New Z Motor for Earp's 260Z

[Ron Earp]

The new 260Z motor is done now after a couple of months down time. Motor has all new bits, new Nissan race cam, 3.1L big more kit, 11.5 compression......just kidding!

The motor is 0.040" over now and has new pistons, all new valves, valve job, some high high buck replacement rings, and good bearings. Got a set of new valve springs too. It got treated to a new oil pump, new water pump, and all new timing gear. Flywheel and pressure plate were re-balanced as an assembly too. Everything seems to be in good order and we're really for the installation later this week.

The compression is about 0.1 lower than max 0.5 IT spec. Seems the head gasket I have now that came from Riely in Lynchburg is thicker than the one that came off the car. The head was surfaced but only like 0.002" or so as it was quite flat apparently and we didn't take off enough to offset the gasket thickness change. Oh well.

I adjusted the valves on Saturday morning and did the best I could to make sure the cam lobes hit the center of the pads. Intake 0.008" and exhaust 0.010". Do you Z guys recommend any different adjustment? And, once I get it fired up and run in a bit how quickly do you go back and check them?

I'm hoping fire up will go well and I'll have a reliable race motor for a couple of years at least. Keeping my fingers crossed!

R

[pballance]

Ron, can't help much on the tech question but I am wondering how well those boat anchors feed the beast

As they say in the south, "It shore is purty" and I know you are glad to have it ready to go back in.

BTW, Nice shop, air-conditioned and beverage cooler close at hand

[JeffYoung]

The flat tops work pretty good. They were set up by ERnie Radatz about 15 years ago, and the car has good power.

[Ron Earp]

Thanks much!

They work ok actually. Mike has to run them as well. The biggest problem is at idle (when adjusted for top end) they are incredibly rich. And, they can foul the plugs as well as make the engine really hard to hot start. I hope that another heat shield might help that hot start problem, but I sort of doubt it.

I have good EGTs now and will adjust them a bit rich to start with and work the rest out via dyno and track.

They are not as bad as folks made them out to be. The motor doesn't lack for mid range and top end power when it is running well. I don't know that it can make 240Z power with the head and all, but I think it can get close.

Two little bits that are interesting in the 260Z - the exhaust valve is a bit larger than the 240Z and the cam is different. The 260Z cam has a bit longer duration with the events shifted later in relation to the 240Z. The intake lift is 0.4mm less than the 240Z, but the exhaust lift is the same.

We (Jeffery Rousell and I) now have four more 260Z motors around and our engine guy will build these up as spares. One IT motor for Jeffery, then two spare short blocks, maybe even long blocks if we have the parts. The bearings etc. are relatively cheap and maybe having the insurance around means I won't have to use it!

Ron

[JeffYoung]

That's interesting on the valve lift. Was that for emissions purposes? How much effect does the lesser amount of lift have? Minimal?

[Ron Earp]

Not sure, I'm betting some emissions crap.

That is about 4% less lift, so it'll have some effect for sure. Cam duration is longer though, but not very much. That would also effect cylinder filling of course.

It is what it is. I have to run it so worrying about what it doesn't do won't help too much

[[email protected]]

Read the section of the manual on the idle circuit, it may help some. Mine is still pig rich at idle, but it doesn't foul plugs.

I am told that there is only one cam avail from Nissan, and as they know how to play the game, it is superseeded sp? to allow the 240, 260, 280's to use it. You might want to check it out.

I am having a heck of a time getting time to work on mine. I'll be spending this weekend in a maximum security prison, Alexander Correctional Institute in Taylorsville NC this weekend as part of a Kairos prison ministries team. Next week I am hosting a training class at work with folks from here and Europe, and then traveling to England in three weeks for a meeting. Still trying to hit VIR in Oct. but since I had more time I now have delrin outer lower control arm bushings in the back and a tubular swaybar, well almost a swaybar. The arms aren't done yet. If I would just leave this beast alone I would be fine!!!

Mike

[Ron Earp]

Hi Mike,

I spoke with Riely at Lynchburg Nissan and the 260Z cam is still available. It costs over $450, but you can still buy them brand new.

He also indicated that Nissan has not and will not supersede that part even if the camshaft were no longer available. It has different specs than the 240/280Z cams so Nissan will not replace it with a 240/280Z cam, the 260Z cam will simply be discontinued.

Now, he also went on to say that back in the day a popular cheat for the 240/280 crowd was to run the 260Z cam. He recalls a few fellows being busted with the 260 cam in their 240/280 cam cars. I don’t have any experience with that, but just passing on some information.

So, the 260Z cam is still available from Nissan therefore I do not think you can move to a 240/280 cam.

Sorry to hear about all the work going on - and not on your car!!! I hope you can make the VIR race. I am planning to and hope to have an enjoyable time just before the enduro.

Ron

[JeffYoung]

So the duration is more important than the lift apparently?

[[email protected]]

Thanks for the clearification. The info I had came from a guy I went to drivers school with years ago, a 240 guy. Oh well! Another reason that these cars are the bastard child of the the Nissan family!

I hate it when work interferes with my hobby, but I knew that going into the new job. It will all work out for the best in the end. Sometimes I have to be patience, one of my areas for improvement!!!!

Hope to see you up there.

Mike

[Ron Earp]

Try and make it, might have a few Zs there for Goblin's Go!

The 260Z cam only has 8 more degrees duration for intake and exhaust, not very much. I imagine if one were to measure all the intake lobes of a cam you might get that much standard deviation in cam lobes. I also bet it is hard to find a cam that has every lobe within a say 5% tolerance for lift and duration. Doesn't sound like it'd be worth it to cheat for that but racers are racers everywhere!

Everything we've got in the piles of 260Z parts are C cams it appears, the correct ones. However, the street motor of the car we went to the crusher has a "C" and "A" mark on it, clear as day. And if that car wasn't a stock motored street car (tag titled last in 1981) I don't know what was - it was all street and all stock to the exhaust manifold bolts, radiator, everthing. And one of the motors from Rex's cast offs has a "C" cam that is drilled hollow like the 240/280 cams.

Riely had not heard of a drilled "C" or a "C" "A" cam.

Jeff came over and worked hard, much thanks, and the motor is in! Should fire up in a day or two then take it out to a parking lot to run it around a bit. I hope she'll run well!

Ron

[kthomas]

Now, he also went on to say that back in the day a popular cheat for the 240/280 crowd was to run the 260Z cam. He recalls a few fellows being busted with the 260 cam in their 240/280 cam cars. I don’t have any experience with that, but just passing on some information.

[/b]

Uh, I have some experience with that. Perhaps I should Ebay the Appeal

The so called "C" cam appeared largely in the 260Z, but as we documented, with sworn affidavits from original owners, it also appeared in some 1973 model 240Z's. As did just about every other letter of the alphabet. You really have to Cam Doctor it to be sure. There is no Nissan documentation (that'd be nada, zero, zip, nyet) that relates the stamp on the back to a particular grind. There are also about 12 different grinds of the so called "A" cam. We think this was due to variations in the machinery and vendors making the cams. The differences are subtle. Regardless of the reality, SCCA, largely due to our infamous case, has decreed that an "A" is a 240 cam and a C is a 260 cam. I guess the grind is free, just put the right stamp on the back.

"So, the 260Z cam is still available from Nissan therefore I do not think you can move to a 240/280 cam."

Even if it was unavailable the "A" does not supercede, so SCCA expects you to find one in a junk yard. Uh, or grind off the A and stamp a C, but you didn't hear that from me.

FWIW, after SCCA rendered our cam, lash pads, small combustion chamber E88 head casting, trailer, beer cooler, and girlfriend's thong "OUT OF COMPLIANCE", we went back to a junkyard "A" cam in an E31 head and went 2 seconds a lap faster at Roebling Road the next race. Then won 10 of 10 the next year. Take that, Jim Creighton. &$%#@.

Point is there's not enough difference in any of them to move you on the grid, so don't fret and sleep well all you "A" cammers.

[Ron Earp]

Uh, I have some experience with that. Perhaps I should Ebay the Appeal

FWIW, after SCCA rendered our cam, lash pads, small combustion chamber E88 head casting, trailer, beer cooler, and girlfriend's thong "OUT OF COMPLIANCE", we went back to a junkyard "A" cam in an E31 head and went 2 seconds a lap faster at Roebling Road the next race. Then won 10 of 10 the next year. Take that, Jim Creighton. &$%#@.

Point is there's not enough difference in any of them to move you on the grid, so don't fret and sleep well all you "A" cammers.
[/b]

Dang, I didn't know you fellows had all that trouble with them. I looked at the specs on the cams and the 8 degrees doesn't seem worth much at all. But it appears there is more to cam and year than simply the wisdom of a "C" cam is 260Z, and "A" cam is 240Z.

Now, the E88 head is what I have to use on the 260z and I thought it was a bit worse than the E31 head, at least by simply looking at them. Was it a preferred race head back in the day? I've got a bunch of them around in case people decide a 260Z is the Z the race! Ha ha on that one, but it is fun having a red headed step child.

I'm sure the "A" cam folks will be quite happy as I've not seen any of us "C" cam folks threatening them for Z car dominance on the track. At least not yet......

Ron

[Parrish57]

Now, the E88 head is what I have to use on the 260z and I thought it was a bit worse than the E31 head, at least by simply looking at them. Was it a preferred race head back in the day? I've got a bunch of them around in case people decide a 260Z is the Z the race! Ha ha on that one, but it is fun having a red headed step child.

Ron
[/b]

Ron... There are two distinctly different E88 heads. According to NISMO the production dates for the "early" E88 are 9/71 thru 6/72. These have a smaller combustion chamber than the "late" E88's. They were and still are the preferred unit for the 240Z. They're just getting harder to find. ( If you have one that you can't use let me know!)

Steve

[Ron Earp]

Steve, thanks for that piece of information. I thought E31 heads were the 240Z head to have. I had no idea that E88 heads were made earlier than 74.

So basically I can run any E88 head then? Not sure as the 260Z was only for 74, looks like I'd be stuck with later E88 heads.

I've got a bunch (four) E88 heads. How can I tell the difference other than measuring the combustion chamber? Do you know what a "good" head chamber cc's out to stock?

Ron

[JeffYoung]

Keith, have read your posts with great interest over the last few years.

It seems to me that in sum, with a Z car, there are a few keys to speed:

1. Use throttle as an on/off switch.

2. Get car to handle, especially with rear grip, so that you can do (1).

3. For power, the key is timing and carb (especially piston dampening) work on a dyno.

On base? Off base?

[Parrish57]

[quote]

I have a book from Nissan Motorsports that lists the chamber volumes as:
E31 42.4cc
Early E88 44.7cc
Late E88 47.8cc
Take these numbers with a grain of salt as they were published as part of a Big Bore Kit. Until I can verify them I would just use them to represent the ratios of the 3 heads. Maybe we could ask Riley?

In any case I think you'd be restricted to the late E88 since it was the only one that came on the 260. Using an earlier head could throw off your max compression from the spec line in the GCR.

[Ron Earp]

Good info Steve, thanks for that.

I (we) don't know what I've got, just that the compression is ~0.1 below the max I gave the engine shop that did the work, which was 0.5 over stock per max allowable IT rules. I'll call them and see if he has the cc measurement, I'm sure he does. I could then ID it to make sure it is a late head.

I agree with you in that the late head would be the only one for me. That is fine, we've got a lot of them if they were stock on 260Zs and we've got five of those motors now. I don't think the head has trouble making the 0.5 over with the stock pistons.

So with the smaller size of the E31 head do Z guys not prefer that? Or do I have something wrong? We had a E31 head that we sold (I think to Ty, can't remember) that came with the 260Z that Jeff Rousell is now building. I guess the previous owner was going to put the E31 on when he got around to it, but that project died and Jeff and I bought it for $600, car, parts, and all.

Ron

[kthomas]

"I have a book from Nissan Motorsports that lists the chamber volumes as:
E31 42.4cc
Early E88 44.7cc
Late E88 47.8cc"

Actually there were 3 E88 heads. The first casting still had the good quench kidney bean like E31 combustion chamber, but with the E88 port layout, which flowed slightly better than an E31. This is the most desireable head for a 240Z in ITS. Call it the early, early E88. The early E88 mentioned above had a boss around the spark plug with what one would call the normal E88, and later N42, shaped combustion chamber. The late E88, which showed up in '73 (with the tall deck, valve relief pistons), had no boss around the sparky plug.

The general rule of thumb for reducing the combustion chamber volume on an E31 or E88 head is about 1cc reduction for every .010 you shave off. However, that's very general. For example, one of our ARRC E31 heads measured 41.1 cc at a thickness of 4.235 inch, which is 4.248-4.235=.013 shaved. You can get an E31 or an early, early E88 down to 37-39cc even when staying within the allowed .025 head shaving rule. That puts you way over 9.5:1 compression ratio, the other limit. Crushed head gasket volume is a huge player, and even the factory gasket varies between 7.2 and 7.8cc so you have to be really, really careful about how much you shave the heads to stay under 9.5. We eventually had our own design solid copper gaskets made so I could control that variable.

"It seems to me that in sum, with a Z car, there are a few keys to speed:

1. Use throttle as an on/off switch.

2. Get car to handle, especially with rear grip, so that you can do (1).

3. For power, the key is timing and carb (especially piston dampening) work on a dyno.

On base? Off base?"

On base. I'd add having enough money to buy and manage your race tires. Lock the timing down at 34 degrees and fuggetaboutit. Properly instrumented tuning (carb) is where its at. Of course, some low tension rings, precison head work, perfectly balanced internals, proper headers, early 71 flywheel, 4 post plugs with Jacobs ignition, blah blah blah, and letting the ozone out of the distributor cap all matters too. i.e. the WHOLE program. But stomping on the gas before the other guy is most of it.

[Parrish57]

The early E88 not only has a slightly larger chamber volume but also larger intake runners. So it's a tradeoff. Less compression but better breathing. At least that's the way I understand it. I've always ran the E31. I wish someone could post pix to show how to definativley identify the early E88.