L79 Camshaft (GM # 3853151); who makes what

[Duke W.]

Re: L79 Camshaft (GM # 3853151); who makes what

Let's set the record straight.

My original recommendation to Gary's question was to install a L-46 cam, advanced four degrees, in lieu of the L-79 cam for technical reasons that I explained in post #8.

As the discussion progressed I also mentioned that the LT-1 cam is an option for owners who want the extended rev range of a mechanical lifter cam. I know of at least one original L-79 that that was rebuilt to my "327 LT-1" configuration that earned a Top Flight, but it didn't go through a PV. Conversely, some owners want to replace the OE mechanical lifter cam with a hydraulic lifter cam that maintains the mechanical lifter cam's general characteristics including idle behavior. Though I discourage it, I have solutions if that's what the owner really wants.

The LT-1 cam is an OE SHP cam, NOT a hot rod cam. No hot rod cam available with duration in the ball park of the LT-1 has the mild dynamics and moderate overlap of the LT-1 cam. All have much more overlap and usually more aggressive dynamics that require much higher spring force.

The combination of long duration, moderate overlap, and mild dynamics is what allows the LT-1 cam along with massaged heads to produce road friendly 80 percent of peak torque at 2000 while making useable power to 7200 - all with the OE valve springs and OE valvetrain durability, and inexpensive aftermarket rods like the Eagle SIR5700 along with the OE forged crank will ensure cranktrain reliability at this level. No other cam that I am aware of will produce this torque and power bandwidth while maintaining OE appearance, including the OE exhaust manifolds.

If you don't like my recommendations and explanations, ignore my posts.

Duke

[Michael H.]

Re: L79 Camshaft (GM # 3853151); who makes what

Let's set the record straight.

My original recommendation to Gary's question was to install a L-46 cam, advanced four degrees, in lieu of the L-79 cam for technical reasons that I explained in post #8.

As the discussion progressed I also mentioned that the LT-1 cam is an option for owners who want the extended rev range of a mechanical lifter cam. I know of at least one original L-79 that that was rebuilt to my "327 LT-1" configuration that earned a Top Flight, but it didn't go through a PV. Conversely, some owners want to replace the OE mechanical lifter cam with a hydraulic lifter cam that maintains the mechanical lifter cam's general characteristics including idle behavior. Though I discourage it, I have solutions if that's what the owner really wants.

The LT-1 cam is an OE SHP cam, NOT a hot rod cam. No hot rod cam available with duration in the ball park of the LT-1 has the mild dynamics and moderate overlap of the LT-1 cam. All have much more overlap and usually more aggressive dynamics that require much higher spring force.

The combination of long duration, moderate overlap, and mild dynamics is what allows the LT-1 cam along with massaged heads to produce road friendly 80 percent of peak torque at 2000 while making useable power to 7200 - all with the OE valve springs and OE valvetrain durability, and inexpensive aftermarket rods like the Eagle SIR5700 along with the OE forged crank will ensure cranktrain reliability at this level. No other cam that I am aware of will produce this torque and power bandwidth while maintaining OE appearance, including the OE exhaust manifolds.

If you don't like my recommendations and explanations, ignore my posts.

Duke

The original poster didn't have any questions about what cam to use. He made it quite clear that he wanted a correct L79 cam. See post #1. No one ever asked about modifying the engine with a different cam.

Recommending something different is like telling someone that you "recommend" he buy a yellow Corvette instead of the red one that he wants.

It's all about what an old Corvette looks like, drives like and sounds like. That's what most people are here for. There are other hot rod sites that recommend different cams and 17" wheels for 60's cars.

I'll never quite understand what you get out of this.

[Joe L.]

Re: L79 Camshaft (GM # 3853151); who makes what

The original poster didn't have any questions about what cam to use. He made it quite clear that he wanted a correct L79 cam.

Michael------


Not exactly. Gary asked two questions. First, if anyone knew of an L-79 camshaft that was 100% USA manufactured. Second, he asked if anyone knew of an hydraulic roller cam equivalent to the L-79 camshaft. This second question probably opened the door to other discussion.

Actually, I don't know of an available hydraulic roller camshaft that's equivalent to the L-79. However, there may be one out there by now as lots of retrofit hydraulic roller grinds have been added since I shopped for one. If not, though, most of the major cam grinders offer custom grinding to just about any specification you want---I suppose the wonders of CNC machining. If I were building an L-79 and I wanted to maintain L-79 characteristics and I could obtain an hydraulic roller camshaft with equivalent L-79 characteristics, I'd use that hydraulic roller without a moments hesitation regardless of what it cost. I don't think that Duke would, though.

[Joe L.]

Re: L79 Camshaft (GM # 3853151); who makes what

Yes but all those mentioned are attempts to save the original parts and mimic original configuration . Adding a solid lifter cam to a L79 is not in the spirit of restoration. It would be a deliberate modification. No different than the so called "hot rod" camshaft.

Joe, the post was in complement to Mike Hanson indicating the replied postings to the OP are the same over and over again.

Gene-----

So, modification in the interests of restoration is OK? I totally agree. I also agree that changing a camshaft profile is a modification that's different from a modification in the interests of restoration. However, it's only a matter of degree. I'll bet there are LOTS of Top Flight cars out there that have non-original camshafts, even ones that can be, as some claim, detected during judging.

A few examples of modifications that folks often make that are not necessary in the interests of restoration:

1) All 1966-82 Corvette small blocks used a camshaft sprocket that was aluminum with nylon teeth. NONE used a cast iron sprocket. I wonder how many folks rebuild a 1966-82 small block with a nylon-tooth sprocket even though they are available if one seeks them out? The noise characteristics of a nylon sprocket versus a cast iron sprocket are slightly different (that's why GM used the nylon sprocket---to reduce noise). Perhaps someone with a "highly tuned "ear (maybe the guys that can distinguish between an L-79 and L-46 camshaft) could discern the difference?

2) ALL 1965-74 Corvette big blocks were originally equipped with an aluminum and nylon camshaft sprocket----ALL including L-88. Those sprockets are still available. In fact, the L-36, L-68, LS-5, and LS-4 sprocket is still available from GM (GM #330814). I wonder how many restored Corvette big blocks even have an original style timing set, let alone one including a nylon-toothed gear? I can assure you that absolutely none that I would build would have the original style.

3) ALL 1955-61 Corvette small blocks were equipped with conventional cast aluminum pistons. ALL 250 and 300 HP 1963-70 Corvette engines were, too. ALL L-36, L-68, LS-5, and LS-4 big blocks were also originally equipped with conventional cast aluminum pistons. Such pistons are still available today, although not from GM. I wonder how many of the heretofore referenced engines are restored with conventional cast aluminum pistons and not, at least, hypereutectic cast aluminum pistons which weren't even invented when the cars were new? I can assure you that I'd NEVER, EVER rebuild an engine with conventional cast pistons.

4) All original Corvette engines except those with aluminum heads (i.e. L-89, L-88, ZL-1, and LS-6) were equipped with steel shim type head gaskets. I wonder how many restored Corvette engines are similarly equipped? I'm sure it's more than those equipped with nylon toothed cam sprockets and conventional cast pistons because this change can be detected. However, if one decides to use shim type gaskets be sure the head and block surfaces are PERFECT (might require "decking" the block).

[Duke W.]

Re: L79 Camshaft (GM # 3853151); who makes what

I don't understand all the pushback I get on my engine configuration recommendations although it seems to be limited to less than a handful of people. All, with one exception, are designed to maintain the original engine's general characteristics, including idle behavior and original appearance. (The one exception is installing a LT-1 cam in an original L-79. I think PV might be a problem due to idle characteristics, but it's the owner's choice based upon their individual objectives. It won't be an issue in Flight judging and many owners stop there and don't go for a PV.)

The difference is that they make more top end power and extend the useable rev range beyond the original redline while maintaining equal or better than OE durability. This can't be detected in Flight judging or a PV, but I caution owners not to try to "impress" the PV judge by revving a Special 300 HP engine to over 6000 or a mechanical lifter engine to 7000. The book says 90 percent of tachometer redline. That's all you need for PV.

For sure we do a lot of "under the covers" improvements as part of the restoration process, some for durability and some for improved performance.

There have been a number of discussions over the years about how to make single stage enamel or BC/CC appear to look like lacquer. IMO this is very difficult to pull off, though there may be a handful of experienced painters around the country that can do it or come close.

I don't recall anyone ever throwing a hissy fit over this "non-original" restoration procedure even though it's usually easy to detect.

Duke

[Gene M.]

Re: L79 Camshaft (GM # 3853151); who makes what

Gene-----

So, modification in the interests of restoration is OK? I totally agree. I also agree that changing a camshaft profile is a modification that's different from a modification in the interests of restoration. However, it's only a matter of degree. I'll bet there are LOTS of Top Flight cars out there that have non-original camshafts, even ones that can be, as some claim, detected during judging.

A few examples of modifications that folks often make that are not necessary in the interests of restoration:

1) All 1966-82 Corvette small blocks used a camshaft sprocket that was aluminum with nylon teeth. NONE used a cast iron sprocket. I wonder how many folks rebuild a 1966-82 small block with a nylon-tooth sprocket even though they are available if one seeks them out? The noise characteristics of a nylon sprocket versus a cast iron sprocket are slightly different (that's why GM used the nylon sprocket---to reduce noise). Perhaps someone with a "highly tuned "ear (maybe the guys that can distinguish between an L-79 and L-46 camshaft) could discern the difference?

2) ALL 1965-74 Corvette big blocks were originally equipped with an aluminum and nylon camshaft sprocket----ALL including L-88. Those sprockets are still available. In fact, the L-36, L-68, LS-5, and LS-4 sprocket is still available from GM (GM #330814). I wonder how many restored Corvette big blocks even have an original style timing set, let alone one including a nylon-toothed gear? I can assure you that absolutely none that I would build would have the original style.

3) ALL 1955-61 Corvette small blocks were equipped with conventional cast aluminum pistons. ALL 250 and 300 HP 1963-70 Corvette engines were, too. ALL L-36, L-68, LS-5, and LS-4 big blocks were also originally equipped with conventional cast aluminum pistons. Such pistons are still available today, although not from GM. I wonder how many of the heretofore referenced engines are restored with conventional cast aluminum pistons and not, at least, hypereutectic cast aluminum pistons which weren't even invented when the cars were new? I can assure you that I'd NEVER, EVER rebuild an engine with conventional cast pistons.

4) All original Corvette engines except those with aluminum heads (i.e. L-89, L-88, ZL-1, and LS-6) were equipped with steel shim type head gaskets. I wonder how many restored Corvette engines are similarly equipped? I'm sure it's more than those equipped with nylon toothed cam sprockets and conventional cast pistons because this change can be detected. However, if one decides to use shim type gaskets be sure the head and block surfaces are PERFECT (might require "decking" the block).

Joe,
Timing chain material and type is getting pretty picky. I can't see the difference in piston material or if its forged. But I can tell you it is very difficult to obtain a set of L79 configuration pistons that mimic the originals with out performance enhancement. Hyperscopic require different wall clearance. Most don't know that. Who cares? But It is not a DELIBERATE change to configuration and performance enhancement as a camshaft change. The steel head gasket thing I deduct for if not correct. That is not a good example for your case. Same for intake gasket configuration. Why not use something more obvious such as clear coated paint jobs. This is not in the theme of restoration.

This all started when Mike Hanson voiced the opinion that "someone" always stipulates a camshaft deviation from original configuration and it's always the same old spiel. I happen to agree with Mike.

[Timothy B.]

Re: L79 Camshaft (GM # 3853151); who makes what

I think it's a healthy debate but the responsibility falls on the owner to be informed about what their goals are for the car. If they install a non production camshaft and don't like the way it runs it's there problem because they made the decision.

I personally would keep the original camshaft with the original engine configuration but that's just how I am. That's not to say I disagree with Duke, that LT-1 camshaft is sweet and I get what he is saying. Both Duke and Michael have so much to offer here, after all this is a technical discussion board.

[Duke W.]

Re: L79 Camshaft (GM # 3853151); who makes what

Gary's original question regarded replacement of a L-79 cam including asking if an "equivalent" roller cam was available.

My primary answer is in post #8.

As the discussion expanded I also offered the option of a LT-1 cam if the owner is looking for greater power and more revs. I also recommended the inexpensive truck timing chain as an alternate to the current replacement silent chain. My God, what nerve I have to recommend a truck part in a Corvette engine.

I don't "dictate" what camshaft an owner should install, but in the projects I've consulted on I extensively query the owner so that both he and I thoroughly understand his objectives. Then I offer the options that I think will best meet his objectives including thorough discussion of any tradeoffs involved. The ultimate choice of final engine configuration is the owner's and the owner's, alone.

The only alternate camshaft recommendation I have that might result in a PV issue is a LT-1 cam in a L-79. I think most PV judges would question the idle behavior, so I recommend not installing a LT-1 cam in an L-79 if the owner has the objective of a Duntov Award, however, the L-46 camshaft, advanced four degrees in a L-79 has the benefits stated in post #8, but is absolutely, positively indistinguishable from the OE L-79 camshaft in Flight or PV judging. The same can be said of the McCagh Special cam in place of the OE base engine cam.

I'm currently working with a TDB contributor on a large displacement small block that will look like the original small displacement engine. This is right down my line. The car is fairly original, but I'm not sure if he plans on any judging. He wants something that's a lot of fun to drive and likes the idea of a stock appearing small displacement small block that performs like a big block. So do I!

I better not say any more because the restoration police are watching.

Duke

[Joe L.]

Re: L79 Camshaft (GM # 3853151); who makes what

Joe,
Timing chain material and type is getting pretty picky. I can't see the difference in piston material or if its forged. But I can tell you it is very difficult to obtain a set of L79 configuration pistons that mimic the originals with out performance enhancement. Hyperscopic require different wall clearance. Most don't know that. Who cares? But It is not a DELIBERATE change to configuration and performance enhancement as a camshaft change. The steel head gasket thing I deduct for if not correct. That is not a good example for your case. Same for intake gasket configuration. Why not use something more obvious such as clear coated paint jobs. This is not in the theme of restoration.

This all started when Mike Hanson voiced the opinion that "someone" always stipulates a camshaft deviation from original configuration and it's always the same old spiel. I happen to agree with Mike.

Gene------


Yes, it is very picky but, from what I understand, there are many things that are judged that are quite picky, too. The difference is these things can be seen and timing sprockets and pistons cannot be seen. I'm quite sure if they could be seen, they'd be judged. Of course, camshafts can't be seen, either. Unless they radically depart from the original configuration or there are other unique differences (e.g. caused by valve lash differences between the L-76/L-84 camshaft and the LT-1), I don't think they can be discerned. A roller cam of the same characteristics as a flat tappet cannot be discerned.

I agree that that there is a difference between a change in camshaft and a change in, for example, a cam sprocket or piston material. However, the change in the latter cases is quite deliberate. The restorer knows (or should know) that a cast iron cam sprocket or hypereutectic pistons are not what was originally used. And, as I mentioned, original-type cam sprockets and pistons are available. The real difference is that these things cannot be seen. But, to someone religiously committed to accurate restoration, it should not matter----seen or unseen it should be as close to original as possible. As I mentioned previously, I'm quite sure that if the cam sprocket could be seen, there would be a deduction.

By the way, with hypereutectic pistons the wall clearance is about the same as conventional cast. The big difference is the top ring END GAP. That's the critical difference. Get that wrong and it can come back to bite in a big way.

[Harry S.]

Re: L79 Camshaft (GM # 3853151); who makes what

Hopefully this does not detract from the original question.

Back in 1999 I purchased a cam from GM to redo my 63 250 hp car. There was a good deal of Edelbrock equipment on the engine.

Anyway, I putchased PN 12353929 Grind 12364050 according to the paperwork. On the end of the cam is 760 862240 with a date of 11 - 25 - 99. Between the lobes is 1539 CWC C8 and E8. Several years ago Joe Lucia helped figure out from the paperwork that is was the 3863151 clone made by Crane.

It lasted in the car about 1000 miles as it would not perform properly with all the other 250 hp gear (heads, carb, headers, etc)


Do the numbers on the cam itself reveal a 3863151 cam.

[Duke W.]

Re: L79 Camshaft (GM # 3853151); who makes what

From my 2006 GMPP catalog, 12364050 is a "kit" of an equivalent 3863151 (L-79) camshaft (built to the GM print) with pin and 16 hydraulic lifters. I'm sure this same part number was listed in the catalog that was current when you made the purchase. The 12364051 is a kit that includes an equivalent 3896929 ("300 HP") cam/pin and sixteen lifters. I have no information on part number 12353929.

The ...929 cam was not actually original to the '63 250/300 HP engines. It replaced an earlier design that dated to 1957. The ...929 went into production in the 1966 time frame and was used in millions of small block passenger car and truck engines for the next 15 years. It's also used for rebuilds of base engines and optional engines that used the base engine cam.

According to some, this is sacrilege because it is not the EXACT OE camshaft, even though its idle behavior and general operating characteristics are identical and indistiguishable to the old '57 design. The ...929 is just easier on the valve train - what I call engineering progress.

Even if you could find the old design I would not recommend it because of the harsh dynamics. Using a...929 in a 'pre-'67 base engine or optional engine that had the base engine camshaft is analogous to installing a L-46 cam, advanced four degrees, instead of the L-79 cam in a L-79. The only way you could tell would be to remove the cam and inspect/decode the cast and stamped data or analyze it on a Cam Doctor machine.

Neither of these camshafts was (is) available separately from GMPP, only as the kit with the 16 lifters. I don't have the lastest GMPP catalog, so I don't know if these two kits are still available.

Most, if not all of the vintage cams that are listed in the GMPP catalogs were manufactured by Crane for GM, and were ground from the one available blank for Gen I flat tappet cams that is supplied by the CWC division of Textron. That's why the blank has "CWC" embedded in the casting. All of the hundreds of different design, commercially available SB flat tappet cams that are offered today regardless of brand or manufacturer are ground from this same cast iron blank!

A GM manufactured ...151 cam has the finished camshaft part number 3863152 embedded in the casting. Likewise 3896930 for the 300 HP cam. The ...151/929 numbers are assemblies of finished cam and indexing pin, which is the only way cams were sold through GMPD. The ...152/930 numbers are the GM drawing numbers for the finished camshaft, less pin. Referring to these as "casting numbers" is a misnomer.

I don't know if Crane still supplies these parts for GM, but whether you buy a FM or Dana OE equivalent or go with the GMPP kit, you can be assured that whatever the data stamped or cast into the cam, it is built to the 3863152 or 3896930 blueprint - unless there was a packaging error.

I don't see why a L-79 cam wouldn't work with a 327/250, but I wouldn't recommend it. The loss of low end torque would not be offset by much improvement in top end power due to the small port heads. It should be reasonably driveable, but not very exciting.

The 327/250 IMO was always an old ball. Why offer a base 327 that has high compression and requires premium fuel with was were essentially 283 heads, inlet manifold, and carburetor. I don't see how it was significantly cheaper to manufacture than the 327/300. My only guess is that it was a marketing ploy - most customers would probably pay the extra 50 bucks for 50 more horsepower, which probably went straight to the bottom line. The 327/250 has limited potential for improved performance. It's very torquey, but if you need more top end power... I'm not surprised it was eventually replaced as the base engine with 327/300.

It's not clear from you post which cam kit you actually intended to buy, but I'm sure the information you needed to choose was in the GMPP catalog that was current when you bought the goods.

Duke

[Joe L.]

Re: L79 Camshaft (GM # 3853151); who makes what

From my 2006 GMPP catalog, 12364050 is a "kit" of an equivalent 3863151 (L-79) camshaft (built to the GM print) with pin and 16 hydraulic lifters. I'm sure this same part number was listed in the catalog that was current when you made the purchase. The 12364051 is a kit that includes an equivalent 3896929 ("300 HP") cam/pin and sixteen lifters. I have no information on part number 12353929.

The ...929 cam was not actually original to the '63 250/300 HP engines. It replaced an earlier design that dated to 1957. The ...929 went into production in the 1966 time frame and was used in millions of small block passenger car and truck engines for the next 15 years. It's also used for rebuilds of base engines and optional engines that used the base engine cam.

According to some, this is sacrilege because it is not the EXACT OE camshaft, even though its idle behavior and general operating characteristics are identical and indistiguishable to the old '57 design. The ...929 is just easier on the valve train - what I call engineering progress.

Even if you could find the old design I would not recommend it because of the harsh dynamics. Using a...929 in a 'pre-'67 base engine or optional engine that had the base engine camshaft is analogous to installing a L-46 cam, advanced four degrees, instead of the L-79 cam in a L-79. The only way you could tell would be to remove the cam and inspect/decode the cast and stamped data or analyze it on a Cam Doctor machine.

Neither of these camshafts was (is) available separately from GMPP, only as the kit with the 16 lifters. I don't have the lastest GMPP catalog, so I don't know if these two kits are still available.

Most, if not all of the vintage cams that are listed in the GMPP catalogs were manufactured by Crane for GM, and were ground from the one available blank for Gen I flat tappet cams that is supplied by the CWC division of Textron. That's why the blank has "CWC" embedded in the casting. All of the hundreds of different design, commercially available SB flat tappet cams that are offered today regardless of brand or manufacturer are ground from this same cast iron blank!

A GM manufactured ...151 cam has the finished camshaft part number 3863152 embedded in the casting. Likewise 3896930 for the 300 HP cam. The ...151/929 numbers are assemblies of finished cam and indexing pin, which is the only way cams were sold through GMPD. The ...152/930 numbers are the GM drawing numbers for the finished camshaft, less pin. Referring to these as "casting numbers" is a misnomer.

I don't know if Crane still supplies these parts for GM, but whether you buy a FM or Dana OE equivalent or go with the GMPP kit, you can be assured that whatever the data stamped or cast into the cam, it is built to the 3863152 or 3896930 blueprint - unless there was a packaging error.

I don't see why a L-79 cam wouldn't work with a 327/250, but I wouldn't recommend it. The loss of low end torque would not be offset by much improvement in top end power due to the small port heads. It should be reasonably driveable, but not very exciting.

The 327/250 IMO was always an old ball. Why offer a base 327 that has high compression and requires premium fuel with was were essentially 283 heads, inlet manifold, and carburetor. I don't see how it was significantly cheaper to manufacture than the 327/300. My only guess is that it was a marketing ploy - most customers would probably pay the extra 50 bucks for 50 more horsepower, which probably went straight to the bottom line. The 327/250 has limited potential for improved performance. It's very torquey, but if you need more top end power... I'm not surprised it was eventually replaced as the base engine with 327/300.

It's not clear from you post which cam kit you actually intended to buy, but I'm sure the information you needed to choose was in the GMPP catalog that was current when you bought the goods.

Duke

Duke-------

None of the Crane-manufactured kits which included reproductions of original GM cams + lifters are currently available from GM and have not been for quite some time. When Crane went out of business, that ended and when they went back in business, it did not get "resurrected". Just what Crane actually manufactures today, I do not know. I do know that their current facility in Daytona Beach is FAR, FAR smaller than the old facility in Daytona Beach. It appears to me that the current facility is not much more than office and warehouse, and a pretty small warehouse, at that. Of course, their products may be manufactured at an S&S (the current Crane owner) manufacturing facility elsewhere.

Any number that is an integral part of a casting is a "casting number" or "part number for a casting". It may also be a finished part number. For example, the left side rear bearing support for 1963-74 Corvettes was GM #3820643. This was BOTH the part number for the casting AND the part number of the finish-machined and released left side bearing support. The right side had the same "part number for the the casting" but the finish-machined and released bearing support was GM part number 3820644.

In the case of the camshafts, the part number seen between the lobes is both the part number for the casting and the part number for the camshaft. However, it is not a part number for a finished and released camshaft because such a part was never released to PRODUCTION or SERVICE. Only the camshaft ASSEMBLY was released to PRODUCTION and SERVICE, so the part number for the camshaft alone is just a COMPONENT of an assembly.

While camshafts are used in PRODUCTION and also available in SERVICE, GM used the specific camshaft cores, generally produced in GM foundries, to manufacture the finished camshaft assemblies. However, after PRODUCTION use ended, with resultant drastic reduction in demand, GM often utilized generic camshaft cores as you describe. However, when these are seen that does not necessarily mean that the camshafts are "outsourced". The Flint engine plant manufactured SERVICE camshafts right up until the time they closed but they were made from generic CWC/Textron cores. Obviously, the ones available today for Gen I and II small blocks are not made at Flint. However, they may be manufactured at Toluca, Mexico or Bay City, Michigan. Or, they may be outsourced. I don't know.

[Harry S.]

Re: L79 Camshaft (GM # 3853151); who makes what

Duke, thanks.

What I thought I ordered and purchased was the 12364051 kit that included an equivalent 3896929 ("300 HP") cam/pin and sixteen lifters. Anyway, that is what is in there now and it runs just fine.

[Joe L.]

Re: L79 Camshaft (GM # 3853151); who makes what

Duke, thanks.

What I thought I ordered and purchased was the 12364051 kit that included an equivalent 3896929 ("300 HP") cam/pin and sixteen lifters. Anyway, that is what is in there now and it runs just fine.

Harry------


The GM #12364051 kit did, indeed, contain a Crane-manufactured reproduction of the GM #3896929 camshaft ("300 HP") + a set of Crane hydraulic lifters. I do not know what part numbers, if any, were assigned to the components of the kit as they were never available separately.

[Gene M.]

Re: L79 Camshaft (GM # 3853151); who makes what

Gene------


Yes, it is very picky but, from what I understand, there are many things that are judged that are quite picky, too. The difference is these things can be seen and timing sprockets and pistons cannot be seen. I'm quite sure if they could be seen, they'd be judged. Of course, camshafts can't be seen, either. Unless they radically depart from the original configuration or there are other unique differences (e.g. caused by valve lash differences between the L-76/L-84 camshaft and the LT-1), I don't think they can be discerned. A roller cam of the same characteristics as a flat tappet cannot be discerned.

I agree that that there is a difference between a change in camshaft and a change in, for example, a cam sprocket or piston material. However, the change in the latter cases is quite deliberate. The restorer knows (or should know) that a cast iron cam sprocket or hypereutectic pistons are not what was originally used. And, as I mentioned, original-type cam sprockets and pistons are available. The real difference is that these things cannot be seen. But, to someone religiously committed to accurate restoration, it should not matter----seen or unseen it should be as close to original as possible. As I mentioned previously, I'm quite sure that if the cam sprocket could be seen, there would be a deduction.

By the way, with hypereutectic pistons the wall clearance is about the same as conventional cast. The big difference is the top ring END GAP. That's the critical difference. Get that wrong and it can come back to bite in a big way.

Joe,
Just as a piece of information to anyone replacing L79 pistons. The forge L79 piston configuration is difficult to obtain even in standard over size. Even the engine shop in our area was only able to come up with configurations of bigger and smaller L79 dome sizes in forged style. But there were several L79 in hypereutectic pistons. A good alternative to the original forged for the average person. No enhancement here. There is also weight difference. But understand, make no mistake the wall clearance in definitely different from hypereutectic pistons vs forged pistons.

I could care less what timing chain one uses. (That timing chain thing really weakens your argument). There is no change in the way the Corvette performs as there would be by changing a stock hydraulic L79 cam to a solid lifter LT1 camshaft. The tappet noise alone is major. No you can't see the timing chain, but you sure as hell can hear and feel the performance of a solid lifter LT1 cam shaft installed in what was a hydraulic lifter engine.