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PostPosted: Wed Apr 06, 2016 8:00 am 
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Location: CT
Flat-top SUs, Karl?

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PostPosted: Wed Apr 06, 2016 9:15 am 
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Location: Somers CT
I had to look at a picture to be sure but yes they were. We thought for a while that the fuel mixture was overheated or at a critical temp where it wouldn't burn correctly since sometimes it would surge and sputter to a stop. There were insulating covers on the fuel lines as well.
After I hit the Steel guardrail head on that night it never acted up again . . . . . :P :P :P :P

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W.Karl Walton
Somers CT



75' - 280Z - HLS30203249 - #304 Gold Metallic (stockish)
96' - 300zx TT - JN1CZ24d3TX960293 - Black on Black (enhanced)


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PostPosted: Wed Apr 06, 2016 10:27 am 
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Vapor lock, fuel starvation and after-boil (percolation) were all issues the flattops suffered (just as Bob stated). They actually could have been a good unit and many Z racers prefer them today for track use only, because they have a single feature the round tops don't have; an acceleration flap. If you can overcome the heat-related issues, the flattops provide smoother, harder, purer acceleration without any stumble or lag.

I've known guys who used clothespins along the fuel line, or wrapped the line in aluminum foil, and one guy in Hawaii who actually built a coffee can full of ice to run his coiled fuel line thru to cool it. It looked like a still! :lol:

If Bob decides to put a set of round tops on his 260, he'll enjoy reliable street use of his car. The flattops are not unique to the 260; the last 240s wore them, too. The 260 simply 'fixed' the issues associated with the flattops by swapping to fuel injection. With an upgraded induction system (Webers/Mikunis, Individual throttle bodies/Roundtop SUs) and appropriate cam, compression and valves, the 260 remains a better engine than either the 240 or the 280.

Bob hasn't said whether he has started his car or not during its 30 yr hibernation. If not, there's a good chance the engine has seized and will require a tear-down to get it running again. When that happens its an easy thing to change the rings and bearings. His valve springs will have to be tested to make sure they haven't taken a set. As long as he's got it opened up, he might as well just have the engine rebuilt (Vinny). If he tries to start it and it's completely dry (no oil on bearing surfaces) he risks the chance of breaking a ring or spinning a dry bearing and destroying the crank or cam (or both). Pretty sure the E88 260 head had an internal oiling system rather than an external oil bar, but I'd have to look that up before I claimed it. Anyway, the L-series engines are cheap and easy to rebuild and Vinny can do them in his sleep (if he ever actually slept) and Bob wouldn't have to sell his kids to pay for his rebuild. While he's got the engine out anyway, he could have it painted all pretty, have the throwout bearing changed and take the opportunity to rebuild his entire brake system (cheap insurance). It will be interesting to follow his progress and watch the grin on his face when he first drives his old sweetheart again.

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PostPosted: Wed Apr 06, 2016 9:10 pm 
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Frank T wrote:
Bob hasn't said whether he has started his car or not during its 30 yr hibernation. If not, there's a good chance the engine has seized and will require a tear-down to get it running again.


Car hasn't run since 1987. :shock:


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PostPosted: Thu Apr 07, 2016 9:22 am 
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I apologiZe for hijacking this thread from a "tire" discussion to an "engine" discussion. But Bob must be careful when turning his engine over for the first time after 30yrs. He should pull the spark plugs and squirt a can of penetrating oil into the cylinders, replace the plugs and let the car sit a few days. He also should pull the cam cover and drool oil all over the cam. Whatever oil is in the pan is already dead after 30yrs and needs to be changed anyway, so mixing some rust-eater oil into it won't make any difference.
After it has sat a few days with the oil working on the cylinders and cam, he should affix a breaker bar and 27mm socket to the front crankshaft nut and SLOWLY work it back and forth to see if he can break the rings free inside. If he can get the engine to turn over by hand, he might not do a lot of damage by spinning it with the starter. The major danger is having a completely dry bearing (they can drain dry in less than one year) adhere to the spinning crankshaft, causing one bearing-half to over-lap the other bearing-half and cover the oil holes in the crank or journal. That will starve a lot of the lower end for oil and it won't take but a moment of running to completely ruin the crankshaft.
Much more gooder to just assume the engine is frozen and pull it out for a quick rebuild. It's cheap and doesn't take long. If he's a 'wrench' and has some spare time, he can probably do it himself by renting an engine hoist and engine stand for a week. Bryan Little's website gives a lot of great info for the DIY rebuilder;

http://www.datsunzgarage.com/

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PostPosted: Mon Apr 11, 2016 5:45 pm 
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Frank,

Sorry about my late acknowledgement of your April 5th post but I just got back from a very busy trip and had no time to respond. Bottom line is your write up was absolutely fascinating! Interesting bit of trivia about Nissan having an oversupply of 7K tachs prompting them to use them in the 260Z rather than an appropriate higher redline tach.....the bottom line on Nissan's financial statements prevailed. Your treatise on a perfectly square engine was very helpful for explaining why the redline for the 260Z was higher than the 240Z. Amazing how AirJockey routinely reved his Z at 8K+!! BTW is a perfectly square engine for DOHC and OHV valve engines optimum for a high reline also or is that true only for OHC engines. Also curious if it is applicable for all configurations (i.e. inline, V and flat)?

Although I haven't decided yet whether I'll keep the car totally stock or mildly warm it up I definitely will consult with Vinny. In fact my plan is have Vinny go through my car once I have new tires on it.

Frank, once again thanks for sharing your views.


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PostPosted: Mon Apr 11, 2016 5:54 pm 
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Frank,

Just read your posts from 4/9.....good stuff about the carbs. BTW I will not be doing any "hero" stuff by trying to start up the engine. The details you provided on what could happen convinced me of that. Once the tires are on the car I'll contact Vinny and let the professional do the right stuff. I'm genuinely excited about the process of making my Z live again and then enjoying it!

-Bob


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PostPosted: Mon Apr 11, 2016 7:55 pm 
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Location: CT
Vinny has a trailer and can transport your Z to his speedshop if you need.

The limiting RPM factors for any engine configuration are reciprocating mass and imbalance. The closer to square any engine gets, the less imbalance there is btwn the crank/pistons. The valve train is the next problem. Pushrod engines (OHV) have the most reciprocating mass and thus the highest resistance and therefore blow themselves up at the lowest RPM (around 5,000rpm). Engines with multiple overhead cams (Dual OHC or Quad OHC per cylinder bank) offer much lower resistance and can rev much higher than can OHV engines. The F-1 Grand Prix cars of the 1960s had dual and quad-OHC engines capable of revving well beyond 15,000 rpm, and the Honda F-1 car ran even faster than that. SOHC engines, with one overhead cam per cylinder bank (our Zs) are a very happy compromise and can reliably sustain high revs without coming apart. Again, the closer they get to being perfectly square, the higher they will rev and the safer they will run, so your 260 engine has a rev advantage over the 240 or 280 engines.

Of course the highest revving practical engines would be a perfectly square, valveless design, in which there are only two or three moving parts; the piston, the connecting rod and the crankshaft. Several extreme-performance air-cooled two-stroke motorcycle engines exist today using that principle. Bultaco, Montessa and OSSA each used perfectly-square small displacement engines during the 1960s to beat bikes of much larger capacity....and we all remember the little 15,000-22,000 rpm Cox Thimble Drome 0.49" model airplane engines of our youth, many of which were either precisely square in bore and stroke or very slightly over-square (like your 260) and had only those three moving parts.

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PostPosted: Mon Apr 11, 2016 8:51 pm 
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Location: Stamford, CT
I would be willing to bet that the Falken RT615K's are top 2 if not the best 14" tire (the other tire im thinking of is the R888 but those only come in lower profile sizes). Only comes in 195/60 in 14" so your speedo should be fine (1mph difference at 60mph, .5mph difference at 30). Theyre quiet, inexpensive, and sticky. I dont think ive ever heard them squeel once. The limit is so high your mind will most likely be the limiting factor in corner entry speed. Probably not the best in standing water but they are pretty great in the rain. I could gush all day about them and Ive only got two on the car right now :lol: Ill never buy all seasons again

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PostPosted: Mon Apr 11, 2016 10:48 pm 
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Frank,

Very cool that Vinny has a trailer and could transport my 260 to his shop. I'd be very concerned that my car could be damaged if I were to use an unknown transporter. That is excellent info! I will contact Vinny once I have new tires on the car.

The background and specific examples of perfectly square (or close) engines you mentioned drive home the point that square designs are preferred. Funny until you educated me on that I always viewed the 260 to be the red headed stepchild of the 240. Now I'm seeing that it is actually a better mix of bore and stroke. I'm thinking that due to the emission tuned carbs that masked the true value of the 260. Now I'm sure Vinny can recommend a better solution. Also the motorcycle examples you mentioned really show the rev attributes of a balanced bore/stroke architecture. Very cool.

Incidentally I have not tried to start my Z. Given what you shared I will leave "getting the car running" to Vinny. I have no plan to try and be a hero and really mess it up....grin.

Relative to wanting a higher reving engine that is certainly cool but is it the holy grail for a street car? A race engine with the higher horsepower in a narrow upper RPM range makes a lot of sense but for a street car isn't torque at lower RPMs the way to go? I'd love to hear your thoughts.

Frank, in all our posts I've never asked about your Z. Could you fill me in.

-Bob


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PostPosted: Mon Apr 11, 2016 11:01 pm 
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Porkbun,

That looks like an excellent recommendation. Thanks.

-Bob


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PostPosted: Tue Apr 12, 2016 8:19 am 
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I feel the 260 deserved a much better fate and a much longer life. The fact that it was in production when the "Park Bench" bumpers came out, caused it to be looked at with a degree of disdain by the 'light bumper' crowd. Also, Datsun introduced the 2+2 body to the S30 line with the 260, extending the wheelbase by a foot. The combination of safety bumpers and a back seat made perfect marketing sense if you think about it, but they were only popular with a small percentage of customers who loved their Z but found themselves with a new family and had to make a practical choice. Add the flattop carbs, or an automatic transmission and air-conditioning to the 2+2 so Mom could drive the car, and the 'performance' image of the 260 just didn't shine thru.

HOWEVER: Our CTZCC member and Executive Advisor, the great Bob Sharp was racing the daylights out of 260 2+2s around the track and beating the pants off the other C Production people because of the car's better overall balance, slightly more rear-biased weight, and higher-revving engine. They built the 260 engine up to its max potential with cams and Webers and altho the likes of Sharp, Fitzy, Newman, Elliot Forbes-Robinson and Tom Cruise beat on the cars to win, none of them succeeded in breaking a single engine during the one Zeason they raced the 260. Other parts failed, (and a blowout destroyed one car and ended Bob's personal driving career), but nobody broke a 260 engine, and the 260 put Bob Sharp Racing on the podium for the 1975 IMSA/GTU championship. Bob Himself actually drove a 260 2+2 around as his personal car all that year. As a Datsun dealer, he had his choice of whatever Datsun he wanted to drive. That has to tell you something.

Here's some comparison info about the 260, relative to the 240 or 280:

https://en.wikipedia.org/wiki/Nissan_S30

Concerning street application of a high-revving engine, you're right ~ a completely flexible engine is far more valuable in traffic than a high-revver is, 99% of the time. And low-speed low end torque can be a blessing or a curse; I drove OHV Healeys for years and they had massive low-end torque and almost no top end revs. The result was my rear tires spinning in the wet during common street driving; so a lot of low torque is not always the answer, either. Try driving a Cobra in the wet.

But that doesn't apply to your Z. The 260 was happy at moderate revs, idling at 600rpm and producing higher hp and torque than the 240 did, well below 5600rpm in stock form. It wasn't as if you needed to rev the engine up to redline to get enough power to get you down the block. The 260 served well as both a race car and a family driver. The added 345lb body weight allowed the lighter 240s to beat the heavier, brand-new 260s off the showroom floor, which was embarrassing to new owners. That dictated a larger engine with better fuel injection system; hence, the 280 was released and the 260 lasted only a single year. Australia never even got the 260, while Europe held onto theirs for several years while the 280 proved itself here (i think I have that right)?

We 800+ Clubbies are a mix of many members, young and old, radical, liberal and conservative, grey hair and long hair. We all love our Zs and get along together so well because we expect different things from our cars; some are show cars, some are investments, some are performance rockets, others are daily drivers. The point is, regardless who we are or why we drive a Z, *SOMETIMES* we get froggy or overwhelmed by the great performance of these cars (or just by the pure sweet sound of the L-6 engine at hi-revs) and find ourselves at/near redline. It may or may not be of value to you to know that your engine can handle that a lot better than the rest of us can.

Here's a motivational film for you. "We don't know this guy" :roll: but we love to hear the L-series engines up at redline:

https://www.youtube.com/watch?v=VSYh69e ... =zigzag240

https://www.youtube.com/watch?v=Rjpmkfd ... =zigzag240

Frank

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PostPosted: Thu Apr 14, 2016 10:47 am 
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Just thought I'd chime in. Toyo R888 are not meant to be used as a street tire. Falken 615K's are an older 200TW compound, but pretty good. Not sure if you need something that aggressive, but if you do, the Direzza II Star Specs are available in 185/60/14 (just a bit narrower than the 195 falkens).

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1986 Z31 NA 2+0


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PostPosted: Mon Apr 18, 2016 12:19 am 
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Hi Frank,

I'm back again after another long trip. Unfortunately it is hard to respond when I'm traveling cause I'm literally flat out time-wise.

In reading your first paragraph it definitely seems that a Brand Manager at Nissan was on top of his game. By adding a 2+2, automatic trans and factory air Nissan offered a viable option for the guy with a standard Z who needed to take care of a new family. Without that option Nissan would have lost him from the franchise. In addition it offered an option to new customers who would have shopped elsewhere. Net, net it helped not to lose existing customers and added new ones. For purist they could continue to love the standard Z. Having said that the standard Z "didn't shine thru" cause of the image of the new optional 2+2 and I would add those emission laden carbs didn't help. Given your commentary about the attributes of the basic 260 engine it is indeed a shame. I guess I lucked out.

Your point is well taken that in-spite of all the above Bob Sharp and company campaigned the 2+2 very successfully.....ironic isn't it. I'm glad you also pointed that not even one of those 260 race engine grenaded. I'm really starting to like the 260 engine.....grin.

Relative to your the horsepower, torque, and RPM combinations you are right.......too much of any of those on any end of the spectrum is not what is wanted in a street car. Funny you mention a low end, high torque Cobra being a "challenge" in the wet cause even in the dry it is a "challenge".

Yup it seems that the 260 was a evolutionary car that upped the Z game by providing shall we say a better balanced car. As you indicated the 280 took care of the carb issue with FI but at the end of the day I prefer the visceral aspects of carbs even if they are more finicky. I suspect with whatever Vinny comes up with for a recommended induction solution for my car that will be history.

Your last paragraph real speaks to the broad appeal of the Z's both in configurations and who it appeals to. Everyone just enjoys their Z's so much that they don't have time not to get along. A good thing. A common bond.

Thanks for the Wikipedia link and of course the youtube links. What wonderful sound!!

-Bob


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PostPosted: Mon Apr 18, 2016 12:25 am 
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jtang,

Thanks for weighing in on the tire options.

-Bob


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