What do I need to watch out for if I do this combination, I heard something about valve clearance on the cylinder walls. Thanks

 

 

Sent from my iPhone using Classic Zcar Club mobile

You'll have barely notch out the tops of the bores on the smaller block. N42 head has bigger valves for the 86mm bores it was paired with and they hit the 83mm e-31 bores.

Google " notching 240z block classiczcars.com". Click on images and you see mine and member Madkaw's too. We both did ours about a year ago. There's tricks that make it easy to. I'll try and gather up some threads you should read, tomorrow. It's beer:30 here.

Edited September 16, 20177 yr by siteunseen

Will I have compression issues?


Sent from my iPhone using Classic Zcar Club mobile

ozdat.com engine calculator I believe. You plug in you info and it calculates compression ratio.

Here's what can happen if you don't remove enough, scares me now because mine look very close to his.

"looks like #1 didn't get clearances correctly on the notching so it cleared itself. Tough motors these are!"

  

Click on my username below to go straight to the post, "siteunseen replied to a topic"

      That's the way I did mine, measured about 900 times made the marks where the valves SHOULD tap and started grinding away.

Here's a good picture of a factory notch job from Nissan I think, for an Australian Cedric???

Here's another picture I found of mine.  I sat a disassembled big valve N47 with the valves loosely in the head on top of my 2.4 block.  Chucked the valve stems to my drill and let them spin.  Here you can see the scratches it put on my 2.4 block.  That's what I used for starting point.  I went way out and overboard doing this because it was all new to me and I only have one good 2.4 block.  Another thing I just remembered was to lay a 280 head gasket over the 240 block and scribe around the cylinders.  It's just 3mm difference but it helped me know how far out the notches needed to be.  And if you'll notice the darker ring around the tops of the cylinders on my block below that was another way of knowing how far to notch them.  So...notch the block before you have it vatted and honed. 

I'm done know, this is my experience with notching a 2.4 block.  Other people will have other opinions.  Put them all together and come up with a plan.  Good luck.

Edited September 17, 20177 yr by siteunseen

I opened my engine that had that combo 2.4 block with N42 head, but there were no notches and no scratches, the bore isn't 83 mm though it is ~83.9 mm +/- 0.05 mm, at least that's what I got, is that 0.9 mm oversize good enough for clearance, because like I said there are no indications on the valves touching. Nick

 

Edit: Upon closer inspection only cylinder #6 has a little scratch where the exhaust valve goes, but that is the only one and it is nothing compared to the one you showed earlier. it is about 4 mm wide.

 

Edited September 17, 20177 yr by footballnick17

If you've ran that combo and it didn't make any ticking noise then whatever overbore you have is adequate I guess? Mine is 83mm and the vales were hitting. Once I had the block notched I put the bigger vales N47 back on there and the valves would fall through the cylinder without any interference.  I had to use clothes pins to hold them up but as I released those the valves dropped right out the bottom.

Alright, thanks, will make a slight notch out just in case overbore is not sufficient. I appreciate it thanks!!