Question about clutches

Problems, ideas and comments specific to engine swaps.
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Diamond1
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Joined: 29 Jun 2009 16:47

Question about clutches

Post by Diamond1 »

This weekend Im gonna hit the local yard to pull off a 1981 datsun 280ZX 5-speed. I Have a Datsun L20B engine, so I just wanna know if I should get the clutch and flywheel off the Z or just leave it, cause I'm not sure if the Z clutch and flywheel is better then the datsun L20B clutch or flywheel. I was also thinking about gettin the 240mm flywheel and clutch, but i heard that the datsun roadster has a waaaay better pressure plate and clutch setup then any other L clutches and flywheel. If this is true, what year and engine should I get this off of. I'm just curious to see what I should get. Any help will do. thanx :D
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Baz
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Re: Question about clutches

Post by Baz »

The 6 cyl flywheels are generally lighter than L20B.
(They are in Oz.)
So the extras mass of the pressure plate is negated.
The U20 pressure plates are Ok, but there are many more to choose from.
The Z clutch is one.
Make sure you get the release bearing & sleeve as plate heights vary.
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okayfine
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Re: Question about clutches

Post by okayfine »

Diamond1 wrote:This weekend Im gonna hit the local yard to pull off a 1981 datsun 280ZX 5-speed. I Have a Datsun L20B engine, so I just wanna know if I should get the clutch and flywheel off the Z or just leave it, cause I'm not sure if the Z clutch and flywheel is better then the datsun L20B clutch or flywheel.
Who knows? We don't know what clutch setup you have on your L20B, so there's no way we can compare it. Aside from that, you're going to pull a clutch setup from a junkyard and install that on your engine? Transmission is one thing, but the consumable parts are false economy. Buy a new clutch setup and not worry about it for 100K miles.
Diamond1 wrote: I was also thinking about gettin the 240mm flywheel and clutch, but i heard that the datsun roadster has a waaaay better pressure plate and clutch setup then any other L clutches and flywheel.
If you are also thinking about gettin [sic] the 240mm flywheel and clutch, maybe you should spend your time instead doing research, 'cause you obviously don't know what you want. No one wants to use the largest clutch setups on their L-series unless they're putting down the power and need the bigger clutch surface for longevity. I don't know if anyone has wanted to compare the 240mm stuff to the Roadster stuff before, either, so congrats.

The Roadster clutch isn't "better," but it is different. Whether different equals better requires, again, a lot of information you haven't provided.
Diamond1 wrote:If this is true, what year and engine should I get this off of.
Uh, a Roadster? :lol:
Diamond1 wrote:I'm just curious to see what I should get. Any help will do. thanx :D
Don't pull a clutch setup from a junkyard. Beyond that, do you need to replace your clutch? When was it last changed? You might be better off to leave well enough alone.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
datzenmike
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Re: Question about clutches

Post by datzenmike »

The L20B from any Nissan car has a 200mm flywheel in it so the Roadster PP fill fit it just fine. If your L20B is from the 620 early 720 2wd it will be 225mm. Only the 280zx turbo had the 240mm, non turbo zx was 225mm.

The flywheel determines what PP will bolt to it. Measure the clutch disc diameter, the round part of the PP diameter or the contact area on the flywheel diameter for the size.

This one is 240mm:
[img]http://i138.photobucket.com/albums ... .jpg[/img]
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
Diamond1
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Re: Question about clutches

Post by Diamond1 »

Thanx datzenmike & Baz for the quick Info. I think When Posting, I should Be more informational. I have a Datsun L20B Engine which I pulled out of a 1982 datsun 720 pick-up, (from the local yard) I didnt quit do any types of measurements cause I was eager to get my 1978 Datsun 620 rolling. When I had purchase it about 3-4 months ago, It had to be towed cause the the prev. owner claim that it had spun a bearing, which in fact the motor had the rod punched through the block. The truck has the pick-up 5-speed, but I heard that everyone uses the Z 5-speed instead cause it's way better. Now, Since I'm goin to the Yard, I just "wanted" to know if there would be any benefits of getting the Z clutch and flywheel set-up. Yes, you are right and I should get a new clutch set up, but since the econmy has me on a budget, sometimes you get lucky and the clutches or other parts out of some of the R.I.P. vehicles are still in very very good shape. I havent seen how the clutch is on this car, but I'm just goin off of assumption.

As for the roadster question, I'm not very familiar about the Datsun Roadster. I dont know what year to what year are better if any. I was just asking if there clutch set-up is better cause I've read that the roadster PP and clutches are preferred by other Datsun Owners. I was trying to get info to see if it's true or not. I know that I may not know much about Datsun, but thats why I'm asking in this forum, to get more infromation for my project. And sometimes when looking online, it seems that all you get are the run arounds. I just like getting information from others that done mods to thaire engines.
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James
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Re: Question about clutches

Post by James »

The roadster clutch has more clamping force than the stock 510 clutch - and is a direct bolt in. I have one bolted to my z 5 speed - really like it.
Finished is better than perfect......
datzenmike
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Re: Question about clutches

Post by datzenmike »

Only the '80 720 had the L20B motor so either it was swapped or you have the year wrong. Hopefully you didn't drag a Z22 engine home. :mrgreen: The Z22 motor has the carb on the passenger side, L20B is on the driver's side. If from a truch it 'should' be a 225mm clutch so measure it.

The '68 620 tranny is exactly the same as the 280x tranny, exactly ratios and all. The '80-83 280zx tranny had different ratios and a very tall overdrive 5th but still the same tranny. If you get an '80 or newer get the shifter... you'll need it.

If on a budget run what you have with a 'regular' clutch.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
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Byron510
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Re: Question about clutches

Post by Byron510 »

I think the misconception about a better clutch is contradictory.
The roadster PP is used because people like the 1400 lb pressure number (stock 510 is 500#ish) and that it’s 200mm diameter makes it lighter than the 225 or 240mm dia PP’s that are available – less rotating mass means = less inertia to overcome = faster revs. If the grabbing of revs isn’t a concern to you – then, not problem :D
The flywheel is another story. L20B flywheels range, in stock form, from 22-34 lbs, depending on their application – trucks usually having the heavier flywheels. I have personally machined them down to 13 lbs, but I consider this DANGEROUSLY light for a cast iron OEM flywheel. 15-16 lbs leave a reasonable amount of material around the hub for strength. (That being said I think I have 10 years of abuse on my 14 lb cast iron flywheel, so I guess my generous radiuses and smooth machining were helpful!)

Hope that helps you a bit.

Byron
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okayfine
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Re: Question about clutches

Post by okayfine »

Diamond1 wrote:The truck has the pick-up 5-speed, but I heard that everyone uses the Z 5-speed instead cause it's way better.
See, Mr. Diamond1, this is where you continue to go wrong. You should be asking questions, for certain, but you should be asking different questions than you are. You should be asking those same people WHY the Z 5-speed is better compared to the pick-up 5-speed. You will also, as you have cottoned on, have to give more information when posting so we don't have to figure out what you have or take the time to ask you what you have. Saves everyone time and assures you get the correct information.

Also disabuse yourself of this notion of "better" as a blanket statement. At least without defining "better."
Diamond1 wrote:Yes, you are right and I should get a new clutch set up, but since the econmy has me on a budget, sometimes you get lucky and the clutches or other parts out of some of the R.I.P. vehicles are still in very very good shape.
False economy. Are you experienced enough to tell when a PP is still good compared to one that might look good but is the reason the car is in the junkyard? You have money to gamble on a JY clutch setup, but don't have money to do it correctly?

Sure, maybe car X got a brand new NOS clutch one day before it went off to the JY. Are you going to spend a week under all the donor cars in the yard, pulling transmissions, with the HOPE that you find the pot of gold?

And, all of this, just to replace a clutch that (apparently) isn't acting up in any way, shape, or form?
Diamond1 wrote:I havent seen how the clutch is on this car, but I'm just goin off of assumption.
What’s your evidence? What are the symptoms? If the clutch is operating well, what do you hope to accomplish by changing to a clutch setup with an unknown history?
Diamond1 wrote:As for the roadster question, I'm not very familiar about the Datsun Roadster. I dont know what year to what year are better if any.
Google.
Diamond1 wrote:I was just asking if there clutch set-up is better cause I've read that the roadster PP and clutches are preferred by other Datsun Owners. I was trying to get info to see if it's true or not.
Again, what’s “better?” Do you think a stiffer clutch pedal is “better?” Do you need “better” (higher) clamping force? For a stock L20B, no, you don’t, and as Mike has indicated, the 200mm pressure plate may not even fit your flywheel. It won’t hurt anything, and many people go that route, but Byron explains the rational behind the Roadster use.
Diamond1 wrote:I know that I may not know much about Datsun, but thats why I'm asking in this forum, to get more infromation for my project.
You need to spend some time doing research on your own. There’s little point in getting all the answers without doing some of the work, else you haven’t learned anything. Moreso when you don’t have the information to ask the proper questions. These things take time and work, but you’ll be better off taking the time to learn, rather than turn The Realm into a quick-hit Q&A session.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
vintageracer
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Re: Question about clutches

Post by vintageracer »

I think you need to know why people have stiff clutches and lightweight flywheels. I know everyone thinks a lightweight flywheel is the way to go. To go where? If you have a set of lower ratio gears in the diff and you car is lightweight and you race or rally or X-cross, you are set up. However, If you have a heavier car with a stock rearend ratio, lightweight flywheels will make it difficult to drive and clutches will be the weak point. I remember a guy here that bought an old Buick. He built an engine, put a 60# flywheel in the car and killed everyone for 1/4 mile. Next, he bought a Sprite, built an engine and put in a 10# flywheel and killed everyone in roadracing. I think the weight of your flywheel/PP/disc unit depend on your needs. I have a lightweight unit in my 240Z and a heavier unit in my stock 510. I prefer to drive the 510 because you just let out the clutch and the engine idles away every time. My wife will not drive the Z but loves driving the Dime. I know people will say, "I have a 7# flywheel and a triple-disc 8" PP and I love driving my Dime." If you have a set of 4.88 in the car, no problem. If you want a cruiser, a stock or heavy flywheel is the way to go. (If you have ever been around Indy Car/CART racing you know how hard these cars are to drive out of the pits.) So take a look at your situation and make your call. You can do whatever you want but be prepared for the conseqences of your action.
dislexicdime
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Re: Question about clutches

Post by dislexicdime »

the first time i put a 16 pond fly wheel and roadster clutch in one of my dimes i must have killed it 20 time when i was breaking in the engine lol
L series only have one header!

i need another garage mine is full of part's
Diamond1
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Re: Question about clutches

Post by Diamond1 »

Okay, after reading all your post, I thank you all. What my goal in all this is to bascially rev faster to have better accaleration. I think thats why I want to have a larger surface grip flywheel but lighten, cause I heard that more surface grip with less wieght = faster rev. for more acceleration. But thats where also a clapping force also kicks in cause I want it to grip. You see when I got my truck, after putting the motor in, we took it for a test drive and me and my machanic had notice that there might be slippage of the clutch and the tranny has a hard time shifting. Thats why I'm going to the yard to get the tranny. But since I was gonna be there, I figured I Might as well take the fly wheel off the Z since I would have easy access to it, and if the clutch is in good shape, then I'll take that too. Yes, buying a clutch would be the way to go, thats more likly what would've happen, but if the clutch on this car was in good shape, all it was gonna run me is about 20-30 bucks for the whole setup + the tranny. But i was trying to get info on the Roadster PP, maybe to see if the roadster PP can fit the Z flywheels(225 or 240) If it cant, o well, i'll just leave it that way, but thats all I wanna do for my truck at this time.
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okayfine
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Re: Question about clutches

Post by okayfine »

Diamond1 wrote:Okay, after reading all your post, I thank you all. What my goal in all this is to bascially rev faster to have better accaleration. I think thats why I want to have a larger surface grip flywheel but lighten, cause I heard that more surface grip with less wieght = faster rev. for more acceleration. But thats where also a clapping force also kicks in cause I want it to grip.
Now we're getting somewhere. It is helpful to understand your end-result goal so that we know where you’re going with your questioning.

To give the engine better response (ability to rev faster) one of the easy ways is to lighten its load. A lighter-than-stock flywheel will help to accomplish this. Weight of the flywheel, in and of itself, is not the only thing you need to pay attention to when dealing with flywheel weight. You also need to look at the associated clutch that will be mated to the flywheel in question.

The larger flywheel you choose (talking about clutch surface), the worse your engine response will be, EVEN IF THE FLYWHEEL IS LIGHTER. Why? Because to that flywheel (light or otherwise) you have to sandwich the clutch disc and bolt on the pressure plate. That pressure plate gets bigger and heavier as you go up in clutch size. I don’t have figures handy, but say a 200mm flywheel weighs 20 lb, disc is 2 lb, and PP is 20 lb. Now, say you have a 15 lb 225mm flywheel, disc of 2.5 lb, and PP of 25 lb. HA!, you say, the 225mm flywheel is lighter! But, overall, due to the increased material necessary to make up the larger PP, overall weight is the same. And we haven’t even got to one of the most important bits about rotational weight, i.e. where that weight is in relation to the diameter of the flywheel. A 200mm 15 lb flywheel with most of its mass around the hub (smaller clutch surface) is more willing to rev than a 225mm 15 lb flywheel with its weight apportioned more evenly over the entire surface (larger clutch surface).

In other words, a 1’ string with a weight at the end is easier to spin than a 3’ string with weight, right?

Now, on to clamping force. You have a stock L20B, correct? Do you have plans to add significant power/torque to that engine? By "significant" I'm talking about 75+ HP? 'Cause, otherwise, the clamping force of a stock OEM 225mm pressure plate is going to be fine. Behind a stock L20B, even one with a pair of side-draft Webers, even with a cam, even with a header and 2.25" pipe out the back, you're not going to stress the OEM 225mm clutch setup. I ran the 225mm OEM Nissan clutch on my KA24DE which actually put down 145HP at the wheels, and it had zero issues.

Going to a Roadster PP will give you more clamping force. But if you don't need it, why bother and put up with the stiffer clutch pedal as a result?

For your edification:
Image
Diamond1 wrote:You see when I got my truck, after putting the motor in, we took it for a test drive and me and my machanic had notice that there might be slippage of the clutch and the tranny has a hard time shifting. Thats why I'm going to the yard to get the tranny.
Likely the transmission is going bad. Could also be that there’s just not enough gear oil inside, or it’s old, or there’s some other reason. Maybe there was more diagnosis than what you’re putting in your post, again, we don’t know. There are things you can do to eliminate easy-to-fix causes of “hard time shifting” that don’t result in wasted money and hours spent on your back in the dirt.

As to the clutch condition, it’s generally cut and dry when a clutch is slipping. What were the conditions that “might” indicate it was slipping?
Diamond1 wrote:But since I was gonna be there, I figured I Might as well take the fly wheel off the Z since I would have easy access to it, and if the clutch is in good shape, then I'll take that too.
How do you determine if the JY clutch is in good shape? Maybe all your setup needs is a new disc? Maybe…well, maybe lots of things. Maybe the Z flywheel is lighter, but if you’re not sure what flywheel you have in your car now, it is impossible to say.
Diamond1 wrote:But i was trying to get info on the Roadster PP, maybe to see if the roadster PP can fit the Z flywheels(225 or 240) If it cant, o well, i'll just leave it that way, but thats all I wanna do for my truck at this time.
But you can search here for Roadster clutch and you’ll find all sorts of information. There’s LOTS of information here, if you just search for it.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
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