1960 Camshaft selection

[Thomas H.]

Some of you may recall my previous post on the 1960 we are working on. https://www.forums.ncrs.org/showthread.php?t=62817

We were able to locate an engine builder in the area that is an "old timer" and has spent many years working on vintage corvette engines. My friend, who owns the car, is now tasked with parts selection for the rebuild. The biggest decision being the camshaft and piston selection. The goal here is to provide an increase in power while maintaining the stock look and sound.

We want to stay with a hydraulic lifter camshaft.

There will be no head work done except for valve replacement, valve job and new springs based on camshaft selection.

The factory intake and Carter carb are going to be used.

The factory exhaust manifolds will be used.

The car was outfitted early in its life with a 4 speed, replacing the factory 3 speed.

The car came factory equipped with 4:11 gears.

Piston selection should be fairly straight forward. I was going to recommend using Hyperutectic(sp?) pistons with a small bump in compression. But when it comes to specifying the cam....
This is where the experts here come in................

Thanks
Tom

[Duke W.]

Re: 1960 Camshaft selection

Your objective is unobtainable!!!

You can get more power with a "bigger" camshaft, but it's going to idle like a 270. If that's what you want go with the L-79 cam. You'll get more power, but it will cost big in terms of low end torque and idle quality.

The secret to power is HEAD FLOW! I repeat.

The secret to power is HEAD FLOW! One more time!

The secret to power is HEAD FLOW!

Trying to get more power with a stock heads and a bigger cam is a fool's game.

The best approach is to "massage" the heads - pocket porting/port matching/multiangle valve seat work that I have discussed many times here and the details are well documented in "How to Hot Rod SB Chevies" and various books by David Vizard.

Working the heads this way (and I also recommend increasing inlet valve size to 1.84") will gain 6-10 percent more top end power and at least 500 more usable revs with absolutely no impact on the smooth 500 RPM idle. There will be a slight loss of low end torque, but with a 4:11 you won't notice it.

The OE cam is no longer available, but the replacement 3896929 cam or the 14088839 that replaced the 929 are the way to go. You can cross reference these numbers at napaonline.com to the Sealed Power replacement. In fact I recommend you buy all Sealed Power OE replacement parts. They have everything you need including pistons, valves, bearings, rings - whatever and everything you need.

The advertised CR of your engine is 9.5, but it is probably lower. Your engine builder should carefully measure deck height, head chamber volume, and get the spec for OE replacement piston volume, then use a compression ratio calculator and select a thin shim type gasket that will yield in the range of a true 9.5-9.8:1.

If you haven't disassembled the short block yet, start by measuring the deck clearance, head gasket thickness and compute the as built CR. Look at the archives. I've discussed this many times before and provided a link on an online CR calculator that you can use once you have the requisite measurements.

OE pistons and a typical thick composition gasket that most "engine builders" use will yield about 8.5:1, which is okay I guess if you want to use regular unleaded, but if you want maximum torque/power across the range and maximum fuel economy design the engine for maximum CR not to exceed 9.8:1. Combine this with some decent head massaging and you will be a happy camper.

The absolute WORST combination is low compression and a high overlap camshaft, which is the stone a lot of guys end up with when they go down the path you are suggesting.

The other potential problem I see is your "old timer" engine guy. Unfortunately this often means 40 year old hot rodder thinking rather than modern engine system engineering.

Duke

[Steven B.]

Re: 1960 Camshaft selection

I agree with Duke. I did an L-82 by first addressing the heads with porting, angle valve job, a real CR about 9.6, etc. then installed an L-79 cam, advanced 4 degrees with a 3.90 rear and 45 series tires. I had the essential gearing, about 4.10, RPMs and power for a street/semi stock autocross car. It did well on the street, also.

Put the few dollars into the heads. It is more than worth it. Air flow is HP.

[Joe L.]

Re: 1960 Camshaft selection

Your objective is unobtainable!!!



The absolute WORST combination is low compression and a high overlap camshaft, which is the stone a lot of guys end up with when they go down the path you are suggesting.

Duke

Duke-----


If you're talking about a REALLY HIGH OVERLAP cam, I agree with you. I would never recommend such a cam for ANY street application for a whole host of reasons. However, as I've mentioned before, the 1971 LS-6 with a relatively high overlap GM #3904362 camshaft AND 9.0:1 compression is one of the best running and best sounding engines EVER installed in a Corvette.

[Joe L.]

Re: 1960 Camshaft selection

I agree with Duke. I did an L-82 by first addressing the heads with porting, angle valve job, a real CR about 9.6, etc. then installed an L-79 cam, advanced 4 degrees with a 3.90 rear and 45 series tires. I had the essential gearing, about 4.10, RPMs and power for a street/semi stock autocross car. It did well on the street, also.

Put the few dollars into the heads. It is more than worth it. Air flow is HP.

Steven-----


I think that most of any performance increase you achieved occurred as a result of the head work you had done. As far as cams go, there is not that much difference between an L-82/L-46 and L-79 camshaft. In fact, for 350 cid or larger small blocks, I think the the L-82/L-46 cam has the edge.

[Duke W.]

Re: 1960 Camshaft selection

L-79 cam:

Duration @ .050" 222 degrees (both sides use the same lobe)
POMLs 110 deg. ATDC/118 deg. BTDC
LSA: 114 deg.
Lobe lift: .29807/.29807"

L-47/82 cam:

Duration @ .050" 224 degrees (both sides, but they are not the same lobe)
POMLs 114 deg ATDC/114 deg. BTDC
LSA: 114 deg.
Lobe lift" .30000/.30667

Basically there is not a dime's worth of difference between the three lobes. The big difference is indexing. If you take the L-79 cam and install it retarded four degrees you basically have the L-46/82 cam, and I don't think a dyno could tell the difference.

Likewise on an L-79 if you replaced the OE cam with the L-46/82 cam installed four degrees advanced, you couldn't tell the difference.

Often a basic lobe design and LSA will work well on similar engines with different strokes, but the longer stroke engine will make more average power across the range with both lobes indexed later.

A good example for which I have test data is installing the OE L-72 cam on on an otherwise OE appearing L-72/71 stroker with up to six degrees retard depending on the stroke.

I don't know why the L-46 cam was designed with new lobes. I've compared the dynamic analysis data many times, and though there are some differences, they just don't seem significant, but I expect the lobe designers must have looked at the L-79 lobe and determined that some improvement was possible, but I'll be damned if I can figure it out.

Duke

[Joe C.]

Re: 1960 Camshaft selection

Steven-----


I think that most of any performance increase you achieved occurred as a result of the head work you had done. As far as cams go, there is not that much difference between an L-82/L-46 and L-79 camshaft. In fact, for 350 cid or larger small blocks, I think the the L-82/L-46 cam has the edge.

I agree fully with this assessment!!
I know someone with a '65 327, with L46/L82 cam installed, with ported small valve "461" heads, CR Muncie, and 3.55 gear, who runs 13.1 @ 107MPH!!!
If I were you, I'd use the L46/L82 cam, WITH CAREFULLY MATCHED COMPRESSION RATIO...............MEASURED AND VERIFIED BY YOUR ENGINE BUILDER. Optimal static C/R for that build will be 10.00:1 if using 91 PON gas. If you have 93 octane available in your area, then 10.2 or so should be achievable with no detonation. This also assumes that stock rocker ratios are used, the cam is installed 4 degrees advanced (as ground, or "mark-to-mark" on the sprockets), and the heads have been ported. Stock, non-ported or restricted heads and/or inlet/exhaust systems will allow slightly more static CR before detonation occurs.

Here is an excellent book which will assist you in making the right choice:

http://www.alibris.com/booksearch?qw...*listing*cover

Joe

[Steven B.]

Re: 1960 Camshaft selection

Steven-----


I think that most of any performance increase you achieved occurred as a result of the head work you had done. As far as cams go, there is not that much difference between an L-82/L-46 and L-79 camshaft. In fact, for 350 cid or larger small blocks, I think the the L-82/L-46 cam has the edge.

You are correct. I tried the L-82 cam, the L-82 advanced 4 and 6 degrees, the L-79 and the L-79 advanced 6 and 4 degrees. I got only +7 HP on the dyno with the L-82 advanced 4 degrees. Not alot and I could have probably gotten that elsewhere --- easier than swapping cams over and over. I got alot more with the head work! My point is the head work, and 4 tube headers, is what got me most of the performance. It was in the inhaling and exhaling.

[Duke W.]

Re: 1960 Camshaft selection

Duke-----


If you're talking about a REALLY HIGH OVERLAP cam, I agree with you. I would never recommend such a cam for ANY street application for a whole host of reasons. However, as I've mentioned before, the 1971 LS-6 with a relatively high overlap GM #3904362 camshaft AND 9.0:1 compression is one of the best running and best sounding engines EVER installed in a Corvette.

I agree, but it will work even better with massaged heads, about 10.25:1 and four degrees retard. Even better is stroking it to 4.25 and six degrees retard! The longer the stroke the more overlap and later phasing the engine can effectively use (and the later the cam phasing the more detonation-free compression the engine can tolerate), so it's a lot easier to "overcam" a 3" stroke 283 than a stroker big block.

Regarding that 13.1/107 MPH 327, the massaged OE heads flow so well that power is still increasing at the 6300 RPM lifter pump-up speed. I've recommended the owner install a LT-1 cam, which will extend the power sweet spot to 7200 without a significant loss of low end torque.

Small blocks with really good reworked OE heads need the extended rev range of a mechanical lifter cam because they will pull useable power well beyond the valvetrain limiting speed of hydraulic lifters.

Duke

[Joe C.]

Re: 1960 Camshaft selection

You are correct. I tried the L-82 cam, the L-82 advanced 4 and 6 degrees, the L-79 and the L-79 advanced 6 and 4 degrees. I got only +7 HP on the dyno with the L-82 advanced 4 degrees. Not alot and I could have probably gotten that elsewhere --- easier than swapping cams over and over. I got alot more with the head work! My point is the head work, and 4 tube headers, is what got me most of the performance. It was in the inhaling and exhaling.

Steven,

I think you meant to say that you got more peak horsepower (but less average torque) with either cam installed "straight up", i.e.: retarded 4 degrees, since both are ground at 110/118 with 114 LSA.

[Steven B.]

Re: 1960 Camshaft selection

Duke, speaking of stroking, I have been looking for a stroker for a 355. I find alot of offshore made junk. Any recommendations for a quality crank at a reasonable price?

[Joe C.]

Re: 1960 Camshaft selection

I agree, but it will work even better with massaged heads, about 10.25:1 and four degrees retard. Even better is stroking it to 4.25 and six degrees retard! The longer the stroke the more overlap and later phasing the engine can effectively use (and the later the cam phasing the more detonation-free compression the engine can tolerate), so it's a lot easier to "overcam" a 3" stroke 283 than a stroker big block.

Regarding that 13.1/107 MPH 327, the massaged OE heads flow so well that power is still increasing at the 6300 RPM lifter pump-up speed. I've recommended the owner install a LT-1 cam, which will extend the power sweet spot to 7200 without a significant loss of low end torque.

Small blocks with really good reworked OE heads need the extended rev range of a mechanical lifter cam because they will pull usable power well beyond the valvetrain limiting speed of hydraulic lifters.

Duke

Well.............here we go again with that infamous LT1 cam!
I agree that the LT1 will take full advantage of the efficiency of his heads, and we have the numbers to prove it. I don't agree that the LT1 wouldn't noticeably reduce low end torque, though. The 346 cam would further reduce low end torque over the LT1, with a slight increase in peak power at a slightly higher rev point. As we know, the gentleman in question prefers a hydraulic camshaft. Considering that constraint, you gotta admit that he made the right camshaft choice, and his engine build was VERY well engineered/machined/assembled.
I'll be interested in hearing how he fares in his effort to get more pump-up free revs out of that hydraulic bumpstick!
Next season, we'll get to see how a well prepped L76 stacks up. Stay tuned.

Joe

[Duke W.]

Re: 1960 Camshaft selection

No, I don't have any specific recommendations. I'm not a fan of stroking small blocks because of the bearing size issues. Remember that engines of otherwise identical configuration, but different stroke will make the about the same peak power at about the same mean piston speed, so my preference for SBs is to make a high rev screamer, which requires a mechanical lifter camshaft.

In the case of big blocks stroking a 427 to 454 is just a matter of installing an OE 454 crank and appropriate compression height pistons - no grinding down the crankshaft journals (and resultant loss of crankshaft stiffness due to less journal overlap) to fit the main bearings.

You don't have to do that on the 350 block, but remember that OE 3.75" stroke SBs had larger (2.65") main bearings compared to 350s (2.45").

Regarding big block strokers, especially when you got to 4.25", even with the L-72 cam they will produce waaaaaay more torque than the chassis and tires can handle, but some owners like the fact that they can light up the tires at 3000 in third gear!

Duke

[Steven B.]

Re: 1960 Camshaft selection

Steven,

I think you meant to say that you got more peak horsepower (but less average torque) with either cam installed "straight up", i.e.: retarded 4 degrees, since both are ground at 110/118 with 114 LSA.

Yes, peak. With the soft tire height and the 3.90's giving about a 4.10 I used the mid and upper range on most courses. HP was about 390 and torque about 400. I still have some of the dyno sheets packed away.

[Duke W.]

Re: 1960 Camshaft selection

Steven,

I think you meant to say that you got more peak horsepower (but less average torque) with either cam installed "straight up", i.e.: retarded 4 degrees, since both are ground at 110/118 with 114 LSA.

You're confusing the issue with this ill-defined "straight up" hot rod lingo.

See my previous post on the POML indexing of the L-79 and L-46/82 cams.

Any discussion of "advance" or "retard" should be relative to the OE POML indexing, which is 110/118 for the L-79 cam and 114/114 for the L-46/82 cam. Effectively, the L-46/82 cam is an L-79 cam installed four degrees retarded from the OE L-79 indexing.

In hot hot lingo the OE L-79 indexing is considered four degrees advanced and the L-46/82 indexing is "staight up", but let's not go there.

Duke