Cylinder Bore Service Limits (Machine or not to machine) - MR2 Owners Club Message Board
 
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post #1 of 6 (permalink) Old June 10th, 2019, 14:34 Thread Starter
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Cylinder Bore Service Limits (Machine or not to machine)

Has anybody ran a motor that was greater than Toyota's 'out of round' cylinder bore limit? What were your results? The Toyota limit is .0004 inches.

I'm consuming about 1 quart of oil every 500 miles. There is oil in the intake manifold. There is oil leaking down the block. Upon inspection, it was determined that all 8 intake valve stems were worn beyond spec. I'll have to replace them.
The valve guides were fine.
The valve stem seals were not doing their job.

I'm trying to determine how much of that oil consumption was coming individually from the head and block.

My block out of bore (oval) measurements:
The bottom of cylinder 1 is .001 inches (Twice the limit).
The top of cylinder 4 is .0015 inches (Three times the limit).
Everything else is perfect or less thank 0.0005 inches.

All cylinders taper out, top to bottom;
Cylinder 1 0.001 inches
Cylinder 2 0.001 inches
Cylinder 3 0.001 inches
Cylinder 4 0.0015 inches
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post #2 of 6 (permalink) Old June 25th, 2019, 23:55
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I probably would ignore it if you're at say 0.0005 or 0.0006". Two and three times the service limit is usually going to lead to problems if you're expecting a nice and tight engine.
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post #3 of 6 (permalink) Old June 27th, 2019, 20:49
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If it is already apart I would get new pistons then bore and hone it. Trying to band aid something like that just leads to more work later on.
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post #4 of 6 (permalink) Old July 2nd, 2019, 16:20 Thread Starter
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Quote:
Originally Posted by DefSport View Post
I probably would ignore it if you're at say 0.0005 or 0.0006". Two and three times the service limit is usually going to lead to problems if you're expecting a nice and tight engine.
Ovality is 0.0015 in one cylinder (That is three-times the factory limit) and 0.001 in another (That is twice the factory limit). I was hoping for some type of empirical feedback. Somebody who was in a similar situation and would have personal experience with the oil consumption outcome.

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Originally Posted by bkperformance19 View Post
If it is already apart I would get new pistons then bore and hone it. Trying to band aid something like that just leads to more work later on.
I'm trying to get this car running for as little as possible, as quickly as possible, while also doing it correctly.

This block has already been bored to 87mm. Based on what I think I know about machining my options are:
1. Bore this block an additional 0.25mm to get everything straightened out. Buy custom 87.25mm pistons. This option would be very prone to failure/cracking.
2. Sleeve the existing block @ 87mm for $500 to $600 & re-use the 87mm JE pistons currently in the block or the 87mm Weisco's I have as spares.
3. Rebuild the factory 3SGTE block I have sitting. I might be able to buy stock drop-in 86mm pistons. I'll plan to measure the cylinder bores over the holiday to verify this.
4. Buy a short block from ATS or KO. They probably wouldn't accept the 87mm bored block I have as a core charge.
5. Run the block as it is.
6. Hone and re-ring the block.
7. Go the 5SFE block route. This is probably a more expensive option. I'd have to get the crank work, new stroker pistons, 5SFE water lines, oil cooler, rear main seal, etc.

Last edited by 1950884; July 3rd, 2019 at 10:38.
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post #5 of 6 (permalink) Old July 4th, 2019, 13:17
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Well, I've seen SR20DET blocks that were roughly around the factory service limit for bore wear generally not burn a ton of oil (not anything egregious, maybe half a quart to one quart over a track weekend, <half a quart in 1000 miles). Who knows how much was coming from the bore, but I imagine 3x the FSM limit is going to lead to a meh-at-best ring seal over at least a portion of the bore.

I'd say it comes down to do you want to spend money on it, or not? Maybe things won't be that bad if you seal up the valve guides since it's only 2 cyl that are worn, but if you're willing to spend $500-ish on machine work + new bearings + new gaskets, why not take your spare block and use your existing 87 mm pistons in it?

I've never seen good results on drop-in factory bore forged pistons, as typically it's tough to take a bunch of existing bores with wear on them and hone them then get all specs good. It can happen on really low mileage engines, but I don't think any 3S-GTE would fit that category now.
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post #6 of 6 (permalink) Old July 11th, 2019, 11:43 Thread Starter
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Quote:
Originally Posted by DefSport View Post
Well, I've seen SR20DET blocks that were roughly around the factory service limit for bore wear generally not burn a ton of oil (not anything egregious, maybe half a quart to one quart over a track weekend, <half a quart in 1000 miles). Who knows how much was coming from the bore, but I imagine 3x the FSM limit is going to lead to a meh-at-best ring seal over at least a portion of the bore.

I'd say it comes down to do you want to spend money on it, or not? Maybe things won't be that bad if you seal up the valve guides since it's only 2 cyl that are worn, but if you're willing to spend $500-ish on machine work + new bearings + new gaskets, why not take your spare block and use your existing 87 mm pistons in it?

I've never seen good results on drop-in factory bore forged pistons, as typically it's tough to take a bunch of existing bores with wear on them and hone them then get all specs good. It can happen on really low mileage engines, but I don't think any 3S-GTE would fit that category now.
Hi Def, I appreciate the feedback. The machinist believes that another option is to hone the existing block and re-use the existing pistons. Considering that piston skirt to wall clearance is supposed to be 0.004 inches, I don't see how that would be possible.


To give you more context, all 8 of the intake valves had fairly extensive wear on the stems and the valve stems seals were in terrible condition. This caused the valve guide to valve steam clearance to be excessive. This is what caused oil in the intake manifold. There was also an oil/gunk mixture by each injector stuck to the intake ports.

As the block sits, I am able to rock the pistons back and forth in the bore when they are at TDC. These are JE pistons that are from the early 2000's. I've read that their metal blend back then caused a large amount of expansion when the get warmer.

The bottom line is that this motor is just tired.

I had the machinist install new Supertech intake valves and valve stem seals. They also milled the head, which may be why I had oil running down the front and back of the block. I am going to leave the block as it is and see what I get.

In the mean time, I'm going to have them prep my original block with 87.5mm pistons, rods, bearings, etc. I considered factory 87mm pistons, but there is rust on the bores. Machinist was adamant that a re-bore was necessary.

I'll try to remember to update this thread about my results.
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