Jake Posted December 13, 2005 Share Posted December 13, 2005 In one place in the Toyota Engine Repair Manual it says the bore is 86.1mm and in another place it says 86.00mm I presume 86.00m is correct, right? The reason I'm asking is because I've just measured the bores on my VVTi engine and I'm seeing measurements from 85.61mm to 85.84mm across the six cylinders. How can that be? Could it be down to the cold weather? It's very cold in my garage. If so, at what temp are you supposed to measure these things? Thanks Quote Link to comment Share on other sites More sharing options...
Pete Posted December 13, 2005 Share Posted December 13, 2005 Dude - get it to an engineering company to check. There's no half measures at this level. Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 I'M GOING TO!!! They aren't open at 9 o'clock at night. Did you think I was going to try to rebore it myself? I'm asking about this in case there's some reason the bore seems to less than the stock bore should be. I don't want to tell the engineering guys to bore it out to 86.5mm and then find that that's too big for my new pistons. (Which I haven't got yet) Quote Link to comment Share on other sites More sharing options...
Pete Posted December 13, 2005 Share Posted December 13, 2005 Ah right!...I'd wait until the pistons arrive and hand the whole lot over to them, crank and all. They can balance it then as well. (No idea if this is worth doing on a standard engine mind...probably not?) Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 The thing is Pete, I'm trying avoid boring it out to 87mm if possible. Until the engineers can tell me if a 86.5mm overbore will remove the bore damage I don't know what size pistons to buy. 86.5 or 87mm Quote Link to comment Share on other sites More sharing options...
Pete Posted December 13, 2005 Share Posted December 13, 2005 The thing is Pete, I'm trying avoid boring it out to 87mm if possible. Until the engineers can tell me if a 86.5mm overbore will remove the bore damage I don't know what size pistons to buy. 86.5 or 87mm Aahh! Right..with you. Well there's your answer. Tell 'em to bore it to 86.5 and see if they say it's ok. Oh I dunno. I leave this stuff up to the experts. My OHC lump got away without needing a rebore, just honed when I rebuilt the kitcar engine. Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 13, 2005 Share Posted December 13, 2005 If you wans to measure anything accurately you should let it soak at 20 degrees C for a day beforehand. Unlikely you'll see any errors at 1 decimal place but that is the standard temperature. What are you measuring with, BTW? Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 Well there's your answer. Tell 'em to bore it to 86.5 and see if they say it's ok. That's not really an answer to my original question of "Why is my bore less than 86mm?" ...and fat chance I've got of getting it answered now that you've thread-jacked me completely. Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 What are you measuring with, BTW? Digital vernier calipers (Mitutoyo Digimatic 500-321) Quote Link to comment Share on other sites More sharing options...
arnout Posted December 13, 2005 Share Posted December 13, 2005 are you measuring with a torqueplate bolted on? Also a vernier gauge is not really the unit to use. It's not precise enough Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 are you measuring with a torqueplate bolted on? Also a vernier gauge is not really the unit to use. It's not precise enough I'm not sure what you mean about a torqueplate Arnout. (I'm a complete amateur at this kind of thing) It was just a bare block bolted to an engine stand from the flywheel end. I realise that my vernier gauge is not the right tool for the job really because it can only measure the top few centimetres of the bore but I think it should be very accurate at what it is measuring. It's supposed to be accurate to 0.01mm Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 13, 2005 Share Posted December 13, 2005 A torqueplate is a plate that goes on top of the block like the cylinder head does and you bolt it on like you would a cylinder head, but it's kinda the shape of the gasket (although a beefy 1cm thick one made of metal). This makes the block the shape it would be with a cylinder head bolted on and torqued up - apparently it makes a difference to the bore alignments, dunno how much because I'm going off book knowledge here, not experience -Ian Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 13, 2005 Share Posted December 13, 2005 TBH its not the tool of choice. Its hard to find the widest point with a normal caliper. If you can get your hands on a internal micrometer it would be better. In OEM world cylinder blocks are not finish machined bolted to a torque plate. The bores should be round enough with the block standing free. Quote Link to comment Share on other sites More sharing options...
Jake Posted December 13, 2005 Author Share Posted December 13, 2005 A torqueplate is a plate that goes on top of the block like the cylinder head does and you bolt it on like you would a cylinder head, but it's kinda the shape of the gasket (although a beefy 1cm thick one made of metal). This makes the block the shape it would be with a cylinder head bolted on and torqued up - apparently it makes a difference to the bore alignments, dunno how much because I'm going off book knowledge here, not experience Blimey. No then. I don't think there was one included in my Fisher Price engine rebuild kit. Quote Link to comment Share on other sites More sharing options...
b_have Posted December 13, 2005 Share Posted December 13, 2005 Jake, I have a Mercer bore comparator here, Its the ONLY way to correctly measure bore size and is acurate to 0.0001". Your welcome to borrow it. To Bore /hone correctly you must measure each piston and add the required clearance to give the finished size. Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 13, 2005 Share Posted December 13, 2005 I think it's kind of a motorsport thang, especially with serious overbores. I found out about this when I read "Tuning Rover V8 Engines" by David Hardcastle - research into a Bowler Tomcat a friend is building Check this quote out: "their twin turbocharger conversion boasts 220-240bhp and over 250ft/lbs of torque at a mere 2700rpm with a 3.5litre engine" - well played lads, 68bhp/litre with twin turbos -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted December 14, 2005 Author Share Posted December 14, 2005 at Ian Jake' date=' I have a Mercer bore comparator here, Its the ONLY way to correctly measure bore size and is acurate to 0.0001". Your welcome to borrow it.[/quote']Thanks Charlie but I was only doing it out of interest. If my tools are probably the reason then there's probably nothing to worry about. I appreciate the offer though - cheers mate To Bore /hone correctly you must measure each piston and add the required clearance to give the finished size. Do you think Toyota do that? I'd be surprised. Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 14, 2005 Share Posted December 14, 2005 Do you think Toyota do that? I'd be surprised. Nope. The bores will be measured on the production line and graded pistons fitted to ensure that the clearance is kept in a tight tolerance band. Quote Link to comment Share on other sites More sharing options...
b_have Posted December 14, 2005 Share Posted December 14, 2005 Not sure, many manufacturers batch mark pistons as maybe "A" "B" etc then are chosen to suit the bore. Most pistons these days are produced to very tight tolerances, but always worth checking. I always supply pistons with block and insist each bore is machined to each numbered piston to a tolerance of Quote Link to comment Share on other sites More sharing options...
Jake Posted December 14, 2005 Author Share Posted December 14, 2005 So how should I proceed? Bearing in mind that I don't know whether a 0.5mm overbore will be sufficient to remove the damage from the bore. (I think it will. Most of the 'damage' on the bore looks like piston detritus to me) Should I order the pistons first (What size?) or should I just say 'sod it' and get some 87mm pistons and have the block bored to suit the pistons when they arrive? Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 14, 2005 Share Posted December 14, 2005 I'd see what pistons are available first of all and then take the block to a machine shop and ask them to remove the very smallest amount that will clean up the bores and take you to a stock piston size. A decent machine shop should also be able to measure them for you. If they can't measure what they say they can machine then don't go there Quote Link to comment Share on other sites More sharing options...
b_have Posted December 14, 2005 Share Posted December 14, 2005 Depends on the damage to the bore, 0.5mm usually removes enough (the damage usually looks far worse than it is) If the block was severely overheated then thats another matter. If its just some piston pickup on the bore, a hone often will surfice. Any pics? Quote Link to comment Share on other sites More sharing options...
b_have Posted December 14, 2005 Share Posted December 14, 2005 Jake,your welcome to bring over the block if you want some exact measurements, If its round and within tolerance, a hone may well clean up the damage (also a LOT cheaper than a rebore/hone) Quote Link to comment Share on other sites More sharing options...
Jake Posted December 14, 2005 Author Share Posted December 14, 2005 I'd see what pistons are available first of all and then take the block to a machine shop and ask them to remove the very smallest amount that will clean up the bores and take you to a stock piston size. A decent machine shop should also be able to measure them for you. If they can't measure what they say they can machine then don't go there The only stock size (86mm) Toyota pistons are available very cheaply (£267 for six pistons and rings). 86.5mm and 87mm aftermarket pistons and rings I've found for about £400 for Wiseco or £550 for CP (Plus VAT and Duty I guess) Quote Link to comment Share on other sites More sharing options...
Jake Posted December 14, 2005 Author Share Posted December 14, 2005 Jake' date='your welcome to bring over the block if you want some exact measurements, If its round and within tolerance, a hone may well clean up the damage (also a LOT cheaper than a rebore/hone)[/quote'] Thanks. Hopefully I can trust the guys that check it to do the minimum amount of material removal required. Who would you trust to make a decent job of a project like this? I'm just picking local firms out of the yellow pages! Quote Link to comment Share on other sites More sharing options...
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