Hello all, long time lurker, first time posting.

I have a L20A engine that I am currently rebuilding and I have some questions I am hoping someone can help me with since there’s not a lot of information on the earlier engines in the US.

First, my problem is the original E30 cylinder head was missing and all I was able to obtain was the E31.  It’s my understanding that the E30 had smaller valve(s) and a smaller combustion chamber.  I think the E30 was 36-38cc and the E31 is 42.5?

My second issue is, the original pistons were garbage, and I can’t seem to find factory replacements. I have been looking at the KAMEARI light weight street pistons (SP-L20401-79) that are 79mm. I understand that I would need to go to a full floating rod to utilize these. I was looking at the CXracing L24 rods which are 133mm long like the L20a rods.

My questions are, possible valve interference with the engine block due to the small boar and the oversized E31 cylinder head valves.  Next, low compression ratio due to the higher cc head and the new pistons.

Any advice on this situation would be much appreciated.

Links for the rods and pistons below:

Pistons

https://www.kameariengineworks.co.jp/4-catalogue/2024.8.7-English-cataloge-v4/E0011.pdf

Connecting Rods

https://www.cxracing.com/ROD-L6-1330x6?srsltid=AfmBOoq1seHAZKHRIzfi8Ty5q1oPRFdG1V-m7n75OsCHTH5WlRE-H_q4i8Y

I happen to have a complete E30 head that I have never been able to sell, quite a niche market for sure. I’m in Western Canada, send me a PM if you want to discuss getting it to you.

You can back out combustion chamber volume using compression ratio and displacement. The 1972 FSM has the numbers. And if you have the head and block in hand you can take some measurements.

Edited 16 hours ago16 hr by Zed Head
too many words, and spelling error. Goal - error and edit in every post.

I got 7.5 for the CR of an L24 head on an L20 block, assuming the L24 head is the dual SU head. Probably want to get with zKars on that L20 head.

Realized that I used the E88 L24 head for the calculations. 8.6 CR instead of 9.0. I'll redo them later. Probably still under 8 CR.

Edited 11 hours ago11 hr by Zed Head

I appreciate the response, also I would be taking the block 1mm over to 79mm for the pistons above. I used a few different calculators and was getting in the mid to high 7’s and that’s what made me worried as well as potential valve clearance issues with the block using the E31 with the larger valves.

I saw that Tony D had mentioned using L24 pistons in the L20 block but I’m guessing it would have to be sleeved? I think that would be my best way out if the block doesn’t need sleeved.

Is there a specific reason that you're trying to save the L20?

It’s a very low number, numbers matching, right hand drive car.

14 hours ago, zKars said:

a complete E30 head that I have never been able to sell

I'd see if you can work out a deal for the proper head if you're looking to be close to a restoration.

I don't want to hurt zKars' position but he did say "never been able to sell". Seems like he's been waiting for you... Good luck.

I redid the math for what should be the E31 head and got 7.7. Didn't add your millimeter overbore though. Also found that some of the engine calculators out on the internet seem to have the wrong chamber volumes. I used the dimensions and reported CR from the FSM to calculate volume. Just for fun.

Hi, I'm sure the compression on a L20 with a E31 head will be misarable.. you need the e30 head.

As i once put a E30 on a 240z 2393cc engine it made far to much compression it needed a really FAT headgasket..

I've got 2! E30 heads in my pile of parts, one complete rebuild and one still in parts.. but they are expensive i have heard.. Also i'm in the Netherlands, Europe.

I think one day they will find theire way to Japan... 😀

Edited 2 hours ago2 hr by dutchzcarguy