Piston shopping - L24

[Arne]

I'm going to need a set of pistons for the L24 I'm rebuilding for my '71. The block will need to be bored to clean up rust pitting (the engine was sitting outdoors when I acquired it), but won't need much so I'm open to any reasonable overbore. Since this car will be a total street machine, I think sticking with cast pistons will be fine.

Anyone have a favorite brand or vendor that they'd care to recommend? Obviously I'd like to spend as little as possible, but I want good quality.

Oh, I noticed the current pistons have valve reliefs in the top. (P30 block, E88 head from a '72 240Z.) I suspect that replacements will need those as well, do they all come with them?

[dspillman]

Hi Arne,

The only engines I've seen reliefs cut in pistons, are the 73 engines...with the "good" 9mm rods. I've only taken apart 3 73 engines. So YMMV When I first started racing, I discovered that new valve springs must be replaced occassionally. Weak valve springs, and over reving/poor down shifting will soon pound the same type of valve reliefs in flat tops:hurt:

......I wouldn't rule out the stock pistons, maybe a chance the block will clean up w/out overbore.

Good luck with the rebuild,

david

[Arne]

Hi Arne,

The only engines I've seen reliefs cut in pistons, are the 73 engines...with the "good" 9mm rods. I've only taken apart 3 73 engines. So YMMV When I first started racing, I discovered that new valve springs must be replaced occassionally. Weak valve springs, and over reving/poor down shifting will soon pound the same type of valve reliefs in flat tops:hurt:

......I wouldn't rule out the stock pistons, maybe a chance the block will clean up w/out overbore.

Well, I was told this engine was from a '72, but maybe it is a '73. It does have an E88 head, and valve reliefs in the pistons.

I thought I might be able to have the bores honed and re-use the pistons, but when I start to remove the rust in one of the cylinders, I can feel some pitting. Now maybe I don't yet have all the rust removed and the "pitting" is really the cylinder wall. But at this point I'm planning on new pistons.

Since I don't need anything real fancy, I'm looking at the set from Black Dragon (the vendor formerly known as VB) for $220 with pins and rings. They only have .030 over, which is more than I'll really need, but...

[Arne]

Update - First, comparing the engine number of my L24 to those on the ZHome.com register, I have decided that my engine is - in fact - from a '73. Not a '72 as I was told. It does have the valve reliefs in all 6 pistons.

As best I can measure (not having a micrometer handy today), the bores appear to be the stock 83 mm, so I don't think it has been bored before. Which is good, since I did more cleaning and am now certain that the cylinder walls are pitted.

On the other hand, take a look at the attached picture. Note the stamped numeral '3' towards the front on the non-valve side of the piston. All six pistons have the 'H' stamp on them, and cyl. 1-5 have the '3'. But cyl. 6 has a '2' instead. Do these look like factory pistons to you guys? Or are they oversize, the first 5 being .030" over and the 6th being .020" over?

So I will definitely be looking for a good buy on cast pistons for an L24.

Last question - assume that I have an E88 head on it, should I be looking for pistons with the valve reliefs, or can I use normal flat-tops?

[dspillman]

Arne,

I'd stick a flat top replacement piston in, with or w/out relief. Don't think it'll make much difference. I've dicussed with several fellow racers about compression ratio changes on the 73 versus 70-72 engines. Those valve reliefs and large chamber size of 73 E88 head, dropped the squezzing ratio quite a bit. Piston (73) may sit up a hair more, but should work. Keep a handle on over reving, missing shifts, fresh springs should keep those valves off the piston tops.........

I'd investigate options on piston overbore sizes reasonably priced, then have block work done to see how deep a bore it takes to clean up.....

david