I need a bit of help guys,

How do you tell the difference between a L18 and an L20 head, I've looked in the engine manuals and they both have valve sizes that are the same for both the L18 and L20.

I don't know if the Port sizes are different or if there a difference in sizes in the combustion chamber.

Can someone help me out!

after consulting the bibles, how to htrod & race and how to modify your sohc l series nissan engine.

l18 intake exhaust diameter (in./mm)
1.65/42 1.30/33

l20 1.50/38 1.30/33


l18 intake exhaust length (in./mm)
4.53/115.2 4.57/116.0

l20 4.36/110.7 4.36/110.7



the L 20 heads part no. is : 11041-u6702

so how i read it you have a gain if you put an l18 head on an l20 but you will have to change the length of the valves, if i doubt ask baz
anymore questions an i will consult the bible

Thanks Guys,

L18 Head is stamped A87

Just be aware that while it has a smaller and more efficeinet combustion chamber, in standard trim it has smaller ports, so putting an A87 on a L20B may not increase performance, it could decrease due to breathing.

One of the best cheapie engines I have seen is a Standard L20B head (which ports standard are almost as large as u can get A87's) 72 Cam and flat top pistons.