Help with camshaft selection for 350 SB

[Duke W.]

Re: Help with camshaft selection for 350 SB

Guys,

I have heard of way too many cam lobes wiping out in the break in for me to be confident putting one in my engine.

Mike

Mike

What you say is true, but those are aftermarket flat tappet cams with aggressive profiles that require much higher spring force than OE. The name Comp Cams comes to mind, especially the XE series. I have consulted with dozens of vintage Corvette owners on engine restoration, and I don't recall any who ever experienced any cam problems IF they followed my advice to use a Federal Mogul manufactured OE replacement cam, OE replacement valve springs, and CJ-4 oil.

If anyone looking at this thread with a F-M OE replacement cam using OE equivalent replacement valve springs has ever had a wiped lobe problem or knows some who has please chime in. And remember, only a F-M manufactured OE replacement cam and OE equivalent valve springs. Aftermarket cams with gorilla valve springs don't count.

Don't drink the Kool-Aid, Mike.

Duke

[Joe L.]

Re: Help with camshaft selection for 350 SB

What you say is true, but those are aftermarket cams with aggressive profiles that require much higher spring force than OE. The name Comp Cams comes to mind. I have consulted with dozens of vintage Corvette owners on engine restoration, and I don't recall any who ever experienced any cam problems IF they followed my advice to use a Federal Mogul manufactured OE replacement cam, OE replacement valve springs, and CJ-4 oil.

If anyone looking at this thread with a F-M OE replacement cam using OE equivalent replacement valve springs has ever had a wiped lobe problem or knows some who has please chime in. And remember, only a F-M manufactured OE replacement cam and OE equivalent valve springs. Aftermarket cams with gorilla valve springs don't count.

Don't drink the Kool-Aid, Mike.

Duke

Duke------


I've heard of the cam failure problem a lot in the last 2 or 3 years. In every instance I'm aware of it did not involve wild cams or high valve spring pressures. Usually, it involved stock-type engines. In fact, I think a few have been reported on this board. Also, folks used either diesel-rated engine oils or GM EOS or both.

Also, keep in mind that when a cam fails like this, it's not just a matter of pulling it and installing another cam. All of the ground up metal particles that were once part of the cam lobe(s) and/or lifter(s) have to be considered. To recover from such a disaster, if one is to do it right, one needs to completely disassemble the engine and clean and inspect everything. Just like doing the engine rebuild all over again.

Why are cams and lifters failing? In my opinion, the quality of flat tappet cams and lifters (and, especially lifters) just is not there anymore.

[Jim D.]

Re: Help with camshaft selection for 350 SB

Duke------


I've heard of the cam failure problem a lot in the last 2 or 3 years. In every instance I'm aware of it did not involve wild cams or high valve spring pressures. Usually, it involved stock-type engines. In fact, I think a few have been reported on this board. Also, folks used either diesel-rated engine oils or GM EOS or both.

That is the opposite of my experience and the many others I know in "the business". As I previously posted, I have NEVER had a flat tappet cam go flat and nobody I know has either. I think it's another "internet phenomenon". I ask - have you ever had one go flat on you?

[Duke W.]

Re: Help with camshaft selection for 350 SB

Duke------


I've heard of the cam failure problem a lot in the last 2 or 3 years. In every instance I'm aware of it did not involve wild cams or high valve spring pressures. Usually, it involved stock-type engines. In fact, I think a few have been reported on this board. Also, folks used either diesel-rated engine oils or GM EOS or both.

The trouble is that without knowing all the details, like manufacturer/part number of the cam and valve springs, it's not what could be called "actionable intelligence".

Duke

[Joe L.]

Re: Help with camshaft selection for 350 SB

That is the opposite of my experience and the many others I know in "the business". As I previously posted, I have NEVER had a flat tappet cam go flat and nobody I know has either. I think it's another "internet phenomenon". I ask - have you ever had one go flat on you?

Jim-------


No, I have not. But, the last time I installed a flat tappet cam was about 35-40 years ago. Every one I have installed since has been hydraulic roller. Not being "in the business" I don't install cams too often. My information is based upon what others have told me and what I have read here-and-there. For many years I never heard of a flat tappet cam failure, either. However, in the last few years I've heard of quite a few whether what I've heard is accurate, or not. However, as I stated previously, in every instance the failure occurred during initial engine operation after a rebuild.

[Mark E.]

Re: Help with camshaft selection for 350 SB

I've got lots of NOS GM camshafts and NOS GM lifters, big block and small block [none for sale], but you'd never catch me using any on an engine of mine. Never.

Not selling them and not using them... why do you have them?

[Gene M.]

Re: Help with camshaft selection for 350 SB

Gene------

A roller cam enables the use of lobe profiles which cannot be used with a flat tappet lobe profile. That is one of the benefits of the use of a roller cam. Period. A flat tappet lifter cannot follow any lobe profile which could be imagined (and which might be beneficial). A roller lifter can follow a much wider range of profiles. Period. This is exactly the reason that mechanical roller camshafts and lifters have been used in racing applications for years. Hydraulic roller lifters bring the same sort of benefits for a street cam that being the ability to use lobe profiles that would not be possible with a flat tappet cam and lifters.

You need not describe the attributes of a roller cam to me. We are not building racing engines here. Bottom line there is no need for it in a vintage Chevrolet engine. The original flat tappet camshaft does all that is required with the cylinder head technology of a 50's & 60's engine. The exotic lobe profiles of a roller is not advantageous in these vintage cylinder head applications. And as for your NON personal experience of wiped out cam lobes, well that is just he said she said rubble.

[Patrick H.]

Re: Help with camshaft selection for 350 SB

Not selling them and not using them... why do you have them?

Because you can, why else?

[Joe L.]

Re: Help with camshaft selection for 350 SB

You need not describe the attributes of a roller cam to me. We are not building racing engines here. Bottom line there is no need for it in a vintage Chevrolet engine. The original flat tappet camshaft does all that is required with the cylinder head technology of a 50's & 60's engine. The exotic lobe profiles of a roller is not advantageous in these vintage cylinder head applications. And as for your NON personal experience of wiped out cam lobes, well that is just he said she said rubble.

Gene-------


GM, Ford, and Chrysler have been manufacturing OHV PRODUCTION engines for over 20 years now and not one of them has been a racing engine. However, all of them have been equipped with hydraulic roller cams (note: Ford did stop building most OHV engines quite some time ago). Do you suppose they did this because flat tappet cams work just as well? Do you suppose that they added much higher cost hydraulic roller cams and lifters virtually across the board because they wanted to spend more money on engines or for some minor benefit? Do you think they did it because automotive buyers, 99% of whom have no idea what cams or lifters are installed, pressured them into it?

Regarding your implication that roller cams are somehow linked to improved cylinder head technology, GM began using hydraulic roller cams in 1987. Cylinder head designs of that period were not substantially different than those of the 60's and 70's.

[Joe C.]

Re: Help with camshaft selection for 350 SB

Mike,
Joe L is 100% spot-on.......................power and torque are a function of how fast and how high the valves are lifted. I have experienced the effect of swapping in a roller cam with no other modifications done, and the torque/power increase is substantial, on the order of 20% using a pair of 2.02/1.6 double hump heads. The immediate effect is that with two cams of equal duration, the faster ramps of a roller lobe can be used to provide higher valve lift than a flat tappet cam of the same duration. That is one reason modern engines make so much power using small duration camshafts. The second reason is that they use higher ratio rocker arms, which increase valve lift but have no effect on duration.

The problem here is that it will be expensive since there are no valve springs suitable for a roller cam, including beehive springs which will fit within the stock spring pockets, so you'll need to have them opened up, as well as having the pushrod guides enlarged. You should also back cut both intake and exhaust valves. No need to forward cut the exhausts unless you plan on a lot of valve overlap.

Since you'll have to remove the heads for machining, IT WOULD BE WISE FOR YOU TO HAVE THE PORTS BLENDED INTO A "PERFORMANCE" MULTI ANGLE VALVE JOB. This modification will get the very best power increase from your fast action valves.

You'll also need a new distributor gear made of melonized iron to replace the original plain iron gear. This gear is available from GM, and was used on all 1st Gen smallblocks originally equipped with roller cams, beginning in 1987. If you don't do this, you will quickly wipe the distributor gear because some cam blanks are steel rather than iron. Milder hydraulic rollers, as well as some solid rollers are made of iron as well, but these are hardened and will destroy a stock, non-hardened iron distributor gear as well.

You'll also be wise to install a double roller timing chain, which requires clearancing of the block. Some people insist that it's necessary to install a cast aluminum timing cover to handle the froward thrust forces developed by a roller cam. I have never seen the need for this, as I always braise in a plate on the inside of a stock cover against which the cam button bears. You MUST set the cam end play with gasket installed on the timing cover. End play can vary, and .005" is a safe bet. It's also a good idea to use a Torrington bearing between the timing gear and the block.

[Gene M.]

Re: Help with camshaft selection for 350 SB

Gene-------


GM, Ford, and Chrysler have been manufacturing OHV PRODUCTION engines for over 20 years now and not one of them has been a racing engine. However, all of them have been equipped with hydraulic roller cams (note: Ford did stop building most OHV engines quite some time ago). Do you suppose they did this because flat tappet cams work just as well? Do you suppose that they added much higher cost hydraulic roller cams and lifters virtually across the board because they wanted to spend more money on engines or for some minor benefit? Do you think they did it because automotive buyers, 99% of whom have no idea what cams or lifters are installed, pressured them into it?

Regarding your implication that roller cams are somehow linked to improved cylinder head technology, GM began using hydraulic roller cams in 1987. Cylinder head designs of that period were not substantially different than those of the 60's and 70's.

Joe L,

Your last statement is total out to lunch. Joe C's post #25 points out a few of the requirements to retrofit a roller in vintage engine/head configurations. But be advised the 20% gain Joe speaks of is an aftermarket roller profile. I would bet he is using complementary valve train to work with it. Understand head and cam should be complementary match to function together. But as you pointed out in earlier post the original poster was not seeking more power. So stay on the same set of tracks, replacement or vintage application.

I don't care why, when and where GM did with roller cams in 1987 and afterwards. That is not the topic. Topic is vintage 350 Chevy engine camshaft.

As Joe C points out if one is seeking more power a roller profile (with all necessary up grades) is a good path to follow. But again reminder the original poster was not seeking that goal.

[Joe R.]

Re: Help with camshaft selection for 350 SB

What you say is true, but those are aftermarket flat tappet cams with aggressive profiles that require much higher spring force than OE. The name Comp Cams comes to mind, especially the XE series. I have consulted with dozens of vintage Corvette owners on engine restoration, and I don't recall any who ever experienced any cam problems IF they followed my advice to use a Federal Mogul manufactured OE replacement cam, OE replacement valve springs, and CJ-4 oil.

If anyone looking at this thread with a F-M OE replacement cam using OE equivalent replacement valve springs has ever had a wiped lobe problem or knows some who has please chime in. And remember, only a F-M manufactured OE replacement cam and OE equivalent valve springs. Aftermarket cams with gorilla valve springs don't count.

Don't drink the Kool-Aid, Mike.

Duke

[Joe C.]

Re: Help with camshaft selection for 350 SB

If the OP has no desire to increase torque and power, then I'd suggest that he retain a flat tappet camshaft, and use a mild "L48/L82" grind (3896962) from Speed Pro. I would have nobody but an older, experienced professional install it, break it in, and warrant it.

The new CK-4 motor oil on the horizon promises to deliver backward compatability for shear strength: i.e: equivalent protection against sliding friction between lobes and tappets.

[Joe L.]

Re: Help with camshaft selection for 350 SB

Joe L,

Your last statement is total out to lunch. Joe C's post #25 points out a few of the requirements to retrofit a roller in vintage engine/head configurations. But be advised the 20% gain Joe speaks of is an aftermarket roller profile. I would bet he is using complementary valve train to work with it. Understand head and cam should be complementary match to function together. But as you pointed out in earlier post the original poster was not seeking more power. So stay on the same set of tracks, replacement or vintage application.

I don't care why, when and where GM did with roller cams in 1987 and afterwards. That is not the topic. Topic is vintage 350 Chevy engine camshaft.

As Joe C points out if one is seeking more power a roller profile (with all necessary up grades) is a good path to follow. But again reminder the original poster was not seeking that goal.

Gene------

Joe is correct; if one uses certain hydraulic roller cams, then one does need to upgrade some other components of the valve train. However, one does not need to do this with ALL hydraulic roller cams. A cam with approximately the same characteristics as the original L-46/L-82 cam, GM #3896962, does not require upgrade of other elements of the valve train. While you ERRONEOUSLY imply that I'm referring to some sort of "wild" cam, I am CLEARLY not. I FULLY recognize the intentions of Michael and I've stated it in previous posts. Now, so that you can fully comprehend it, let me say this: I'm talking about and recommending an hydraulic roller cam with characteristics similar to the original 3896962. Period.

If one uses an hydraulic roller camshaft of the type that I'm suggesting, one does not need to upgrade other components of the valve train. For example, GM small blocks of the 1987-91 period with hydraulic roller cams used the exact same valve springs as the vast majority of other small blocks from 1967 to 1986, GM #3911068 (or Federal-Mogul VS-677). An hydraulic roller cam with characteristics similar to the 3896962 can use the same valve springs with no problem, at all. Period. If one wants a little more valve spring, one can use the 92-95 LT1 spring, GM #10206040 (Federal-Mogul VS-1662). This spring has a slightly larger OD than the 3911068 but it will fit in a stock spring pocket used for early heads. For even a little more valve spring, one can use GM #10134358 (my favorite small block valve spring). This valve spring will fit in stock spring pockets, too, and use stock retainers.

You may not care "why, when and where GM did with roller cams in 1987 and afterwards" but I do. I believe there's a lot to be learned from what GM did in later years and, to some degree, can be "exported" to earlier years. I also consider it HIGHLY RELEVANT to the discussion here.

In any event, if you wish to use and recommend original, flat tappet cams, please do. In most cases, I do not recommend them now and I'm not likely to recommend them in the future. I recommend and use hydraulic roller cams of the appropriate grind for the application.

[Gene M.]

Re: Help with camshaft selection for 350 SB

Gene------

Joe is correct; if one uses certain hydraulic roller cams, then one does need to upgrade some other components of the valve train. However, one does not need to do this with ALL hydraulic roller cams. A cam with approximately the same characteristics as the original L-46/L-82 cam, GM #3896962, does not require upgrade of other elements of the valve train. While you ERRONEOUSLY imply that I'm referring to some sort of "wild" cam, I am CLEARLY not. I FULLY recognize the intentions of Michael and I've stated it in previous posts. Now, so that you can fully comprehend it, let me say this: I'm talking about and recommending an hydraulic roller cam with characteristics similar to the original 3896962. Period.

If one uses an hydraulic roller camshaft of the type that I'm suggesting, one does not need to upgrade other components of the valve train. For example, GM small blocks of the 1987-91 period with hydraulic roller cams used the exact same valve springs as the vast majority of other small blocks from 1967 to 1986, GM #3911068 (or Federal-Mogul VS-677). An hydraulic roller cam with characteristics similar to the 3896962 can use the same valve springs with no problem, at all. Period. If one wants a little more valve spring, one can use the 92-95 LT1 spring, GM #10206040 (Federal-Mogul VS-1662). This spring has a slightly larger OD than the 3911068 but it will fit in a stock spring pocket used for early heads. For even a little more valve spring, one can use GM #10134358 (my favorite small block valve spring). This valve spring will fit in stock spring pockets, too, and use stock retainers.

You may not care "why, when and where GM did with roller cams in 1987 and afterwards" but I do. I believe there's a lot to be learned from what GM did in later years and, to some degree, can be "exported" to earlier years. I also consider it HIGHLY RELEVANT to the discussion here.

In any event, if you wish to use and recommend original, flat tappet cams, please do. In most cases, I do not recommend them now and I'm not likely to recommend them in the future. I recommend and use hydraulic roller cams of the appropriate grind for the application.

Joe L,

If one is not going to (performance wise) use a roller cam of extended power potential than your entire point going to a roller just has no reasoning other than to just have a roller. A flat tappet cam in the vintage situation is all one would need. A change for the sake of change is senseless. And by the way one does not just drop in a roller cam in a vintage block without proper changes.

Your HIGHLY RELEVANT and I quote " GM, Ford, and Chrysler have been manufacturing OHV PRODUCTION engines for over 20 years now and not one of them has been a racing engine. However, all of them have been equipped with hydraulic roller cams (note: Ford did stop building most OHV engines quite some time ago). Do you suppose they did this because flat tappet cams work just as well? Do you suppose that they added much higher cost hydraulic roller cams and lifters virtually across the board because they wanted to spend more money on engines or for some minor benefit? Do you think they did it because automotive buyers, 99% of whom have no idea what cams or lifters are installed, pressured them into it? "

No matter how you cut it says nothing justifying a roller in vintage engine that is not going to be use for performance application. Period. I'm not going to respond any further to you since there is no open minded reasoning to your stand.