Internal engine interchange.

IMACHU2 · Post by **IMACHU2** » January 5th, 2009, 5:10 pm

I have a couple of nube questions. A 1.8L V6 and a 2.5L V6 are related, but how close are they?? How did Mazda come up with the 2.5L?? Is it the crankshaft (stroke) or was it a bore change?? Or both?? For example Could you put a 2.5L crank and rods into a 1.8L block?? Or is the block different?? I am going to buy a KLZE, but I just wondered since I have a worn-out 1.8L V6 sitting in my shop.

Nd4SpdSe · Post by **Nd4SpdSe** » January 5th, 2009, 5:24 pm

IMACHU2 wrote:I have a couple of nube questions. A 1.8L V6 and a 2.5L V6 are related, but how close are they?? How did Mazda come up with the 2.5L?? Is it the crankshaft (stroke) or was it a bore change?? Or both?? For example Could you put a 2.5L crank and rods into a 1.8L block?? Or is the block different?? I am going to buy a KLZE, but I just wondered since I have a worn-out 1.8L V6 sitting in my shop. :D

You know, I've always wondered by you can bore them out considering their external dimensions are the same. You can use the crank, but it's expensive work for what I've been told (Mr.Spanky with his turbo stroked 1.8)

Easiest thing to say, everything internal to the motor you can't change, everything external you can.

wytbishop · Post by **wytbishop** » January 5th, 2009, 5:27 pm

Googled this "Mazda K series bore and stroke" and immediately found this

http://www.tsentraal.ee/mx6/engine/SAE920677.htm" onclick="window.open(this.href);return false;

wytbishop · Post by **wytbishop** » January 5th, 2009, 5:40 pm

Can't bore the K8 too much because you will break into the water jackets. Regardless of bore dimensions the thickness of the sleeve has to be pretty consistant to achieve the same cooling.

RX8SE3P · Post by **RX8SE3P** » January 6th, 2009, 3:18 am

Too much difference. Bore and stroke are different. I'm sure there's a load of other internal differences too.

I suggest selling the K8 engine for whatever you can, or rebuilding it for fun...

IMACHU2 · Post by **IMACHU2** » January 6th, 2009, 9:45 am

Thanks guys, I was more curious then anything. So a K8 is like a 305 Chevy, yes it is a small block Chevy but, don't F'n bother

I tought maybe it was more like a 350 Chev or a 302 Ford. I could change the crank and make a 383 or a 347......or in this case turn a K8 (109.82 C.I.D) into a KL (152.53 C.I.D).

wytbishop: Great link thanks!

klmx08 · Post by **klmx08** » January 7th, 2009, 12:24 am

isnt the 2.5 just a bored out k8?

kiwimx3 · Post by **kiwimx3** » January 7th, 2009, 1:24 am

klmx08 wrote:isnt the 2.5 just a bored out k8?

No, the K8 block internally is totally different to a klze block
with cooling and oil passages abd returns in different places
hence why k8 head do not fit a klze block.

IMACHU2 · Post by **IMACHU2** » January 7th, 2009, 10:40 am

Factory Forged crank shaft. Aw-right!

mx3boyze · Post by **mx3boyze** » January 7th, 2009, 9:54 pm

IMACHU2 wrote:Factory Forged crank shaft. Aw-right!

Amen Brother.

klmx08 · Post by **klmx08** » January 11th, 2009, 8:23 pm

wow i did not know that the are almost the same externally though right thats why it drops right in the mx engine bay i know the heads dont fit i ment genrally not exactly

nlsolja123 · Post by **nlsolja123** » January 13th, 2009, 7:54 pm

will klde or klze cams fit in a k8? also will kl cams or k8 cams fit in a kf?

veltpak6 · Post by **veltpak6** » February 1st, 2009, 12:02 am

i'm curious if the main journals on the crankshaft are the same size b/w the K* and KL crank?

wytbishop · Post by **wytbishop** » February 1st, 2009, 12:38 am

As far as I know all the cams interchange.

I don't know if the crank mains are the same diameter. I've never read anyone posting that information.

veltpak6 · Post by **veltpak6** » February 4th, 2009, 3:10 pm

alright! found out some info

it looks like the mains are the same, 62mm

What I want to do now is stroke a K8 with a KL crank and rods (piston pins are 1mm smaller on K8 pistons)..why? I dont know... i think it would be interesting to have a near-square K-block... 75mm bore x 74.2mm stroke with 1.85rod ratio... it would displace 2.0L (square bore stroke unlike the KF) if it were NA and all left the same, I'd estimate it would make about 150hp 148ft/lbs... with all the K8 ancillary stock things left alone.

Then I'd like to take a K8 crank and aftermarket Honda rods (48mm) and put it in a KLZE with KLDE pistons... this yeilds a super oversquare 84.5mm bore x 69,6mm stroke with a high 2.01 rod ratio....it would displace 2.3L. The reduced stroke reduces the Compression Ratio lower than 9,2, probably about 8,8 if IIRC and even with stock DE pistons, would boost quite nicely..
The dynamics of this geometry would lend itself to a torque peak pushed up a few thousand RPM, combined with a higher rod ratio would increase combustion efficiency by prolonging piston dwell. I'd imagine for peak HP numbers, this engine would shine. How would it differ from a boosted KL? well the reduced stroke would reduce the torque peak figure from a crankthrow perspective, psi for psi, but carry the torque peak higher in the RPM band, allowing a higher HP number, psi fo psi over a KL. This is aside from the increased combustion efficiency and longer peak cylinder pressures acheived by the 2.01 rod ratio, which oculd very well compensate for the reduced stroke's peak torque #.

I dream about this stuff, I can hear these engines in my head! lol

MX-3.com

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