OK, it's apparent that you haven't played with too many of these, so i will add what little i can to make it simplified.

The rods are the same length as standard 1200 /A12 ones, with the exception of the larger wrist pin eye. My existing 1200 GX engine uses A14 pistons with the little end opened out to take the larger pin. This time i elected to go with a factory stock part. A13 [big bore version] & A12a rods are dimentionally interchangeable

The A14 crank will fit the 1200 /A12 block without alteration. There is quite enough room in the blocks that we tried.
The lathe work was't to allow the crank to fit the block, but to ensure that the counterweights miss the bottom of the pistons when the pistons are at BDC.

Could you do the necessary mods to the crank with an angle grinder? Hell yes, you could do it with a hand file if you were really really patient, but i seriously question why you would have an angle grinder in your engine assembly area. Is this the best engine work that you can do?
The the only part that actually needs work is the small part of the counterweight that would intefere with the piston. The best way to check this is to simply assemble an old A12 rod & piston onto the crank [with a suitable bearing] & rotate it around the journal. Then grind away the part where it interferes. Repeat for the other three journals.
Even a blacksmith could do that. That's all the dummy fitment that was required in the first engine, so we can put that small fortune back into our pockets. Wasn't that simple?

Balancing is always done on all my engines as a standard procedure, so what's the problem here? Don't you balance yours?
The A15 pistons should rise to be almost flush with the block, so this is not a special part of the build. Just standard rebuild stuff here. The A15 pistons were selected because they are shorter in the pin to crown measurement & a dummy trial fitup showed that it would work, so the first engine was built from leftovers.

For me, saving money on a cost effective & very practical A14 transplant is not the prime objective here, although it could, & probably should be for many,... geting the combination of parts that i want IS the prime objective.
I try to save money by using what little skills i have gathered after almost 40 years as a mechanic, & by doing as much as i can myself.

Now you seem to have overlooked the fact that i have not asked, nor even suggested that you,... or anyone else for that matter, should duplicate this engine, nor do i suggest that anyone should spend money on having engineers build engines for them un-necessarily, only you are suggesting this.

It's an exercise that will cost ME about the same as a regular "improved performance" engine buildup & will take roughly the same investment in time, effort & other resources. Since i am not looking for ultimate performance, the points that you labour upon, like rod angle & the alleged reduction in "mechanical efficiency", along with this reduction in sensitivity to valve timing [whatever that's supposed to mean] are all rather moot.

We have one of these engines running here in a 1200 coupe already & after more than a year of flogging, it still runs strongly. Mine will be in a milder state of tune & I expect that it will serve me well in its intended role.

If it doesn't work, then i will know why from first hand experience, instead of coming up with a great confection of rhetoric revolving around some airy fairy theories about "reduced volumetric efficiency" based on nothing more than a foundation of "I reckon"

You seem to be obsessed with absolute minimal costs & blacksmith engineering, & for a low cost project, i'm sure that this approach would be fine for you, but for me, this car is a plaything & i want to do as good a job as i can. Quality is always appreciated, & it's all fun.

The criteria for its existance?
No visible or un-necessary home grown engineering
To make the finished product appear to be a factory built car if possible
To assemble a maximum capacity engine for this car built from readily available standard Datsun /Nissan parts, & based on core components already on hand, with a minimum of special engineering.

I'll be sure to let you know how it runs.
The End

whoa, I didn't mean to insult your rods - I take it back, they're perfectly normal A series rods. albeit from the other side of the planet. All I was saying is that I was not sure what length rod you had used (but they had to be short), and I couldn't recall if you said they were A13 or A12a rods, I just knew they were out of one of those oddball A series engines.

As for this...Quote:
I don't know what I was thinking. Yes, simplicity itself! So easy in fact, I think I'll go do it tonight. Just pop it in me lathe... ah, hang on... will this here angle grinder do?
I seem to recall your mate did this for you in his home made lathe, but for 99.9% of us machining doesn't come cheap. You say it took 35 minutes to machine the crank. An engineer however, is going to charge for time spent measuring the block and crank, and double checking everything to make sure it actually fits after the operation, then there's the trial fitment, which will involve a dummy assembly of the bottom end (crank, rods and pistons), which I'm sure the engineer would also insist on so that he knows it's not going to come back. Conservatively, you'd be looking at 4hours, and at cheap charge-out rates that bill would come to arond $340. did I mention that's a real conservative estimate?

Then you have to balance the reciprocating assembly wether its just going to be a street motor or not. But that's probably simplicity itself and free too... For the rest of us, you'd be looking at another couple of hundred. This would be an optional extra if you were building a street A14.

OR, you could drop in the A14 engine. And then spend the five or six hundred dollars you saved yourself on stuff that will make it go faster. Anyone who owns a hacksaw and an electric drill can do the conversion - That is simplicity itself! Or if you want to get really fancy and make it look factory at first glance (that's all your A12 block will do anyway), just unpick the mounting brackets off the x-member and weld on some 120Y ones - that will invlove such exotic tools as an electric drill, cold chisel and a hammer. Then take it to someone to weld it up - might cost you a carton.

All this begs the question - why did the Datsun engineers go to the trouble of using a taller block and longer rods for the A14?

It's a pretty big assignment to explain how the rod to stroke ratio affects engine performance on a web forum. It has taken much more cleverer people than me chapters to explain this. I think if you go read the Racer Brown stuff Datsport has one thier website, you'll get a good broad grounding in this and other aspects of engine building.

Well, let me see.
Mod plate, what's that. The only one here to mention mod plate was yourself, so that not an issue, just a red herring.
Since i am boring the block, i needed new pistons, so i bought A15 ones. Nothing hard about that.

Difficulty & expense in fitting the A14 crank? Surely you are joking. It's simplicity itself.
I swapped something that i didn't need for the crank, so stop spreading stories about "expense" & the machining was done in 35 minutes for free. As for dificulty, it just fits up the same as a stock one. I suspect that you are thinking of something else. It's neither expensive nor difficult in this instance.

The rods? I don't know about weird, Perhaps you could elaborate on what is weird about a stock A series con rod. Yes, they are rare here in Australia, because the 1237cc A12a engine was not sold here. Tell me more, most particularly about the weird part.

Rod angle increase, yes, but at street speeds, it shouldn't be a problem for me. It hasn't been a problem for the only other example of this engine that i know of. My engine will be red-lined at 6,500 as this is the mark on my stock tach & the other engine is regularly run to more than that. In fact, it gets flogged mercilessly, but surprisingly, it would seem, it still runs good. Very bloody good.
It's the torque that i'm after, not dazzling revs, & all in a sneaky 1200 block.

Reduced volumetric efficiency? With a bore & stroke of a stock A14 with a 1mm overbore, & an improved 12GX head, you will need to provide a detailed explanation before i will swallow that.

Less sensitive to valve timing? Again, an explanation will be necessary.

The only special machining required was to chuck the A14 crank into a lathe & reduce its overall diameter by a few milimeters. Basicly we cleaned the dags off the counterweights. Big deal.

Basicly, everything in this engine carries a stock Datsun part number. It's just an innocent little 1200,... honest, so i don't know what you mean about "going to all this trouble." No part of this exercise has been any trouble, but ALL of it has been FUN,...... for me.

Talk is cheap when decrying a design, but if you know why all of the points noted above are negative ones, please let us all know, in exquisite detail, so that others don't make the same mistake.

If i was going to rally, i wouldn't use this engine either, but i'm not rallying, i'm just street cruising, so it will be OK for me.

I had an A14 in my old 1000 coupe - it's not exactly difficult. Certainly not compared to the difficulties, and expense, of fitting the A14 crank to the A12 block.

I could almost understand a rally competitor doing it though, because they're restricted to using the standard or homologated block with free internals. But for a street engine it seems an awful expensive way to avoid the need for a mod plate.

And even after all that trouble, you won't quite end up with the same result as a normal A14, because your rod to stroke ratio takes a fair bit of a battering (but I don't know what length rod Dodgeman used - didn't he get some weird rare A series rod from USA?). Which essentially means reduced safe rpm limit, reduced mechanical efficiency, and makes the engine less sensitive to valve timing - meaning you won't get full advantage out of your sporty reground cam. And following on from that, I reckon it would reduce volumetric efficiency too. If I was going to rally a 1200, I'd stick with the A12 crank and 76mm bore.

Quote:I am using a 1200 block, with an A14 crank that uses A12a rods to move the 77mm A15 pistons up & down.

I am doing this....
Because the A12 block fits the KB10 chassis without mods.
Because it still looks like a 1200 when finished. To the untrained eye, it may even be mistaken for the original A10.
Because the whole thing can be made to appear "factory."
Because it's relatively unique, as i'm sure that very few will duplicate it.
Because i can.

I see 77mm as a practical upper limit & my block is already at 76.5mm, so i guess that i will give it one more try.

Chris`s a12 stroker is to avoid difficulties with non genuine mounts and engineering into a kb10. I have this problem with the a14 I have in my b10.

I'm sceptical of a 79mm bore in an A12 block....77 was the utter limit for me, like I say, it took 5 blocks to find one that would take it...
Someone here (dodgeman perhaps) has put an A14 crank in an A12A block, which is interesting from an engineering point of view, but seems like a lot of work to achieve what an A14 does anyway....

bump

What clearancing would be needed to fit the a15 crank in? Just the crank or block as well?
I suppose thats whats needed to get 1600cc from an a12 right?
If so it means this particular a12 will need 79mm bores which is amazing.

I bored one to 3mm over and used toyota pistons engine was 1270cc..

SLY OLD FOX.....