1960 Camshaft selection

[Steven B.]

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

Thanks Duke! I have a 292 "270"+ HP and love that 097!

[Joe C.]

Re: 1960 Camshaft selection

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

Duke, I wasn't confusing OE POML indexing. I was of the impression that the L46/L82 camshaft is (essentially-222/222 and .450/.460 versus 221/221 and .447/.447). However, in addition to these differences, the L46/L82 cam is indexed 4 degrees retarded relative to a L79 camshaft, using 114/114 rather than 110/118 centers. The LSA for both is 114 degrees.
I find the "hot rod" lingo very confusing, and only used the vernacular term "straight-up" for the benefit of those who prefer to use it. You did notice, though, that I qualified the "straight-up" terminology with "4 degrees retarded" in the case of the L79 (but not the L82/L46, since it is ground on 110/118 lobe centers).
I prefer to use my own terminology of "mark-to-mark on the sprockets", which clearly means "installed as ground, using as ground lobe centers". All of the "vintage reproduction" camshafts are ground using OE POML indexing.

[Duke W.]

Re: 1960 Camshaft selection

You did notice, though, that I qualified the "straight-up" terminology with "4 degrees retarded" in the case of the L79 (but not the L82/L46, since it is ground on 110/118 lobe centers).
I prefer to use my own terminology of "mark-to-mark on the sprockets", which clearly means "installed as ground, using as ground lobe centers". All of the "vintage reproduction" camshafts are ground using OE POML indexing.

See, you are confused. In hot rod lingo the L-79 cam (110/118) is considered "ground four degrees advanced" and the L-46/82 cam (114/114) is "ground straight up."

Duke

[Thomas H.]

Re: 1960 Camshaft selection

Wow.......

Ok, let's make this simple-er.

Who makes a cam that would be an equivalent replacement for the factory cam in a 1960 283 230hp?

Thanks,

Tom

[Thomas H.]

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

Duke,

Thanks for the detailed reply.

I am familiar with the gains to be had by a well prepped cylinder head. I raced a big block Camaro for years and did all of my own engine work. I enjoyed cc'ing heads, measuring deck height and selecting head gaskets to try and meet my CR goals. I work as an engineering manager so I understand the engineering required to achieve a desired result.

Unfourtunately the engine in question is not mine, although I do have some input as to what should be done in order to have a well built, reliable engine installed back into the car.

I suppose I was hoping for a quick "been there, done that, use these parts" answer since my experience is with big blocks and there are many here with vast experience in small block configurations and know what works and what doesn't, especially for the 283 in question.

I think I will start by recommending the replacement parts that would be equivalent to the parts installed at the factory. I will then do some research on a cam (looking into some that were mentioned in other posts in this thread) that would provide a bit more power and recommend the appropriate cylinder head massaging and CR (based on measurements) be used. This way he has a few options on how he wants to proceed.

As for the actual engine builder, he is nowhere near 40, probably closer to 70. He comes well recommended by several people we know in both the racing and restoration world. He has scaled back his operation over the years, but is willing to take on this project since he has an affinity for C1 corvettes.

I will suggest that they cc the heads and try to get the deck height measured, but that may be a problem since the lower half is seized. If I can at least get the chamber volume, that will help. I have the original head gaskets so they can be measured.

We'll see where this goes over the next few months. Should be interesting!

Thanks for the reply. I always learn something from your posts and appreciate your "enthusiasm" for the engineering that should go into engine rebuilds.

[Duke W.]

Re: 1960 Camshaft selection

http://www.napaonline.com/NOLPPSE/(S...)/Welcome.aspx

Use the interchange for either of the two part numbers I previously posted. This Web page is a good resource for obtaining the Sealed Power replacement part number for any OE part.

Several of us with old P&A catalogs can usually be counted on to provide an OE GM part number whenever one is needed.

You can also type in the make/model/year from the napaonline.com home page to find the Sealed Power OE replacement part for virtually any OE engine part.

Duke

[Thomas H.]

Re: 1960 Camshaft selection

I'm on it!

Thanks,

Tom