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another 5m block 7m head bs idea

5K views 51 replies 11 participants last post by  DylanM 
#1 ·
I'm just throwing out something different. Why can I modify the 5m cam gears to fit the 7m head? That way I don't people don't piss with the crank gear, but they would have to use 5m accessories :( (dam squeky belts)
 
#21 ·
The 7m sprocket fits just fine on the 5m crank, no mods necesary. We just went over all this in another thread.

Using 5m cam gears on a 7m wouldn't solve any issues, you have to use 7m lower timing belt stuff because the 7m head is physically longer then the 5m one. Just use all 7m stuff, including inner and outer lower timing covers. A 7m head on a 5m bottom is straight bolt together. You may need to shorten the inside of the 5m pulley though to get it to sit at the right depth. You will also need custom pistons to get proper valve reliefs and compression ratio, and if you want to turbo it you should invest in some custom forged 5m rods.

Not wanting the longer stroke of the 6m\7m because your worried about traction is silly and totaly the wrong reason to build this hybrid motor. People act like 6ms and 7ms have stump pulling torque or something. Its a moderate upgrade over a 5m torque wise, its noticable, but very subtly. Buy some decent tires already! You should be wanting to build this motor to gain another 500-700 of safe and usable rpm. Whats with all this 9-11k rpm nonsense? These are inline 6s for christs sake, the only crank design worse for high revs are inline 8s! You build an "8m" (I don't really care for that name, it doesn't follow Toyotas incrementation usage. Technically it would be a 5.5m, or a negative 6m lol) to make a 2jzge out of M motor parts, and suprise, you end up with 2j like revs and power range. Or, you could just save yourself 1500 bucks in machine work and custom parts and by a 2jzge for 500 bucks with ecu, harness and tranny.

Yeah I'm party pooper, its late and I'm tired.
 
#11 ·
What's wrong with the longer stroke besides some traction issues? I got the 6M beast in the Celica and I love it and so does anyone that has been for a ride in it.
 
#12 ·
Here are your options, run a 7m with redline of 6250 rpms and be happy. Or since people have used 7m pulleys for 6m hybrids (7m with 5m head and pistons) it could probably be done in reverse with a 5m pulley on a 7/5m mutant baby (2.8-24v). And the only reason this should be done is to achieve either higher rpms or a closer relationship between bore and stroke. The 2jz has an 85mm stroke which is the same stroke as the 5m crank, however the 2j has an 85mm bore as well. The M series motors have 83.5mm bore which could be changed up to 86mm which I don't think would be safe but 85mm could be ideal for a low comp turbo setup with supporting mods with oil pressure, fuel delivery, mhg that sort of stuff. Really if you are staying N/a go 7mge, if you have a lot of money and time have at the "8mg" idea. In the end the 7m and 5m have the same redline so if your staying N/a the 7m has more torque, more head flow, larger injectors, the list goes on. And the shorter stroke on an 8mge N/a setup wouldn't do much but improve the rod ratio which means less stress on the rods. I am however all for the idea if it is played out right with a ct-26, mhg, 85mm bore and stroke, gte electronics, increased oil pres., increased redline, and the list goes on... It would cost some money though and if done correctly would require a custom pulley. And that's why I said fuck it, 7mge here i come! lol
 
#14 ·
dylan
the 8m was meant to be a high reving motor
thats why i have a daughterboard on a ecu this would put more stress on the rods alot more stress
now the early 7m has a redline of 6500 so in other words you need to be 9k to make the power of a stock 7m unless you spend some serious money it wont work
when i did the math the 8m was meant to rev to 11k
and produce 250 with a ct26
this was a rev monster
axel has this motor in his supra and dynoed it is putting out 252 but it runs out of boost fast so he is curently upgrading the turbo.
it revs fast
ill post a vid
 
#16 ·
11k rpms= BOOM plain and simple
I wouldn't expect a 2j to do that let alone a 5m mutant. The thing is for every 1k rpms gained 10psi oils pressure should be added (for the m series it is not always like that, they are targeted for oil flow specifically). So the thing about high rpm motors is the relationship between oil flow and oil pressure (if it is not considered in a build with high rpms then something will fail).
 
#15 ·
^ (CJ011) bigger tires (preferably less sidewall) and a better suspension setup. And the only way a 7m wouldn't pick up good is if it had too much power for the tire and suspension setup. The 7mge i don't think that will need any tire or susp upgrades anymore than a 5m car would, although I do believe it would be much better than a 5mge. Also if it is a cress get some 14 inch p type rims with 60 series and traction wont be a problem for a while.
 
#17 ·
Hmmm... all good points. I say it maybe possible to spin 10-11k on the 7m head with valve train work. Gene Berg spun 9600 rpms over 20 years ago in his flat 4.

Dylan, you do bring up a very important point though about necessary oil pressure.
 
#18 ·
dylan
in the 8mgte Axel has it makes power till 11k
he is also running a 85 oil pump with a overdrive oil gear :)
it is not impossiable at all it wont go boom either lol

plus my 7m can rev to 8k :) ha ha rev limiter lol thank you daughterboard :)
ive done it too so its not impossiable
 
#19 ·
Longevity is sacrificed at that point, even if you do a proper setup to withstand 11k rpms the longevity is sacrificed. A part has so many turns, uses, or revolutions before it gives. And if you beat the piss out of it at a rpm range almost double of what the factory set the limit at it will go boom. Not trying to be harsh just realistic.
 
#22 ·
^ epic.... I really can't disagree with anything there, I know for damn sure toyota put the rev limit in the 6000 rpm range for a reason. More rpm's requires more oil pressure, possibly flow because the 5m crank has one oil port and the 7m has one comparable to the 5m's and a smaller additional port IIRC. Also the 7m rods have small oil ports, toyota was gaining an understanding on how to correct the rod bearing issues. (if only they could get decent owners)(and seals):eekfacepalm: So yeah the "5.5" or "8m" would require a lot of headache to even consider, and the benifits would require forced induction, bigger bore, higher comp, or some means to make up from the lost torque.
 
#24 ·
So yeah the "5.5" or "8m" would require a lot of headache to even consider, and the benifits would require forced induction, bigger bore, higher comp, or some means to make up from the lost torque.
No I don't think the benefits would require forced induction. IMO the 8m (ok, thought about it some more. Considering the next 3.0l inline 6 toytota made is a 2j and a 5m bottom with a big overbore and a 7m head pretty much equals a 2j spec wise I suppose the 8m designation is somewhat appropriate. -6m is still more accurate though :p) is the best M motor configuration for natural aspiration. As for the lost torque, there wouldn't be any as you already have to have custom pistons made so get them done for an 85mm bore and up the compression. 85x85 bore to stroke, nice and square and it makes aprox 2900cc. A stock 7m is aprox 29500cc and a 2j is almost exactly 3000cc. Add in a big cam that can breathe in the higher rpms and you're going to be making more power then any other M configuration as the same torque at a higher rpm makes more hp. You could probably get away with an 85.5mm bore too.

But again, you still end up with a motor that is slightly inferior to a stock 2j. Just the price of the custom pistons would cover everything you need for a 2j swap, and then you can spend the rest of it working the 2j and end up with something even better.
 
#23 · (Edited)
Great points and no one is being a party pooper.
On one side: no oiling issues and all stock parts
Other: Higher rpm's, better rod ratio, more revolutions per minute, money lost to machine work
The debate continues.... I must say this is probally the most productive 7m head/5m block I have come across.

There is more that I am considering than just traction, but until I get my mind properly around some info, I am keeping it to myself so it's not just useless rambling.
 
#26 ·
In regards to the 2jz, I like the motor but prefer tinkering and I would find it funny to nail jz's with a supposidly outdated motor. Kind of like stretching cars with an 80's turbo dodges. It may not be the coolest or fastest, but dam that shits fun.

Suprafriend, you have you 7m about perfectly matched with that cam combo. I'm just not fully convinced that a 7m running high rpms isn't dealing with alot of stress from the rod ratio. I can see it possible due to the efficiency of the inline 6 design. I definately can see a cammed 7m pulling like hell to about 8,000 or so. With that stroke, rod ratio, and cam... I bet it's fun. The reason why I and others are interested in the idea is that the 5m had a 1.8ish rod ratio. It simply deals with alot less stress on the sidewalls. The problem it has is when the combo needs air, the head is running out of air. I definately believe that Dylan's engine revs fast as hell. Am I saying that I am right.... Nope. I am just experimenting. If it breaks, oh well. No I am not going for the 85x85 or 86x86 combos. What I interested in finding is whether a longer stroke dwelling or an engine operating with less tension/stress will end up marginally or drastically better.
There is more that I am brain storming, but that just comes down to the cost of machine work.

In regards to cost of pistons, speed is expensive. Now, depending on how far the bore can be opened up will determine if I even use Supra pistons. That may end opening the door to dirt cheap piston with a higher pin height. I'm not sure though. I do believe that Toyota was on the right path with the 1jz, but they used a crank in relation with too small of a bore. Could I just be full of it.... probally. I'm just learning and playing.
 
#27 ·
Seamus, nice try. The ironic thing is, that nowadays a nice n/a 2J can be had for less than the cost of the pistons for this "puff the magic dragon" wonder engine. It comes with a square bore, and a crank thats good for a "few" more revs than any M series....
 
#28 ·
Here is the deal, if you want high rpms with an M series as described these issues must be resolved. Oil management (pressure v.s. flow), you have air/fuel management (stock fuel cut and rpm limiter), at high rpms you have cooling to worry about (running lean and too much heat for the stock aluminum pistons to handle), Throw bigger injectors on and you'll more than likely run too rich, without a way to dial it in that is. So no matter what if you want higher rpms it leads to needing a way to tune and build the engine for the extra revolutions. A lot of variables are needed to consider, first off the objective, second the budget, and third is whether the 2jz would meet these goals with less time and money put into it.
 
#29 ·
Oil management (pressure v.s. flow), you have air/fuel management (stock fuel cut and rpm limiter), at high rpms you have cooling to worry about (running lean and too much heat for the stock aluminum pistons to handle), Throw bigger injectors on and you'll more than likely run too rich, .

dylan you have alot of misinformation here

1)oil management
the m series motor makes way more then enough oil pressure and flow so totally forget about this TOTALLY!!

2) fuel and air
the 8m is sopposed to be a major ported 5m which achieves major rpm's so of course you have to get rid of the rev limiter and fuel cut on a NA forget about it ! if so it is very easy to put some other device then stock if needed.

3)at high rpms you have too worry about cooling???? DYLAN REALLY
cooling wont even get over half at high rpm usage heck it wont even move (ask me how i know)
dylan if the 7mgte will not overheat with a turbo charger then the 8m wont either
and if it does you can just add a core to your rad and call it a day!

4)to much heat for pistons
no unless you are running crazy timing and low octane fuel YOU SHOULD NOT HAVE TO WORRY ABOUT THIS or your super lean well then you deserve to lose a piston

5)bigger injectors ok it might run rich and it might run lean when you change injectors you should always have some way to tune them!! easily put!
remember it is always safer to run a engine rich then lean
now if you like running a motor lean then you can always increase you fuel octane or retard timing

and third is whether the 2jz would meet these goals with less time and money put into it.
dylan the point of this 8m is to have a unique motor
everyone has a 1j or 2j in there car
the point of the 8m was never to make huge amounts of power but it was meant to be different!
 
#30 ·
Ok if oil pressure and flow aren't an issue why are there so many rod knock cases? Why did toyota go from 1 oil port on the 2m crank journals, to two on the 6/7m crank, because oil delivery is crucial don't ever think it is not. And what does a ported 5m have to do with anything? We are talking a 7m head not a ported 5m, you describe how you would build an engine with a 11k rpm redline and I'll shut up.
 
#31 ·
Ok if oil pressure and flow aren't an issue why are there so many rod knock cases?
this is not a oiling problem
alot of rodknock cases are from BHG's
now the other cases are because it has so much wear and tear on it
and that the crank is out of roundness and it slips

the 2 oil port is just an advance in tech also




now a motor that can achieve 10k to 11k
KNIFE EDGED CRANK first off
all forged components light rods and pistons
5m bottom end all new
7m top end with some cams and a ported head
then a stand alone for sure
pretty positive you can spin it to 10k then ;) but not with a turbo

We are talking a 7m head not a ported 5m, .
dylan the 8m is basically a super ported 5m!!! because your flowing so much air through the head
 
#32 ·
Bhg and rod knocks are completely different cases. Bhg= poor torque values, rod knock= low oil pressure, no oil flow (or no oil period) or just being abused. What I posted Is basically a fact of things that need modified or looked into as you go to another 1-2k rpms higher than the stock redline. Please explain how to get rid of fuel cut and the rpm limiter with the ability to tune the air to fuel ratio at those rpms above 6250.

Ok i didn't even see what you wrote below, my question is who is gonna spend that kinda money and not go jz seriously. And a turbo motor would have less static pressure than an n/a throughout the entire rpm range which means it will be more likely to withstand those extreme conditions, seriously you are talking about almost doubling the stock redline, what that makes me wonder is is it even worth it to have that higher redline? I'd say go by the dyno, and where the torque or hp drops set that as redline and be happy.
 
#33 ·
well first off there is no fuel cut on a NA motor
i have proof :) also the my motor is on stock electronics and i DO NOT lean out at 7k or 8k well thats what my fuel air gauge is telling me
lets just say my motor hit 8500 when robidunno was over at my house and he can attest! :)and 1 to 2k is not a lot not at all!!!
plus both of those will be gone when you go standalone
duahhhh lol :)
and your deffiniton of rod know is not always the case either not with these motors at least
so your misinformed there
some times it runs dry because someone forgot to put oil in it and sometimes the bearings are no good and allow exxsive play resulting ina rod knock
 
#34 ·
Bearing aren't just "no good" they have to have a reason to go out, one reason is if the main seal leaks, owner doesn't pay attention it goes to shit... that is the most common case I have read up on. I have been in possesion of three engines all with rod knocks. It's how I got into this with a good budget standpoint. I didn't read the part with standalone, but in the history of this site I have never seen or heard of an actual 7m head/5m crank engine being built let alone built with expensive ass forged rods and pistons, and an aftermarket ecu. Let me know when someone does it and I'll shit myself in awe.:eek:

My 5m had a main seal leak and rod knock, my 7m had an oil pan leak that was patched up poorly and has a rod knock, my other 5m 82 p type had a rod knock and was driven with it by a kid. They said it was at least 3 cylinders that were bad (they were beating it)
With that said what are the cases of rod knocks you have dealt with?
 
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