L20 crank

[caZee]

A couple of qustions for the brain trust please....

Is a crank stamped M90 a standard L20 crank?

Can a 219 head be used on L16-L20, or is it for a specific size motor?

Thanks

Steve

[James]

Don't know about the crank. The head can be used on any l-series. The only issue with an L-20 is compression ratio increase, depending on your pistons etc. Tell us what you are considering with the motor and I'm sure someone could weigh in and give you better advice....

[datzenmike]

Could it be upside down? W60. I have a U60 crank.

219 will fit any L/Z series block. Compression with an L20B is 8.9

[okayfine]

Is a crank stamped M90 a standard L20 crank

Only for-sure way to know what you have is to mic the bearing surfaces and check in the FSM.

[Baz]

L20B crank has much larger main bearings.
visual inspection is all thats needed.
stamping # on cranks varies.
Some later cranks have undercut radius on journals.
Also the LD20 crank can be used. identical in all dimensions.
This crank is made from different material than petrol engines.
bullet proof if you can find one.
would recommend the A87 head for L20B use.

[datzenmike]

L20b are also 6 bolt and fully counter weighted, will fit the Z20 motors. I've had two Z20E cranks, can't tell them apart

[caZee]

Is the LD crank a diesel crank? That is what I am trying to determain. I just bought this motor from a guy here on the Realm and was told it might have a diesel crank in it. If so, is it a longer stroke than the gas motors as the Z motors are?

What kind of compression ratio will be required to get an honest 200 hp at the crank out of an L20 with the 219 head and duel side drafts?

It's awesome to have access to people who actually know what they are talking about rather than a bunch of people who want to share their opinions, as is the case on a lot of forums.

Thanks

Steve

[caZee]

Just re-read advice from BAZ. Motor has an A87 head on it now, with some obvious porting work done. Better than 219? I thought 219's were the "holy grail"

Steve

[Baz]

Is the LD crank a diesel crank? That is what I am trying to determain. I just bought this motor from a guy here on the Realm and was told it might have a diesel crank in it. If so, is it a longer stroke than the gas motors as the Z motors are?

What kind of compression ratio will be required to get an honest 200 hp at the crank out of an L20 with the 219 head and duel side drafts?

It's awesome to have access to people who actually know what they are talking about rather than a bunch of people who want to share their opinions, as is the case on a lot of forums.

Thanks

Steve

An honest 200HP fly wheel is an expensive exercise.
example.
L20B:1952cc nissan factory FIA head, 76degree cam, works headers. 50mm solex carbs
11:1 comp. Factory crate motor
Makes 195HP

with 2140cc ported head makes 209hp

Heads now done in Oz will make up to 230HP with 48mm webers.

Be aware that these heads & headers will set you back $4.5K

[datzenmike]

This one of them baz?

Is the LD crank a diesel crank? That is what I am trying to determain. I just bought this motor from a guy here on the Realm and was told it might have a diesel crank in it. If so, is it a longer stroke than the gas motors as the Z motors are?

What kind of compression ratio will be required to get an honest 200 hp at the crank out of an L20 with the 219 head and duel side drafts?

Some other things that you must consider:

200hp is double the L20B stock output and a bit more. Some thought must be given to modifying the internal parts to withstand the added stress. In theory as you double your revs you double your hp. True power is in the head and how well and how fast it gets air in and out, or breathes. So the path to hp is to breathe as much air as possible and rev the motor. An engine's strength and longevity is in the block. High hp/high RPM risks a failure of components never designed to reliably work this hard. For most applications the stock crank is fine and if anything it's the rods that would fail first so a diesel crank won't prevent a spun rod bearing any more than a stock one would. A diesel crank and forged rods/pistons would be a bullet proof combo though.

Compression, side drafts and an SSS head won't do it alone. You will need a much 'bigger' cam to orchestrate the breathing at these RPMs, a low restriction exhaust system, a reliable ignition system, an improved oiling system (including an oil cooler and cam spray bar) a revised capacity cooling system that will handle at least twice the heat, fuel delivery system capable of double the supply.... on and on. It's like a pyramid, the higher you go the wider the base you need to support it.

Compression increases makes a motor more efficient at extracting power... but only so far. It quickly becomes a case of diminishing returns and special high octane fuels must be used to control detonation and this is prohibitive for street use.

[okayfine]

Just re-read advice from BAZ. Motor has an A87 head on it now, with some obvious porting work done. Better than 219? I thought 219's were the "holy grail"

Slow down there, chief. "A87" doesn't mean much, as there are both open and closed combustion chamber heads with that marking. For the crank, you're still going to have to measure it out if you want to be sure it is an L20B and not a Z22 or the LD20, which would be rare since we never got that. With the head, you will have to pull it to see the chamber shape, there is no other way to tell.

200HP from an L20B is doable, but will cost more than an SR20DET swap, be less reliable, and need race gas. What is your budget for this project?

[two_68_510s]

Whatta thread, great info. Meaty Thanks.

[caZee]

Thanks for the replys guys.

This motor is going in my 710 track car. It's vin number 000026 (a track or race car it's entire life) so sticking true to an L motor is paramont IMHO.

I am running about 12 or 13:1 compression in my 240-Z L28 motor, which does indeed require race gas. 110 octane seems to be fine. Several 100 hours with no problems.

I will pull the A87 head off this weekend and post a picture and also mic a crank journel to get your thoughts on what pieces I am really starting with.

Have already sourced a 6-7 quart baffled oil pan and have a spray bar coming in the mail. Advice on cam specs for a track only engine would be interesting.

Great forum.

Steve

[caZee]

So I measured the crank journels tonight and came up with 49 mm rod and 59 mm main. 6 bolt flywheel with a definate M90 stamped in the casting of the crank.

Does this help at all to verify what this crank is?

Steve

[okayfine]

Crank throw? The measurements you gave are going to be the same for L20B and all Z cranks.

Even then, the L20B and Z20 cranks still have the same main/rod/stroke dimensions.