2jz block bored out with 1jz crank?

[is300ss]

my current engine is a 1jzgte
I have 2jz block I want to make use of. however I like the 1jz because it loves to rev.

so my question is...
(as a fixed variable lets pretend the head i will be using is fully built)
(you should also know that I would use the right size connecting rod for the correct compression ratio)

does there have to be a balance between bore and stroke to achieve the highest possible USABLE redline
OR is it simply up to the stroke length? i say usable as in having the max hp close to redline, however high that red line can be. LOL this makes sense to me, dont know bout you guys.

I hope that is a clear enough way to put it.

so what (using stock crank) the max you can bore the 2jz is to a 3.4L I believe.
volume is volume right? sooo if i did use the 1jz crank in a fully bored 2jz block id have a 2.9L short stroked 2j.

I want max displacement and highest redline possible know what i'm saying?

 

[is300ss]

bump. wtf help me out someone

 

[bmoss85]

iirc the 2jz 3.4l is bored to 87mm and stroked to 94mm, vs the stock 86mm bore x 86mm stroke.

this is a good post even though its geared towards the 7m, but same priciples apply
http://www.supramania.com/forums/showpost.php?p=180719&postcount=18

 

[Poodles]

Properly built 2J will rev as high as a 1J all day everyday...

The 2J block is taller as well, there's too many variables in this...

 

[is300ss]

thanks, yeah that link helps. i guess Ill just research engine geometry.

bored to 87? thats it?

thats just for safety right? do you know how far you can bore it?

 

[Jeff Lange]

I personally wouldn't go any further than 87mm, but you may get away with 87.5mm.

That being said, using a 2JZ block would make very little sense. You'd need to use longer rods which would add weight, or use custom pistons with a different wrist pin location, but that would be quite a bit of piston above the pin, not the best idea.

You gain nothing from using a 1JZ crank in a 2JZ block. You get the same displacement boring out a 1JZ block with a 1JZ crank.

My point is, deck height has nothing to do with the displacement, so you're making your life harder by trying to use a 2JZ block.

Run whatever built head on a bored 1JZ block.

Jeff

 

[Mark Conte]

Properly built 2J will rev as high as a 1J all day everyday...

The 2J block is taller as well, there's too many variables in this...

Correct.

thanks, yeah that link helps. i guess Ill just research engine geometry.

bored to 87? thats it?

thats just for safety right? do you know how far you can bore it?

First question is why? I've had high end 2JZs easily from 9,000 up to around 10,200 (not that anyone needs to go up there). The 2JZ really has no issue with RPM, throw some valvetrain in it, a good piston and rod and it will turn pretty much as fast as it needs to to keep up with any size turbo you'll probably ever put on it.

Why would you want a bigger bore? That just shrinks the cylinder wall and will reduce the block's life. Much easier to crack a cylinder the larger you go.

 

[Adjuster]

I'm with the reality that larger bore is not the (best) way to gain displacement.

Stroke is better, when you can get it.

Bore only works if you have verified the bore wall thickness, or are using liners. (especially on open deck designs, if we are discussing any engines here, the 7M is closed deck, IIRC so are the 1J and 2J designs.)

I know on the open deck blocks, liners that lock up at the top, and keep the bores from flexing out of place better than stock can give some bore increase with out problems, but again, it's better to get the displacement from stroke if you can.

If you want more displacement than the factory, it's time to get another motor. (I have a stroked 7M, and if I was going to do it all again, I'd go the route Ian is now, a 6.3 V8 with a medium sized turbo hung off it.)

LOL I'm actually looking at a 572ci big block mated up to a 5 speed auto in a MK3.. That would really piss off some folks, but then again, most of them would be looking at the back end of my car anyway....

 

[rayray]

a 2j block with (assuming unmodified 1jz crank) is basically a taller 1j with no difference in stroke of that of a standard 1j

if you keep bore on the 2j and 1j the same in this case, and the only thing changing between the two is the crank, the only thing you're changing is the length of the stock 1jz rods to suit the deck height of the 2j. you end up with a taller, heaver 1j that will have identical stroke and bore of a stock 1j.

if you're aiming to get more stroke with a 1j, you're better off starting with a 2j. if you want a short stroke with increased displacement, bore out a 1j.

 

[rayray]

and it's not just the bore that is changed on a 2j block to achieve 3.4L. if it were that simple everybody would have a 3.4L. rod length and stroke (as well as bore) is changed.

theoretically even if you used 90mm bore pistons in a 2j, you would only achieve 3.28L

the same theoritical 90mm bore magical piston in a 1j would only get you a whopping 2.74L... again changing bore only.

 

[Marotta1]

Just boring out will not get you much displacement gain at all. The benefit of using a 2jz block would be you could use longer rods with the same short 1jz stroke. In so doing you could build yourself an even higher revving motor than a regular 2jz, or just a less stressed motor. Longer rods with the same short stroke put less stress on the crank and rods due to lower rod angles. It's a smoother/smaller less jerky motion.

You can get the same or sometimes higher piston speed with less stress on components. Long rods with short stroke can reduce peak piston velocity & acceleration and thereby inertial loads on the rod and crank bearings. There can be less cylinder sidewall stress as well. A long rod can minimize rod angles and thrust load and friction losses at the piston skirt.

 

[Poodles]

Would require custom pistons, and overall it's a waste.

 

[IJ.]

"Siman school of automotive design and engineering"..... :nono:

 

[rayray]

with rough calculations there IS a rod angle difference of about 12-14% and about a 2-3% difference in crank angle (based off what info i could find on 1j/2j rod lengths) when comparing this long rod 1jz vs a standard 1jz. this will decrease the stress on some parts and on cyl walls somewhat...

but again, without increasing stroke or bore (again assuming stock 1j crank and standard bore on a 2jz block), you are talking about one helluva an expensive 2.5L engine. if you want to have anywhere near 3L, you're probably better off modifying a 2JZ crank or making a new one altogether to utilize a longer rod and shorter stroke using 2JZ components.

and by changing all of this, you are also affecting other characteristics of the engine as well

 

[rayray]

i found this too, which may or may not help your decision. i don't know if this calculator is accurate, but i found mine to be within a degree or two chicken scratching on the back of receipts.

http://2.3liter.com/Calc2.htm#PistSpeed

according to that calculator there is probably going to be less than 4% improvement in negative piston acceleration and a slight increase in piston accerlation during positive piston acceleration at/near TDC at 9000rpms. unless you plan to rev the piss outta the thing, it is likely you won't see much of an improvement in reality.

also keep in mind, with stroke being constant, a short rod will have faster piston speed near TDC and slower at BDC. a long rod will be the opposite with it being slower up top and faster near BDC. so changing the rod and so forth will also change other characteristics of the engine... not just making the engine "higher revving"

my 2 cents is that although intriguing, the costs totally outweigh the benefits... but that's just me

 

[Poodles]

It's still more mass moving around as it's a longer rod. It's completely pointless.

 

[rayray]

another good read http://www.stahlheaders.com/RodLength.PDF

 

[Mark Conte]

a 2j block with (assuming unmodified 1jz crank) is basically a taller 1j with no difference in stroke of that of a standard 1j

if you keep bore on the 2j and 1j the same in this case, and the only thing changing between the two is the crank, the only thing you're changing is the length of the stock 1jz rods to suit the deck height of the 2j. you end up with a taller, heaver 1j that will have identical stroke and bore of a stock 1j.

if you're aiming to get more stroke with a 1j, you're better off starting with a 2j. if you want a short stroke with increased displacement, bore out a 1j.

Usually the deck height of a 2JZ is 8.621" FYI (give or take around 1-3 thou)

and it's not just the bore that is changed on a 2j block to achieve 3.4L. if it were that simple everybody would have a 3.4L. rod length and stroke (as well as bore) is changed.

theoretically even if you used 90mm bore pistons in a 2j, you would only achieve 3.28L

the same theoritical 90mm bore magical piston in a 1j would only get you a whopping 2.74L... again changing bore only.

Rod length on "3.4" liter 2JZ's stays the same @ 5.590", the stroke goes up to 94mm - 3.701" and the pin goes up to a honda-spec 1.181"

 

[rayray]

didn't know the rod length on a 3.4L stayed the same. so the center to center is identical to stock? well i guess if you're moving the pin instead that makes sense. i assumed the opposite