7m head on 5m block?

[andrew_mx83]

soon as the gte short block arrives no prob (once i borrow a camera)

atm my "current" motor still has the head etc on til i work out EXACTLY what im doing with it all

[andrew_mx83]

so, i have been doing some thinking about the crank and it does seem as tho the snout will not be long enough to run a timing BELT pulley and a harmonic balancer (even the smaller/lighter 5m one i am planning to use), especially if i try and bolt the rather large 7m front timing cover 2 piece jobie on.

the link that supra967 posted details a bloke getting his welded etc to be lengthened which i would rather not go for, a) too expensive and B) i dont like the idea of welding a crank!
plus it failed lol

i have access to a pretty decent engineering workshop and an experienced machinist/engineer (my dad) to make pretty much anything i can think of. how feasible would it be to machine up an "extension" to the crank with a thread on the end which then screws into the existing balancer bolt. the extension would obviously have a threaded hole in the end for the bolt.
in order to secure it i was thinking of then drilling through the side of the crank and through the threaded section of the extension and fitting a large-ish pin. in addition to this i would mill a new keyway into the extension and fix in a longer keyway which would also lock it into the crank preventing rotation.

excuse crappy laptop touchpad + mspaint diagram but its gives you the idea.



a) crank end
b) extension
c) assembled.


is this possible or a recipie for disaster? will it hold up at 8000rpm and decent horsepower? keep in mind that the balancer will most likely sit over the join to stop any flex, although there will not be a lot of load on that part of the crank anyway.

[wiseco7mgt]

Don't be surprised if your gte block doesn't have oil squirters, pretty sure the earlier jap models didn't have them.
Don't worry too much about shimming the pump, your pressure should be good if you machine the crank and get your main bearings sizes spot on combined with junking the stock oil filter adapter and going a full flow oil setup with remote filter.
I'd add a new oil pump to the list if it was me, they are cheap from " driftmotion.com"
.
Not sure about your crank idea, will the extension fit over the end of the crank with a key way like a harmonic balancer normally would ?

[crowncustom]

Why not try sourcing a 5MGE crank and block.Why I say block is that it has a different sized no.1 main bearing than the 7M and 5ME.
Just a thought.
Cheers Brett.

[Supra967]

any bending on the snout would be taken (at the weakest point) in the smaller diameter threaded section of the extension. The key and pin won't help any bending there. If there was enough force to break the welded section (larger diameter) on the other guys crank, you'd have to wonder about this way.

Might be better off just using the 7m crank with some lighter weight pistons and rods?

[andrew_mx83]

any bending on the snout would be taken (at the weakest point) in the smaller diameter threaded section of the extension. The key and pin won't help any bending there. If there was enough force to break the welded section (larger diameter) on the other guys crank, you'd have to wonder about this way.

good point.... i wonder if 2 pins (one at the front and one at the back of the thread) would help? the thread is plenty long enough.

my last option if i cant make this work will jsut be to buy a set of forged 7m rods but i would really like to try and get this going if its possible without ridiculous amounts of $$


the 5m-ge short block sounds like it might be the way to go, and just bolt my head on with the rest of it fairly complete. does anyone have any pics of the front of motor/timing gear?



wiseco7mgt - the extension would sit on the end of the crank with a joined keyway/long key and the balancer would probably sit over the join as normal (havent measured it all up yet)

[Supra967]

It think its just creating an unnecessary weak point. The 5M-GE might be a better idea, but they are harder to come by. 7M's are cheap and plentiful.

Is the lower stroke worth that much? Have you done the calcs on acceleration to see the difference? I think you'll benefit more from lighter weight pistons and maybe rods. Stock rods are meant to be forged. And that Jens guy on SM weighed the 5M pistons 40grams lighter than 7M (after he cut them i think) and they were higher compression as well.

[andrew_mx83]

the only calcs i have done are on piston speed. at 8000 rpm the piston speed of the 5m is less than the 7m at 7500 rpm = less stress on the engine at higher engine speed. seeing as i want to be able to sit over 5000rpm all day without having to worry about it getting hot or breaking, this would seem like a big benefit, plus it will spin up faster.

pretty sure the stock rods arent forged....but with the strong aussie $$ i can probably land a set of eagle forgies for around 500 (not too bad) if i end up having to stick to the 91mm stroke.

i dont think i can use the 5m pistons with the 7m crank (iis that what u were suggesting?)


thanks for the diagram btw, u need to start improving them upto my mspaint standard

i see ur point about the bending, and that section of the extension would only be around 12-14mm (at a guess). but on the other side of the equation u have the balancer acting as a sleave over the join and also the 2 faces (crank end and extension) butt up against each other there is no room for it to bend.

but i do see ur point, and am concerned about the strength of the whole deal. its jsut an idea floating round my head at this stage

[ed]

offset grind the 7m crank and use different rods

[Supra967]

Hmmm, the guy on SM is using 5M pistons on 6M bottom end for 3L capacity. Are 6M and 7M rods the same (length/pin diameter)? I know the 7M got a 6M crank.

500rpm out of decreasing stroke doesn't seem that worth while. Getting the 5M pistons off the shelf would be cheap, if your old man can machine the valve cutouts, you've got light weight, high comp pistons cheap and readily available. Maybe you should wait and see if Jens' motor works or not

Mass is the other side of the stress calcs. Piston speed (acceleration) is related to engine speed more than crank radius, but mass is directly proportional to force.

I'd go with Ed's idea if you're dead set on the stroke thing

Edit: just found this:
http://www.celicasupra.com/forums/sh...ad.php?t=12741
says 6M/7M rods have the same dimensions, and 5M rods are just over 3mm longer. If deck heights are the same for 5/6/7Ms, it would mean the 5/7M piston/rod would have pretty much the same deck-crown distance as a 7/7M piston/rod.

[crowncustom]

I will try and get a front pic of 5MGE as I have the front off mine at the moment.
I can tell you that the snout on the 7M is larger in diameter than the 5MG but the 5MG is stepped down from the front face of the cam belt cog(cam belt cog is same diameter as 7M).
As I said in an earlier reply I have 4M,5ME,5MG and 7MG in my garage so if there is anything you need to compare just let me know.
Cheers Brett.

[andrew_mx83]

couple of random pics (it fits!):






i have started getting old motor ready to go back in the car with a new set of bearings, was starting to think about taking shortcuts building the new motor cos im itching to get the car going again. will put the old one in and just not give it a hard time so i can build the new one right, will probably be 6 or 12 months

i now have complete bottom ends of 5m-g, 7m-ge and 7m-gte here and will start measuring and cc'ing components shortly to find out what combination is going to work best

[gianttomato]

Seriously, a $600 2JZGE > all of this.

[andrew_mx83]

seriously! i have no interest in putting a 2j in it!

i want to see what i can do with the 7m

[andrew_mx83]

bit of an update.... i had forgotten about this thread.

might start a new one soon from scratch as i have changed direction a little with it.

motor is now being built with a much healthier budget, the goal is to rev its ring off with an emphasis on reliability -want it to be able to stay over 4000rpm for 15-20min sessions without getting hot or destroying itself. will be a square motor @ 85mm bore and 85mm stroke


parts i have so far for it:
7M-GTE block
7M-GE head
5m-e crank
5m-e rods: linished, polished & shot peened
5m-e dizzy, coil & ignitor
cams: 280duration 8.5mm lift
Davies Craig electric water pump
dry sump pump
twin oil coolers
fuel: 30lt poly fuel cell, holley red pump & 650 double pumper with mech secondaries (2 x 34mm + 2 x 50mm throttles), custom plenum mounting carby to existing runners
custom urethane engine mounts



parts still to get:
3s-gte exhaust valves
mazda bp18 intake valves
85mm forged flat top pistons with coating on skirts & crowns giving around 12:1 comp (on standby to be made)
arp undercut head studs, main studs, rod bolts & flywheel bolts
1mm metal head gasket
15lt dry sump tank (boot mount)

expected redline 9000rpm.... should be good fun