Didn't track order of valve lifters

Thanks, I'll let you know in a few days, hopefully. This valve clearance thing was the last of the big hurdles, now I'm down to simple reassembly

 

Sympathetic wear only has the actual effect of increasing clearances due to wear. You've checked all of the clearances and placed them in spec. If any of them are close to out of spec now is the time to replace them with a new, properly sized lifter.

 

No, I rearranged them so that that each is pretty much dead center within the specified range

 

Sounds like you need to butter them up with assembly lube and get that puppy buttoned up!

 

This: http://lucasoil.com/products/engine-oil-additives/engine-break-in-oil-additive-tb-zinc-plus

?

 

This: http://www.motosport.com/product?ps...e=&network=g&gclid=CPT72OLsxscCFQuQaQodKzAL_w

 

are you sure ? that's marketed for dirt bikes

 

Assembly lube is assembly lube is assembly lube.

 

I came to an odd discovery after measuring valve clearances. I found that three consecutive intake valves in the left engine bank (positions 2, 3, and 4 from the front of the engine) each had a total clearance between the tip of the valve and the cam when the camshaft in the proper position that even the thickest lifter I had (#46 -- 5.46 mm) would still leave too much clearance (Toyota says the clearance ranges should be 0.15-0.25 mm for intake and 0.29-0.39 mm for exhaust). One was just slightly out of the range at just over .25 mm but the other two were substantial (around 0.3 mm each. so at least 0.05 mm off). Luckily, it is possible to order thicker lifters to close the gap and get the clearance in the range. All the other valves, after my carefully analyzed rearrangement, fit not only within the range but also very close to the sweet spot right in the middle of the range.

I can think of several explanations to this:

1. Factory f**ked up when assembling (not likely but possible)
2. Cylinder head warped so the area where the three valves are sort of caved in a little to open a bigger gap between the lifters and cams
3. Cams got smaller by distortion or something (I guess I should measure them with a caliper).
4. I messed up my reassembly of valves (really not likely, I exercised Nazi-like quality assurance and made sure the valves sit in tight and there are no leaks)

So I calculated the new lifter gauges that I need to use in order to close the gap and ordered them.

My question is, in case of scenarios 1 and 2 above, which means that the clearances were too big before I took the engine apart, how would this deviation manifest itself ? I am guessing that, due to a bigger gap, the valves would not be opening as much as they should be. But how would that affect the engine's functioning ?

 

Typically clearances get tighter as the valves wear into the head if that makes sense. If the gaps increase it could mean there's carbon fouling going on but that's typically only on exhaust valves and rare in my experience. The gaps on spec are pretty large for the 1GR being .1mm; if it's out of spec .05 on the loose side you'll get less power since the valve isn't open as long as when it's in spec. Tight valves are much worse then loose valves but both aren't good over a long period of time. Try setting the gap you measure with the feelers to the middle to loose (larger) end of the spec. So .39mm for exhaust and .25mm for intake.

FWIW my motorcycle tolerances are .05 mm in range i.e. .10mm-.15mm intake and .25-.30 for exhaust. I change shims out for my adjustments, and if it's an option between being at .11mm for intake or .16mm for intake I go to .16mm even though it's slightly loose out of spec. I know for my bike that .16 gap will close to about .13mm in 10,000 miles or so and so I probably won't have to change the shim on it for two valve checks. Granted my bike needs valve adjustments and shim changes every 10-15k miles but it's a much higher stressed motor then the 1GR.

Did you turn (by hand) the crank/engine a few times and remeasure?

 

Yes, so that the lifters set in tight

 

After an engine breaks in a bit usually the valve clearances stabilize some and stop getting bigger especially in lower stressed engines, at least in bikes.

Edited my last post to fix some numbers.

 

Yes, those were pretty much my target clearances. But with those three, I couldn't achieve that with the present set of lifters because none were thick enough to get in the range so I had to order thicker lifters.

 

How many miles since the last check, and how many on the engine?

 

This is the first time I ever did it. 123K mi

 

Changing a few out wouldn't be unexpected at that mileage. Why they're loose and not tight is slightly puzzling but I wouldn't worry too much about it; just get them in spec. Are you the first/only owner?

 

Another explanation is that the corresponding camshaft lobes got chewed up by wear so they shrunk in size.

Still, the offs are not too drastic, 0.05 (1/20) mm the worst, which gives me hope it is not some sever warpage. I bought the truck with only 6K mi back in 2007, I think it was repoed, so I am defacto the only owner.

 

Is there any pitting on the cam lobe? Typically cams are super hardened and don't wear a noticeable amount but in theory it's possible.

 

what do you mean by "pitting" ? i don't understand that word in the context.

 

That's pitting on the end of a cam lobe. That's very bad. It should be smooth.