Core Shift

From Holdenpaedia
Jump to: navigation, search

Page created by T Jan 24th 2008:

Back to the Engine Section

Click to Enlargen. Photo by HQ_SS.

Core Shift:

A term that describes distortion that occurs during the casting process.  

Valve Lifter Oil Starvation Caused by Core Shift:

I mentioned that ages ago. It happened on cyl 5&7 mainly, so drivers side rear. Core shift was the culprit and it became more apparent as the dies aged. I spoke to the bloke sourcing Brocky's blocks(Shepherd? can't remember) and he said he'd be paying closer attention to it from that point on, given that they'd had a few engines fail and those actual cyls were apparently where the failures occurred.
Seems they just replaced the failed engines without properly diagnosing the cause. Rich buggers huh... Mick Webb had heard of it too. Les Small was also aware of it. I made a small tool, electric powered with a modified grinding stone attached at one end, and used a rubber O ring to drive it. It slipped down the lifter port and enabled me to bore out the holes to whatever size wanted. It also meant my lifter ports remained as new. Took a while to grind out each hole, but I only had to do about 6 of them. The oil feed holes at the front of the block are about as round as a 1 cent piece, and as they went toward the rear, they progressively reduced until they were smaller in diameter than a cigarette, so yeah, big difference. You'll know if this is your problem simply by looking at the lifter, pushrod and rocker gear on the affected cyls, they'll be blue from heat. Regards,

Click to Enlargen. Photo by HQ_SS.
Click to Enlargen. Photo by HQ_SS.


HQ_SS' Shed 

Lifter Bore Holes Too Small



Back to the Engine Section