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Valve Timing

by eyevahn, May 6, 2015

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2002 Corolla 173k miles, dinking 1qt of oil per 200 miles.

I recently pulled and disassembled my cylinder head. The entire combustion chamber was black. The tops of the pistons, bottoms of the intake and exhaust valves... everything caked in thick layer of burnt oil. The exhaust valves were caked half way up which increases my suspicion in a plugged catalytic converter.

Anyways, I had .010 machined off the head and will be reassembling it and reinstalling it soon. Will .010 throw the cam clearances and timing off? What do I need to do to adjust for the change in cyclinder head. Thanks.

Your inlet and exhaust timing will then be retarted by almost nothing. No need to be concerned about it. It can't be adjusted anyway... You're replacing the timing chain, and the valve seals?

To stop it from burning oil, you'd have to remove the pistons to free up the rings, clean out the ring grooves, and drill out your clogged oil holes.

The chain is in good shape, I have oem toyota rings ready to install after I pull the Pistons out. I was going to add the extra 2 holes in the pistons as well.

I'm doing new O2 sensors and catalytic converter too. The upper O2 sensor was completely charred. I'm assuming the cat and lower O2 sensor are cooked as well. I was having all kinds of rich/lean hesitation issues before I started this project.

So, I should be good to just throw the head on there without any concern for the .010 difference? Thanks for the reply.

Factory service manual recommends against the head being shaved down. Mating surfaces can be cleaned with a scouring pad, but no material is recommended to be machined off. If the head's flatness if outside of spec, the head is replaced. Decking the head won't affect the clearances with your valves and camshaft, but they could issue with potential interference between the valves and the piston (remember, the 1ZZ-FE is an interference type engine and there is a reason for that dished piston top with valve reliefs).

That said - I don't think the 0.010" difference will be a deal breaker. Only time where that could come back and get you is if it continues to consume oil. Those extra deposits could cause the piston to actually make contact with the head. If I remember correctly, the taper squish design (how the edges of the piston top turn up with the corresponding combustion chamber bowl shape) doesn't have a lot of wiggle room before it makes contact. Don't think 0.010" will make that difference - but add that same about in carbon deposits on both sides, then it is a different story. Since it sounds like the work was already done - just throw the head on there, get the rest of the engine built up, and hope that the oil consumption has been nipped.

Yup - good call on the O2 sensors and cat. At the rate you were consuming oil - petty much everything downstream of the engine will likely have a good coating of oil / carbon deposits. Additives in the oil, if they didn't clog the cat, would have greatly shortened its lifespan (poisoned). Same with your O2 sensors, both upstream and downstream - once additives make their way past the shroud and contaminate the central electrode - readings would be compromised, would explain the funny behavior you saw.

Alright, so I've got pistons 2 and 3 out right now. I've got them pretty clean compared to what they looked like when I pulled them out. The grooves for the rings were caked in buildup as expected as well as the holes completely clogged. I drilled out the 4 existing holes and added 2 new holes, 1 in between each of the pairs of existing ones. I've got a question though. I've slightly scored the upper edges of the groove, is that going to be a big deal?

Also, I'm going to go ahead and replace the bearings. Do you just pop the old ones out and slide the new ones in with a little oil?

This is my first time messing with pistons/bearings so I'm hoping I'm not screwing anything up.

One short slight score on upper edge of ring groove is not too bad, as long as the ring doesn't snag... Maybe just buff out any protruding material with fine emery cloth.

Believe it or not, submerging the pistons in a bucket of water overnight is a great way to clean them all out. It breaks down the carbon, leaving the pistons immaculate and undamaged.



Forgot to ask earlier, is the engine in the car or is it out of the car?

As for the bearings, assuming you mean the rod bearings (fit in the big end of the connecting rod, contacts the crankshaft? Unless they are out of spec, damaged, or you've experienced some rod knock - not necessary to replace them. Though since you have the engine open - might as well do everything you can.

As replacing them - it is pretty much as you said, pop them off and replace them coating them with a little oil or assembly lube (depends on the bearing manufacturer). You will need to get some Plastigauge to check bearing clearances, if you don't already have it on hand.

Engine is still in the car.

And yes, the rod bearings is what I was referring to. Could you explain what plastigauge is and the process of checking the bearing clearance.

I went with OEM head gasket from toyota. Most of the gaskets I got were oem toyota but I did get a few from rockauto.

So, as of today, all 4 pistons are out, new holes drilled, cleaned and oiled. I'm waiting for my new bearings to come in so I can put the pistons back in.

I ended up ordering all new exhaust valves for my head because the old ones had so much buildup on them almost halfway up. By the time I got it all off they looked dull, like there finish was all off. So I just said screw it and ordered new ones From Rockauto.

Engine is still in. I've got all 4 pistons out now and cleaned, with new holes drilled.

As far as the rod bearing clearance goes, what do I need to be looking for? And what is a plastigauge?

I'm using oem toyota head gasket, intake and exhaust manifold gasket, and valve cover gasket. I got fel-pro for the valve seals, throttle body, and headbolts.

I just ordered all new DNJ exhaust valves. After cleaning my old ones they had no shine to them, not sure if that matters or not. I was just wondering if the finish was stripped off or something. Also have DNJ bearings coming in.

Thought my first post didn't stick... oops

Plastigauge is a precision plastic feeler gauge - so to speak. It allows you to check bearing clearances or clearances in hard to reach areas. Basically place a strip of the gauge material on the bearing - torque the part down, disassembly and use the provided measurement card to check the width of the now flattened plastic strip. How much that strip flattened out will tell you what the clearance is. More info - check out the website:

Great to hear of your parts lists - OEM gaskets are a plus, you know there will be no clearance issues and they will be guaranteed to fit/work right. DNJ components are pretty decent for O.E. replacement needs. I actually lived really close to one of their locations back in the day. They've been around for some time, mostly known in the domestic market, but making a name for themselves with the imports.

As for the exhaust valves - no shine should not be a concern. Might have picked up that some old school engine builders like to make the exhaust side as smooth and polished as possible to promote efficient exhaust flow, the intake side intentionally set up rough to promote air tumble for better fuel atomization. Some shops still go on this mantra - though with the design of the 1ZZ-FE induction and combustion chambers - pretty much negates any benefit of good old "hot rod" tuning.

Just make sure there are no carbon deposits or heavy gouges in the combustion chamber (potential hot spots) and you should be good to go.

You do need to reset any of this forum's pages lately, to see it in its updated state with the last post showing.

What about lapping compound? I was told by a friend to make sure to use it to help with valve seating.

Also, when I go to tap the pistons back in, is it possible that the rod bearing could pop out? Or do the stay tight in their spot?

Thanks for all the feedback.

Lapping is not necessary unless you find that the valves are not sealing well (use a dye on there, close the valve and check the imprint). Only need to clean up the area with a little scouring pad - should not cut these seats like in older cars, as the water jacket is actually touching the seat to help cool it, not much material that can be removed before damage occurs.

Bearings usually stay in place - especially with assembly lube on them. But I have seen a special plastic sleeves that hold prevent the bolts from scratching the crank journals that also hold the bearing. Haven't used those myself, bearings that I put in seem to hold on pretty snuggly. Tapping in the piston shouldn't be so hard that it pops the bearing off, if it does - might need to check to make sure the rings are in right / end gap clearance is set right.

Update: Pistons, new rings, new bearings installed. Rod caps torqued to spec.

I'm working on assembling the head now. Should be ready to go on tomorrow.

Right now I'm trying to figure out what to do with my exhaust. The O2 sensors and cat are toast. I'd like to just replace the entire exhaust from below the manifold. OE is just too expensive. Do you guys have any preferences with exhausts? I'm looking at walker or eastern cat but don't know much about either.

Walker makes exhausts for lots of OEMs - from what I hear, they are OK. Eastern, I don't have that much experience with, so I can't really say if they are good or not.

Might look into a custom exhaust - lots of times, those can be built up at a fraction of the cost of a premium aftermarket - but not sure if you want to take it to a shop, or just want something that is OE like - bolt on and go sort of thing.

Okay, thanks.

So, I've got the head fully assembled. The only issue I had was tapping the valve seals in. I tapped until the sound of the tap changed and it appeared that the seal was down as far as it would go. But I guess it just makes me nervous because you can't get a great visual looking down the holes. Is there anyway to make 100% sure they are tapped down far enough or not too much?

Sounds like you got it right, they should bottom out on the bushing that they sit over. Just make sure they are going on straight and not get cocked as they are going on.

Alright, so I put the cams on the head to check the valve clearance. All of my intake clearances fall between 0.010-0.006, but not a single exhaust clearance was in spec, which is 0.010-0.014. I had some in the 0.003 range. How do I adjust the valve clearance on my exhaust side to get them to spec?

Are you sure your camshafts are properly timed and positioned at crankshaft's TDC ? Are the inlet and exhaust lobes of the clearances you're checking at equal angles (\ --- /) ? Valve clearances should not have changed much. Did they reseat the valves as well, when they shaved the head?

Valve lash clearances are adjusted by replacing the shim-less bucket-type solid lifters. I adjusted all 16 valves from loose to tight with 7 new lifters, and by switching the other ones around. Valve lifter thickness is clearly marked underneath, which does correspond to actual micrometer measurements. They're available in 35 different thicknesses in 0.02 mm increments, from 5.06 to 5.74 mm. Some original lifters are in 0.01 mm increments. A "49" marked on lifter means it's 5.49 mm thick.

I'm measuring the clearance with the head off. I wanted to make sure it was good before putting the head back on.

I'm using a wrench to manually turn the camshafts and measuring the clearance above each lifter with the lobed side up, or perpendicular I guess. All the intakes were fine but the exhausts were all out of spec.

I looked in the operating manual after you mentioned it and it looks like I'll just need to get new lifters for the exhaust side. There's a formula to follow using the existing lifter size and current clearance to determine new lifter size.

I'm just curious how this happened, or mainly, how to prevent it from happening again.

My cat is plugged up so my guess is exhaust was not able to freely move out of the combustion chamber which is why my exhaust valves were totally caked in carbon buildup.

I guess what really confuses me is the "how" with a loss in clearance.

My valve seats haven't changed, I used brand new exhaust valves, and the springs are set with the keepers... so the lifters are the only place an increase in height could have occurred, lowering the clearance from 0.014-0.010 to 0.003 in some cases.

The lifters fit smoothly in their place so how did the clearance change?

You didn't get the lifters mixed up by accident? Good that the lifters fit smoothly, as I was going to ask if they were binding up on you. Got the order right when you replaced it? From bottom to top, spring seat, valve seal, valve (pushed through the seal easily, no rips or tears), valve spring, spring retainer, then keepers.

The exhaust valves are the same size, correct? They made two different sized valves - one was specific to the 1ZZ-FE found on the Celica GT, MR-S, and some Matrix models - it is slightly oversized compared to the standard fare valves. Not sure what that will do if you have them installed. Same with the reverse - if you installed standard sized exhausts valves in a head that had the larger valves.

Could be a pool of excess oil pushing up on a lifter? Hard to say - might just let it sit for a big and recheck. Might automagically "fix" itself.

It is absolutely crucial to have the cams in their precise and natural position as they are when properly timed with the chain to check valve clearances, not perpendicular but on an outward angle: \ --- /

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