tighten. A truck that gets used for prolonged hard towing would likly see the valves open up.

Does this make sense? Comments?

John