99 Black Bird T/A

iTrader: (4)

I haven't ran into anyone with a HCI set up with 100,000+ miles on the HCI combo. I'm just trying to get a feel for areas of concern and learn about possible upgrades. I'd like my 99 TA's HCI set to last as long as possible.

I've read that 8620 aircraft grade, vacuum degassed, carburized steel cam cores offer a significant wear advantage over the 5150 cam cores. I'm kicking around the idea of a new cam for my old 99 TA.

How much of an advantage?
Can anyone provide specific details?
Can you run more spring pressure with the harder cores?
Are lifter failures less common?
Does the harder 8620 cam core require special after market lifters for best longevity?

Reason for asking my HCI 99 TA has a Comp Came 224/224 XER cam with 120,000+ miles and lots of hard fun time flogging. Overall, the engine and lifters have 153,000+ miles on them. The rockers were shimmed to get as close to the same preload as possible. The engine sounds the same like a sewing machine and runs the same today as it did back in 2002. Its had valve springs replaced when needed regular Mobile 1 oil changes & always warmed to full temprature before going over 3000 rpm.

At what point should I start worrying about durability of my 5150 cam core XER cam?
When should I have concerns about lifters?

Darth_V8r

iTrader: (4)

I can give you the point of view as a metallurgist if that's what you're looking for...

5150 is very simply chrome steel. 1% chromium and 0.5% carbon. The higher carbon content makes it have very good surface hardenability. You've actually got good everyday experience with this grade of steel. It's the most common grade used for coil springs because of its shape memory. Not your valve springs, but your suspension springs. For years and years, this grade of steels primary use was coil and led springs. So much so that it is commonly called spring steel. Where it suffers is it has relatively poor surface toughness. I had a customer using it to make giant nails and the heads kept breaking off. I recommended they switch to 4140, which is commonly called chrome moly steel, and the problem completely went away. If you're getting valve float or loft, 5150 will generally only dent a little bit before the hardened surface chips off. Although with a 0.5% carbon, that hardened surface can be quite thick.

8620 is nickel chrome moly steel. Has a better grain structure and better toughness than even 4140. The vacuum degassing means it has less chance of porosity and almost certainly fewer inclusions which should contribute to even better fracture resistance. With the lower carbon content, it can be a much more versatile material. That said, you're going to get about a 40-45 Rockwell C on 8620 vs a 55-60 on 5150. Don't let that scare you though. There is a such thing as too hard and therefore brittle. 8620 is very often used in some pretty high demand applications where you need a hard, wear resident surface AND the ability to really take some abuse. In general, 5150 is going to fail long before 8620.

So what does that mean for your situation? Well, I don't think you need to swap your cam out simply to go to 8620 because it's better. You've got good life out of your current cam and it's not likely to give you any issues. The XER lobes tend to be quite aggressive and are sort of falling out of favor, as newer evidence is showing we are getting more power out of softer ramp rates due to better valve control. And a quieter running engine. I would switch cams for that reason rather than the grade of steel.

Hope all that helps

redtan

iTrader: (5)

While the 8620 steel is overall more reliable than 5150, I dont think the reason you don't see 100k mile HCI setups is because the cam core is wearing out. There are many more factors than camshaft composition which matter for reliability or lackthereof in these HCIs you talk about.

99 Black Bird T/A

iTrader: (4)

Darth & Red, thank for the insights and comments. Metallurgical point are very interesting.

What material are the rollers on various roller lifters made from?

Are their any concerns of material compatibility between cam & lifter?

Tagent question, do flat tappent cams made from 8620 have a lower risk of failure on break in than 5150 cams?

MuhThugga

Agreed.

Some times it has to do with a factory defect in the camshaft, but most times, a setup fails due to a lack of maintenance, mismatched parts, or installer error.

Jason 98 TA

iTrader: (4)

You can get gun drilled 8620 camshafts from Texas Speed no problem. The thing is people got worried about 5150 cams when so many failures were happening. The failures is the exact reason Texas Speed decided to invest over a million dollars in a camshaft grinding program that's second to none. With the worlds first landis lt1 ve grinder we were able to bring he latest grinding technology to the ls market. Could we have done camshaft grinder with a berco grinder that costs the same as a Camaro? Sure but the lobe designs and power output would have suffered.

bottom line is if you use a good camshaft core and don't grinder burn the camshaft you'll have a package that will live a long long time!

99 Black Bird T/A

iTrader: (4)

Gun drilled cam sounds pretty trick and is definitely a plus for the 8620 cam core.

dr_whigham

iTrader: (49)

Redtan is alluding to it...

Let's tell a story real quick...

So a well known manufacturer started to incur an obscene amount of cam failures. Well, this is a big name company so said corporation decides to send their top engineer to Caterpillar who has a 1,000,000 mile warranty on theirs. Wanna take a guess what it's made of?

1010. Yes, you read that correctly. 1010 steel.... million mile warranty. It doesn't spin as fast but the principle is the same.

As redtan alluded to, there's SO MUCH MORE to a camshaft than the material it's made out of. What shape is the lobe? Is it concave or convex? Is it FLAT? How's the polish finish?

03EBZ06

For the same price as most other cam mfgs or less you can get the cam core you want from them. For a cam with low spring pressures, you likely will not likely see problems with any of the mfgs that grind them.

99 Black Bird T/A

iTrader: (4)

This is very interesting. Where does 9310 cam cores fit into the picture?

From what I've read elsewhere the general view seems to be 5150 is ok for street hydraulic rollers and that's about it. What's the cut off on spring pressure for the various grad materials?

Redtan, Darth V8er, Dr Whigham would like to hear your views.

Darth_V8r

iTrader: (4)

Figure a 9310 is similar to 8620, but can achieve higher surface hardness AND be significantly tougher than 8620. Its aircraft turbine quality stuff and can get pricey fast. It would need to be a pretty extreme application to need 9310 instead of 8620 to be honest.