L20 crank journals can be ground down - most people wouldn't bother because you just start with a L20 block anyway - heaps cheaper. However there's plenty of people who don't want to let
people know exactly how big their engine really is and cheat this way - it used to be a VERY common trick in Class N rallying in South East Australia (capacity restrictions and all that).

The point here to Mareo was the originality and the sentimental value of the car, not doing things the cheapest way....

The blocks can be taken out a bloody long way beyond what is considered reasonable. Toyota Corona Pistons (88 mm instead of stock 83 mm) used to be an old favorite for oversize bores. 120"
overbore was never a problem on L16 or L24 motors. Bigger is possible, but at signifcant cost and risk. Strangely with a 5mm overbore your stroke to bore ratio comes out pretty good....

Even using the 88mm pistons brings you out near to 2250cc using a stock 20b crank, let alone one with increased stroke (hey - if you're regrinding the base circle of the crank anyway!!).
Doubt me not people, the money some of these rally guys were throwing away was enormous - and eventually led to changes in rules of the class to ban such cars.

L18's were a stroke job only of L16's so using an L18 crank in an L16 gave L18 not L17.... At least that's the way it was with Australian models. Likewise L26 was only a stroke job of L24 (
(83*73.7 to 73*79mm).

2150 is considered a "normal" overbore size, and I have seen this used on L series blocks running in excess of 25psi boost (T3, T3/4 hybrid and T4 turbo) with no problems.
A friend of mine was running such an engine in their bluebird until they lit it up just a bit too much at a roundabout one day....

Aussie Zoom readers would have seen a SA 1600 running a 2150 twin turbo setup in an L series - Greedy's yellow one - later shown with blue paint and an SR20 conversion.


As far as U20's being the basis for L24 engines, that's to do with the whole development from Roadster to the Z which replaced it. Note that the L series never ran anything like those carbs
until the Z came out, but twin Su's and Solex's were used on the 2000 roadster. I've got the interim design drawings from Roadster to Z in some books here.

I know there were L20 and L23 motors around at a similar time - check the carburetion and cam profiles compared to the Z....no similarity at all.

Note Japanese models of the Z are still called the Fairlady, and early Japanese Z's had a number of different engines in them, including a number of different 2 litre SOHC, DOHC models not
seen elsewhere - such as the 432R DOHC S20 engine, with triple 42DCOE webers (from the standard 2 litre triple solexes).

Checking out a few internet links shows significant differences between Aussie delivered roadsters and American ones, but I think you're right about the R16 not the J16 - J series engines
were used in a Datsun 1500 and 1600 utes of the same error and may be the cause of my confusion - we wrecked one and rebuilt one the other day at a mates wrecking yard. The two are different
engines, but I dunno how similar they are or anything about parts compatability - there's very few of either of these types of engines left in Aus.

Did america get the 3 seat roadster?

Anyway it's been a long time since I've seen much of the inside of a roadster with a genuine engine - something like 8 years since I helped a mate restore one. the few I've had a good look at
since then have got L16's, L18's or fuel injected jobs.

Maybe if I sell the ute I'll get one.

My responses follow Andrew's comments.


L20 crank journals can be ground down - most people wouldn't bother because you just start with a L20 block anyway - heaps cheaper. it used to be a VERY common trick in Class N rallying in
South East Australia (capacity restrictions and all that).

I figured that was how those guys were making their 2 liter L-18 motors. Seems like the rod to stroke ratio would suck and these motors would wear the cylinder walls more.


Strangely with a 5mm overbore your stroke to bore ratio comes out pretty good....

It was "pretty good" to begin with. The L-16 or L-18 motor is already "over-square" (likes high rpm's) so it's stroke to bore characteristics don't really change, you just have a bigger motor
that may like to rev even more.


Even using the 88mm pistons brings you out near to 2250cc using a stock 20b crank,

W/ 88mm pistons and a 86mm crank I get 2092cc, look here for some info on a long rod L-21b: http://home.att.net/~jason510/longrod21.htm


let alone one with increased stroke (hey - if you're regrinding the base circle of the crank anyway!!).

Why not just use a Z22 crank? Unless you want the fully counterweighted L20-b crank.


L18's were a stroke job only of L16's so using an L18 crank in an L16 gave L18 not L17.... At least that's the way it was with Australian models.

Ozzie models my arse You guys must be using L-18 (larger bore) pistons or something.

Here's a easy math trick for 4-cylinders:
Square the dia. of the bore (in cm.) X pi X the stroke (in cm.) and you get the volume in cc.

Using the dia. as opposed to the radius of the bore gives you the 4 (after the dia. is squared) for the 4 cylinders. You can then multiple by 1.5 if you're dealing with a 6 cylinder. No more
dividing that bore in half.

L-16
8.3cm (bore) squared X pi X 7.37cm (stroke)= 1594cc

L-17 (L-16 bore w/ L-18 crank)
8.3cm (bore) squared X pi X 7.8cm (stroke)= 1687cc which rounds up to 1700cc or and L-17.

Don't make me argue that again, too much math talk:)


As far as U20's being the basis for L24 engines, that's to do with the whole development from Roadster to the Z which replaced it.

The Nissan L-series engine was a copy of Mercedes' early 60's OHC design. Mercedes timing chains work on an L-series motor.


Note that the L series never ran anything like those carbs until the Z came out, but twin Su's and Solex's were used on the 2000 roadster.

Wait, Both the z-car and 510 got SU carbs like on the roadster. The 610 had EFI on an L-16 or L-18. And Nismo sold the same Solex set-ups for the z and 510.


I know there were L20 and L23 motors around at a similar time

Actually the Z had been in production 5 years before the L20-b came out (1975). And Nissan never made a L23, L24 and Z22 yes, but not L-23. That motor is a "hybrid"; Z20 block, 6" rod, 89-
90mm bore, Z22 (92.0mm) crank.


- check the carburetion and cam profiles compared to the Z....no similarity at all.

Again, yes on the SU's and the 4-cyl. even got efi like the later Z's. And I believe the specs on the 4 cyl. SSS (or L-20b) cam are much like the Z's. What was the point you were trying to
make about the Z motors?


DOHC models not seen elsewhere - such as the 432R DOHC S20 engine, with triple 42DCOE webers (from the standard 2 litre triple solexes).

Ther were also TWO versions of this head for 4-cylinders. One made by Nissan and One by OS Giken, there's a picture on the Datsun Soul Website and in the U.S. "Datsun... Modify" books.


Did america get the 3 seat roadster?

Yeah, I think up until 1966 when they switched to the R16 motor.

Cheers,
Daniel

Ok Ive looked at the article on the l20b with the ka24e head.

I would like to know if its possible to do the same to the l18 block and using custom pistons to take the bore to 88mm for the use of the ka24e head?

I really like the though of a 1900cc L18 bottom end with the better crossflow 12 valve head capable of flowing much more than any L series head. Harry has convinced me from the start of my days here that the L18 is a great engine and even more capable than an l20b when it comes to its lighter weight, lower deck height and revvy 78mm stroke.

Of course if this is possible then I will scrap the rotary idea instantly as I would love to keep it all nissan.

thanks 4 diggin up this post.......Didnt even know about a J Series Motor

hehe...maybe this would be a good time to mention that our really good L18 we had last year had an 82mm stroke...

but yes, other than the height of the block the L18 is identical to the L20 block, so the KA head could be fitted. It would change the timing chain requirements obviously. I don't know what capacity the KA24 combustion chamber is, but with custom forged pistons you could pick a suitable CR.

personally, I think there are better and easier options for good revvy multivalve 1800cc Nissan engines - and I'm now getting the ball rolling on one of them for my 1200...

After reading right through this thread, it would seem that the confusion between the diferent versions of A12 & the A12A engines was not resolved. I will attempt to provide a simple clarification that i hope we can all live with.
There are two versions of the engine that Nissan identified as the A12

Datsun 1200 engine.
This is the engine used in Datsun 1200 passenger cars & utes from 1970 untill the change of model in '73. It has a 73mm bore & a 70mm stroke & displaced 1171cc. The main identifying feature is the front mounted distributor & the A12 prefix to the engine number. While these are true A12 engines, i believe that they should always be refered to as Datsun 1200 engines. The standard model came with a round port head, while the GX used an oval port head. These engines used a separate drilling in the head & block to get oil to the rockers.

Datsun [Nissan] A12 engines.
Like the earlier engines, these too were stamped with the A12 prefix & share the 73mm bore & 70mm stroke & displace 1171cc. They differ primarily in the position of the distributor which was relocated to a position under the No. 3 spark plug. While these engines were fitted to the '74 & later Datsun 1200 utes, they are not a true Datsun 1200 engine [see above] & i suggest that only this version of the engine should be refered to as the A12. The standard model came with a round port head, while the GX came with an oval port head. The extra drilling for the rocker oiling was eliminated as the oil now flows up alongside a head bolt.

Nissan A12A engine.
This engine was not used in Australian models, but did make an appearance in US & Asian market cars in the period covered by the B310 model run. It is to all intents & purposes the same basic engine as the A12, but has a bore of 75mm & retained the 70mm stroke. The block is to all intents & purposes a bored out A12. These engines have a displacement of 1237cc. The cylinder heads had oval ports of smaller dimention than the ports used on the 1200 /A12 GX engines. These engines were stamped with A12A as the engine number prefix

So thats my suggestion, call them Datsun 1200 engines if they came from a 1970 to '73 Datsun 1200 & have a foward mounted distributor.

Call them A12 if they came from a 74 & later model, have the distributor under No. 3 spark plug, & are stamped with A12 as the engine number prefix

Call them A12A if thats what is stamped as the engine number prefix. Note that the letter 'A' will be an upper case character in the same font in both the prefix & suffix position.

This is the best & simplest way that i can think of to clearly identify these lovely engines.
Any thoughts?

jeez that was me... my old user name i couldnt remeber the password for.....ive still got that gx head too in my shed... i look at the box and laugh about it now. Man i was pissed off that christmas

Well Harry I think there are many easier options but "without pollution gear" whats available in 1800-2000cc multivalve??? nothing except LZ heads and that isnt an option anyway.

As for 82mm stroke what crank and wouldnt you need the taller block for this as the rods are getting a bit short for the l18 block very interesting!!?

an the L18 with 88mm bores and Ka24e head should be the best option no?

Chris you might know but I found some taiwanese head gasket websites that specify the a13 in two forms. 76mm bore x 76mm stroke and 73mm bore with 77mm stroke in another
.
http://www.taihonet.co.jp/e/ebc/nissan.pdf

http://www.tonghong.com/cht/product.php?mode=show&cid=260&pid=429