L20b 2.4 build

[Lorenzo p]

Hey guys, haven’t been on here in a while. I have a 1972, 521 nice and patina. I’m building the L 20 b with the 2.4. I’ve already I’ve already had the rotating assembly balanced, engine board to 89 mm and I’m currently in the process of doing some head work to my u67. My question is what head gasket should I use? The head gasket from a 2.4 but then the front covers don’t lineup and water passages need to be drilled/cut out or the original one and it overhangs into the cylinder? Thank you in advance.

Edited November 18, 2022 by Lorenzo p
More info

[]2eDeYe]

Welcome back. 

 

Not sure on the specifics of that, but I am sure someone will have an answer for you soon. 🙂

 

[datzenmike]

You're using a U67 on a Z24 block? The Z24 is already at 89mm. Surely you didn't bore the 85mm L20B block all the way out to 89mm!!!!!!!

 

I used the Z24 timing cover and the Z24 head gasket rather than the L20B timing cover and a 3/4" aluminum spacer to make up the difference. The L head just barely pinches the Z24 head gasket in one spot so I just added a little JB weld. you can't use the two 10mm bolts on the L head so just lightly smear some RTV around the front of the timing chain area.

 

You still need to lengthen the Z24 timing chain to fit the higher position of the L cam sprocket.

 

 

[Lorenzo p]

Hey mike, might be some miss communication. I’m using the l20 block   ( and yes, bored to 89mm! Finger crosssed) u67 head. Which head gasket do I use? 

[Crashtd420]

I was gonna say the l series nismo head gasket but when I looked it's only 88.5mm

I'd say you'd have to modify one from a z24 to suit....

Another route is this company but I think they are expensive....

https://redlinegaskets.co.za/?gasket=nissan-datsun-l-series

[Lorenzo p]

Thanks for the reply. Yeah I was thinking I might have to cut the front off both gaskets and swap them hoping for a good seal? 

[Lorenzo p]

Just checked out the website. Looks like I may have to go this route. Thanks man

[uberkevin]

When I built mine. I just cut the front off of both like said above. Just make sure you cut at the right spot.. 

 

To bad about the nismo head gasket.. 

It's oval-shaped..

 

I used a z22 block I believe..

Had to drill water passage holes.. I'm guessing by using the l20 you don't have to that.. ??

 

I think the l20b block walls are thiner when bored to 89.mm is the only reason I used a Z block. 

 

Good luck man! 

[datzenmike]

Now that you are at 89mm what are you using for pistons, rods and crankshaft????

 

 

 

Use the Z24 gasket as it's already sized to 89mm. Compare it to the L20B gasket and add holes as needed. The Z series gaskets tend to have fewer holes on the left side. The front around the timing chain is not critical and a trimmed old L gasket is fine. There's no compression to seal just vapors and oil spray. Use RTV on both sides sparingly. 

 

I reworked the combustion chamber as there's no shortage of compression.

[Lorenzo p]

1 hour ago, Crashtd420 said:

I was gonna say the l series nismo head gasket but when I looked it's only 88.5mm

I'd say you'd have to modify one from a z24 to suit....

Another route is this company but I think they are expensive....

https://redlinegaskets.co.za/?gasket=nissan-datsun-l-series

 

11 minutes ago, uberkevin said:

When I built mine. I just cut the front off of both like said above. Just make sure you cut at the right spot.. 

 

To bad about the nismo head gasket.. 

It's oval-shaped..

 

I used a z22 block I believe..

Had to drill water passage holes.. I'm guessing by using the l20 you don't have to that.. ??

 

I think the l20b block walls are thiner when bored to 89.mm is the only reason I used a Z block. 

 

Good luck man! 

There are a couple water passage holes that need cut. Ok so it works with using parts from both gaskets(cool)

[Lorenzo p]

3 minutes ago, datzenmike said:

Now that you are at 89mm what are you using for pistons, rods and crankshaft????

I have the z24 pistons, l20b rods, and z24 crank(cranks is already cut and balanced). Waiting on my main bearings to start putting bottom end together. I’m curious if I have to mill the tops of the z24 pistons. I’ve read in previous post that it may be needed. Thanks mike

[datzenmike]

There's a reason the Z24 is 2 cm taller than the L20B/Z22. With so much stroke the pistons will have a lot of side load on them. Not saying this will not run. But will be interesting. Did you clearance the cylinder bores for the larger crank throws?

 

At TDC, from the center of the crankshaft to the top of the deck on an L20B is 227.45mm. With a crankshaft throw of 96/2=48mm, rod length of 145.9mm and piston pin height of 34mm this adds to 227.90 or 0.45 above the deck. Popular wisdom says up to 1/3mm above is sufficient for allowable rod stretch at high RPMs that it not impact the head surface.  0.45mm - 0.3mm = 0.15mm. There is a 1.2mm crushed head gasket that separates the block from the head. So there's that.

 

Rather than trimming the raised ring around the piston tops you could use the Z24 gasket to mark the 89mm cylinder bore size on the 85mm open chamber U67 head. That's 2mm all the way round with a die grinder, barely any depth at all and now there is ample clearance. The U67 on a Z24 displacement is 9.47 compression so anything removed won't upset anything.

 

I have a similar project U67 on a Z24 block. Piston clearance is not a problem as they stop about 0.5mm below the deck. So I scribed the gasket onto the head and removed any metal out to 89mm that in any way shrouded the valves. Unshrouding the valves is usually done on the L20B so pulling 20% more air in seem like a practical idea. I rounded the combustion chamber wall like the flair on a velocity stack. Lightly ground below the valve seats and gasket matched the two manifolds. Hopefully you are using a header or the L16 4 into 2 cast iron manifold. 

 

[Lorenzo p]

50 minutes ago, datzenmike said:

There's a reason the Z24 is 2 cm taller than the L20B/Z22. With so much stroke the pistons will have a lot of side load on them. Not saying this will not run. But will be interesting. Did you to clearance the cylinder bores for the larger crank throws?

 

At TDC, from the center of the crankshaft to the top of the deck on an L20B is 227.45mm. With a crankshaft throw of 96/2=48mm, rod length of 145.9mm and piston pin height of 34mm this adds to 227.90 or 0.45 above the deck. Popular wisdom says up to 1/3mm above is sufficient for allowable rod stretch at high RPMs that it not impact the head surface.  0.45mm - 0.3mm = 0.15mm. There is a 1.2mm crushed head gasket that separates the block from the head. So there's that.

 

Rather than trimming the raised ring around the piston tops you could use the Z24 gasket to mark the 89mm cylinder bore size on the 85mm open chamber U67 head. That's 2mm all the way round with a die grinder, barely any depth at all and now there is ample clearance. The U67 on a Z24 displacement id 9.47 compression so anything removed won't upset anything.

 

I have a similar project U67 on a Z24 block. Piston clearance is not a problem as the stop about 0.5mm below the deck. So I scribed the gasket onto the head and removed any metal out to 89mm that in any way shrouded the valves. Unshrouding the valves is usually done on the L20B so pulling 20% more air in seem like a practical idea. I rounded the combustion chamber wall like the flair on a velocity stack. Lightly ground below the valve seats and gasket matched the two manifolds. Hopefully you are using a header or the L16 4 into 2 cast iron manifold. 

 

 https://imgur.com/a/rPbfMdO

heres my exhaust. 

[Lorenzo p]

Mike, also yes I had machine shop clearance the the cylinder bores. 

[Stoffregen Motorsports]

89mm is big for an L20B, but it's been done many times. The issue is the cylinder wall thickness. When compared to a Z20, the L20B walls are about .040" thinner (if I recall correctly), but yes, many L20Bs have been bored to 89mm. Some guys will even go to 90mm, but that's crazy...

 

Use the Z24 gasket. Cut off the corner ears that you don't need and stuff them into the spots that you need them. You also may need to clearance one area on the gasket so it clears the 6mm bolt. Smear black or grey RTV on the top of the front cover and the underside of the front of the head. Use enough that it pukes out, then wipe it off. The Right Stuff black RTV is the best brand I have ever used for this type of application. This cut and paste gasket will eventually leak, but if you do it right, it should be good for a long time.

 

The water passages in the back of the block may be different. If so, you could punch a hole in the gasket with a leather punch, a gasket punch or even with a utility knife. I avoid using a drill because it can grab and tear at the gasket.

[Lorenzo p]

14 minutes ago, Stoffregen Motorsports said:

89mm is big for an L20B, but it's been done many times. The issue is the cylinder wall thickness. When compared to a Z20, the L20B walls are about .040" thinner (if I recall correctly), but yes, many L20Bs have been bored to 89mm. Some guys will even go to 90mm, but that's crazy...

 

Use the Z24 gasket. Cut off the corner ears that you don't need and stuff them into the spots that you need them. You also may need to clearance one area on the gasket so it clears the 6mm bolt. Smear black or grey RTV on the top of the front cover and the underside of the front of the head. Use enough that it pukes out, then wipe it off. The Right Stuff black RTV is the best brand I have ever used for this type of application. This cut and paste gasket will eventually leak, but if you do it right, it should be good for a long time.

 

The water passages in the back of the block may be different. If so, you could punch a hole in the gasket with a leather punch, a gasket punch or even with a utility knife. I avoid using a drill because it can grab and tear at the gasket.

Great advice man. I really appreciate it. 

[Stoffregen Motorsports]

Yep. Anytime.

[datzenmike]

 

There are two of this design... this is far and away the better of the two. I used SS studs on the down pipe side. Heat will oxidize the steel ones faster. SS will make removal of the down pipe a much simpler job. If stripped over size and tap them. 

 

Also those air pump tubes... protrude onto the head ports. Unscrew and remove them entirely and just weld the holes up.

[Lorenzo p]

3 hours ago, datzenmike said:

 

There are two of this design... this is far and away the better of the two. I used SS studs on the down pipe side. Heat will oxidize the steel ones faster. SS will make removal of the down pipe a much simpler job. If stripped over size and tap them. 

 

Also those air pump tubes... protrude onto the head ports. Unscrew and remove them entirely and just weld the holes up.

https://imgur.com/a/McjW73x
just welded them up

[Lorenzo p]

Here is the truck. https://imgur.com/a/JeJp3DW

[datzenmike]

 

I hate links.

[Lorenzo p]

How do I post directly to the thread ? I tried a couple time with no luck. Is it because I’m on my phone?

[datzenmike]

I only know home computer.

 

Go to your imgur account, click on the picture you want and there is a drop down on the right. Select Direct Link and click on COPY. Come back to you post and hit CTRL and V at the same time.

 

Sunrise over Lesqueti Island Nov 02 from Mallard Rd.

 

There may be many other ways but I found this first and stick with it.

[Lorenzo p]

Do you think I need to increase the intake valves on the head? I don’t plan on reving out past 6000rpm( due to the z24 crank in it and side load on the pistons) But I do plan on putting a small cam in it( nothing over 460 lift)

Edited December 1, 2022 by Lorenzo p
Forgot info

[Stoffregen Motorsports]

Big valves really wake them up, but big valves won't do you any good unless you increase the size of the valve seats, open up the bowls and do some porting.