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The mkiv Supra Owners Club

86mm bore?


Jake

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I usually use an old guy local to me for the final hone (get it bored elsewhere) He takes great pride in achieving perfect sizing and roundness, insists on showing me all the measurements when its finished! Unfortunately he is off work at the mo, If you get stuck , give me a shout.

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Always try and get away with the least overbore you can. Also choose a machine shop of known quality , That is vital. I'm yet to find one round my way. All pistons like bores have a + and - tolerances so it is advisable to have each piston meassured and the bores machined to the clearance spec..Ie match them to the bores. Like it has been said most damage does look worse than it is and most if not all I have done have been workable on the 86.5 bore. A quality machine shop, if they are worth their weight, will be able to tell you if the damage will machine out to 86.5. But dont let them bore it until they have the pistons in hand. If they are any good they should refuse to bore it until the have them anyway. It's nice not to go to the max overbore if you can help it 1. it gives room for if (unlucky) it happens again then you can step up to the next size 2. if you step up to 87 from the ofset and the worst happens then it's either linner it or bin the block .Liners is also an option here.

 

HTH

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I don't understand why you can't just let a machine shop measure it properly, then tell you so you can then order the relevant pistons?

I very much doubt Toyota would have made the bore under the specified technical size.

Why do you have to tell them the bore size you want right away?

This whole measuring the cylinders in the garage at night is a bit :blink:

Or are you just in a rush? (always a bad idea)

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I don't understand why you can't just let a machine shop measure it properly, then tell you so you can then order the relevant pistons?

I very much doubt Toyota would have made the bore under the specified technical size.

Why do you have to tell them the bore size you want right away?

This whole measuring the cylinders in the garage at night is a bit :blink:

Or are you just in a rush? (always a bad idea)

 

Nail on the head ..Bear in mind there is only set sizes for the 2jz engine on pistons , I think this is Jakes worry as he has only 86.5 or 87mm after stock to go for from the shelf . Well unless he is going to be all flash and get a set made. But like said many times ...machine shop will tell you ..or a good meassure up .

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I don't understand why you can't just let a machine shop measure it properly, then tell you so you can then order the relevant pistons?
I can. I was just asking questions to establish the best way of doing it. I didn't know whether it was best to do it that way or whether to order the pistons first.

I don't know wtf I'm doing so I ask questions on here. Sorry if they seem stupid questions but it's gotta be better to check than to do it wrong.

This whole measuring the cylinders in the garage at night is a bit :blink:

Or are you just in a rush? (always a bad idea)

I was only measuring it out of interest. I only mentioned it because I was suprised by the measurements. There's no rush at all. What's wrong with working in a well lit and spotlessly clean garage at night anyway?
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What's wrong with working in a well lit and spotlessly clean garage at night anyway?

Nowt....if you know what you're doing! LOL

Sorry Jake, I didn't mean to appear argumentative or anything. It's just all a little academic really if you don't have the right tools. Hope it goes ok :thumbs:

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Right, I've taken the block and head to a engine specialist place down portsmouth. They seemed to know what they're doing.

The guy said 86.5mm pistons would definitely be adequate to remove the bore damage but said he wouldn't be able to do the job until I give him the pistons to measure. He's going to check and skim the head, reseat all the valves and reshim as well.

I've left the block and head with him but he won't do owt to it until I take the pistons and cams down to him.

 

I better pull my finger out and find some pistons.

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Jake

i've been off the air for a while so missed this, its obvious you've popped the motor, i have considered this horendous event myself and thought if i do this i would look at a replacement engine, please dont take this the wrong way i am genuinly interested why you chose the re-build route rather than replace the motor (and lots of pics please) if i'me covering old ground here just point me to the thread and i'll be on my way

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please dont take this the wrong way i am genuinly interested why you chose the re-build route rather than replace the motor

I'm guessing here.... but VVTi engines don't grow on trees. Also I'd think it best to have a lovely new rebuild which should last a bit longer than the last time he bought a second hand engine. :(

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Jake

its obvious you've popped the motor, i have considered this horendous event myself and thought if i do this i would look at a replacement engine, please dont take this the wrong way i am genuinly interested why you chose the re-build route rather than replace the motor (and lots of pics please)

Like Pete says, used VVTi engines are a bit thin on the ground. I could buy a new short engine for about £1650 from MVP but it's almost as much work. To be honest I quite fancied doing it myself anyway, I've got the time seeing as I'm out of work at the mo.

The cheapest option would have been to buy a used non-VVTi engine and to swap the head, turbos, intake etc etc over to it but 2nd hand engines are a bit of a gamble. Also, the car is low mileage (56,000 Kms) and I think it would be a shame to stick an old higher mileage motor in it.

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Ahh you mean a bore gauge I was wondering what the feck a comparator was.

 

Proabably in the same way as my nephew had a look that said WTF when my gran asked him to turn down the wireless.

 

Actually i meant comparator, as it takes a reading compared to an exact measurement (taken from a micrometer).Works in a similar way to a DTI to give a +/- measurement.

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