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G8KeaPoR

Which head

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On inspection of the a87 head I picked up I noted that the cam towers look like there was some debri in the motor as the bores are really messed up.  Do they even make replacements for these anymore?  If so anyone got a part number?

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You mentioned you have a U67 head, on that Z20s block you would have slightly over 10 to 1 CR, the U67 head already has large valves and larger intake ports, maybe not 1.5" but a lot less porting would have to be done.

Is your A87 head you have now a closed chamber head, with the same sized valves as the U67 head, does it have 1.5" intake ports?

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The A87 is a closed chamber.  I haven't measured the ports yet but they didn't look like 1.5".  At this point aside from checking for warpage and a visual inspection nothing has really been done on it.   

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Closed chamber A-87 head on L20B with Z20 flattops is going to be too high a compression. U67 would be better. None of them have 1.5" intake ports. More like 1.38". I uses the Felpro and gasket match the ports and the intake and exhaust to it.

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219 head has 1.5" intake ports that match the 1.5" ports on a dual SU manifold.

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That's what it was made for.

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On 2/3/2020 at 4:03 PM, datzenmike said:

Closed chamber A-87 head on L20B with Z20 flattops is going to be too high a compression. U67 would be better. None of them have 1.5" intake ports. More like 1.38". I uses the Felpro and gasket match the ports and the intake and exhaust to it.

So I have two motors now.  An recently rebuilt running l20b with u67 and a z20s plus I picked up the a87 head for dirt cheap.  The a87 needs a full overhaul as it has rusty guides, nicked seats etc.  I planned to just port them both and wanted to experiment getting to the 12:1 mark as a maximum on the long rod.  We have the ethanol free gas at the pump that is 93 that I already ran since the car has dcoe 40 non emission type carbs so running the higher cost fuel doesn’t bother me.  A z20 bored to 89mm with long rods and the higher pin pistons a87 head wouldn’t that be right around 12:1?  I mean Datsun are new to me as I have spent all my mechanical career building Porsche stree/track cars as well as Mercedes, bmws, and even some Aston Martins where difference in builds and what they can streetable produce is astronomical so if I sound like an idiot on these engines and want to go down the path to destruction just bear with me. Trust me I am taking all the info in here to heart and paying full attention and appreciate it.  That all said the first thing to do is port the a87 as it needs the most work and will provide me the most experience when dealing with these motors in my opinion so I am starting there and if all else fails I’ll just revert to the l20b. 

 

Edited by G8KeaPoR

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The guides are Manganese Bronze, they won't rust.

 

There are no 89mm pistons that would work with that combination of crank and rod. Not to mention the 3mm over bore. Do-able barely. The closest is the ones from a VG30 but they are 87mm.... or 88mm if you buy oversize. An L20B or Z20 block bored to 88mm with Z20E long rods and VG30 pistons would make a 2,100 cc engine with 10.56 compression with an open chamber head and 11.35 with a closed chamber.

 

IF you had a magical 89mm piston that had a pin height similar to the VG30 pistons and was a flattop, this would make a 2,138cc engine with 11.16compression with an open chamber head and 12.04 with a closed one.

 

 

 

I wouldn't worry about chasing maximum compression on a street engine. It's a fool's errand. Get a Z24 and put a U67 head that has larger valves, un-shrouded combustion chamber, well ported, multiple side drafts and a big cam. Almost 9.45 and will live forever making 150+ hp and monster torque.  NO ONE will be able to tell it isn't an L20B by looking at it.

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The cylinder one intake valve rusted and coated the guide with rust.  I assume the valve was in an open position while it sat cause the inside of the guide is damaged. Either way though I would just replace them.  I have to rebuild the rest of the head.  
 

I don’t see why 89mm is barely doable on the z20 block.  Looks to be plenty of meat there.  Besides it could always be sleeved.  
 

EDIT. All that said 88m might be the way to go depending on availability of the vg30 oversized pistons are concerned.  Worst case I can have my partner turn some out on the lathe and then I could just mill the pockets on the pistons but that seems like a long way to go for something that I’m not positive I will keep long term.

 

i do have to say though that I am going to leave my l20b in tact with the u67 on it.  That motor is a fresh motor and best kept as a backup motor that I could just drop in minus swapping the Webber’s back over.  That way if I do go for the fool’s errand and blow it up I still have a working motor I can use.

Edited by G8KeaPoR

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 It's do-able but the walls will be thinner than if you started with a Z22 block. It's just safer/stronger is all. Nissan block castings are straight so little risk of this just thinner walls.

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On 1/31/2020 at 9:59 AM, banzai510(hainz) said:

the Felpro brand about 13$ will be the 1.5 inch all round version.  same as the SSS gasket but not graphite.

I actually netted a factory gasket with round 1.5 ports at the dealer here. They practically gave it to me for 7 bucks.  It was collecting dust in the parts room.  Already 3d scanned it to mill a metal template in the event I ever need to do this on another head.

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So a question here.  When using the z20s block and l20b head what timing cover do I use?  I would think I would use the l series cover cause of the head differences but I want to be positive.

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You use the L front cover, you use just about everything from an L block to make an LZ20.

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The only real differences between the L20B and a Z20 are the heads, the oil and and the front cover. I put an L head on a Z24 using the Z24 timing cover and it does cover well enough to work but the small 10mm bolts don't line up so I left them off. 

 

RN9P30h.jpg

 

The only place the L gasket was even close was right here below the fuel pump. I added a small amount of JB weld and filed it down. The gasket only seals in fumes and oil spray so not that critical. I used a smear of RTV on the front.

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I have both so Ill just use the l-cover.  Wanted to check before I parted ways with the z cover to someone.

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I used it because there is no L equivalent for a 247.45 block height. This leaves a 2cm gap between the L front cover and the underside of the L head when put on a Z24 block. I'm really surprised someone hasn't tried this.

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