Camshaft damage (picture)

[jp]

This is the stock camshaft from my Gen1 engine. Must say I'm suprised about the bad condition. Is it common that there is pices missing from the lobes? At least 7 lobes have visible damage. The engine has 16000 miles...
I'm glad I bought a billet core for my new custom grind.

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[Mike Adams]

Had anything else ever been done to the car and do you have pictures of any of the other lobes ?

 

[jp]

The engine is stock. In the picture above you can you se 3 lobes with damage. It seems as the damage is on the top of the lobes. And it is on Intake AND exhaust lobes.
When I took the engine apart did I also find that some of the Pushrods did have wear marks on the lifter side.
One more picture:

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[Vip-RT10]

Wow, that is comforting...maybe we should all take a look and be aware of this problem. I would show that to some official person and see what they do about it.

 

[joe117]

I've never seen anything like this. Did you tear down the engine due to lifter noise? What do the rollers look like?

 

[jp]

I'm doing a major topend/camshaft job on the engine. No abnormal valvetrain noise. The roller-lifters look perfect...strange. (haven't yet had time to go through them all though)

 

[Mike Adams]

Does look odd. I can say I have ever seen that kind of issue on any car I have done. You may want to send off a picture to Crower and as for their opinion. But I have not seen any vipers with this damage in my shop.

 

[Anthony - 98 GTS]

Could it be nitrous related??

 

[jp]

Nope...
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Anthony - 98 GTS:
Could it be nitrous related??

<HR></BLOCKQUOTE>

 

[LETHAL GTS]

Is that not out of the same engine you were showing us pictures of just the other day? You know the picture with the scratches on the cylinder wall.

 

[Doug Supercharged Vipers]

Hello JP -
The damage to your cam was caused by insufficient spring pressure....

The cause: Your valve springs are too weak or "dead." Inadequate spring pressure causes the lifters to bounce off the cam inflicting damage to the lobes. Since you are indeed refreshing the top end, the new cam/spring combo will cure your symptoms.

Unfortunately, you have a token of the ill-effects
from inadequate spring pressure

.

The pictures are worth their weight in gold.

Regards,
Doug

 

[Ron]

<FONT face="Comic Sans MS">JP;

Thanks to Doug's comments, we know it's not oil related, but just curious as to what type of oil you use.

Doug;

What would cause the springs to "deaden" in 16,000 miles? Over-reving and valve float?

Thanks</FONT f>

 

[HP]

JP - you are rough a motor - did you upgrade to the 1.7 rockers-
that(plus high RPM/inadequate oil pressure) could have accelerated the problem with the weak springs and lifter bounce.

Please keep the pictures coming - you're schooling all of
us on what can happen - worst case scenario

 

[Doug Supercharged Vipers]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Ron:
<FONT face="Comic Sans MS">JP;

Thanks to Doug's comments, we know it's not oil related, but just curious as to what type of oil you use.

Doug;

What would cause the springs to "deaden" in 16,000 miles? Over-reving and valve float?

Thanks</FONT f>

<HR></BLOCKQUOTE>Oscillating frequencies create heat in the spring coils which causes failure of the spring coils. As heat builds the molecules in the metal (springs) move and cause weak spots in the coils, inevitably they will break. I'm not a metallurgist, but we know the acoustics from an internal combustion engine have their own precarious way of damaging metal components. For example, if you operated the said engine without the damper, the ill-effects would be astronomical caused by the oscillating frequencies.

Another example would be If you operated the engine at, let's say, only 200 rpm day-in and day-out. The valve springs would last 160,000 miles easily. But if you operated the same engine at 6000 rpm, the springs would last about 16,000 miles ;-).

I hope you understand my point,
Best Regards,
Doug

 

[99 R/T 10]

This question is directed to Doug. Is this damage common with all Gen I engines? Should we are be looking at this as a future issue. Will 1.7 rockers negatively affect the cam as these pictures show? Thanks,

Mike

 

[Ron]

<FONT face="Comic Sans MS">Thanks Doug, makes sense.

One then wonders if there should be a preventative replacement of valve springs if high RPM use is the norm.</FONT f>

 

[Marc Lublin]

The cam on my 94 looked the exact same, I have pictures of it somewhere. Mine was due to bad rockers that Hennessey installed back in 94. They were not riding true on the valve stems and they mashed a few of the valve stems. This caused excess clearance which was banging on the cam instead of riding on the cam. This in essence is the same thing as the weaker valve springs. The difference it my was present at idle so it was easier to hear. With bad springs it happens at higher rpm when the motor is much louder, so you could have missed the excessive valvetrain noise.

 

[Doug Supercharged Vipers]

&lt;&lt; Is this damage common with all Gen I engines? Should we are be looking at this as a future issue. Will 1.7 rockers negatively affect the cam as these pictures show? &gt;&gt;
Mike

No, I've inspected, built and modified many Gen I engines and haven't found any inherent issues involving severe cam damage as we've seen with JP's engine. Any engine, normally aspirated, with or without nitrous can suffer the same detriments from valve float. The transition from 1.6 to 1.7 rocker arms is not an extreme amount of additional lift. Although, 1.7 rocker arms will net another .032" more lift. I know, .032" doesn't seem like a lot more lift but the more you compress a spring the more it will fatigue in time.
On the flip side, roller rockers eliminate frictional contact from that of the stamped steel rocker arms that drag across valve tips. Hence, eliminating heat in the valvetrain. And remember, as I said before, as heat builds the molecules in the metal (springs) move and cause weak spots in the coils, in time the spring could brake. Personally, I would use the 1.7 with confidence.

&lt;&lt; Thanks Doug, makes sense.
One then wonders if there should be a preventative replacement of valve springs if high RPM use is the norm &gt;&gt;
Ron

Your very welcome,
The key is a "game plan." Discuss your specifications with your tuner or tell your machine shop the gross lift of your cam and rocker arm ratio so you can build a set of heads with the proper height and spring rates for your performance package.

Regards,
Doug

 

[Sniper]

What would cause bent pushrods in a stock Gen I motor?

 

[HP]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Matt Kovac:
What would cause bent pushrods in a stock Gen I motor?

<HR></BLOCKQUOTE>

Valve hitting piston, rocker not tracking right, or lifter
collapse causing pushrod to get lose.----------------
Hugh Perkins
96 RT Black/Blue Stripes
514ci - APEX stage III heads, 1 3/4" headers, 3" exhaust,NOS/propane, 3.55gears, aluminum flywheel/kevlar clutch, HD halfshafts, TechEdge 1.5 Wideband O2, GenII injectors, Dastek chip, fuel pump booster, Ripper shifter, more to come....

<FONT COLOR="#ff0000" SIZE="1" FACE="Verdana, Arial">This message has been edited by HP on 01-29-2003 at 07:49 PM</font>

 

[Jack B]

Just another possibility - the damage does not look like impact or accelerated wear. It looks more like porosity caused by a bad mold during the casting process, if indeed this is a casting.

 

[Greg Good Cylinder Heads]

I don't know if this applies in this situation, but this looks to me like it might be related to the surface hardness of the cam, along with the valve float catalyst. Does anyone know what the Rockwell hardness of these cam lobes are?

I have seen this type of damage on several steel billet roller cams sold by some of the aftermarket cam grinders that were made on the "black", induction hardened, cam cores. When I say "black", I'm referring to the black color between the lobes and cam bearing journals. I've seen black core cams that had hunks of material missing from the lobes. Other lobes on the cam would have patches where there were lots of small cracks criss-crossing. The older "gold" core cams are flame hardened, and are softer. They will develop "tracks" from the roller lifter more easily, but they won't crack and lose chunks of lobe.

Synthetic oil seems to advance this condition. Some non-Viper racing engines I did heads for had this problem a few years back. A tech at Comp Cams described it as being from the lifter "skidding" along the lobe surface instead of "rolling" when synthetic oil was used. Not enough friction between the roller lifter and the cam lobe to make the roller "roll". I know it sounds far fetched but he said that was what they found in their research. The skidding action caused the lobe to wear harden too much and the cracking started, then the cracked material would start to break away. What they found that helped was to bead blast the lobes. That, or don't run syntheticson a black, or similarly hard, cam core.

The engine builders I knew that had the problem decided to specify gold cores when they ordered their cams instead.

 

[jp]

Tracy, yes it is the same engine. After taking it all apart, did it not look as bad as it did first. A little honing and new rings will be ok.

Doug, I will test the stock springs and compare to stock specifications. I'll let you know.

Ron, Always used Mobile1, I personally don't like it, it's so friggin sticky! When racing is the engine never shiftet above 4500 prm.

Hugh, The pictures are from a bone stock engine. My idea about a board is to share experiences with other members.

The new combination in this engine is based on a gold core billet camshaft with springs matched to the cam values. The valves will be chevy valves with longer and wider stems, bonze guides etc, etc. So based on Greg and Dougs thoughts above does it look like I'm on the right track.

 

[joe117]

I'm thinking that a 16k mile street Viper engine with a rpm limiter is not the kind of situation where I would expect to see valve float caused by weak valve springs. The surface hardness answer seems more like it to me.

 

[Qualitywires.com]

Man Doug Levin is the man! I learn something from that guy every time he opens his mouth!