short stroke l28

[trowa47]

I am wanting to build a l28 with l20a crank and conrods

p90 head and t3/t4 turbo.

 

I know it is best to go with as much CC as you can get but I i love the short stroke of the l20a,

 

I am using the l28 for the large bore. so is there any thing that will make this not work i know i will need custom pistons but other then that is there any thing any one can tell me Thank.

[OlderThanMe]

You could just use stock pistons...you will have a 2.4 or 2.5 liter motor IIRC with that cam and block

you would want to use the 1973 L24 connecting rods FYI...they are nice and long. With the L20A connecting rods your CR will be like 2:1...lol

That motor combo should spin up nice with a 10-11 lb flywheel!

All I can say is, Go for it!!!

[trowa47]

L engine build is telling me the l20a conrods are 135mm

[OlderThanMe]

http://www.ozdat.com/ozdatonline/enginedesign/

[SUNMASTER]

I think You will have to measure the rod's to get the right length. I also checked both programs ............not the same:icon5:

[thehelix112]

I wrote the ozdat utility. I initially copied the values over from the L building program, but was informed by a L20A owner the length was wrong and corrected it based on his info.

 

I stand to be corrected again.

 

Dave

[ozconnection]

L20A engines came in two variants...a robust and a gracile

The robust version used L24 rods and a special piston to suit the small bore. Those rods are 133mm c to c

The gracile version was like the Maxima L24 with the small big end and pin . The beam is very thin and that rod isn't ideal for performance work.

[ozconnection]

I am also considering the virtues of an L28 destroked with the L20A crank

It builds a 2.5 litre engine with a 40 thou overbore.

The compression is suitable for boosting with a flat top piston and the E88 R30 L24E head, stock gasket

I intend to keep it NA for the time being but a Rotrex supercharger isn't out of the question into the future.

I track my machine and run a CD00A 6 speed and low 4.625 gears. 

A rev motor would be awesome and the song it sings, delicious....

[AydinZ71]

@ozconnection

 

Short-stroke motor’s are great for maximizing HP with limited displacement. I think your limiting component will be the head though 😕 . Custom rods will get you safely past 7500 rpm. I’d pour the rest of my time/money in the head. 2 valves per cylinder and restrictive ports takes a lot of work to maintain torque past 6500rpm. Good luck! 
 

PS: Kameari and Tomei still sell parts for the L20A, but they are crazy expensive 

[ozconnection]

I have spent a lot of money on the head as it turns out. It's CNC ported by a Datsun specialist, SWR, here in Sydney Australia.

 

I think the limiting factor is the crankshaft. 

 

Going to the expense of building a billet crankshaft, it would be cheaper to supercharge the motor.

 

 

 

 

[jonbill]

I think a short stroke engine is cool, but even the LD crankshaft isn't super long stroke and will rev. 

I'm revving mine to 7700, and my previous engine with l28 crank went well past 8. (in the end it was valve train that limited the rpm) 

[AydinZ71]

Gosh you know, all the L engines are oversquare, so you are right. It’s relative. Even at 86mm stock bore and 83mm V07 crank, I’m sure she revs great.

 

a credible source in the S30 racing scene said he isn’t a fan and feels the longer stroke tended to break things prematurely. Didn’t get into much detail, but he prefers an L24 crank on an L28 block 🤷🏽‍♂️. As always, I’m sure there is some truth, some opinion, and some experience mixed in. I have not had an opportunity to discuss 3.0+L motor longevity in a pure, competitive racing application (many laps at max power band). They are not legal in most classes (except “open” classes), which explains some of it.