Increasing cam core size in a B.B.C.

[swampbuggy]

What is possible as far as increasing the camshaft core size in a B.B.C. passenger block or any GM block below a Bowtie block ?? Mark H. A friend just had a STD size BBC steel billet cam break. Blown/injected alky-----mechanical fuel pump driven off nose of camshaft. Thanks Mark H.

[swampbuggy]

By is this question unanswerable or did I make everybody mad or what

[user-17438]

Depends on how much work you are willing to pay for. Anytime we increased Cam bore, we would increase/true the lifter bores. Depending on base circle sometimes you will need bushings to move the oil band. You could go 50mm/55mm But you would be better off investing that money towards an aftermarket block. I never suggest doing that stuff to a stock block, I would rather order in a new block.(At no markup) the extra $1000 is cheap insurance.

Call Camking or LSM, Bullet whoever you choose and see if your problem was material related. Not all billets are the same. 5350-8620-9310-8660-1010 etc.

[mag2555]

Why does he not have a non releaved Cam ground up to back down on the twisting force?

[swampbuggy]

Mag2255 , not sure what you are asking, ground up ????? , hang with me, reword your question plz. Mark. H.

[Newold1]

Obviously the engine is back apart or coming apart for a fix. Yes, a BBC bowtie block can be bored for a 55 mm core camshaft and a bigger cam core will be stronger, but if things are not carefully checked, adjusted and lined up on the front of that engine it can happen again!
On a blown alky engine like that a big wide blower belt is pushing that cam drive and fuel pump out there away from the face of the block and if that pump drive shaft is off center or tweaked out of line the vibrations on the front of this blower drive and the eccentricity of this pump drive with its oscillations can transfer to the cam and whamo it snaps. The right core material and a bigger core will make it stronger, but if the drive and pump are crooked or misaligned its going to be hard on timing set and cam bearings. I've also seen engines like this with a pump drive support for the pump.

[Alan Roehrich]

Commonly, people are running a 54MM cam on babbit bearings in stock production blocks. It's the most cost effective. And 0.904" lifters.

If you're actually breaking a steel billet roller cam in a big block Chevy, something is terribly wrong. We run 400# on the seat, and close to 1200# open at 9,000 RPM, no cam breakage. And that's enough spring to control 3/8" stem stainless valves at that RPM and making near 2HP per cube (795HP at 411 cubes), restricted.

[mag2555]

Where did his Cam break off, up front?

[CREngines]

Lets start with what color is the broken cam core between the lobes?

If its black you have your answer- cheap induction hardened core that has no business in a race engine.

[swampbuggy]

Cam was made in Memphis, Tn. And has copper color between lobes, probably 8620. Have not had a chance yet to view cam, however i have learned that after partial teardown that something came loose. On the road now waiting for more info . Thanks to ALL , Mark H.

[CamKing]

Cam was made in Memphis, Tn. And has copper color between lobes, probably 8620. Have not had a chance yet to view cam, however i have learned that after partial teardown that something came loose. On the road now waiting for more info . Thanks to ALL , Mark H.

The core wasn't made in Memphis.
Even if it's 8620, it could have a barrel diameter as small as .900", and that's a lot weaker then a cam with a .970" barrel diameter.

[swampbuggy]

Yes Camking you are correct----i just wanted all to know who the cam was supplied by. I will update information when i can, maybe somebody can learn from the end cause ??? Mark H.