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Just how far can you rev an L series?
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Author:  dangero [ Wed Feb 20, 2013 9:39 am ]
Post subject:  Just how far can you rev an L series?

So... to the brains trust out there with more experience than me.


I am interested in the limit of components in an L series. It's a law of diminishing returns of course and I am once you get to 7000rpm things get expensive but just how expensive and what needs to be replaced.

The reason I ask is I saw a video of a BRE 1600 revving to 10,200 RPM and I wanted to know what or how close you can get to this without a spare bazillion dollars. Saying that, can anyone elaborate n the following?


1. Valve train, the stock valve train is a good design and I imagine would be good for 8,000 rpm providing the correct springs were used. I imagine over that you would want to use a low friction roller assembly to replace the stock rockers?

2. Rotating assembly, I have heard of ford drivers putting L series cranks in ford blocks due to their strength, I have also seen just how close an L series crank is to balanced and its pretty good. if it was perfectly balanced how high could you rev it before swapping for a forged unit? Rods also look pretty stout and same question applies...

3. Oil pump and harmonic balancer?

now of course we are talking forged light pistons, cam designed to suit rev range, bigger lash pads, better head studs cap bolts and rod bolts, competition bearings and headwork including bigger valves, lots of port work ect...

Even without the forged crank and rods we are still talking north of $5,000 for an engine that will not out perform a new engine of the same capacity, but I just want to know what the limits of each component are... If you don't know why I am asking. listed to an L series revving to 10k :)

Cheers!

Author:  lampy [ Wed Feb 20, 2013 10:22 am ]
Post subject:  Re: Just how far can you rev an L series?

To get an L series to do 10000rpm will be very expensive.
See my build for an engine that will only do 9500 and thats with a twin cam head that flows a lot more than a l series head will ever
http://www.ozdat.com/forum/viewtopic.php?f=59&t=20290&start=75

The problem is valve weight.
To get an l series to flow enough air to rev to 10000 it needs to have large valves. Eg 46-47mm inlets. It is very hard to control a valve of this size at high rpm.
Titanium valves and berrillium seats are needed. Good valves like these are $1500 per 4
I am fairly sure the BRE l16 runs titanium
There is a local L16 in australia that has all the good bits, including titanium valves and custom crank and it only does 9000-9500.

Standard crank wont last very long at 9000+
It doesnt really matter so much how balanced the crank is, although it is good. Cracks start from the rifle drilled oil holes internally in the crank. It is a place that is nearly impossible to polish
Custom crank is the way to go.

Author:  Baz [ Wed Feb 20, 2013 10:30 pm ]
Post subject:  Re: Just how far can you rev an L series?

In my experience L13 rev the hardest & L2.4 strokers the lowest.
It depends on fuel & usage as to what is needed.

Standard components (with tweaks) will take over 8K
Its for how long is the question.

Author:  datzenmike [ Thu Feb 21, 2013 1:18 pm ]
Post subject:  Re: Just how far can you rev an L series?

Stock? reliably? 7000 all day, though you won't be making any power above 5,500 stock. Above that, (7,000) custom rods, and if going that far... forged pistons. A local fella has been running this on a stock crank in his 510 for 13 years (of summer driving that is) he has a 10.5 compression, blow through turbo L20B making about 250RWHP (185kw???) 21PSI on aviation gas. He said he's never had the crank out that's how good they are. Makes power well above 8,000 and a missed shift buzzed it to over 9,000.

This motor was made to last at over 7K. Inter cooler, oil cooler, high volume/pressure KA oil pump, alcohol injection, exhaust temp gauge, air/fuel gauge, windage tray, high volume oil pan, on and on things too numerous to remember.

Author:  dangero [ Thu Feb 21, 2013 2:54 pm ]
Post subject:  Re: Just how far can you rev an L series?

Interesting!


great reading thanks all, I had not considered the weight of valves. so the law of diminishing returns plays a big part in terms of revs.

all the info I could have asked for is here.

Thanks!

Author:  dat2kman [ Thu Feb 21, 2013 11:40 pm ]
Post subject:  Re: Just how far can you rev an L series?

I gotta FJ24 that starts to drop off power at 9600
The L14's can, with certain prep , run up to 10k plus
Some of the race 240z's with short stroke/long rod run up to 8500

Limitation is valve train, there are alternative lighter components.

Author:  datzenmike [ Fri Feb 22, 2013 8:40 am ]
Post subject:  Re: Just how far can you rev an L series?

dangero wrote:
Interesting!


great reading ...so the law of diminishing returns plays a big part in terms of revs.

Thanks!



Yes, just like women.

Author:  birdirt [ Fri Feb 22, 2013 10:55 am ]
Post subject:  Re: Just how far can you rev an L series?

Sorry to digress slightly, just some examples that have stuck in my mind.

Years ago, a mate told me that one year at the nats, the organisers tested a 180B to see how long it would go for at full throttle, after they drained all the oil from the motor. They put a brick on the accellerator and the thing screamed for about 40 minutes before it seized.

Another time a few decades ago I was with a mate in his mums 120Y, he told me the temp guage was broken as it was clocked on High permanently. That did not stop him from flogging it to death. After a day of this, we ran out of juice and went to re fuel. I checked the oil and it was totally empty! ...and not even a registering on the dipstick. So after we had a chuckle, I put some oil in, the motor purred, and the temp went back to normal, and never seemed to have any problems as a result.

And finally, a mate in a 180B was flatout in second and went to smash it into third, but managed to jam it back into first by mistake. The car was full of people, and due to the weight did not lockup, instead the motor screamed worst than full throttle in neutral, and was stuck in first till we slowed down. It sounded so bad, I thought something would have let go, but the motor was totally fine, no worries at all.

That's why I love the good old datto, they are so faithful.

Author:  datzenmike [ Fri Feb 22, 2013 2:28 pm ]
Post subject:  Re: Just how far can you rev an L series?

Let me show you something.....
Image

Can anyone identify these main bearing shells????

Author:  Boyracer [ Sun Feb 24, 2013 10:52 pm ]
Post subject:  Re: Just how far can you rev an L series?

Old Datsun fanatic I know had some fairly hot L18's and L20's in the day, used to rebuild them fairly regularly and I believe spent some money on them. Reckoned 9k was the most he'd seen on the tacho after a glance on a stage. Though he did mention one stage where he'd had it flat for so long that the motor just cut out... wondered what the hell had gone on for a moment before the motor coughed and burst back into life... reckon's it was spinning so hard it lost control of the valves and needed a second or two to sort itself out.

Author:  d [ Mon Feb 25, 2013 12:35 am ]
Post subject:  Re: Just how far can you rev an L series?

wow those bearings are very different Mike just no idea except some surface rust on one of them meaning it could be tin while the other alloy ?

Author:  datzenmike [ Mon Feb 25, 2013 6:43 am ]
Post subject:  Re: Just how far can you rev an L series?

The bearing on the left is the L20B/Z20/22/24 main bearing. Reasonably sized for an L/Z series motor you would think until you realize that the bearing on the right is from an S13 KA24E motor!!! That makes 50% more power. It will support a KA-ETurbo making 300 hp so the left one is totally over engineered for the L series. The L series is one of the toughest motors ever built and has 5 of these supporting the crank. When I see one with a rod through the side (very rare, maybe twice) I have a hard time to imagine the neglect and abuse needed to do this.

The rust is just because I found this in a blown KA motor laying in the dirt.

Author:  Baz [ Mon Feb 25, 2013 9:27 am ]
Post subject:  Re: Just how far can you rev an L series?

L20B bearings a large, due to the fact that the L20B was originally the LD20, a diesel.

Author:  d [ Mon Feb 25, 2013 11:52 am ]
Post subject:  Re: Just how far can you rev an L series?

definitely over-bearing stuff!

Author:  datzenmike [ Mon Feb 25, 2013 12:16 pm ]
Post subject:  Re: Just how far can you rev an L series?

Baz wrote:
L20B bearings a large, due to the fact that the L20B was originally the LD20, a diesel.



Surely the L series came long before the LD20. L16/18s had the same width bearings but smaller diameter. The L20B was a progression of this design introduced in '75 here. I can't find any mention of the LD20 before '78 in the Vanette and '79 in the 910.

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