[Jay S]

I asked because I was not sure if Bullet sold the 4/7 swap on 8620s or went to 5150’s yet. Comp has went to mostly 5150’s and I think the industries has some pressure to switch because 5150 billet cores are a little cheaper and each core is more flexible for a bigger variety of durations. The 5150’s induction hardening is deeper than the 8620 but not as strong. The 8620 is tougher, has a tougher very high quality finish and is more expensive. I expect more out of a 8620 core versus a 5150, but it cost more too. Either work, and shouldn’t make a difference, but the extra cost of the 8620 is certainly adding some level of quality over the 1050’s and 5150’s.

The prefix’s effect the aggressiveness of the cam some, it can be bad or good, just depends on what the application is.

[scott70]

Originally Posted by Jay S

I asked because I was not sure if Bullet sold the 4/7 swap on 8620s or went to 5150’s yet. Comp has went to mostly 5150’s and I think the industries has some pressure to switch because 5150 billet cores are a little cheaper and each core is more flexible for a bigger variety of durations. The 5150’s induction hardening is deeper than the 8620 but not as strong. The 8620 is tougher, has a tougher very high quality finish and is more expensive. I expect more out of a 8620 core versus a 5150, but it cost more too. Either work, and shouldn’t make a difference, but the extra cost of the 8620 is certainly adding some level of quality over the 1050’s and 5150’s.

The prefix’s effect the aggressiveness of the cam some, it can be bad or good, just depends on what the application is.

I asked the machine shop to take a peek after you mentioned that. He said it’s just a normal grey color. I believe the first comp cam I got that I sent back was copper colored.

[TXSTARFIRE]

What is the purpose of the 4/7 swap? This is the first time that I am hearing of it.

[scott70]

Originally Posted by TXSTARFIRE

What is the purpose of the 4/7 swap? This is the first time that I am hearing of it.

This is all bullet had for Pontiac HR cores but the swapping of 4 and 7 is supposed to be easier on bearings and run a little smoother. Supposedly on engines pistons four and seven are at top dead center at the same time. Swapping the firing I guess makes it more even on the crank as far as firing pulses

[Steve C.]

Regarding the use of the engine prefix number.

Personally I've never seen anything used other than the number 51 for a traditional Pontiac engine.

Example, I've used two Comp Cams solid roller cams and both had part number 51-000-9

As noted the 54 is the engine prefix number for Pontiac.
The 000 indicates a custom grind.
The 9 indicates a steel billet roller core.

( another common core code used is -11 )

I have a copy of a Comp cam card with part number 51-000-10 and it stated 2.165 journals and a handwritten note indicating 55mm journal size. It was also a 4/7 firing order.

I've never used a hydraulic roller cam but I have seen cam cards for the early SD Performance Old Faithful cam with part number 51-000-9 and another two Old Faithful cams with part number 51-000-11.
Then two SD Performance revised stump puller hyd rollers, both with part number 51-000-11

All used the number 51


.

[scott70]

Originally Posted by Jay S

I asked because I was not sure if Bullet sold the 4/7 swap on 8620s or went to 5150’s yet. Comp has went to mostly 5150’s and I think the industries has some pressure to switch because 5150 billet cores are a little cheaper and each core is more flexible for a bigger variety of durations. The 5150’s induction hardening is deeper than the 8620 but not as strong. The 8620 is tougher, has a tougher very high quality finish and is more expensive. I expect more out of a 8620 core versus a 5150, but it cost more too. Either work, and shouldn’t make a difference, but the extra cost of the 8620 is certainly adding some level of quality over the 1050’s and 5150’s.

The prefix’s effect the aggressiveness of the cam some, it can be bad or good, just depends on what the application is.

Is the only way to tell what the material of the cam I got is to call Bullet and ask them? It is at least billet steel? Doesnt look like theres any info on the cam card saying whats what.

[Steve C.]

A FWIW....
I have a solid roller from Bullet received quite some time ago, currently now in storage. I looked and it has hints of copper between the lobes.
There where no issues with it but I decided to change cams. The solid roller cam that I replaced it with and installed is also from Bullet. No clue if it is similar though.


.

[Jay S]

Originally Posted by scott70

Is the only way to tell what the material of the cam I got is to call Bullet and ask them? It is at least billet steel? Doesnt look like theres any info on the cam card saying whats what.

Yes, you would have to call and ask. It is a Billet steel cam, it is most likely a 5150. But I could only possibly tell the 1055, 5150 or a 8660 apart if I was holding them in my hands. All the billet cores work fine on these mild HR applications.

I have a 1055 in a .640” lift shifting at 7000 running around on the street. The 1055 is one of the weaker core types, and even it holds up well for most HR applications.

Picking the best distributer gear for the application is a good reason to know what the core is for street cars. But since most people run the BOP composite gear on Pontiac’s, which works with all the Billet cam types, the core really won’t make much difference as long as it is one of the Billets.

[Jay S]

Originally Posted by Steve C.

A FWIW....
I have a solid roller from Bullet received quite some time ago, currently now in storage. I looked and it has hints of copper between the lobes.
There where no issues with it but I decided to change cams. The solid roller cam that I replaced it with and installed is also from Bullet. No clue if it is similar though.


.

Ever looked at that and wondered where all the copper went? LOL.

[Steve C.]

Jay,
I never paid much attention to it until many years ago the subject cam up regarding a Comp Cams solid roller.
I had used two solid rollers from Comp at the time. Up until then most were from UltraDyne direct and then after those two from Comp Cams then UltraDyne lobes from Bullet.

"Copper coating between the lobes prevents the flame hardening from making the cam brittle."

https://www.hotrod.com/features/tech...982-1559-148-1


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[Steve C.]

Why Copper Coating is Used

Preventing Embrittlement: While the cam lobes need to be extremely hard to resist wear, the core (shaft) must remain ductile to withstand the immense torsional stress and high spring pressures in the valvetrain. If the whole shaft were hardened, it would likely snap under load.

Comp Cams Camshaft Heat Treatment Explained
https://performancewholesale.com.au/...ment-explained


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[scott70]

At bullet Mark went and asked what the material would be. They weren’t exactly sure they said it’s either the 1055 or 5150. Said it was most likely the 1055.

[Jay S]

Originally Posted by scott70

At bullet Mark went and asked what the material would be. They weren’t exactly sure they said it’s either the 1055 or 5150. Said it was most likely the 1055.

On 1055 cores I usually use the factory distributer gear. We check it at about a 1000 miles for wear and end up just putting it back in. Most aftermarket distributer’s come with some type of a melonized gear, they work fine on the 1055s too. I like the HR cams ground on 1055s when limited on distributer gear options.

Since you don’t know for sure, you would find out soon enough if it is a 5150 core, it requires at least melonized gear, it will quickly eat the stock factory distributer gear. You would want to check distributer gear much sooner for wear. Persoanlly I would break a 5150 in with a stock gear then switch to a BOP if it shows any wear. Make sure they install the orificed galley plug to lubricate the gear.

The other cores like the 5160, 8660 and 8620 all require bronze or a composite to last any time at all on the street. The BOP gear works for all of the above, so will most bronze gears. Generally I break the cam in with bronze then switch to the BOP composite on all but the 1055 and the 5150. Many start out with the BOP and don’t do anything for breaking the gear in. I am guessing that is your plan. That works fine of the majority of the time, but I don’t generally run the BOP at first..

[scott70]

I did drop off the bop poly gear at the engine shop. The dist I’ve been using is a msd ready to run. That’s at the engine shop too.