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Al71

Info Req'd On Fitting Ka24twin Cam Head To L-series Block

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Hi

Can anyone help with info on fitting a Ka24 twin cam head to an L-series block. I've heard it has been done but have never found any info or seen a car with the conversion?

I picked up a Ka24 twin cam head off a Bluebird SSS today and am going to attempt the converion in my spare time. I am a fitter and turner so making bits isn't a problem but it is always good to speak to people who have done it before.

Cheers

Al

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I know of a couple of conversions that were being built. These are all long term projects, I don't know of any that are complete.

Its also one of my long term projects. The main difficulty is that the timing chain arrangements are completely different - different type of chain, different number of teeth, different tensioner setup. My plan was to get the KA24 crank sprocket and modify it to fit the L-series crank - the KA24 one has a smaller inside diameter, so can be opened up to fit an L-series crank (hopefully there is enough "meat" in the sprocket to do this). Then cut a new keyway in the sprocket and make spacers to locate the sprocket in the correct place on the crank to get it to line up with the idler sprocket in the KA24 head. Or you could turn the "nose" of the L-series crank down to match the KA24 sprocket inner diameter, but then you'd need to sort out oil-pump drive and crank pulley (which now won't fit the smaller crank nose). I was looking at this option, and I reckon a KA24 (or was it a CA18 ?) crank pulley would work with some modification. You'd then end up with a multi-rib crank pulley, so you'd need to get multi-rib pulleys for the alternotor and water pump as well. I was looking at this option when I was thinking of using this head on my supercharged motor - the multi-rib belt would then drive the blower. Gave up on this idea when I decided to stick with an L-series head on the blown L18 project.

Chain guides - I reckon you can get away with modifying the KA24 guides. Will probably have to drill and tap the end of the block to get them in the right spot, as they won't line up with the L-series guide holes. The KA24 guides I have aren't "bonded" like an L-series guide, rather the "plastic" lining is able to be removed from the alloy guide itself. I was going to remove the lining, modify the alloy backing, then permanently bond the lining back onto the modified backing. Likewise with tensioners - you'll need to adapt the KA24 ones onto the L-series block.

Another option I was tossing up was making something like the Kameari-brand L-series chain tensioner, which consists of small sprockets rather than guides and tensioners.

Then there's just welding up an oil drain hole at the back of the head and possibly making some sort of external oil return so the head doesn't fill with oil and starve the bottom end. May not be neccessary, but I'd do it personally.

If you manage all this, the rest should be pretty easy. Just need to weld a few bits of alloy onto the top of the L-series timing cover so it'll match the different shape of the front of the KA24 head. The Ka head has a removeable section at the front of the head, you could also make a complete custom piece here to meet up with the L-series timing cover (assuming you can fit the cam sprockets inside it, something I haven't measured up yet). Then modify the water outlet from the head to face the right way, maybe a few other minor bits and pieces like making blanking pieces for the hole where the dizzy used to be on the back of the KA head, probably a few other things I've forgotten. also have to work out what to use for a dizzy (the L-series dizzy may fit, I was going to adapt a CA18 CAS in tis place, or I had thought about getting a KA24 dizzy from the US out of an S13 240SX). You may also have to weld up a few of the semi-circular water passages slightly on the exhaust side of the head - they look like they are pretty close to hanging over the edge of the block top face.

Then there's the matter of pistons, Shouldn't be too difficult, but you'll probably need ones with cutouts for 4 valves. I have a set of Z22 pistons, which surprisingly (for a 2 valve motor) have 4 cutouts and looked like they would be a pretty close fit. Another option I looked at was running an L-16 crank in a big bore L18 block, FJ20 rods and VG30 pistons. Maybe not ideal for a street motor, but might be a good basis for a short stroke, high-revving track only setup. Then again. maybe not ;)

Your best bet (and what I did) is grab a complete timing chain kit from the US. I got a new kit for under $150, including shipping. This had all the chains, sprockets, guides and tensioners. Then you have all the timing setup to work with - I found it easier to visualise how it could work once I had this gear. you could get one here, but I couldn't find any at a reasonable price - the US ones were way cheaper. If you do go this way, make sure you get an earlier setup. The later ones had a single row top timing chain, which doesn't work on the bluebird heads as they have a double row upper timing chain. Can't help with exact years / models the double row ones came on though. I found out because mine only had the single row chain when it arrived <_<

Its not an easy conversion, but I reckon its definitely do-able. If I ever get it done, it'll end up powering my track 1600. Plan is to run 20V toyota quad throttles, with cams from the US (Crower make reasonably priced ones)

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Cheers for that your a champion.

I cant understand why there is not much info around fromthe us though?

I would have thought someone would have at least posted some pics of one of these conversions.

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The only person to have reportedly done the conversion (that I've heard of) is from the US. He is also fairly cagey about exactly how he did it.

Have a look on Ozdat - there's a few threads about the conversion (including one where the above-mentioned guy - deviousKA - chips in).

I guess the easy option over there is to just whack the whole KA24DE in. They seem to be pretty cheap and easy to get hold of, since the US market S13's had KA24's in them.

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haha so true,jamies always flat out but does very good work,has helped out with all my cars

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