'68 Cam CS165R original specs v.s. LS6 Nostalgia Plus

[Gary K.]

Have combed through posts cannot find exact discussion on this. My question is whether the replacement Sealed Power CS165R, also Comp Cams "Factory Muscle 143S" with specs close or identical to original chevy cam for 427/435hp is really the best way to go. Great stick but I've already broken the factory seal so any minor changes now is the time.

There are many articles out there describing the LS6 cam or Comp Cams "Nostalgia Plus N+LS6S" as very close to original specs but offering somewhat better performance. In a nutshell argument goes "close, same sound, better breathing". I am not good with cam mathematics and I want to avoid sacrificing the superb original muscle sound and stock performance.

I've read the articles. Now looking for some real-life opinions from those who may have done this swap out before. My car is a driver. It is important but not imperative to be 100% stock so a little better performance will work for me if thats the case. Thanks in advance for your opinions.

[Patrick H.]

Re: '68 Cam CS165R original specs v.s. LS6 Nostalgia Plus

A friend did a stock rebuild on his 1969 435 horse car, and ran the engine on the dyno this past fall. The Nostalgia Plus LS-6 cam did quite a bit better than the factory replacement cam (don't know which one, sorry) that he tried first. I wasn't involved in the details enough to give you exact numbers; perhaps he will stop by here and give you some info.

[Duke W.]

Re: '68 Cam CS165R original specs v.s. LS6 Nostalgia Plus

I don't see how that's possible, everything else the same. There had to be other changes.

The high level specs on this Comp cam are identical to the OE cam except the inlet POML is speced at 107 deg ATDC rather than 108. That's not enough to make a difference outside normal dyno run variance. The CS165R is built exactly to the 3904366 GM print, which is the big block SHP camshaft (without pin) that was used from '67-up. It does not have a rear journal groove, which is required on '65-'66 SHP big blocks, but the lobes and lobe phasing are identical to the earlier cam with the grooved rear journal.

My first cam manufacturer choices are Federal Mogul and Dana Corp. They are current Tier I OE suppliers, and the same quality standards apply to replacement parts, but they don't spend millions advertising their products in hot rod magazines.

My second choice is Crane. Comp is near the bottom of the list. There are probably more "flat lobe" stories on the Web involving Comp cams than any other vendor.

If you want a L-71 to have more power, more low end torque, and lower fuel consumption without altering observable OE operating characteristics like idle behanvior, massage the heads and install the 1.88" exhaust valves. Use the FM CS165R cam and FM OE replacement pistons targeting a NTE CR of 10.3. Convert the vacuum advance to full time with a B26 VAC and quicken the centrifugal curve to the limit of detonation with 8-10 initial.

Duke

[Douglas P.]

Re: '68 Cam CS165R original specs v.s. LS6 Nostalgia Plus

Gary,

Patrick is correct, when I had my 1969 L71 rebuilt last year, I first installed the Crane BluePrinted Series 3863143 (Crane #969961) camshaft, but after less than expected results on the dyno and trouble holding vacuum at idle, I replaced the cam (and lifters) with the Comp Cams Nostalgia Plus N+LS6S (Comp Cams #11-671-4). The Nostalgia Plus N+LS6S provided more low-end torque than the Crane and it resulted in much smoother operation. My results were in-line and slightly exceeded those published in the "Building A 427 For Today's World" article published by Corvette Fever, September 2005 (available on-line at URL: http://www.corvettefever.com/techart...d/viewall.html). With the Nostalgia N+LS6S cam installed, my motor achieved peak torque of 480lb-ft at 3500RPM, with max HP of 488HP at 6000RPM.

Duke is correct, the cam was not the only change with this build... although, with exception to using KB Icon IC777.030's and Cloyes roller timing chain set, everything else was pretty much re-built as original. I had originally spec'ed use of Speed Pro LF2268's, but the decision was made to use KB Icon IC777's instead to lower the compression ratio to ~10.25:1 (these have a -18cc dome vs. original -36cc) to ensure good performance on 93 octane. [Note: The point regarding running the L71 on modern pump gas has been discussed at length and there are many varying opinions, see Corvette Restorer article entitled "The Ping" in Volume 39 Number 4 Spring 2013 pg. 36-39 and also the numerous postings in the NCRS TDB archive. I decided to err on the side of conservatism with my rebuild...and from the results it appears to have been a good decision.]

I haven't had the car on the road yet so I cannot comment on the motor's in vehicle performance, but on the dyno the motor exceeded my expectations. Hope this helps.

Doug

A friend did a stock rebuild on his 1969 435 horse car, and ran the engine on the dyno this past fall. The Nostalgia Plus LS-6 cam did quite a bit better than the factory replacement cam (don't know which one, sorry) that he tried first. I wasn't involved in the details enough to give you exact numbers; perhaps he will stop by here and give you some info.

[Joe L.]

Re: '68 Cam CS165R original specs v.s. LS6 Nostalgia Plus

I had originally spec'ed use of Speed Pro LF2268's, but the decision was made to use KB Icon IC777's instead to lower the compression ratio to ~10.25:1 (these have a -18cc dome vs. original -36cc) to ensure good performance on 93 octane. [Note: The point regarding running the L71 on modern pump gas has been discussed at length and there are many varying opinions, see Corvette Restorer article entitled "The Ping" in Volume 39 Number 4 Spring 2013 pg. 36-39 and also the numerous postings in the NCRS TDB archive. I decided to err on the side of conservatism with my rebuild...and from the results it appears to have been a good decision.]



Doug

Doug------


This was a very good decision. It's absolutely not worth taking the chance on going with higher compression and ending up with detonation. It's miserable to drive a car that suffers from that. It's also miserable to get stuck with having to use ultra expensive racing fuel or aviation fuel, both of which present logistical headaches when you want to get out "on the road". In my opinion, anything higher in compression than you've got now is asking for trouble later. In fact, I wouldn't even have gone as high as you did but you'll probably be OK.