[dblotii]

Advice from a long-time engine engineer: It is a really, really bad idea to consider reusing any pistons with more than 200k miles. To even consider reusing a piston, there is a lot to inspect with very high precision, like piston diameters (at different locations on the skirt) the dimensions and trueness of the ring grooves, and the piston pin bores and pins. Even if the skirts look OK, it is very unlikely that the ring grooves will all be within spec.
It is normal for the honing cross-hatching to be there after all this time. The cross-hatching is there to hold oil on the cylinder surface to lubricate the rings. Once the cross-hatching is worn-through, ring wear rate gets very high.
I recommend getting new OEM or aftermarket pistons, and getting them oversized. You deliver the new pistons with your block to a machine shop and they will bore and hone the cylinders to fit the pistons. You can't just buy a set of pistons that will fit your bores because the piston-to-bore tolerances are way too tight. Take a look at the piston-to-bore tolerances in the shop manual. I know that MWR sells .5mm oversized pistons for the 1zz. I don't know if Toyota has rebuild pistons. The 1zz has cast iron cylinder liners cast-into the aluminum, so these are straightforward for an automotive machine shop to rebore and hone to spec.
If you have avoid the cost of bock machining and new piston set, I would carefully inspect your pistons per the manual after cleaning them really well. I would drill the oil holes as others have detailed in Spyderchat, and buy a set of new rings. I would also do a flex-hone job on the bores, especially if there are shiny areas in your bores (no visible cross-hatching). This is something you can do with just a hand drill and some skill. Only do this if your bores are in-spec.

Dave

 

[jerchamberlin]

Advice from a long-time engine engineer: It is a really, really bad idea to consider reusing any pistons with more than 200k miles. To even consider reusing a piston, there is a lot to inspect with very high precision, like piston diameters (at different locations on the skirt) the dimensions and trueness of the ring grooves, and the piston pin bores and pins. Even if the skirts look OK, it is very unlikely that the ring grooves will all be within spec.
It is normal for the honing cross-hatching to be there after all this time. The cross-hatching is there to hold oil on the cylinder surface to lubricate the rings. Once the cross-hatching is worn-through, ring wear rate gets very high.
I recommend getting new OEM or aftermarket pistons, and getting them oversized. You deliver the new pistons with your block to a machine shop and they will bore and hone the cylinders to fit the pistons. You can't just buy a set of pistons that will fit your bores because the piston-to-bore tolerances are way too tight. Take a look at the piston-to-bore tolerances in the shop manual. I know that MWR sells .5mm oversized pistons for the 1zz. I don't know if Toyota has rebuild pistons. The 1zz has cast iron cylinder liners cast-into the aluminum, so these are straightforward for an automotive machine shop to rebore and hone to spec.
If you have avoid the cost of bock machining and new piston set, I would carefully inspect your pistons per the manual after cleaning them really well. I would drill the oil holes as others have detailed in Spyderchat, and buy a set of new rings. I would also do a flex-hone job on the bores, especially if there are shiny areas in your bores (no visible cross-hatching). This is something you can do with just a hand drill and some skill. Only do this if your bores are in-spec.

Dave

I have a set of mics from my first rebuild, but nothing to grab bore diameter. I'm an engineer as well, just with little experience in engine internals. Rather leave precision work to the professionals.

got it. cross hatching = flaking of machine ways.. I live in a pretty handy area with industrial shops still around. Got the crank ground last time a couple blocks from my house. I'll call tomorrow about matching bore/pistons. Is it best to allow them to purchase the rings to match the new bore? Last time they matched the conrod bearings to the reground crank. Do I need to think about decking the block/grinding the head? any hp advantages? I wouldn't really want to stray from 87 octane if I can help it.

MWR, is this an aftermarket site? If so can you link? I'll be honest I only stalk MR2 forums whenever the car blows its engine. At least this time I didn't spin a bearing.

The goal of this rebuild is to make the last long enough for an electric conversion to be practical or someone to come out with minimalist mid priced electric powered sports car in the theme of the MR2. So I'd think I'd need 5-10 more years out of it?

 

[Billy C]

For the price of that rebuild you could probably find a fresh 1zz ready to go. I guess it depends on machinist pricing and availably in your area. There ends up being a lot of "while your in there" items that add up when rebuilding an engine to last.

 

[jerchamberlin]

For the price of that rebuild you could probably find a fresh 1zz ready to go. I guess it depends on machinist pricing and availably in your area. There ends up being a lot of "while your in there" items that add up when rebuilding an engine to last.

You're definitely right, A short block can be had for about $1600; my parts list is at $1100, my local machine shop would charge $200 to rebore. Then I need to fuss with resizing the bearings. From my experience with this engine, I wouldn't trust anyone's fresh unless I knew the specific work/that went into it. So I would probably still be doing "while you're in there" work.

 

[dblotii]

I have a set of mics from my first rebuild, but nothing to grab bore diameter. I'm an engineer as well, just with little experience in engine internals. Rather leave precision work to the professionals.

got it. cross hatching = flaking of machine ways.. I live in a pretty handy area with industrial shops still around. Got the crank ground last time a couple blocks from my house. I'll call tomorrow about matching bore/pistons. Is it best to allow them to purchase the rings to match the new bore? Last time they matched the conrod bearings to the reground crank. Do I need to think about decking the block/grinding the head? any hp advantages? I wouldn't really want to stray from 87 octane if I can help it.

MWR, is this an aftermarket site? If so can you link? I'll be honest I only stalk MR2 forums whenever the car blows its engine. At least this time I didn't spin a bearing.

The goal of this rebuild is to make the last long enough for an electric conversion to be practical or someone to come out with minimalist mid priced electric powered sports car in the theme of the MR2. So I'd think I'd need 5-10 more years out of it?

MWR is probably not the only source for oversized piston sets. but here is their link" Toyota MR2-S 00-05
Setting ring gaps is detailed in the factory shop manual. Read the procedure and decide for yourself if you do it yourself (you will need a ring grinding tool)
After you thoroughly clean up the head, and you do it without scratching the sealing surface, you should have it measured for flatness per the procedure and specs in the manual. Most good machine shops can take an under .010 skim cut leaving a good sealing surface without a significant effect on compression ratio. If cutting the head is not necessary, don't do it because it takes some thickness out of the deck which yields a small loss of stiffness. Only deck the block if it is needed to restore flatness or get rid of scratches.

 

[carlbecker]

Cam timing will also change a bit if either the block or head is milled.

 

[jerchamberlin]

Pulled up the BGB to look at crankshaft bearing specs. If I understood what is listed correctly I should be aiming for 0.0006-0.0013"; with No-go greater than 0.0020". These measurements look to be on the low end of what green plastigage can measure. Am I coming at this wrong?

 

[Cap Weir]

That is my understanding as well.. I think I shot for .001-.0015.. It's really hard to get repeatable readings..

Cap

 

[jerchamberlin]

Hi guys I'm back.

Same engine, rebuilt it, same problem. Seems to be mostly white smoke, with blue smoke when you punch it. Runs smoother than before the rebuild.

Work that I did.
Stripped the block.
New MWR 79.5 mm pistons
Overbored the block
New main/thrust bearing
Timing chains, slippers, tensioners
Polished and magnafluxed cranks
new connecting rod bearing
New front/rear main seal
New head gasket
New pcv

Oil doesn't look like milkshake, doesn't seem to be using coolant. I've only ran it for 10-15. Engine overheated last spring when I lost a hose, but I drove it several more months without a problem I knew of except the vacuum leak mentioned at the top of the post. I know I'm going to need to tear it back apart, but where do I look for the problem? I think I've ruled out the pcv as I disconnected the hose and plugged it and still smoked..

Head work? I haven't done anything to it over the years, and all of these problems started after I replaced vacuum lines. Could it be multiple problems? Maybe warped head from the overheat? With the tinge of blue from bad guides?

 

[rmeller]

... Maybe warped head from the overheat?

If you didn't verify that the head was planar while you had it apart, I would say that you dropped the ball on that. A warped head from overheating is probably the most common cause of head gasket failure. But, if you torque the headbolts to spec on the same warped head, it will seal worse than before you released them.

 

[FormInFunction]

If you didn't verify that the head was planar while you had it apart, I would say that you dropped the ball on that. A warped head from overheating is probably the most common cause of head gasket failure. But, if you torque the headbolts to spec on the same warped head, it will seal worse than before you released them.

This was my first thought as well. FYI blue smoke = burning oil, not coolant. You can burn oil without having it mix with coolant as having some amount of gasoline mix with oil is much harder to notice, except for the blue smoke from the tailpipe

 

[jerchamberlin]

This was my first thought as well. FYI blue smoke = burning oil, not coolant. You can burn oil without having it mix with coolant as having some amount of gasoline mix with oil is much harder to notice, except for the blue smoke from the tailpipe

I was meaning to imply lots of white smoke, but if you blipped the throttle you could see a little blue smoke. I continued to fuss with the engine a little last night. I think the blue smoke may have been leftover from before the rebuild. It seemed to be cleared. . Rings had failed (see higher in thread) bad enough that it was pushing liquid oil out of the header/cat joint.

Each time I started the engine it seemed to smoke less. I pulled the plugs, cleaned them, ran the engine pulled them again. They are wet. In my less than expert opinion I don't think it is oil, but when I wipe them with a clean rag there is a little black.

I surfed a few other 1zz powered car forums. My plan of attack is to try retorquing the head as a last ditch effort to save this build. Otherwise pull it and try try again.

 

[FormInFunction]

Best of luck. If you do end up pulling it apart verify the mating surfaces are not warped before putting time & money into additional parts

 

[Cap Weir]

AND change the Valve Guide Seals.. That can be a Passage to get Oil into things..

Cap

 

[jerchamberlin]

Best of luck. If you do end up pulling it apart verify the mating surfaces are not warped before putting time & money into additional parts

I didn't have an appropriate straight edge earlier; a good one should be arriving Wednesday.

AND change the Valve Guide Seals.. That can be a Passage to get Oil into things..

Cap

Agreed. I feel the only paths available for oil to get to the combustion chamber left is valve seals and if I didn't get the rings installed right.

Opinion on polishing valve seats, other head work, etc? Guess I should look at the BGB and see what list of atrocities that I should consider. My "machine shop" and measuring tools is pretty limited. Not against tooling up for more detailed work. (that's how I ended up with a nice woodshop).

If the head is warped can I deck it? Research seems to have mixed results.

 

[Cap Weir]

I can do head work.. I Don't choose too.. It's a PITA on the Overhead Valve Cam Puck Motors.. trying to get the retainers in and out..

I had my head guy ( Local A+ Shop ) and not a single problem.. Used the same Bucketts in the same spot.. he knows what he is doing..

Yes the head can be decked..

Cap

 

[dblotii]

I didn't have an appropriate straight edge earlier; a good one should be arriving Wednesday.



Agreed. I feel the only paths available for oil to get to the combustion chamber left is valve seals and if I didn't get the rings installed right.

Opinion on polishing valve seats, other head work, etc? Guess I should look at the BGB and see what list of atrocities that I should consider. My "machine shop" and measuring tools is pretty limited. Not against tooling up for more detailed work. (that's how I ended up with a nice woodshop).

If the head is warped can I deck it? Research seems to have mixed results.

White billowy smoke is burning antifreeze for sure. It means there is a leak directly from a coolant passage past the fire-ring in the head gasket. Less likely is a cracked cylinder head, but possible after a major overheat. No need to check for flatness yourself; the machine shop will determine the minimum amount they have to remove from the deck to clean it up. If you are stripping down the head for the machine shop, you should remove all of the valvetrain components including the valves and valve-stem seals. Inspect the valve-stem to guide clearance per the shop manual (easy to do) before you send it to the machine shop to make sure you do not need any new guides. Buy a new set of valve stem seals.

Dave

 

[merlinyoda]

If you didn't verify that the head was planar while you had it apart, I would say that you dropped the ball on that. A warped head from overheating is probably the most common cause of head gasket failure. But, if you torque the headbolts to spec on the same warped head, it will seal worse than before you released them.

Dam might have the same problem

 

[jerchamberlin]

All, Pulled the engine (again) I'm getting pretty fast at this!! Engine failed .05mm between cyl. 2-3 on block when checked diagonally. The head failed between cylinders 1-2 and 2-3 when checked straight down the engine. Dropped it off at the machine shop monday for surfacing and a valve job. As I don't trust the job writer there I plan on giving them a call today to have them define "valve job" I want all new guides, seals and at least lapping the seats. Additionally, should I be getting a thicker head gasket to make up for whatever they take off? I have no clue how much material that will probably be, so I'd prefer if I need to pick up a non stock gasket that the shop purchases it depending on what they remove.

 

[dblotii]

All, Pulled the engine (again) I'm getting pretty fast at this!! Engine failed .05mm between cyl. 2-3 on block when checked diagonally. The head failed between cylinders 1-2 and 2-3 when checked straight down the engine. Dropped it off at the machine shop monday for surfacing and a valve job. As I don't trust the job writer there I plan on giving them a call today to have them define "valve job" I want all new guides, seals and at least lapping the seats. Additionally, should I be getting a thicker head gasket to make up for whatever they take off? I have no clue how much material that will probably be, so I'd prefer if I need to pick up a non stock gasket that the shop purchases it depending on what they remove.

If you want the head gasket to seal, use the OEM gasket and don't worry about the increase in CR from the head milling. The head gasket joint is highly-engineered. Anyway the sight increase in CR will yield a slight increase in performance. Also, make sure the machine shop has experience with the Toyota head because the 1zz does not have valve seat inserts. The seats are laser-clad and I seriously recommend not allowing them to machine the head for inserts. Anyway, the seat material is really tough and probably will be fine with just lapping. I also would not change guides if they are not worn. Make sure you follow the head bolt tightening procedure in the shop manual very carefully when reinstalling.