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L20B Long Rod Conversion.

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As the heading described, im building a Long Rod L20b engine.

Ive had the idea for a while, for years ive researched many combinatiomns for the old L banger, and have decided to build this one, and see how it performs over the std bore / std stroke L20b..

Ive built a few L20b's over the last few years, and want to see what the difference is between them all, versus the $$ outlaid..

On this L20b, ive started with a std bore, std bearings L20b. I had the deck milled to clean up the gasket surface ( a must with the age of these blocks..) and bored to suit the Z22 pistons (87mm). There was 2 types of pistons to use.. one with the pin height of ?? and one with the pin height of ??

I sourced a set of Z20 rods, apparently the one to use with this combo.

Here is some pics of the progress..

firstly, i started with the conrod. I had to modify a rod , so i could remove the pin & piston without the press. If you R & R the piston on & of the rod too many times, you can stuff them. It means this rod is a 'floating' rod, and only good for the dummy assembly...

I found an old set of 'reamers', my Pop left me 20 odd years ago.. they were in mint condition, stil in their wax paper, and perfect for my application..





Here is a pic of an L20b rod (my dummy assemble rod) & the Z20 rod . much longer.



here's a pic of a flat top L20b piston & the Z22 piston. Notice how short the skirt is on the Z22. Its alot lighter than the L20b one also. I'll weigh them up the compare.


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Love your work there Mark, Awesome, can't wait to see it smoken up the road,

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I chased this idea too Mark. I did this sort of mod to one of my L28's, a longer rod and a shorter pin height piston with shorter skirts and less weight.

It improved the rod to stroke ratio from 1.63 (stock L28) to 1.73.

I noticed that the way the engine revved to be much 'easier' with good top end response. Its such a subjective thing but since you've built a lot of L20B's you'll notice the difference with this one you're building. It mightn't make more power, but it'll certainly feel pirkier.

Great work.

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Thanks Shawn.. I love building motors .. Probably the best thing about working for old millhouse , we both worked for way back when !!

I started with a freshly bored block ( to suit the pistons). its 87mm. (2mm or +80 th). Also had the deck surface machined, so i had a clean surface for the headgasket. These surfaces need to be done, when you do a decent rebuild on an L series.. Im not a big fan of headgasket failure, over a <$100 machine..


I fitted up the piston to the 'dummy Z20 rod i machined the little end on. Also fitted a single top ring , to keep the piston in the centre of the bore..


A bit of a dish on these pistons. I'll have to cc them to get the final comp ratio. Depends on what head i'll use.. I Won't have to machine too much of a valve relief in these. Mainly in the corners of the crown..


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hi what z22 piston did you use?? pin height of 31.9mm or 35.5mm??

and where did you get them from?

im looking for some 87mm z22s pistons (35.5mm comp height) to use with an z24 crank in an l20b and apparently they cant be bought anymore, only .5mm oversize but i need 87mm.

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Yes plenty of experience for you there with old cranky MillHouse, wish I was there longer to gain all that experience, But not to be, I was there way back in 1995,

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Old millhouse now thats a blast from the past.i remember stopping there to have a look at datto shell back in the nineties.it was probably one of yours mark.

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