Any cam as durable as the stock one?

[SinistrV6]

I've got to have a cam for my new motor and a roller cam is beyond my budget. I've searched the archivesa and seen some good and quite a bit of bad about most of the cams in use today. I don't want to tear this motor out again 10k miles from now (or 50k for that matter ) because of a cam failure. Can't anyone make a cam that's as durable as the stock ones? My other GN had 170k miles on the stocker and ran great. I've got a Postons 110T from the last build (not damaged, normal wear, but it was in the car when I bought it and I don't know the mileage) and a Comp Cams 218/218 that's coming (uninstalled) with my short block (used cam 15-16 passes at strip). I'm pretty sure the 218 is more cam than I want so I'll end up selling it and the Poston's 110T too probably.

Suggestions?

 

[SinistrV6]

TTT

TTT

 

[Intercooler]

Originally posted by SinistrV6
I've got to have a cam for my new motor and a roller cam is beyond my budget. I've searched the archivesa and seen some good and quite a bit of bad about most of the cams in use today. I don't want to tear this motor out again 10k miles from now (or 50k for that matter ) because of a cam failure. Can't anyone make a cam that's as durable as the stock ones? My other GN had 170k miles on the stocker and ran great. I've got a Postons 110T from the last build (not damaged, normal wear, but it was in the car when I bought it and I don't know the mileage) and a Comp Cams 218/218 that's coming (uninstalled) with my short block (used cam 15-16 passes at strip). I'm pretty sure the 218 is more cam than I want so I'll end up selling it and the Poston's 110T too probably.

Suggestions?

They are all ok if installed and broken in properly. Never had a problem yet. 50k miles? You will have it blown up to put a new one in it before that if you race it or beat it much

 

[SinistrV6]

Why such poor quality in aftermarket cams?

I hear you Intercooler and you may well be right. I'd just like it to be torn down by choice instead of part failure. I'm amazed that cams for these motors are so unreliable (compared to the stocker). Is the stock cam that much better quality or what? My car may go to the track 2x a year at best. Mostly street driven, so reliablility is definitely a consideration. With all of the mods my car has I feel like putting a stock cam back in there would be hamstringing the motor but if that's the only way to get reliability, I may have to do that!
C'mon guys. I've heard and read lots of horror stories of cam failures. ANYBODY had GOOD results from an aftermarket cam manufacturer??

 

[rastaz]

I think alot of cam failures are due to guys running too big a spring and/or breaking in their cams with too big a spring. Big springs put alot of pressure on the lobes and thus increase the chances of wiping one...

 

[Intercooler]

Re: Why such poor quality in aftermarket cams?

Originally posted by SinistrV6
I hear you Intercooler and you may well be right. I'd just like it to be torn down by choice instead of part failure. I'm amazed that cams for these motors are so unreliable (compared to the stocker). Is the stock cam that much better quality or what? My car may go to the track 2x a year at best. Mostly street driven, so reliablility is definitely a consideration. With all of the mods my car has I feel like putting a stock cam back in there would be hamstringing the motor but if that's the only way to get reliability, I may have to do that!
C'mon guys. I've heard and read lots of horror stories of cam failures. ANYBODY had GOOD results from an aftermarket cam manufacturer??

The added spring pressure wears the aftermarket cams out faster but I would think a decent installed cam will go until you need to freshen the motor anyways. FWIW most cams comes with a cam warranty if that means anything to you. Your choices are few since the stocker is gone. Don't go real big and you can keep the spring pressures down. May not give the best race results

 

[Steve Wood]

It is not necessarily the cam. If you pull the lifters out of their bores, you will notice that some bores are centered on the lobe, or very close to the center, rather than being offset to one side as is correct.

Cam lobes for flat tappet cams are normally ground with about 2 degs of taper across the face of the lobe. The bottom of the lifter is convex. When the lifter sits properly to the side of the lobe, this combination of lobe taper and the convex lifter bottom serve to create rotation in the lifter.

If the bore is centered on the lobe (as is common on #3 exhaust in particular), the lifter does not rotate properly and the lifter/lobe may fail quickly as the metal is scrubbed off by the rubbing action that is not offset by rotation.

Some blocks have a worse problem than others when it comes to proper lifter bore location with relationship to the cam.

Now, the factory cam has gentle lobes and soft springs. Between the two, the lifter has a better chance of rotation and the reduction in spring pressure does not grind the two pieces together as badly as some upgrades.

The LT1 springs that used to be suggested are about 20-25% stronger than the factory springs...they don't do the lobe/lifter any good..then the longer duration cams that we use generally have steeper ramps on the lobes and this increases the wiping pressure and can lead to lobe failure more quickly.

The Lunati cams currently sold by the GSCA are alleged to have a 4 deg taper on the lobe which is supposed to increase lifter rotation. This may help.

Using springs closer to the factory spec (like the CC980 without the factory cups) will probably make the problem better. Proper break in of the cam upon start up will certainly greatly reduce the potential of problems.

A properly hardened blank helps.

Some people have a dry film lubricant applied to the lobes prior to installation in order to improve break in risks....

You pays your money and you takes your chances...not getting carried away with spring pressures and a proper break in technique will certain improve your chances.

 

[Scott231]

Gotta hand it to you Steve, that was prolly the most well-laid out cam post I've seen in years.

Years ago on GTTYPE Ken Mosher reported on some research he did with cams. As I recall, there were only 3 cam blank manuafacturers (CWC being one, who also supplied the factory GM blanks). From those manufacturers, the cams go to "cam shops" for cutting (i.e. from the same blank, Comp cams can cut a 206/206 or a 218/212).

The lifter bore alignment problem has been well documented. David Chase found a company that identified this problem back in the late 80's, ordered several blocks from GM without drilled lifter bores, drilled the holes themselves and proved that the alignment problem was contributing to the cam wiping problem. However, the improper break-in and the excessive spring pressure/aggresive cam ramp speed matters cannot be resolved with proper lifter bore alignment.

In conclusion, using a flat-tappet camshaft is kind of a 50/50 deal as many blocks have the alignment problem, many don't. Proper break-in procedures, non-excessive spring pressures, and not-too-aggressive cam ramp speeds can't necessarily overcome improper lifter bore alignment, but as seen with 100% stock motors, they can allow the cam to last a long, long time.

Hope that helps!

 

[87SFI]

Roller

I had a couple of cam nightmares, but that was because I had a internal water leak. I'll never know how long those aftermarket flat tappets would last and after reading about other peoples nightmares it got me paranoid. So I decided to go roller, I know it's alot of money but it's like buying insurance and it puts your mind at ease while your driving your car and that's where it's worth it to me. From what I hear, you can't idle those aftermarket flat tappet cams very long, you have to keep the rpms going to keep it properly oiled. If you are that worried, bite the bullet and get the roller (not the budget ones) or take your gamble to pull your motor out again.
How much would it cost now?


Just my .02
George

 

[SinistrV6]

Excellent answers

Excellent replies from all and a lot of good food for thought. I guess I'll go hydraulic flat tappet and just watch the spring pressure closely.
I recently saw a feature on Winston Cup motors and they used weaker springs for break in, then replaced them for race conditions. Anyone ever tried this? Of course, "weak" springs in an 8800 rpm SB2 Chevy may be vastly different than what we're talking about!

Is there anyway to check the lifter bore alignment beforehand?
With the motor out and apart this seems like the perfect time. I assume if the bore is off-center there is nothing you can do about it?!? I did see some offset lifter (roller) in GMHTP recently for an LS1 though....hmmmm.......

I know opinions on cam selection varies widely but I'll ask anyway.... what cam should I use with my combo (see sig)? I'm looking for mid-high 11's (very occasionally!)

Thanks again,

 

[Steve Wood]

Just stick the cam in the block and look thru the lifter bores at the lobes...if the lobe is centered under the hole rather than being offset to the side, then that lifter/lobe is more likely to fail to rotate correctly.

When using very stiff springs...we use a set of light springs for initial break in. As you note, we are talking about springs capable of preventing valve float at 9000 rpm.

I don't think this is really applicable in our case but I have known people to use a set of worn out stock springs to break the cam in with.

For a street engine, I prefer something close to stock and not more than the 206. These engines will last longer and be more fun to drive with a cam that will build some low pressure cylinder pressure that gives some snap at low boost with instaneous turbo spool. If you are building a race car, then there are many ways to approach it.