L20B head on Z24

[TommyBsolid]

Do the centers of the cylinders between the block and head? Timing chain & cam? Would it bolt on? What sort of modifications to the head gasket would be required? Would I use a Z24 or L20B gasket? Would there br any benefits to suck a conversion? Reason I’m asking is I’m thinking of turboing a Z24 and it would be nice to have intake and exhaust on one side, I have also read that the L series heads have a better port angle allowing more air flow.

Edited July 28, 2020 by TommyBsolid

[wayno]

I made an LZ23 out of a Z22 block, I bored the Z22 block out to except Z24 pistons, I had to use a modified Z24 head gasket.

[Stoffregen Motorsports]

17 hours ago, TommyBsolid said:

Do the centers of the cylinders between the block and head? Timing chain & cam? Would it bolt on? What sort of modifications to the head gasket would be required? Would I use a Z24 or L20B gasket? Would there br any benefits to suck a conversion? Reason I’m asking is I’m thinking of turboing a Z24 and it would be nice to have intake and exhaust on one side, I have also read that the L series heads have a better port angle allowing more air flow.

Yes, it will bolt on. The gasket will need to be modified slightly, which is evident when comparing the two. The front cover needs two bolt holes added to it at the top (done by welding gobs of aluminum and drill/tap.

 

Be careful of high compression ratio. Take some measurements and do the engine math first. There are many different L heads with different combustion chamber shapes and sizes.

 

If you have the Z24 bottom end, it's not a bad way to go, but as Wayno mentioned, I would ditch the Z24 and build a custom 2200 or 2300 instead.

[datzenmike]

 

Here's an open chamber U67 head that I scratched the 98mm head gasket cylinders on then unshrouded around the valves. An untouched head will give 9.47 compression so remove all the material you like. Better flow is more desirable than higher compression.

 

Gasket matched the intake and exhaust ports for maximum flow. The head is going to have to move 20% more air. A 'larger' cam will help and the increased displacement will make up for any low RPM losses. Red line on a Z24 is 6250 RPM. If an L20B makes 93 hp (on a good day) then a 20% displacement increase should increase this to about 111 with nothing else not even the compression added in. The Z24 makes about 130 torque at 2,800 so a better flowing head won't be less. The Z24 is known as a stump puller. We only got it in the heavy assed 720.

 

With R1 motorcycle carbs, 510 cast iron header, baffled oil pan, windage and crank scraper (the last two was just because I could) I'm expecting 120-130. I have an old Isky 0.490" cam I can add if not. 

[Stoffregen Motorsports]

Swapping the L head onto the Z bottom end qualifies as a "custom engine build" and should not be done without attention to detail. As Mike mentioned above, open up the combustion chamber to match the 89mm head gasket. This will aid not only with flow, but will also help with detonation.

 

10:1 on pump gas is perfectly acceptable, but some tuning (distributor curve, ignition timing, cam timing, carb jetting) should be done to maximize performance and to give longevity to the engine in general.

[datzenmike]

I should mention that this engine was in an '84 but when pulled the TC said D21 so a newer Z24i retro-ed into the '84. It ran quiet and smooth, cylinders were clean. I replaced the main and rod bearings (they were also fine) gaskets and seals I had laying around going to waste. The head I just lapped the valves and put in new seals. If it gives me any problems it's easy enough to replace in the vehicle.

 

Two things.

 

1/ The Z24 is 2cm or 3/4" taller and an L20B timing cover won't reach up high enough. I found the Z24 timing cover can be used... it does cover and seal up against the L head bottom at the front, but you can't use the bolts. I just used a skim of RTV on both sides of the HG. It only has to seal in oil spray and fumes. I added a small fillet of JB weld at a 'close spot' just for insurance...

 

 

The 89mm Z24 HG is close to leaking at this hole so again a small fillet of JB just gives a larger seal surface.

 

 

 

2/ The timing chain needs 4 links added to an L20B chain to allow for the 2cm extra height.

 

 

Grind one side of the rivet head off, punch out rivet. Assemble using old rivet and tack with weld.

 

[banzai510(hainz)]

I remember said some used a Mercedes chain

 

but this is good to know

 

 

[datzenmike]

Master link from a Mecedes chain, you'll need two and some extra chain?