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PostPosted: Mon Apr 04, 2016 4:52 pm 
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Posts: 29
My 1974 260Z has been hibernating in a closed garage unused and untouched since 1987....for shame but at least no rust. I purchased the car new from Bob Sharp Motors and enjoyed it for several years. Interestingly enough even though the car has 70K miles on it only once did I need to replace the original OEM tires. Those replacement tires, which are still on the car and totally flat, are Semperit Hi-Life M501 (175 SR 14 SST). Having said that I want to enjoy the car again and not sure what tires to put on the car inasmuch as the 175 SR 14 SST size designation doesn't correlate to today's nomenclature. My plan is keep it as a street car driven only somewhat aggressively. BTW the car has the stock rims which I'd like to keep on the car. Any help anyone can give me as to a recommended size, brand and model tire that would work correctly with the speedo and not rub on anything would really be appreciated.


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PostPosted: Mon Apr 04, 2016 8:26 pm 
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Happy to see you made it on! :D

Paging Frank Thomas, paging Frank Thomas!


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PostPosted: Mon Apr 04, 2016 9:22 pm 
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Filipe,

Yes I did. No problems at all. Thanks for your help.
Apparently Frank Thomas is the tire expert you alluded to. I look forward to hearing from him.


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PostPosted: Mon Apr 04, 2016 9:32 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 12728
Location: CT
Preston ~

We've had a lot of trouble getting good name-brand tires in 14" lately. Many of us have simply swapped up to 15" rims and enjoyed the great rubber of Goodyear Eagles, Pirelli, Michelin, Dunlop, etc. The speedo does suffer a bit, but not enough to get you into any real trouble.There is actually no cog gear which will make your speedO dead-on accurate with 15" wheels, because the difference is that slight. The different color cogs are more a function of coordination with the rear axle ratios than with the tire siZes. The cars handle nearly as well with 15" wheels (a bit more body roll) but fly down the highway with greater ease (and a few lower revs), and because the larger tires wear more slowly than the smaller ones, they don't need to get replaced as often.

There are 14" Pacific rim brands (Hankook comes to mind) and we're seeing a lot of those types appear on the Z cars and people say they perform well. But if you want name-brand rubber you almost have to switch to 15". There's plenty of fender well room so nothing rubs with the extra inch. Anything larger (16"+) can cause your inside toe to sometimes touch the frame rail during a full-lock turn, and fatter-than-stock tires can rub the inside rear wheel well under loads.

I managed to find what was probably the final set of BF Goodrich GT Radials in 14" which have shown to be outstanding rubber except for a little more road noise than I would prefer. Not sure you can find any more of those.

Glad to hear you have a 260! Sold for a single year, they are among the rarest Zs remaining today. The engine was their strong-point; nearly square (83mm x 79mm), it gave great torque, high revs, and 163hp (capable of lots more). The 260s began with carbs and switched to fuel injection, and the early ones had the lightweight chrome bumpers while the later ones had the "park bench" safety bumpers, which affected balance and weight of the car.

You can expect your 260 to raise in value. If you had one of the ultra-rare 2+2s with an automatic, you could be fighting off buyers each time you showed the car.

Frank

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1970 240Z


Last edited by Frank T on Mon Apr 04, 2016 9:49 pm, edited 3 times in total.

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PostPosted: Mon Apr 04, 2016 9:37 pm 
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My guy Frank T never lets me down. :lol: :thumbs_up: :thumbs_up:


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PostPosted: Mon Apr 04, 2016 9:56 pm 
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Location: CT
Heyyyyyy....... 8)

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1970 240Z


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PostPosted: Mon Apr 04, 2016 10:16 pm 
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Heh Frank,

Cool on Preston....my middle name.

I think I'll give then 14" BF Goodrich GT Radials a shot. I love a challenge! If that doesn't work out I'll check out the other options you mentioned. Thanks.

Yes my 260 is an early chrome bumper car. The only real problem I had with it were the carbs. Can you spell vapor lock....lol! If it turns out that the car's drive train doesn't need a ton of work I'm thinking maybe Webers. We will see.

Very interesting that you feel 260's will go up in price. Somehow I figured the 240's would always out perform them price-wise. Also even though they are rare somehow it surprises me that a 260 2+2 with automatic would be a good investment.....somehow it just isn't my type of Z.

In any case thanks for all the valuable information. I appreciate it. Filippe was right...you know your stuff.

-Bob

P.S. Speaking of tires if anyone should come across non-DOT 7.75x15 redlines please let me know. I've been looking for them forever. Thanks.


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PostPosted: Mon Apr 04, 2016 10:33 pm 
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Location: CT
The 260s are going no place but UP in price. They were far more solid than the 240s and therefore rode better, sounded quieter and offered far more comfort than the original 240 cars did. They were the difference btwn a true sportscar and an actual GranTouring car. My lightweight 240 could out-race a 260 to about 70mph, when the bigger cubes and longer legs of the 260 just walked away from me. The 260 engine is only 3mm away from being perfectly "square", and it should have enjoyed a much, much longer life.

Nobody doubts my love for the early lightweight 240Z. But the design had flaws which were worked out by the time the 260 came along. The fact that you had carbs and chrome on your early 260 makes it the winner everybody wants. If you can find a pair of early 3-or-4-screw "round top" SUs for your car, you will be amaZed at how well it performs. If you actually do go to Webers or Mikunis, please talk with either Bryan Little or Vinny Bedini first about your compression ratio and your cam.

I'm not a 2+2 automatic guy, either, but the 260 was the first Datsun to recogniZe that they were losing revenue of loyal young drivers who loved their 240, but suddenly found themselves needing a carseat and having a wife who could only drive an automatic. Unless the kid had enough discretionary income to own two cars, he had to make his only car fit his family. The 260 2+2 with AT did just that. Since joining this Club I've come to hold the 260Z in much higher regard than I ever did when they first came out. They were wonderful cars and just the right balance btwn lightweight sportscar and solid GT road car.

Frank T

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1970 240Z


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PostPosted: Tue Apr 05, 2016 12:01 am 
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Frank,

I hear you loud and clear on the various points you made and indeed they make sense. As you inferred in your post it depends on what you like, what you need and what you are willing to compromise on....grin. It makes sense as the car evolved from the first 240's to the 260's flaws were minimized. That make perfect sense. It always seems however....no matter the make.....that as they "improve" they always seem to put on weight.... weight in my view is the enemy.....as well as lose their edginess. In addition it must be recognized that Nissan is in the business to sell cars and hence they soften them....suspension, power this and that, automatics, etc......so they appeal to a bigger, broader audience. Certainly as you articulated the 2+2 auto furthers the original 240's reach.

Net, net I tend to like rawer, edgier, visceral, no power steering, no power brake, stick shift street cars. But that's just me. As you said that's fine but "to each their own" and "variety is the spice of life".....cool I used 2 clichés in 1 sentence..... and that sells more cars.

Frank, thanks again for your advice and I am really enjoying our dialog.

-Bob

P.S. Quick question: with the increased displacement of a 260 over a 240 via stroking the engine and not boring it did the redline go down? Thanks.


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PostPosted: Tue Apr 05, 2016 12:11 am 
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Hey Frank,

Bob is gonna need some work to get his 260 road worthy again...think it's a good idea to send him to Vinny? That's who I recommended. 8)


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PostPosted: Tue Apr 05, 2016 9:04 am 
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Joined: Wed Apr 09, 2008 5:53 pm
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Location: CT
The 260 redline remained advertised at 7,000 rpm, but only because Datsun had warehouses full of the standard tachometers which showed 7G redlines. In truth, the closer you get an engine to perfectly "square" (equal bore and stroke), the higher the rev limit becomes. Several hi-performance vehicles use perfectly "square" engines today, including the Bugatti Veyron, some Toyota performance cars and several motorcycles. If you can't have a square engine, a slightly over-square engine (bore larger than stroke) becomes the next most-desireable option, which is what all Datsuns (except the diesel) and all US cars since the 1950s have adhered to. The 260 just does that best, with an engine which is only 3mm over-square. The least-desireable are the under-square engines, meaning the stroke is longer than the bore. Those are found in Europe/England, where the car tax is determined by the engine bore, and on special application low-revving engines, where torque is more important than horsepower (marine engines, diesels, tractors, stationary work engines, etc). The long-stroke under-square sportscar engines (Jaguar, Healey, Triumph, MG) made good torque but were limited to lower redlines (5-6K rpm) before they came apart, and many great British sportscars (notably Triumph) have blown themselves up trying to catch the over-square 240Z on the racetrack (think Bob Tullius in the TR6 trying to catch Bob Sharp in the 240Z thru the 1970s). The high-revving 240 actually killed the US market for the Triumph TR-6 because Tillius (who was a more experienced driver than Sharp) kept blowing his cars up trying to catch the younger driver, and the world was watching.

Among all the Datsuns, the 260 factually had the highest redline, and it was indeed above 7,000rpm (if all internal parts were new and correct). In fact, the only L-series engine I've ever seen blow a rod thru the block was a 260. Our member AirJockey specifically chose the 260 engine for his exposition drifting car because it would rev so much higher than the other L-series engines. He routinely held the car well beyond the tachometer redline (breathing thru triple Webers) and limiting it "by ear". He said it sounded happiest and strongest well up into 8,000+ rpm. One day he held a drift too long and all the oil surged away from the pickup, starved the bearings and put a single rod thru the side of the 'bulletproof' L26 block. It was the siZe of my fist and I have pictures of it somewhere. Had he used a baffled oil pan, that wouldn't have happened.
So yes, we have empirical experience which shows the 260 can endure higher revs than the tachometer recommends. Among all the Datsun L-series engines, the 260 comes closest to the magical 'square engine' design, missing it by only 3mm. Except for race-prepared hi-output L-series engines, the stock 260 is the highest-revving, safest-revving engine in Datsun's stable.

And YES, if Bob has any questions or ideas about modifying his L26, he should begin with a call to Vinny Bedini in New Milford (860-355-182nine) [ http://www.ctzcc.com/images/bedini.pdf ] or a chat with Bryan Little [ http://www.datsunzgarage.com/ ] (both are our members). Vinny is the CTZCC S30 Guru, and has built and raced Datsun engines since the late 1960s. He has built competition engines which still hold world records today. Big-named racers hired him to build them winning engines so often, he hardly had time to race himself. Vinny can prevent Bob from being disappointed by simply sticking a stack of Webers or Mikunis on his engine and expecting big results. Tripling the air/fuel intake alone, without increasing the compression, cam lift and timing to handle it, can cause any engine to simply bog down with over-carburation, actually making the car SLOWER than it was stock. The later 260 heads had larger valves than the earlier 260s had, which improved breathing, as well. Those later heads fit right onto the earlier cars and make a noticeable improvement.

The 260 engine has amaZing performance potential. But the money today is in closest-to-stock classic Z cars. I salute Bob for his initial idea of keeping his baby as close to original as possible. :thumbs_up:

Frank T

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1970 240Z


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PostPosted: Tue Apr 05, 2016 11:46 am 
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Joined: Mon Apr 04, 2016 12:50 pm
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Frank,

I'm just heading to the airport and since I will be "out of pocket" until Sunday so I just printed out your post and will read during my flight. I'll will try and get in to the Forum during my trip but if not Sunday for sure. Thanks for your post and I look forward to reading it.

-Bob


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PostPosted: Tue Apr 05, 2016 5:35 pm 
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Joined: Sat Jun 01, 2013 5:38 pm
Posts: 535
Location: Orange, CT
Hi Bob I'm sure we all will love seeing your 260.
Just to clarify on what Frank said, BFG no longer makes the GT radial.
They make a T/A Radial which is an all-season made for hot rods and classics.
These tires are made in lots of sizes and are very good all around.
It's not a high tech tire like their g-Force but if you're sticking with 14" wheels they are the only choice.
I have the largest size possible in a 14" that keeps the stock circumference, 225/60 14
They rub slightly when in reverse turning left but I think my bodywork is off.

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Nov/70 late series one HLS3014777 Sunshine Yellow 919


Last edited by SurferD on Tue Apr 05, 2016 7:43 pm, edited 2 times in total.

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PostPosted: Tue Apr 05, 2016 5:45 pm 
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Joined: Mon Apr 04, 2016 12:50 pm
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Very cool SurferD. Thanks for the clarification.

-Bob


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PostPosted: Tue Apr 05, 2016 7:25 pm 
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Joined: Sat Feb 01, 2014 9:21 am
Posts: 691
Location: Somers CT
My 1974 260 got up to 145 on Rt 91 North of Greenfield on that long straightaway below the VT line one day. Did you know that dotted lines look solid above 125 or so :mrgreen:

The problem I had with mine was that Datsun had not figured out the new pollution control system in the early models. Mine had an issue where it would shut off dead at one spot on the temp gauge when started from cold. It would start again after the temp rose above that point and then it would run flawlessly after that for the rest of the session. We never did figure out what caused it. :roll:

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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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