1969honda Posted June 24, 2017 Share Posted June 24, 2017 (edited) Little background, I'm putting a vk56 in my 1971 S30 with T56 and a modified mustang irs, shooting for north of 600 RWHP. I was originally going to SC the car with an early Roush TVS but I've since decided TT is how I'm going to go. Car is purely intended to be a fun streets let make Camaros and mustangs cry play toy. I might take it to the strip at some point just for being numbers but I enjoy canyon drives and open roads, which are plentiful in the Rockies where I live. I have got the adapter plate all drawn up in SolidWorks for my T56 to VK56 bellhousing, and I'm planning on 0.500" steel similar to what the big companies offer for the SBC retrofit plates. I also have a 0.500" helicoiled aluminum version drawn up just to compare prices and weight. I'm going to see if I can get local printer to print off a flare pattern on a really thick card stock or get a cnc'd mdf/plastic plate made to verify all of my hole placements, and that it will actually center the transmission input shaft correctly to the crankshaft. This leads me to the reason for my question in the title, I'm contemplating clutches. From what I've seen my choices are a traditional gm 10.5" from McLeod/Monster/Spec/Mantic for $800-1400 without the flywheel r some of the snake twin plate from the and mfgs. However my flex plate has a step in it towards the outside edge which means I only have about 10.5" total diameter to mount a prayer plate: also the flex plate contains my CAS sensor pickup pattern on the edge, so a standard 10.5" clutch probably isn't going to fit. Clutch Masters apparently makes a flywheel and 8.5" race clutch for the 350/370z with the correct bolt pattern already drilled, but they want $2k+ for a clutch kit and they haven't confirmed the torque rating yet. I know of stock vk56 swapped S13s putting down 450+RWTQ on the dyno by 2700 RPM, and that's quiet a bit more than a VQ v6 but less than a Turbo vk56... (Seen dyno reports of an m56 at 7 psi over 600 RWTQ) I found out looking thru stuff on LS1tech last night that PowerTrain Technologies started making some 7.25" organic compound discs in .200" to .250" thickness that come in 2-3 disc packs. I know that the smaller clutches are more of an on/off switch, but the organics are supposed to be able to slip more than the standard sintered metal or ceramic clutches, and 3 plates would hold more heat than 2. PTT claims they are supposed to be compatible with all the big name brand standard 7.25" clutch covers and floaters as well. My thoughts right now are to have QM drill a 7.25" flywheel button in the pattern I need, and purchase a race team overstock new 7.25" clutch and some PTT organic discs. Average disc pack seems to be about $200, then $125-250 for a race clutch cover assembly and another $150-$250 for the button. It's still close to the regular high TQ LS1 clutch offerings in price but smaller, lighter and in my mind seems easier to adapt and mount. Am I crazy? Does anybody have any experience with the smaller diameter clutches that can chime in with recommendations? My last option I've read about is a few guys using the CD009 with about a 1" spacer and a 350z flywheel after taking the starter ring gear off, then turning the diameter a little. That's for a Nissan 1" x 23 or 24T input shaft and not a 1 5/32 x 26T input though and a stock vk56. Edited June 24, 2017 by 1969honda Quote Link to comment Share on other sites More sharing options...
tube80z Posted June 25, 2017 Share Posted June 25, 2017 You mention using this on the street. The clutch you mention is similar to a rally clutch where a 3 disc race setup is stacked up the same using two thicker cerametallic discs, which allows for more slip. This setup isn't as grabby but still is fairly violent on take up. And when in neutral they are loud with the discs banging about. If you plan on having good launches you're going to need more weight than the traditional button allows. This is streetable but doesn't have the best manners and you need to make sure you don't slip it too much. A number of friends are running these in CP autox cars and an LS2 powered XP RX-7. In the RX-7 it doesn't seem too hard to take off and not kill it but you need to raise the revs and be fairly quick on engagement. Jon Mortensen uses one in his XP car too if you want more of data points. I don't think you can go any smaller than 7.25 and still drive on the street. The smaller options don't have enough heat capacity. Although I know you didn't ask that. Hope that helps, Cary Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 25, 2017 Author Share Posted June 25, 2017 Cary thank you for the input! I do plan for mostly street driving, I've looked for an 8.5-9" but haven't seen much offered in those sizes. I know Clutch Masters have an 8.5 that a few z33/34 and one s130 car are using, but CM quoted me $2700 for a similar 8.5" setup. I can bring myself to see this as the "best" or most cost efficient solution. I haven't looked at anything smaller than the 7.25 for the reasons you mentioned, heat and lack of MOI on launch creating a stall and hard starting out from a stop. I hadn't really thought there mouse could be too bad, I've heard they can be rattly but I've never been around one, so I don't really have reference. I work with the old Detroit two stroke diesels and gm 6.2/6.5l engines on a daily basis and if it's anything like sitting in a humvee at idle I'll keep looking for a different solution. Hopefully a few more chime in with their experiences and I'll put together a few questions to PM Jon if he doesn't appear in this thread. I just want to make sure I figure out the most practical and effective solution for the engine and combo choices I've made. Again thank you for your input and sharing you experiences and observations. Quote Link to comment Share on other sites More sharing options...
jt1 Posted June 25, 2017 Share Posted June 25, 2017 I've used a 7.25" Tilton triple quite a bit, in a mostly track/barely streetable car. It's great for track, holds 600 crank hp with no problem, but it's very quick and hard to modulate for a smooth takeoff. Playing with master cyl diameter helped some, but it's still easy to spin the tires, kill the motor, or jerk away from a start like you're in the wrong gear. Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 26, 2017 Author Share Posted June 26, 2017 Thanks JT1, that's one of my biggest concerns with the smaller clutch is having to choose between roasting the tires or stalling the engine at a stop light. We have a pretty big classic car show and parade every year about this time, but in the past 10 years or so they have really cracked down on any tires slipping or burnouts. It used to be you could get away with a back road street race and they'd pull you over, ask about your car and either give you a warning or a regular speeding ticket and tell you to get off the streets; now days they impound your car, cite you for exhibition of speed and wreckless driving. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 26, 2017 Share Posted June 26, 2017 Mine is a dual 7.25". I finished my car in Oct '15 and took it out once, then my biz took a crap and I haven't had it out again. Biz is back in the black, so I'll probably be out again soon. From what I can tell, the clutch is really grabby and I did basically what Cary said; got the revs up and let it out quickly. Never stalled it but it wasn't "easy" to drive. Not a bit deal to spin the tires on the line at an autox, so street driving may be different... Revs fast though! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 26, 2017 Share Posted June 26, 2017 FWIW, I tried to change down to a 5/8" clutch master to make it easier to slip, didn't have enough throw to disengage the clutch. Stick with 3/4, based on my experience. Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 26, 2017 Author Share Posted June 26, 2017 Thanks Jon, I'll definitely take your advice on the master cylinder if I commit to a 7.25". Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted June 26, 2017 Share Posted June 26, 2017 Most of these small diameter clutches (Tilton/Quartermaster) are hard to drive because of the sintered metallic material. If it's that coppery coler, it's going to be hard to modulate regardless of clutch diameter. I have driven a 5.5" 4-plate with a special lining (designed to slip) and a 5.5" carbon-carbon 3-plate and both were easy to modulate. To the point that having very little inertia wasn't a problem. If you're replacing the discs, remember that you'll need to ensure the total stack height is the same. If I recall correctly, you can take a 4-disc tilton/quartermaster basket, and make it a 3-disc organic using the .2" thick PTT discs and be really close to the original stack height. I think this would be a sweet setup, and I plan to do a 5.5" version for my car in the future. I was quoted $430 for the 5.5" organic 3-disc pack. I think super low inertia makes for a really fun car to drive. Don't forget, you'll need an annular release bearing for most of these clutches. Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 26, 2017 Author Share Posted June 26, 2017 Flexicoker, that's a good tip about the organic discs needing a 3-4 disc cover to account for the thicker disc material. I've been thinking 7.25" 2 disc with the .250" discs, but wondering if 3 wouldn't help with heat, and then using a tilton 6000 series release bearing that covers 5.5-8.5" clutches. The carbon would sure be a sweet setup, but I definitely don't have that kind of cash laying around Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 26, 2017 Author Share Posted June 26, 2017 Talked with Vicky from PTT a few moments ago, she informed me the organic discs are not recommended for anything above 400TQ, my v8 makes almost that in stock form. She did say however that they have a metallic that is much smoother engaging than their competition that they would recommend for dual use on the street for the same price as the organic discs. Vicky also quoted me a blank button 7.25" button for close to $160 and then I can get it drilled to what ever pattern I want locally. So if I do go their discs are between $250-360 depending on the thickness and number if discs I order and another $160 for a flywheel that I can mount to my stock flexplate. The other nice thing is they actually have the mounting hole dimensions and thickness of their flywheel buttons on the catalogue page so I can mock it up on CAD and see how things should line up. Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted June 26, 2017 Share Posted June 26, 2017 One other thing I'm unclear on with such a setup is if the PTT organic discs are marceled, and if they are does that cause any engagement issues? You've only got 0.030" of allowable pack wear so if the marcel uses up that much you'll be reducing clamp load and potentially have a long engagement window. I don't have enough experience there to say but it might be worth asking if the organic discs are still an option for you. Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 26, 2017 Author Share Posted June 26, 2017 I'm not sure in that either, but where she said they aren't rated in any combination over 400TQ it's a no go in my situation anyways. Vicky said that anything over 400 the organic wears really fast and that they would recommend a ceramettalic compound of theirs. That compound should hold the heat better, engage smoother than other metallic compounds and allow for a small amount of slip. Quote Link to comment Share on other sites More sharing options...
tube80z Posted June 30, 2017 Share Posted June 30, 2017 Talked with Vicky from PTT a few moments ago, she informed me the organic discs are not recommended for anything above 400TQ, my v8 makes almost that in stock form. She did say however that they have a metallic that is much smoother engaging than their competition that they would recommend for dual use on the street for the same price as the organic discs. Vicky also quoted me a blank button 7.25" button for close to $160 and then I can get it drilled to what ever pattern I want locally. So if I do go their discs are between $250-360 depending on the thickness and number if discs I order and another $160 for a flywheel that I can mount to my stock flexplate. The other nice thing is they actually have the mounting hole dimensions and thickness of their flywheel buttons on the catalogue page so I can mock it up on CAD and see how things should line up. Their online material (http://www.powertraintech.com/Files/PDFs/Clutch%20Facts.pdf) states 400 TQ per disk. So you may want to verify. That sounds like it might be an okay way to go. My limited experience is that you raise the revs and do a couple quick dips to get the car rolling and then fully engage (pit driving). I think as long as you use the button and the stock flexplate it will be a little better. Mine is a button and ring gear that's mounted to the clutch cover. This is using a low ground clearance bellhousing and reverse starter. If you're planning to ebay a cheap cover I'd go with a Tilton as they had hardened pads for the disks to touch. I have a quartermaster cover and they are just hard anodized from the look of it. As to how loud they are it's fairly obnoxious when in neutral. It sounds like something is broken or about to fall off. Many of the street dual disk systems employ some kind of strapping between the disks to keep them from rattling back and forth. Cary Quote Link to comment Share on other sites More sharing options...
1969honda Posted June 30, 2017 Author Share Posted June 30, 2017 Cary, I'll double check the torque again with PTT as it sounded fairly low to me as well, the literature does clearly say per disc as your referenced. 400 TQ is a base LS1 with simple bolt-ons, I'll call again tomorrow. I also need to verify if their blank buttons use a "pot" or "step" type clutch cover. The eBay clutch covers are tempting, if I can get a good deal on a full clutch setup and a button flywheel from PTT I'll probably bite the bullet. I haven't seen anyone other than Clutch Masters offering 8.5" clutches, there's one QM 8.5" single disc on eBay currently I've been eyeing, but as mentioned I'm looking at an easy 600 tq. Also thanks for the noise warning. Quote Link to comment Share on other sites More sharing options...
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