N42 head with flat top pistons?

[superfunk]

Will it work?

I've read around a bunch of articles, none of them really answering my question.

Thanks,

Adam

[240ZX]

It will raise your compression to roughly 10.5 to 1. Some guys have said they get some detination with a stock cam....a higher lift/longer duration cam improves upon the situation. Plus, a thicker head gasket may help. I've contemplated flat top pistons in my N42 motor, upon rebuilding it, with the addition of a larger cam. I'm running SU's, 6-2-1 headers, and electronic ignition currently. However, I may just forgo the rebuild, spend the dough, and purchase a Rebello engine.....time will tell!!!

Tom

[superfunk]

Thanks,

Is the compression ration for an L28. I forgot to mention that this is an L24. Is there a difference in stroke of these two? Im pretty much getting it back on the street, I wont have time for a proper rebuild for a little while. At that time i'll definately find an L28 block to build.

[beandip]

The differences between the L-24 and the L-26 & L-28 , is the length of stroke . the bore is larger on the L-28 and this engine has dished pistons . F-54s all have flat top pistons unless it is a turbo engine. Then they are dished . Gary

[Ed]

I have an L28/N42 combo sitting in my garage, dished pistons. If your interesed in it send me a PM.

[Ksteve]

Adam,

In order to put an N42 head on the L24 block you need to cut notches into the rim of the cylinder bore on the block to give enough clearance to the larger valves.

I did this on my 73 because I had a block with good compression and a good N42 head I found cheap. Using a compression calculator mine came out to a little over 9:1 factoring in some valve releif work and the notches in the block and using a 1mm Felpro gasket.

If you search this forum under "block notch" or "eyebrow" there is at least one thread on it, and there are some pictures in the member galeries somewhere (I couldn't find them just now when I looked).

This was just a means of getting the car on the road on a limited budget. In the future I do plan to put in an F54 block with flat top pistons. I think this would be a good high compression combo with the N42.

Hope this helps.

Steve

[c david]

i am building a l28(flat top f54) with an n42 head ported to an n36 ect...

below is a link to some very good info for most things z.

http://www.geocities.com/zgarage2001/heads.html

[=Enigma=]

It will raise your compression to roughly 10.5 to 1.

I'm not so sure about that.

According to the www.ozdat.com calculator:

http://www.ozdat.com/ozdatonline/enginedesign/

L24 w/N42, flat top pistons and 1.25mm gasket = 8.824:1.

L28 w/N42, dished pistons and 1.25 mm gasket = 8.257:1

L28 w/N42, flat top pistons with 1.25mm gasket = 9.768:1

And according to Lengine.exe with a standard OEM gasket:

L24 w/N42, flat top pistons and OEM gasket = 8.78:1

L28 w/N42, dished pistons and OEM gasket = 8.29:1

L28 w/N42, flat top pistons and OEM gasket = 9.82:1

So there are some slight differences which may be the gasket measurement.

[superfunk]

Thanks for the tip KSteve. Sure saved me some headaches there. Does anyone have pictures of their block after it's been notched?

[Ksteve]

Check out MadKaw's gallery, he has pictures of the notches on his L24 (nice looking engine Steve).

My comp. ratio came out a little higher because the head had been shaved a couple times and I have a positive deck height, close to 1mm.

Steve

[superfunk]

Thanks,

I have been talking to a couple people locally who are telling me that with a stock cam interference is not an issue. I am looking at picking up a stock N42. They say that only when you change the lift that you have to notch the block. Anyone know about this?

[ktm]

Not true. You need to notch the L24 block if you put on an N42 head. They may be talking about swapping on N42 head onto an L28 block. The valves are a larger in the N42 head than they are in your, presumably, E88 head. It's the larger valves coupled with the smaller bore in your L24 block that precipitate the need to notch the block.