It's time to buy a clutch and pressure plate. I know Joe Lucia has recommended Luk in the past; however, Luk does not make a clutch for my application. It's a '70 454 with an 11 inch disc and a 10 spline shaft. The factory spec is 500 ft/lbs of torque. Does anyone have any recommendations? Thanks.
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Re: Replacement Clutch Selection
Joe,
I contacted Luk a few months ago and was told that the replacement series 04-049 uses an LC551 clutch disc with a maximum torque rating of 425ft/lbs. The Luk technical guy told me that it would be insufficient for this application and did not recommend using it. He told me that they have a "Gold Series" line of clutches with higher torque capabilities, but they don't make a Gold Series clutch/pressure plate for this application. I called again this morning to verify and another tech guy told me the same thing.
Any other ideas? Thanks.Comment
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Re: Replacement Clutch Selection
Go with SACHS, GM's current supplier.Comment
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Re: Replacement Clutch Selection
Tom----
The disc in the 04-049 kit is equivalent to the GM #3908960 and the pressure plate is equivalent to the GM #3893236. These were the parts used in PRODUCTION for your application.
You can't compare the factory-advertised torque of an engine against the torque ratings specified for driveline components. For example, a Muncie M-20 or M-21 has a torque rating of less than 400 lb/ft. So, using your analysis, the factory should never have installed one behind a 1970 LS-5. But, we all know, for sure, they did.
The highest rated Richmond Super T-10 (which transmission line is considerably stronger than Muncies and used in various forms of competitive racing) is rated at 375 lb/ft.
If one takes the above described torque information together with your desire to have driveline components matching or exceeding the factory-rated engine torque, then one would have to come to the conclusion that there is NO 4 speed trans that could be used behind your engine.
The same thing applies to clutches. I am very confident that the 04-049 kit will work just fine for you and I would use it without hesitation in your application. But, it's your decision.In Appreciation of John HinckleyComment
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Re: Replacement Clutch Selection
The SACHS kit is part #K5552-05 for a 454 Corvette.Comment
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Re: Replacement Clutch Selection
Ken-----
Well, either I am mis-informed or there has been some "re-alignment" in automotive supplier businesses. I seem to recall some time ago reading in Automotive News that Sachs had purchased LUK. Maybe they later sold it or maybe my recollection is bad. In any event, I think that the actual parts that one will find in the box of either LUK or Sachs for any particular application will be the same.
Also, the Sachs kit for a 1970 LS-5 Corvette is K5552-03. The K5552-05 is the same kit EXCEPT the friction disc has 26 splines versus the 10 spline disc supplied with the K5552-03. All 1970 Corvettes used 10 spline clutch discs. 1971 and most (but not all) later used 26 spline.In Appreciation of John HinckleyComment
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Re: Replacement Clutch Selection
That was gross torque on a lab dyno, and it was likely overrated by as much as ten percent as were most ratings in the era of SAE gross ratings.
Even a blueprinted, massaged head, supertuned, high compression '70 454 with the OE cast iron manifolds and exhaust system will likely not put out more than 450 lb-ft SAE net at the crankshaft.
Have the car tested on a chassis dyno with SAE air density correction and divide the peak torque by 0.85 to get a good estimate of actual SAE net torque at the crankshaft.
Like Joe said, the maximum specified torque inputs of many drivetrain components are very conservative. Unless you plan to drag race with 5000 rev clutch drops the Sachs/LUK OE replacements should perform fine.
I've got chassis dyno tests on a '67 30-over L-71 stroker (4.25" for 496 CID) - blueprinted, nicely massaged heads with 1.88" exhaust valves, 11+:1 true CR (needs some race gas blended in) OE cam retarded 6 degrees through OE manifolds and side pipes and using the above calculation peak SAE net torque at the flywheel is 449 lb-ft @ 3900. The engine is absolutely original in appearance.
FWIW peak SAE corrected RWHP was 376@ 5800 (442 SAE net at the flywheel), and I know the OE sidepipes are just killing the top end output. A set of OE looking large diameter "cheater sidepipes" will be installed, and that should bring the peak RWHP to over 400 (over 470 SAE net at the flywheel) and increase peak torque somewhat, too. It will be closing in on modern LS7 power level.
The engine is very docile in normal driving, but if you jump on it in any gear below third it gets sideways real fast! The owner is easy to recognize - the guy with the perpetual grin on his face.
DukeComment
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