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Location:
Lost in the K hole
Registered:
May 2002
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to bore or not to bore.....how to tell??
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Wed, 10 July 2002 12:01
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heya,
just picked up a new block, and i find that sometime in its life, its been bored out 40thou. now i dont think theres much meat left to pay with, so i have to decide whether or not the bore as it is is good enough to rebuild with new pistons/rings etc. will be honed of course.
what are the limits or wear within the bore i should look for etc?
any ideas??
cheers
de
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 01:24
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Ed, firstly, we know that the 5M block can be taken out to 85mm safely. The problem is finding pistons with the correct compression height and gudgeon pin diameter to fit. Datsun L18-20 pistons....remember?  If you want to do a more comprehensive search, go to www.acl.com.au and download their piston catalogue. It has all that shit in there, as well as available overbore size pistons. Go to customer service, then scroll down the tab to catlogues.
As for determining when to bore, you need to measure the bore with an internal micrometer and check for bore taper. This is then checked against the factory manual (which I don't have  ) and a determination can then be made. Also one should look for obvious scores or rust holes in the bore (if it's been sitting around with no head on). The easiest way is to take it to an engine machinist and let them sus it out for you.
By the way keep the 40 thou over pistons. 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 03:13
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i remember the 85mm bore limit, but looking at the block, 85mm doesnt leave a whole lot of love between cyls! i think 84mm would be safer if the bore is good. and what you want those pistons for!??
nice use of smilies by the way! 
ill get an internal micrometer and have a look. not sure the manual states the limits of wear in these dimensions tho. bore seems very smooth with not feelable ridge at the bore lip. but ill measure anyway.
figuring out the pistons is going to be a little dicey without that M crank. even if the 5M/M blocks both have the same 230mm deck height, im going to need a very different 84mm piston (compared to stock 5M) to make up the 5mm less stroke when the M crank meets the 5M block.
well, perhaps not 'that' different, you'd figure you'd need just 5mm taller, but thats assuming the conrods are the same. BLAGH!
need to get that M crank/rods off you i think!!!
bugger....
cheers
ed
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 03:48
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I'll rip out an MTEU piston/rod tonight and measure the compression heights. Hopefully the comp height is around the same and the rods are somewhat longer (like around 5 mm)!
I knew someone with 2 MEU's but he junked them for the $10 in scrap metal....I told you they would come in handy Allan  ....now who's scrounging around for oil pumps! 
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Location:
Sydney
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 04:28
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I have a 5m block with pistons etc In my shed...
I also would have the 5m oil pump..
If you guys are interested let me know.. thanks..
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 04:38
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here's hoping for 5mm longer rods! 
please tell me allan didnt junk 2x meu's for $10
also, ive got a spare 5M oil pump with front sump pickup here if someone needs it.
did the dyno 2000 thing on both 85mm and 75mm stroke configurations. torque + power are VERY similar, but both torque and power curves are much flatter, and shifted up 600rpm with the 75mm crank. revvy, and flat curve...hmmmm
yum
and again, why am i keeping these 40thou pistons (looks rather new, would be surprised if it were rebuilt over 40k ago)
cheers
ed
(you at work huh?)
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 04:45
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corvid...
you got a dizzy on that block? dibs!
- starter motor?
- alternator?
also, looking at the head off that engine, i wouldnt be wanting to base a rebuild around it. the cooling system had not been looked after at all.
but will keep it in mind.
cheers
ed
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 05:16
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I'll let Allan tell you what he did with those 2 MEU's. 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 05:33
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i checked the specs: maximum out of round or taper is 0,0008" or 0,02mm. (god knows how im going to measure that with any decent accuracy).
my question is though, assuming i can measure it: im measuring the amount of taper down the cylinder bore with mesurements starting about 5mm from the block deck... ie: NOT including the dia of the 'ridge' at the top of the bore??? so if i start measuring just under that top 'ridge' and then measure down, im wanting a tolerance of under 0.02mm yeah? im guessing that the 'ridge' at the top of the cyl bore is not measured in the assesment of the bore?
note: not that there's much of a ridge, but its obviously not as polished as the rest of the bore.
cheers
ed
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Location:
Mentone
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 06:10
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That ridge is where the piston rings stop. It is carbon buildup from the combustion process and has no bearing on the bore size like you said.
Brad
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I supported Toymods
Location:
Brisbane, QLD
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 07:08
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Since you are building a revvvvy engine, maybe you should be a little bit cautious about the extent of boring... A revy engine would generate more heat due to increased friction to begin with and with less metal in the block to absorb and transfer heat (because of the boring) the engine might want to run fairly hot compared to the standard.
Slightly off topic, the other issue that just popped into my head was the con rods. All conrods have some level of elasticity and as such, at higher revs, they are sure to get slightly more elongated. Therefore, maybe you should increase the piston clearance as well a tad bit? Oh yeah, the more the engine revs, more precisely balanced the components would need to be too...
Just a few thoughts...
Cheers
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 07:37
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nishad,
just did the dyno 2000 figures, and both the torque and power curves are shifted only about 600rpm up the axis. so wont be a hellishly revvy engine, just more than the 85mm stock stroker.
the good bit is both the curves are flatter with the 75mm crank, and dont peak as much as the 85mm. torque is down about 5% with 75mm one though.
i really gotta get me an engine stand
cheers
ed
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I supported Toymods
Location:
Brisbane, QLD
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 08:00
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Engine crane, brand new, 2 ton new heavy duty foldaway $375, 100lbs engine stand $85, 1250lbs $125. Vijay's Power Tools MASCOT 02-9700 8440
<- off tradingpost... maybe give them a ring? 
Cheers
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Location:
Sydney
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 08:28
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Edman,
Yeh i got the starter and the alt.. also got the dizzy somewhere.. and leads..
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Location:
Melbourne
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 09:36
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yep scraped em both, at the time it looked as tho i was going to end up with a couple more M series engines but thay didnt eventuate,
the m and 5m blocks are exactly the same from what i could see if there was difference all the timing gear at the front would of been different so throw your m crank rods and 5m pistons in (pin hight is your only worry) and you end up with a bore:stroke ratio the same as the 1jz i HIGHLY suggest esp with a turbo engine you dont use a bored block thare are plenty of good 5m blocks that only need a light hone/deglaze out of the 5 M engines i have opened up only a couple have not still had visable factory crosshatch left, mind you hay have all been EFI supra engines maybe toyota grades the blocks for "sports use" and a granny driven engine will have worse ridges at the top then an engie that sees 5500+ often
anyway why are you worrying about this your geting one of the sexyest 5m-e blocks i have seen and that aqua color will give you an extra 10kw!!!
Allan
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Thu, 11 July 2002 11:59
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allan, you know GT's engine is a 40thou overbore yeah?
cheers
ed
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Location:
Lost in the K hole
Registered:
May 2002
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Re: to bore or not to bore.....how to tell??
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Fri, 12 July 2002 04:34
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well, ladies and gentlemen...
IT'S F_CKED!
'not to bore + chuck it out' is the answer to the question.
had a guy look at it today, and immediately says..."needs a bore, dont need a micrometer to tell you that".
rule of thumb, apparently, is if the crosshatching of the last hone has gone completley, so the bore has a mirror finish, then there will be taper. taper=rebore.
GT: im not comfortable going to 85mm. sure, i might find some 85mm pistons to fit (remember the piston pins on the L18/20 is 20mm so i'd have to make inserts for the conrod eyes to bring 22mm down to 20mm) its also possible that an 85mm 2T or 3T piston would work depending on rod length... BUT i just dont reckon theres enough meat left in the block to hack it.
SO
new block....
CORVID: can you measure the bore on that block youve got, and tell me if its 83mm? plus, can you have a peak in the water jackets, and see if theres much shit in there??
cheers
ed
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