E-31 Milling Questions

[ToolBoy]

Hello to all. 18 months into my little 19500 project car and I'm working on an engine. Series 1 car was purchased with a swapped out, non operable and likely useless L-26 engine installed. I bought a 73 L-24 engine for not much money on ebay from a guy in the midwest who raced em years ago, expecting to use it for parts. Seemed to be in good shape at first but pressure tested and found gaping corrosion hole in the head rendering that part useless. I then looked around and found a slightly pricey, complete E-31 head that had never been done, and is really flat. Head, block and crank are now at the machine shop and my guy is looking for the bigger valves, new pistons etc. He said if we can find stainless valves, the seats are ok as they are. I'm asking the Z community  ( you guys ) for any pertinent info and a source for the valves I'm looking for and anything else you want to throw in there at this stage of the game. I think I read somewhere that the bigger valves come from 280Z or ZX? I'm planning to use the block and crank I bought earlier from the 73 engine as they seem to be in good shape.  Thanks in advance and any input is greatly appreciated. . . Best. . . Tool Boy 

[siteunseen]

My e31 had steel seats installed and my guy said they were common size, the Chrysler Hemi uses the same size. Mallory is the brand. It's not expensive to do so I would say do it while you're at that stage.

 

 

[ToolBoy]

Hey siteunseen. . . . Thanks for that. Are those seats for the original E-31 valves or the upsized replacement I'm hearing about?  Thx.

 

[siteunseen]

My guy put the same size seats which happened to be readily available. I had to lap them in myself and that's no nig deal plus actually what you want to do to get a good seal. Talk to your machinest. Make sure he's 50 or 60 at least and knows the L head. My guy has forgotten he claims but did a great job. Said he'd done 100s back in the day.

You should also consider the spray bar on the older heads. I run a newer turbo oil pump on mine and it floods the valve train. That's what you want too.

Does your e31 cam have holes in the lobe? It shouldn't but could've been upgraded to an oiler cam. Those e31 need to be researched as best as you can. They are old and many mods have been done since '70. 

Good luck with it, they're scarce as hens teeth kinda of a holy grail for our Zs.

 

[Zup]

Stainless swirled valves

From the description:

Quote

These valves have undercut stem and are fully swirl polished. These are great for street performance upgrade and light/moderate performance heads. These are the standard N42/N47 size valves (44mm/35mm). Perfect for use in L24 heads,

If you are serious contact Eiji at Datsun Spirit.

 

[heyitsrama]

IIRC its the unleaded fuel that required the use of a steel valve seat. But if you go to a larger valve wont you need to modify the seats anyway? Or is the intention to just cut out the old seats a little more? I think larger valve would also need the block to have a relief cut done to it..... There's a good book you should look at `how to modify your nissan/datsun OHC engine`.

[siteunseen]

Larger valves will require larger seats too. And then you'll need to notch the bores on the 2.4 block to accept the larger 2.8 valves.

 

Edited September 30, 2021 by siteunseen

[ToolBoy]

Hello To All. . . Getting a little further along and with the E-31 head. Stainless Spirit Datsun valves are here. Super nice. Can anyone refer me to any older existing posts that get into suggested modifications to this head? I've seen oil spray bar, cam oil circulation changes and relieving the cylinder wall for the bigger valves. Are there any older posts that go into detail on these mods. Photos are always good too. Thanks!!

[Racer X]

2 hours ago, ToolBoy said:

Hello To All. . . Getting a little further along and with the E-31 head. Stainless Spirit Datsun valves are here. Super nice. Can anyone refer me to any older existing posts that get into suggested modifications to this head? I've seen oil spray bar, cam oil circulation changes and relieving the cylinder wall for the bigger valves. Are there any older posts that go into detail on these mods. Photos are always good too. Thanks!!

I unshroud the valves on all the L series engines I build. When I get home I’ll take a picture and post it here.

I use a hard roll on a die grinder to cut the relief. I take it down to just above the mark where the piston ring stops traveling upwards, and out to the mark on the cylinder block deck where the head gasket opening is.

 

[madkaw]

Put the head gasket against the block and mark to un-shroud . I’d use a 1” drum sander with 80 grit in your cordless drill to open up the chamber . CC-ing the chambers would be easy . Check out the short side radius on all ports - they will need work. I’d take a good wack off the mating surface . 
Notch the cylinder bores to clear larger valves . Get a BIG cam and drive it like you stole it . 

[siteunseen]

Here's some good stuff with good pics too. 

Go back on this link to the main page then click on "engine".

@240260280 is the man! He put this together from info on his computer and his buddies help. It's the 1st page I go to when I need help.

https://www.atlanticz.ca/zclub/techtips/headporting/index.htm

 

 

[ToolBoy]

Wow, Thanks. . have to study these.