LT-1 Cam Available?
A L46/L82 cam is currently in our 1972 LT-1. Is an original spec LT-1 cam still available through GM, or the aftermarket?
Thanks!
Larry
Thanks!
Larry
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Re: LT-1 Cam Available?
The LT-1 mechanical lifter cam is Speed Pro or Sealed Power (Federal Mogul) CS1145R. I don't have a Clevite (Dana Corp.) number.
The basic specs are: duration at .050" lifter rise, 242/254; POMLs, 110/122, LSA 116; gross lobe lift .306/.323", which translates to gross lift at the valve at zero lash of .459/485" at the 1.5:1 "design" rocker ratio.
The effective duration at .050" above the tops of the clearance ramps, which is measured at .062/.070" lifter rise is 231/239. These are the duration numbers you must use to compare to a hydraulic lifter cam.
The L46/82 hydraulic lifter cam is Speed Pro or Sealed Power (Federal Mogul), CS1095R; Clevite (Dana Corp.) part number, 229-1615.
The basic specs are: .050" lifter rise duration, 224/224; POMLs, 114/114; LSA 114; .30000/.30667" lobe lift, which translates to .450/.460" valve lift at the 1.5:1 "design" rocker ratio.
These two cams make very similar torque/power curves, but the LT-1 cam will extend the useable peak power range another 500 revs assuming both have valve springs set at the minimum height to enable maximum revs before hydraulic lifter pump-up or the beginning of valve float with mechanical lifters.
Duke -
Re: LT-1 Cam Available?
Duke, Thank you for all the specs. Appreciate your info.
LarryComment
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Re: LT-1 Cam Available?
Larry------
The LT-1 camshaft, once available under GM #3972178, is no longer available from GM in SERVICE.
By the way, the L-46/L-82 camshaft, GM #3896962, is still available from GM in SERVICE. One reason that it's still available is that this cam is still used to this day in some GM crate engine assemblies! It must be a good one to have survived for more than 42 years and still be in use for a currently manufactured engine. Of course, we all know it is a great cam.In Appreciation of John HinckleyComment
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Re: LT-1 Cam Available?
Joe,
Very interesting to learn that. Never would have thought an 'antique' like that would still be offered in a currently sold engine.
Thanks,
LarryComment
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Re: LT-1 Cam Available?
The part you get from GM, FM, or Dana was probably manufactured in the same plant, but one can usually get a better price through aftermarket channels.
With proper valve spring setup, the L-46 cam should rev to at least 6500 before lifter pump-up occurs, so it's a good choice for an engine like the L-46 that has a fairly restrictive inlet manifold. With massaged heads and the LT-1 induction system this will cut off useable power at the top end. A massaged head LT-1 will make useable power to 7000 with the OE cam.
A massaged head SHP/FI 327 would be restricted to 6500 with the L-46 cam, but the LT-1 cam will allow 7000+, so you have an extra 500 revs of useable power.
The L-46 cam has very similar high level specs to the L-79 cam, but is effectively retarded four degrees. Although the L-46 cam's duration's on both sides are the same, the lobes are actually different. The L-79 cam uses the same lobe on both sides.
The differences between the three lobes are subtle, and I've never quite figured out why GM redesigned the L-79 lobe, but they must have determined that they could get better dynamics for what is essentially the same duration and lift.
In any event, replacing an OE L-79 with the L-46 cam, advanced four degrees from the standard out-of-the-box indexing might improve the L-79's performance.
DukeComment
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Re: LT-1 Cam Available?
The best news is the LT1 cam from FM can be bought for under $100. Chech the price at Crane etc.Comment
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