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Napz and L Motor

Andy T.

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The Z20/22/24 blocks are basically L series bored and stroked with a performance challenged head on then.


Andy you can fit an L head on any Z series engine. The compression can help but go up, and the L heads breath much better. Now the problem is the Z series lean about 60 to the left or driver's side of vertical. The L series lean 120 right of vertical so an L head exhaust and intake (with carb) will be 18 degrees tilted from it's normal. Like driving with the passenger side wheels on top of the curb. This might be an advantage if racing left hand turns only. lol.

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What everyone is saying is that you will need L block mount hardware and L block components including an L block transmission and the oil pan to fit your vehicle, you need an L20b block for parts, if you have a Z24 engine you will also need information on how to use an L head on that block.

Circle track guys running L blocks are running 7000rpms+, not sure if a Z24 will do that, a Z22 block with an L head might do that, I expect it depends on the crank/rods/pistons.

What block do you have in it now, Z20, Z22, Z24?

What is the vehicle your racing?

Where is Oregon are you?

Edited by wayno
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Stroke determines red line. Well piston speed actually. Pistons move faster on a longer stroke engine at the same RPMs. They have to travel father in the same time. You want a piston speed of no more than 4,000 feet per minute on stock rods and pistons. Imagine an L20B crankshaft rolling on the pavement while you are driving along at 89.8 MPH. That's how fast it would be spinning. More than 4,000 FPM and the rods and rod bolts risk stretching from the tremendous g forces decelerating and compression on accelerations. Piston rings can flutter up and down in the ring lands. 


L20B and Z20 86mm stroke 7,000


Z22 92mm stroke 6,650


Z24 96mm stroke 6,350

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On 8/8/2020 at 4:18 PM, Andy T. said:

Hello. I'm curious if you can pull a Napz out and put an L motor in its place...I have a friend who races mini stock and we are looking for options...also would one be better than the other for circle track racing? Thanks very much

Circle track racers tend to rev the piss out of their motors, instead of shifting gears. Totally understandable since shifting wastes time. Dropping in a bigger motor with a longer stroke will change your rev capabilities. If you had a Z20, this is the best revving motor out of the Z family, since it has the shortest stroke (same as L20B). The Z22 and Z24 had much longer stroke.


If you are able (and willing) to change out the diff gears to better match the motor to the track, any of the three motors would be usable. But with the Z22 or Z24 you may have to lug the car out of the corner at a lower RPM to make use of the torque and not run out of gear by the end of the straight.


If budget allows, the best motor combination would be a custom build, which means mixing and matching parts and the use of custom pistons and rods. Once you have this knowledge and skill, it opens all kinds of doors. You are no longer relying on stock junk nor are you paying a motor builder thousands of dollars. When I was building race motors for a living, a lot of budget racers would build their own bottom ends but have us do their cylinder heads and valvetrain, saving them some serious money.

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