| Author | Topic |
|---|
Location:
Brisbane Qld
Registered:
May 2002
|
|
7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 13:18
|
 |
This is probably more a question for Ed or GT.
Does anyone know the bore spacing for a 7m? (and also the 2jz)
Toysport recommend a maximum overbore of 85.5mm
HKS appear to have a head gasket for 86mm bore and I'm toying with the idea of using 2jzge pistons at 86mm for the next silly motor for my cressida. 3.2 litre capacity seems like a good number for a NA motor  I just don't know if there is enough meat in the block for a 3mm ovebore. I have another engine coming in a week or two, but early info will help with planning.
Its a toss up between 7mge and 2jzge, both will have to be full rebuilds but a 3.2 7mge is looking really attractive if its possible
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 13:56
|
|
from what i recall, 85.00mm is the maximum overbore. and that would be seriously stretching the relationship.
85.50mm - i think youd have an engine on your hands just about ready to crap its daks
86.00mm - nope
ill measure the bore separation in 5 mins for you ill also measure the bore dia of the HKS mhg i have here.
you want to talk NA 7m's?? i can chew your ear off 
7m has lots and lots of potential. but the redline is more restrictive than the 2jz (damn stroke and rod ratios...)
admitedly, the 2jz is the better motor, but for reasonably affordable, and easily doable modifications (that have massive power yield), the 7m is sweet !! but if youve got the bucks, id do a 2jz...
if youve got any q's fire away!
cheers
ed
|
|
|
I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 14:14
|
|
I'll defer the 7M bore spacing to Ed, but the 2JZ is approx 94mm from memory....I can confirm this over the weekend.
I probably wouldn't go nuts overboring 7Ms - you might just be tempting fate! I'd be using the best head clamping technology known to man!
Another thing to consider is the compression height of the 2JZGE pistons vs. the 7M pistons. The 7M is 32.5 and the 2JZ is 34mm. Not sure where the piston crown for the 7M sits relative to the block deck, but Ed will know for sure. Gudgeon pin diameter is 22mm for both so no grief there. Hopefully the 7M piston sits 40 thou (1mm) shy of the block deck at TDC so potentially you could then correct for the 2JZ piston sitting 0.5mm proud of the 7M block by using a thicker head gasket. What all of this will do to your squish area is something else to consider.
Certainly Jun, HKS and Toyomoto (in the States) offer stroker kits for the 2JZ(GTE) which bring the capacity out to 3.2 or 3.4 litres (depending on manufacturer). The Jun 3.2 litre kit is 1 million Yen (~ $14000 AUD) and includes a billet crank, forged rods and turbo pistons (however for that price, I'm sure if you specified a high comp piston, they might be obliging....).
Sounds like a real tinkery kind of thing to do. I'd probably get a stuffed 7M and a 2JZ piston, have one bore bored to 86 mm and start measuring things.
You could just drop a 1UZ in there for a lot less than this is going to cost you....I have to mention it!
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 14:31
|
|
hehehe...ok
with an 83.5mm bore, youre looking at a grande 6.78mm between the bores. you bore the sucker out to 86.00mm, and youll have 4.28mm between the bores 
the HKS mhg bore dia is 85.80mm, and this is not allowing for any reduction in dia when you torque the head down and compress the gasket. dont forget, the head gasket needs block material at its edge to bite into, ie you cant have the mhg the exact same dia as the block bore. so, at a wild guess, id say 85.00mm is the max bore size catered for by that mhg.
like i mentioned above, *smart* machining of existing components will yield you a pretty high performance 7m. there is plenty of scope within the factory tolerances to be quite creative.
redline is your only enemy unfortunately. probably maxing out around the ~7000k mark. the 7m's talent is in its bottom end torque (thankyou stroke) and its best to remember this when planing mods. attempts to make it a high revving beast are misplaced...
its not all bad, brute numbers are still on its side
thats where the 2jz is different, you lose the low end torque, but gain rpm freedom (and overall just higher torque figures at higher rpm) with which to play (8000rpm). this opens up a can of worms with cams etc which are not as well utilised by the 7m. but with cams comes BIG $$$$
2 different engines really. i just like the 7m cause theyre so plentiful and relatively cheap, you can go nuts hacking into them, and if you balls it up, its not much of a saga
that and i cant afford the cams, so the 7m can offer me more in other areas which i can maximise without having to spend too much 
i dont wreckon 2.989891 Litres, 11:1comp/r, twin throttles, head port and extractors will go too shabbily (all on the stock ecu)
cheers
ed
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 14:46
|
|
| gianttomato wrote on Thu, 14 August 2003 00:14 |
The 7M is 32.5 and the 2JZ is 34mm. Not sure where the piston crown for the 7M sits relative to the block deck, but Ed will know for sure...Hopefully the 7M piston sits 40 thou (1mm) shy of the block deck at TDC
|
bzzzzt!
no such luck im afraid... 7m pistons are almost smack on flush with the deck height (give or take 1thou)
| gianttomato wrote on Thu, 14 August 2003 00:14 |
so potentially you could then correct for the 2JZ piston sitting 0.5mm proud of the 7M block by using a thicker head gasket. What all of this will do to your squish area is something else to consider.
|
OR, you could simply machine the top of the 2jz pistons down. if theyre anything like the 7m pistons, there is *plenty* of meat, and valve/piston clearance to be very enthusiatis in piston crown modification (maybe not 2.0mm worth, but enough to put you in a workable ballpark)...
but this thought proces is futile as the bore spacing is too prohibitive to be considering this option.
| gianttomato wrote on Thu, 14 August 2003 00:14 |
Certainly Jun, HKS and Toyomoto (in the States) offer stroker kits for the 2JZ(GTE) which bring the capacity out to 3.2 or 3.4 litres (depending on manufacturer)
|
and it'd end up being a tractor engine like the 7m
ok if you were going to push lots of boost through it, and not rev it out, but i dunno about that configuration for an NA application...
| gianttomato wrote on Thu, 14 August 2003 00:14 |
Sounds like a real tinkery kind of thing to do. I'd probably get a stuffed 7M and a 2JZ piston, have one bore bored to 86 mm and start measuring things.
|
yeah, i think that road would end in tears... sorry
cheers
ed
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 15:35
|
|
which actually reminds me dave:
do you have a spare 2jz rod you can measure?
big end dia?
eye-eye length?
any idea what the crank centreline to deck height is?
cheers
ed
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Wed, 13 August 2003 22:45
|
|
Thanks Gentlemen,
The original plan was to do a 7mgte or 1uz, but I've gone cold on the idea. I'm too old to have a turbo sticker on my car and like BMW I've always been a fan of grunty straight sixes. Plus the whole "Yes Ossifer, its standard!" thing makes me smile
The current search is for a 2JZGE vvti front sump but my pet importer hasn't found one yet and the wiring compatability has me a little concerned with such a late model motor - multiplexed harnesses and integrated security system seem to be the norm now for Lexus so I assume the Toyota offerings are the same?
The piccys a while ago comparing the 2jz pistons obviously got me thinking, and whichever way I go I'm looking at a tear down of the motor so, why not start with a 2 to 3 hundred dollar motor rather than a 2 to 3 thousand one.
Ed, I agree, 4.2 odd mm between bores is not going to cut it so it looks like the 2jz is back in the running.
As I'm looking for throttle response and increased torque for normal driving would it be better to wait for a vvti engine and take a punt on the harness stuff or grab an early 2jzge as i can have one of those now. Either way I'll still be doing a 7M as we have 2 cressidas in the garage now so please keep us posted on the high compression monster.
Thanks again for your late night measuring!
|
|
|
I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 00:18
|
|
Ed, I'd be pretty unkeen to machine 1.5mm off the top of the stock pistons, and agreed, I'm not interested in stroking a 2JZ either......it's a lot of dollars for only a couple hundred cc of capacity and a whole lot less 'revability'.
OK. Well if you are going to do the 2JZ thing, the VVTi one is very nice. I do know the IS300 one integrates with (?) at least 6 computers! An aftermarket ECU will eliminate all of this nonsense. I know a Motec will run the VVTi solenoid, but I'm not sure whether anything else will. I picked up a VVTi 2JZGE with loom and ECU for less than $1K (no accessories).
If you use a 1UZ, the Crown has a separate ECU and auto trans ECU so that may make the wiring for the auto easier.
|
|
|
Registered:
August 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 01:30
|
|
|
How easy is it to do cam work on a VVTI 2jzge thou?
|
|
|
I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 01:47
|
|
Glen, no idea. Of course, the VVTi isn't on the exhaust cam, so you still have some liberties there. There is a lot less recess in the piston tops so I suspect you couldn't be quite so aggressive with the lift.
The VVTi 2JZGE IS an interference engine so you will have to be pretty spot on with timing etc.
TRD do cams for the BEAMS 3SGE VVTi whilst still running the VVTi so a bit of research along those lines might be warranted.
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 02:50
|
|
ah crap - why does everyone always dump the NA 7m idea... 
oh well, back to my hole.
cheers
ed
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 08:58
|
|
Sorry Ed, I've not dumped the idea at all so come back please!!!
If someone can suggest a serious setup of the 7m that will approximate the output of a 2j I'M ALL EARS.
My capacity increase idea with nice coated factory pistons went out the window after your excellent application of tape measure and vernier. But still definitely interested. I remember years ago reading a British magazine article on a old engine guru that did the ma6x supra engines for group A and unfortunately can no longer find it but he was getting awesome power from the 6mg so similar mods should be possible without "cheating" as someone so eloquently put it in another thread. Plus the engine importer has a nice 7mge with traction control manifold!! sitting on the floor.
I have collected a great deal of info and still have no real idea how to proceed.
Options are in order of preference:
7MGE with more grunt - possible but unknown - need 20kw and 30nm to match 2jz
2JZGE vvti - US market ecu for OBDII data logging and no limiters
2JZGE - with US market ecu for OBDII data logging and no limiters etc but develops peak torque at higher rpm
As for the 7mge, for my intended use, I'm thinking early non turbo inlet manifolds, high torque cams off cressida (yes they are different with shorter duration) slight bore increase and compression up to 10:1, maybe gte block for the oil squirters and stuff, port matching and dowels. After that I'm open to suggestions.
If toyota with their millions in research can do it, surely some Aussies can replicate the engineering at home
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 09:02
|
|
PS:
GT,
2jzge vvti for under 1K ???? wow!
|
|
|
Registered:
August 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 09:32
|
|
| Quote: |
need 20kw and 30nm to match 2jz
|
Doesn't that just make the 2j a far more attractive starting block before mods?
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 09:57
|
|
Yes and No.
It develops more power but at higher revs unless its a vvti version.
VVti with an A350E five speed auto would be perfect but expensive and a PITA to fit although an IS300 engine cover would look cool in a cressida
the same money spent on the 7m and would probably also include gold plating of the cam covers if needed and still leave change
|
|
|
Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 10:11
|
|
| stevevp wrote on Thu, 14 August 2003 18:58 |
Sorry If toyota with their millions in research can do it, surely some Aussies can replicate the engineering at home
|
LOL  that's the spirit!!!!
dunno what the 7M or xJZ are really like, but from afar it sounds like the comparison of K vs A... raw and grunty old tech, like a motor _should_ be, vs smoother and quieter new tech, like a motor _can_ be (after the millions have been spent).... what do you prefer?
i like the backyard raw motor that you KNOW you are driving
Cya, Stewart
hmm, can you destroke the 7M, use longer rods, and then SC it? then you get your revs back, and no lag... downside is fuel consumption... but 80% of peak torque just off idle is tempting..
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 11:13
|
|
| stevevp wrote on Thu, 14 August 2003 18:58 |
If someone can suggest a serious setup of the 7m that will approximate the output of a 2j I'M ALL EARS.
7MGE with more grunt - possible but unknown - need 20kw and 30nm to match 2jz
|
too easy....
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 11:48
|
|
| oldcorollas wrote on Thu, 14 August 2003 20:11 |
hmm, can you destroke the 7M, use longer rods, and then SC it? then you get your revs back, and no lag... downside is fuel consumption... but 80% of peak torque just off idle is tempting..
|
kinda like, say, a 2.8L 5M or a 2.0L M ??
stevevp - think quick, if you want to do a 7m, grab those OS valve with both hands, and dont let go, youll NEVER get cheaper...
but anyway - where do you want me to start?
fwiw, if you want to believe my desktop dyno software, it estimates my 7m will put out 281hp @ 6500rpm, and 256ft/lbs @ 5000 (and for an idea - its making 223ft/lbs by 2500rpm)
now dont think i believe these absolute numbers for a second, but its gives you some idea of the gains im looking for...
cheers
ed
...\...\...
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 13:09
|
|
| oldcorollas wrote on Thu, 14 August 2003 20:11 |
raw and grunty old tech, like a motor _should_ be...i like the backyard raw motor
|
stewart, you and i, bud, have some beers to be sunk between us
anyway, steve, here's a *basic* list of what you can easily do to a 7m to shake it up a bit. keep in mind, there are many, many conversations to be had with regards to each of these points, and each of them can be taken to 'silly' extremes - but then youre running into serious motec only territory...
intake:
-cai
-intake pipe
-throttle body/ies
-single vs twin inlet plenum with ACIS
-custom chop manifold with ITB's
-manifold porting and plenum porting
-port matching
head:
-intake porting, from mild to wild
-bowl can have massive improvemnets
-valve seats and seat cutting
-OS valves
-chamber shaping
-decking for CR increase (plenty of meat)
-valve unshrouding
-polishing
-ex valve porting - big gains again
-ex seat cutting
-headers 6-2-1 or 6-3-1 (dunno there?)
-hi flow 2.5" zorst
CAMS
-up to 9mm lift before head recess machining and Shim under modification required
-duration up the ying yang
-valve springs (?)
PISTONS
-truly mssive piston valve clearance
-allows plenty of scope with cam choice, compression machining etc
-pistom crown shaping and polishing
-rings - your call
RODS
-grind and beam polish and peen
-ARP bolts essential
BLOCK:
-GTE block w/ oil squirters (reduce temps a LOT)
-again, given piston tolerances, you can decrease the block deck height significantly (i chopped mine 40thou!!)
-oil return chamfering etc
-external oil cooler fitting stock on some 7mge's
-2 cranks available - single counterweight and double (later models) single is lighter, but less balanced
-i dunno if thyre all like this, but my crank is forged (out of a GTE)
-crank machining, lightening etc
OTHER:
-squish clearance is in your hands - can go to 35thou with stock 7m rods.
-piston squish surface area is ~30%
-head squish area is around ~20-25%
ive happliy squeezed 10.7:1 with basic non-dodgy machining (up from 9.2), and could easily get 11:1... and get this - such machining STILL maintains a non-interference piston/valve fit!!
if you wanted total interference fit, you could go easily to 11.5-12:1 AND run big lift big duration cams, and STILL not have clearance issues (this is with plain old cast ACL jobbies - so not sure how crazy you'd want to go on them anyway!) if you wanted to go custom pistons, the world is yours...
its all shades of grey really - how far down the scale youre prepared to go, what youre prepared to spend and risk, and what you reckon the ECU will run before a motec is required
hope thats a start as i said each point is a conversation piece!
cheers
ed
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 13:47
|
|
Thanks Ed,
Plenty of food for thought and I'm sure I'll have *many* questions as I progress. Let the games begin!
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Thu, 14 August 2003 22:32
|
|
Ed,
I noticed on you website you were after cam specs for the 7mge
Aust delivered supra (MA70)
intake open 6deg BTDC close 54deg ABDC
ex open 54deg BBDC close 6deg ATDC
Aust delivered Cressida (MX83)
intake open 6deg BTDC close 40deg ABDC
ex open 53deg BBDC close 3deg ATDC
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Fri, 15 August 2003 02:57
|
|
where on earth did you dig those number up from? 
well, im happy: ive got the 86 ma70 cams in mine (i think!)
might have to get a dial gauge and a degree wheel out for this one!
cheers
ed
|
|
|
Location:
Brisbane Qld
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Fri, 15 August 2003 06:50
|
|
The original Australian press kit for the MA70 and MX83 has a wealth of information
From the text:
| Quote: |
With the re-examination of the valve timing, the crankshaft has been modified to improve the torque at the low speed range
|
so I assume they mean the later and heavier crank complements the new shorter duration cams (and it appears to be direct JapLish too)
Did you know the Cressida's body is mostly galvanised and the exterior panels are a non corrosive steel alloy called Excelite?
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Fri, 15 August 2003 08:07
|
|
| stevevp wrote on Fri, 15 August 2003 16:50 |
so I assume they mean the later and heavier crank complements the new shorter duration cams
|
pretty much...
damn try as i might, i could only ever find 1 single counterweight crank, and it was fubar (plus i couldnt get the frigging crank pulley off the sucker)
painfully heavy, but shell be smooth
|
|
|
Location:
Sydney
Registered:
March 2003
|
|
Re: 7MGE bore spacing and overbore limit
|
Mon, 18 August 2003 01:55
|
|
| ed_ma61 wrote on Thu, 14 August 2003 23:09 |
CAMS
-up to 9mm lift before head recess machining and Shim under modification required
-duration up the ying yang
-valve springs (?)
|
The valve springs I used in my old Anchor M had 100lbs seat pressure and supported 12.4 or 12.8mm of lift before binding. I can't remember which Mitsubishi engine they were for but with minor modification to the seat they worked a treat.
You'd hate to be hearing this but I basically gave the TRD unit's I had away for nothing.
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Mon, 18 August 2003 14:17
|
|
| Stenno wrote on Mon, 18 August 2003 11:55 |
You'd hate to be hearing this but I basically gave the TRD unit's I had away for nothing.
|
I'M GOING TO CRY!!
godammit stenno - i couldve given you 'some' cash for em...
damn damn damn damn
damn
ed
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Mon, 18 August 2003 14:37
|
|
dont suppose the guy you 'gave' em too would be looking to sell them on again for a smal profit??
he doesnt really want them does he???
|
|
|
Location:
Sydney
Registered:
March 2003
|
|
Re: 7MGE bore spacing and overbore limit
|
Tue, 19 August 2003 05:18
|
|
| ed_ma61 wrote on Tue, 19 August 2003 00:37 |
dont suppose the guy you 'gave' em too would be looking to sell them on again for a smal profit??
he doesnt really want them does he???
|
I have no idea, as they went with the motor, don't have his number anymore either.
I think he was planning on throwing a TD06 on it and using the cams, but I'd say they'll sit in boxes due to the cost of buckets.
|
|
|
Location:
Lost in the K hole
Registered:
May 2002
|
|
Re: 7MGE bore spacing and overbore limit
|
Tue, 19 August 2003 11:16
|
|
well, i guess, if you ever run into his contact details, email, phone, anything, if you could let me know, that'd be greatly appreciated.
spose i should give him a few months to stew on the idea, before he realises that theyre not a great a idea, and he wants to ditch them... hehehe
god only hopes he doesnt try runing them without SUB...
|
|
|
