New Z Motor for Earp's 260Z

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. :D
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Keith, thanks.

I assume that the video you can buy at Z.com or whatever where you filmed the carb dampening process is the way to go on carb tuning? Is it all about dampening to maintain consistent A/F over the midrange to the top? Do you make your own springs for the carbs? On my carbs, I've got three "tensions" available and run the firmest. I suspect something custom would be better.

You prefer Jacobs to MSD?

Ozone out of the distributor cap? You lost this neophyte with that one...lol...what does that mean?
 
Ozone out of the distributor cap? You lost this neophyte with that one...lol...what does that mean?
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Oops, I just let out the secret to winning the ARRC. Well, that and Chet Wittel.

I'll elaborate on all that when I get home tonight.
 
Ozone out of the distributor cap? You lost this neophyte with that one...lol...what does that mean?
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I think he is only being a "little" tongue in cheek on the Ozone thing. Here are a couple things to remember and hopefully Katman will set me straight.

In the distributor and any voltage discharge environment you will generate Ozone. That is the odor you get after a summer time thunderstorm with lots of lightning. Ozone is an oxidizer and I am assuming that venting a distributor cap to release the ozone generated by the arcs that occur when the mechanical contacts rotate inside of the cap is meant to reduce oxidation of the contact surfaces.

Again assuming that the venting is meant to reduce the oxidation of the contact surfaces because and oxidation causes an increase in electrical resistances. Reduce the resistance (AKA stop the oxidation) of the contact surfaces inside of a cap then a higher spark voltage can be maintained to the spark plug thus increasing the speed by which combustion occurs.

Methinks this is BS because the oxidation of the cap and the resultant increase in voltage loss to the plug is miniscule when looked at in total.

OK Keith, set us straight...................
 
Yup, something like that. Ozone is created by high energy electricity, and said ozone encourages crossfire. That's also why we used a larger diameter ZX distributor cap, and why on street cars after HEI and CD ignitions became the rage you started seeing big caps with vents. I drilled a hole in our caps between the center post and number one post so I could check the distributor phasing with a timing light. At least as much horsepower as a carbon fiber shift knob, fer sure. I also never bolted on a part with mismatched hardware. If the widget took 3 screws then I found 3 of the exact same screw. Had to be some horsepower in that kharma too.

The Jacobs ignition gave us about 2 hp over an MSD. One thing we did discover though was the Jacobs Energy Pak ignition has a "boost" circuit that you can wire to a switch on the gas pedal. It was designed for drag racing. Jacobs said it'd be the cat's meow. Well, it was good for another pony or two, but in road racing the duty cycle is too quick, so it would overheat after a few straights and actually drop a couple horsepower versus not having it. We discovered that on the dyno by accident.

Ah, the old Z-Therapy video. I forgot about that. What you see on that is that when you get above 4000 rpm with the throttle WFO the damper is pretty much full up, which means the needle isn't controlling mixture so much as the pressure drop across the bridge is. In stock form you usually are fat to about 5500, not bad from 5500 to 6000, and then too lean above that. Make it good for 7000 and you're way too fat below 6000. SM needles and those silly shaved-in-half Rebombo, er I mean Rebello needles are waaaay too rich. It's no wonder a Rebello engine never beat us in 10 years. Had to find ways to encourage the slide to take it's time getting up (yes, springs and oil and clearance between the slide and the suction chamber), and make needles that leaned you out enough below 6000 or so (they basically look like a telephone pole, virtually no taper, in our case. YMMV). When we finally terminated the engine program at Sunbelt, at about 205-208 hp (that's east coast hp baby!) we were still a wee lean from 7000-7400. The Z-therapy tining video is great for tuning your street car, but you really need something like a Halmeter-30 in the exhaust for each carb and some serious dyno time for racing. I guess knowing what I know now I could do it on car, but you still need the instrumentation.

Before we were allowed to use forged we bought 73 stock pistons once to get 6 for one motor (yes, I said 73). About mid 1990's Nissan started mixing up the "lot". Used to be when you bought a set of 6 they were at least all from the same "pour" at the foundry, so we'd buy two or three sets, keep 1 and give 2 sets back. Then they started mixing them up. I don't even want to say how many junkyard cams we Cam Doctor'd. That was the kind of anal retentiveness we used to go through.

:wacko:
 
VERY good information.

I have the same issue on my car with the carbs (and similar carbs). I'm pretty sure the pistons are full open very quickly such that the needle has little to do with mixture.

So, based on the above, I need to get to the dyno with different oils and springs, and have at it? I also need an O2 sensor operating off of each carb (and EGT is not enough I suppose) to watch A/F over the rev range?

The "street" belief on my carbs is that a bit rich makes the most power - true of the SU knock offs on the Z as well? Or just something you need to test to see?

Ron, I see a full dyno day for both cars here shortly. Lots of improvements to be made I think.

Thanks a bunch Keith.
 
Yeah, EGT gages are too slow. You need a real lambda or A/F meter. We found leaner is meaner, but test and see. I think we had N58's on Chet's last motor, but I know Sunbelt actually made some needles for a couple of their later motors.

A non trivial amount of your tuning success will depend on the headers.

There are guys out there that swear no oil in the suction chambers, just let the slides slam up there. More air is better. Yea! That wasn't our experience. I believe those guys are running so stinkin' rich that's the only way that will work. Regardless, I never got beat by that theory. My cars alway's idled like a street car and ran nicely at all throttle settings.

best of luck.
 
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. [/b]
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Nah, it wasn't me. You did sell me one of your extra gearboxes, though.

The only E31 head I have is sitting with a 240 block that I'm saving for when I have to build a new car. I've now got a nice 240 tub waiting. Hopefully that won't be too soon.

Now, to get started on my new motor. Have to start with a 'fresh' block this time; the one we put in last month isn't salvagable. Although I looked around near turn 2, I couldn't find all of the pieces of the block to take to the welder.

Who'd you borrow that torque plate from again Ron? I think I need a new engine builder. :(
 
Now, to get started on my new motor. Have to start with a 'fresh' block this time; the one we put in last month isn't salvagable. Although I looked around near turn 2, I couldn't find all of the pieces of the block to take to the welder.[/b]
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Hey Ty, check with Nancy, the sound Nazi, I think she may have some of those missing pieces... :blink:
 
Lots of good info on this thread!

The motor got in last week and we fired it up yesterday. Ran well from the start. Got the timing dialed in, heat cycled it a couple of times, then took it out to an industrial park to put a load on it and seat the rings. It sounds great, runs smoothly, and we don't hear anything bad. No leaks, so far, so I think we're in good shape.

Oil pressure is about 25-30 psi at idle, around 50-60 psi at 3k so that seems to be ok. It is extremely rich, but that is a problem we have with the flat tops and getting them to run well. Have to work on that.

In short, I think the #38 260Z is back!

Ron
 
There are E88 heads and E88 heads, this is a way to know what you are looking at. Well, I guess I don't know how to change the font size. One is 1/4" font, the other is 1/2" font or there abouts.

Mike
 
Well the size of the "E88" stamp means, well, the size of the E88 stamp. I've never seen any correlation between the size of the casting stamp and the combustion chamber. You still have to look at the chamber to see which of the 3 E88's you have, and unfortunately only the big chamber with no spark plug boss is what would be argued as legal for a L26.
 
Hey Steve,

The flat top will be out I think!

Mike and katman, I agree the 74 head is the only one legal for the 260Z. Now I need to identify my head to make sure it is legal. Heck, I didn't even know there were various E88 heads until a couple days ago. In fact, I thought E88 heads were "the mark of the devil" and along with flat tops were hated Z parts. I'd always thought E31 and round tops were what people wished to have. Sounds like the reality of it is a early E88 head with a 260Z cam can make a good Z car.

I am at work and looked at a bone stock complete motor that I have in the warehouse. It has E88 on it, maybe about 1/4" to 3/8" high. It definitely has no bosses around the spark plug holes. I don't remember if my race head has bosses or not, but I will look as soon as I get home. I'm hoping I have no bosses as I don't want an illegal head on the car.

I'll report back. Damn that will make me unhappy if we have an illegal head on the motor.

Ron
 
I’ve read through the thread and I’ve got a question to ask. I understand that tuning using EGTs isn’t really the best method, but you should still be able to gather a general understanding on how happy the engine is running. The only thing I don’t know for sure is what the EGTs should be at each respective point (Idle, WOT at low, mid, then high RPMS, and under deceleration)

Right now we only have a dual EGT gauge with a probe in 1 and 6 (one for each carb.) I do have an innovative WB but have yet to weld a bung in our exhaust. So without dyno time, what would your suggestions be to get a decent baseline using the EGTs at first then later on the wideband stuck in the tailpipe (or a bung after the collector)
 
Well, you'll get a lot of opinions on this one I think. And, the temperature you are shooting for will depend on a few factors.

I also have EGTs in 1 and 6 and I think that is the wrong place. If you look at the manifold path it appears 2 and 5 are the ones that will have fuel/air separation issues due to the sharp bend in the intake wall. I'd imagine those will run a bit leaner than the other two.

So, based on that I'd be trying for around 1200-1300 F on 1 and 6, maybe less, to make sure 2 and 5 are happy. Mind you this is speculation on the 2 and 5 issue and you'd need to test those with EGTs to make sure they are indeed lean. But, I think with the range I'm going for I can keep my motor happy.

I also want to put on a wide band. I have a AEM on my Lightning and like it. But, when put in a collector it can't tell you what individual cylinders are doing. And the more carbs present the more useless the single wide band becomes.

Ron
 
At what RPM would you want the EGT in that range, and would this reading be taken under a load? Also where can we find different springs for the dampener on the su's? BTW your new engine looks good. I'm glad to see so many of you Z-guys running out there. Hopefully we will have one more joining you in the near future.
 
The reading must be taken under load. And remember, I don't get the good round top carbs like you will have on a 240z - I got the boat anchors.

For my car, with flat tops, I'm looking for proper EGTs in the 4.5-7k range. Below that they will be cool I think based on my experience with the flat tops. And even in my range I expect to see some differences but I'll be tuning to not see anything over the values stated.

Ron
 
Ty - I have the torque plate, Email me.

With regard to the pipe that the EGT goes into. - Relatively cool air comes in the front of the car, and as you move to #6 the pipes get hotter. Not a lot, but when you are looking at 20+/- degree differences, it doesn't take much. With O2 sensors you get good data without regard to temp. Something to keep in mind.

Mike
 
Oh, and happy to report - my head has no bosses on it for the spark plugs. I know compression is okay, but I hope that having no bosses means it is not an early, and illegal, head.

Text size for E88 is exactly as the stock 260Z motor/head I have in the warehouse.

Ron
 
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