L20 hp

[Bama boy]

I have A 79 620. I would like to build an engine for offroading and towing. I have read that the intake valves for a mid to low range power band need to be on the small side. Anyone have any specifics on the appropriate size? Also I have been collecting parts for a L22. I would like to get in the 150HP range or a little more if cost allows it. Parts that I currently have are U67 and W58 heads. I have read conflicting options as to whether the W58 is a suitable head for building Hp. I would prefer to use this head only because the Doug Thorley header that I have is round however I think there is enough material on the mounting surface of the header to square it up to match the U67 if I had to. I also have a Offenhauser intake for A weber 32/36, Z22 crank, and Z22S pistons. Even though I have the parts for the L22 all of them are new in box and I can sell them on EBAY if I decide to go another rout . Ideas, suggestions, diagrams,blueprints ,and donations gratefully appreciated.

Edited November 29, 2008 by Bama boy

[datzenmike]

I have A 79 620. I would like to build an engine for offroading and towing. I have read that the intake valves for a mid to low range power band need to be on the small side. Anyone have any specifics on the appropriate size? Also I have been collecting parts for a L22. I would like to get in the 150HP range or a little more if cost allows it. Parts that I currently have are U67 and W58 heads. I have read conflicting options as to whether the W58 is a suitable head for building Hp. I would prefer to use this head only because the Doug Thorley header that I have is round however I think there is enough material on the mounting surface of the header to square it up to match the U67 if I had to. I also have a Offenhauser intake for A weber 32/38, Z22 crank, and Z22S pistons. Even though I have the parts for the L22 all of them are new in box and I can sell them on EBAY if I decide to go another rout . Ideas, suggestions, diagrams,blueprints ,and donations gratefully appreciated.

 

Round header on square port is not the best idea. Square header on round port is usually OK though.

 

The W-58 is known as a smog head because it has steel liners in the exhaust ports. There are several 'bumps' on the port to hold it away from the wall so it gets hot, so hot it glows red. This glowing hot liner helps to burn off hydrocarbons in the exhaust. I removed them on an old head I had using a hammer and small cold chisel. The first port took 40 minutes (to learn on) the last was 10 minutes. You have to remove the valves to do this but worth it to use the correct port/header shape.

 

Using the Z22 internals you will still have to over bore the L20B block.

 

As for valve size, smaller ports keep the air speed high at low speed and increases cylinder filling but choke off power at higher RPMs. This would be fine in a car around town. The W-58 and U-67 heads /valves/port size are fine for an L20B and will be flowing faster to supply an LZ22 anyway.

 

With an after market cam all this should give you 110-115 rwhp. Maybe a little higher. Here's a dyno slip for an LZ22 with big cam and EFI. It did have dual side drafts on it an still made 132rwhp the year before. FI netted an 6 hp gain. I would guess engine hp would be... 20-30 hp higher???

 

http://i138.photobucket.com/albums/q251/datzenmike/DynoRun2007ByronsLZ22.jpg[/img]"]

Edited November 29, 2008 by datzenmike

[Rubberman]

datzenmike, which head do you suggest? I also have both heads for my rebuild. I've seen posts about the peanut head, what makes it better? if it is.

[datzenmike]

Compressing a gas raises it's temperature. This is how a diesel engine works. The air heats to over 1,200 degrees and when fuel is added it burns without a spark plug. Gas engines work on a lower compression but the air does heat up and there is risk of it igniting by itself but usually much too soon before Top Dead Center. Too early and the force tries to push the piston back against the upward direction it is going instead of later after TDC when it is traveling on the down stroke. This is called pre-ignition or 'pinging' because of it's distinctive sound and is the equivalent of a sledge hammer pounding on the piston top. Modern hyper-eutectic pistons are very hard and brittle and will not survive much of this pounding.

 

Pre-ignition can be controlled by keeping compression levels down, by using a higher octane gas and by the combustion chamber shape. Pre-ignition is often caused by trapped heat left over in the head forming a 'hot spot'. Perhaps in a part of the chamber that has a sharp edge or poor flow or even an area where carbon deposits build up and trap heat. If the cold intake air does not reach it and cool it, it will get glowing hot and all it takes is a little compression to set it off.

 

If you look at any open chamber head you'll see that it extends over the whole cylinder area forming a circular shape. If you look at the closed chamber head you'll see that it is never circular and can have one or more areas where the head surface is flat across the cylinder opening and the piston at TDC is actually only the gasket width away from it. The L closed chamber head is called a p-nut only because of the shape resembling a peanut or kidney bean.

 

Why is a closed chamber head is preferable? Remember the 'hot spots' and the reason they form because of poor circulation of cooling intake air? Well imagine what happens as the piston approaches TDC. The air trapped in the tiny area between the flat head surface and the fast approaching piston is violently pinched out into the open area with great force. This causes a swirling effect, or turbulence, which further mixes the gasses as they burn thus, there is a more homogenized temperature in the cylinder and less chance or a trapped 'hot spot'. The L p-nut chamber head is smaller, so a higher compression is achieved but also is a closed chamber design so pre-ignition is reduced at the same time.

 

The area where the head is flat across the top of the cylinder and is separated from the piston by just the gasket thickness is known as the quench or 'squish' area.

 

 

 

As for which head to use: once the liners in the W-58 are removed there isn't much difference from the U-67 except the exhaust port shape. The W-58 has coolant holes that match the intake runners for warming the intake air. The U-67 may not have these but they are easily drilled out. Your pick.

Edited November 29, 2008 by datzenmike

[Bama boy]

115 Hp! Thats pretty close to stock isn't it? I want to build an engine that will easily tow about 1,900 lb but still you cant have all work and no play so I would like the finished product to be a little punchy on the take off. I don't know am I wasting my time with the L20b ?

[Cuts metal like mad]

Stock is rated at 100hp at the crank (overrated from the factory), 115 at the wheels is NOT close to stock

[datzenmike]

The amount at the end of the crank (BHP) is always higher than at the rear wheels because of frictional losses. Stock L20Bs have been dyno'd at about 85-90 rear wheel hp. (RWHP) At the crank, that's just over 100 BHP.

 

115 RWHP would be somewhere around 135BHP? This is an estimate because while there is an easy a way to measure hp at the wheels, but to measure the engine it would have to be removed and power a dyno directly... who does that.

 

The chart of Byron's 510 with 138 RWHP is actually a staggering amount when you figure that at the crank he has probably 15-20% more.

[Jason]

To be honest with you Byron's LZ has a stock bottom end which means that he is rev limited to output. The head was setup to run up to 7500rpm or more and produce power :eek: ....

[Bama boy]

They claim in this article that this truck has 150 hp, yet they retain factory stroke and bore. How is that? Let me clarify the kind of engine I am trying to build--not tractor, not nascar--rally car. ;)

 

 

 

btw, if anyone wants to read the rest of this article let me know and I'll post it.

[ppeters914]

Geez, notice the first mod? 12:1 pistons.....:eek:

 

Yeah, okay, fine on fully leaded premium gas that cost approx SIXTY CENTS A GALLON in 1976 (when that article was written). Not so practical today.

[Cuts metal like mad]

12 to 1 compression, bigger valves, port work, bigger cam, stiffer springs, basically a full race motor...

[datzenmike]

First, never believe it without a dyno slip. This could be a rear wheel reading and an arbitrary 20% or more added for 'drive train losses' to make it look good. To almost double an L20Bs hp will cost many thousands of dollars and you will end up with a un-driveable street car or truck that makes almost all it's power above 5,500 RPM and peak at 7-8,000. 12.5 compression is insane for the street.

 

For way less you could swap a VG30 and tranny into your '79. Way over 150 hp and runs on reg gas. Idles at 700 RPM, smooth power, monster torque all the way up. One of the toughest engines Nissan ever built. Needs gas and oil, pound on it all day and it's ready the next. Will drive in traffic as well as a stock L20B but has twice the power.

[ppeters914]

Yeah, even a Datsun n00b like me has read enough to know a KA24 or VG30 is the answer if you want torque.

[Bama boy]

The mere thought of putting A VG30 in the 620 makes me giddy. If I decide to go on with this swap I know that the drive shaft and engine mounts will have to be modified. Will I also have to get A beefier drive shaft ,what about the rear end?

Edited December 1, 2008 by Bama boy
not sure what i sayed was factual .

[Cuts metal like mad]

You may run into exhaust issues with the torsion bars, though no one has has gone far enough to make this theory a fact yet. One way to avoid this problem is to go with coilovers in the front... Another is to run the exhaust around the frame, although this creates new issues altogether, ka24 is the way to go, lots of aftermarket parts out there, and the truck ka is rear sump... Take a look at Icehouse's ka instal article, he loves his.

[datzenmike]

The H-190 should handle a stock VG. If you have a standard in that '79 you'll have 4.11 gears. The tires will be the safety valve, they'll break loose long before the rear will. Only trouble with an open diff is one tire fires. It's rough on the side gears.

[Bama boy]

Whats the size difference between the 510 and 620's engine compartment if any? I found this site http://www.vg30.com/510vg30install.htmland it made me wonder about possibilities.

Edited December 3, 2008 by Bama boy

[Phlebmaster]

Sorry for the thread jack...but this has me thinking about my L20b HP.

 

This waiting till Friday to install my L20b is KILLING ME! :lol: I know, I know...I sound like a virgin asking about what sex feels like...but comon guys I wanna know. ;)

 

Here is what I am puting in to replace my L16:

 

L20B out of a 78 or 79 something.

W58 closed chamber head with ported intakes and my BIG cam you all have heard run in my L16.

Offenhauser dual port intake.

Weber 32/36 tuned to rip (not save gas)

 

I am just curious what the power difference will be. Does anyone here run something similar? Can you tell me what to expect? In other words...will I be replacing rear tires every month..:lol: What is an aproximate HP rating?

 

The suspense is driving me mad...:blink:

[Bleach]

am I wasting my time with the L20b ?

 

YES! :mellow:

[philip1]

I agree with the others the L20b is old tech a KA24 would meet your power requirements with minimal work.

[datsunfish]

Compared to the L16 a L20b is a fucking monster! I can hardly spin my tires with L16,cam and sidedrafts. With a stock L20b I could do power breaker burnouts with ease. Of course a KA is way better but then again so is a chev 350 or a rotary or turbo anything. The L20b is a direct bolt in swap. And Phleb, I guarantee you will be super happy with the swap. I cant wait to throw mine in place of my L16.

[rat tail dragger]

my l20 is kick ass cant keep the tires in the rear from spinnin or tossen that hooker sideways much fun

[banzai510(hainz)]

PLEBMASTER

I sound like a virgin asking about what sex feels like?????

Beat off, then youll know and it doesnt talk back and ASK why you dont hold me!

 

I think youl get a maybe 5-8hp and maybe 9-12 if sidedrafts mikunis/dcoe carbs.

 

let us know

 

use the same motormounts,oil pan ect that was on the L16 and if you have a thein aircleaner as the aircleaner could hit the hood.

also the exhaust must move up 1/2 to 3/4 inch which could hit the floor pan.

 

 

I assume you have the correct clutch set up for the L20 if 200mm then the L16/18 stuff will work.

If 225 mm you got the correct T/O bearing sleeve set up for that

Edited December 3, 2008 by banzai510(hainz)

[Phlebmaster]

Well, I now have my answer....

 

http://forum.ratsun.net/showthread.php?t=3393

 

Check out the video of my L16 with comp cam then listen to the L20b with peanut head and the same comp cam. :D :D :D :D

 

I am sooo happeee. :lol: Sorry for the thread jack Bama Boy ;)

Edited December 12, 2008 by Phlebmaster