Engine talk, Again!
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
More info on the "myth" of core shift from your testing, please...
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
I'm avoiding comment on this thread, but I had to hear more about this - you've proved that GEN I's don't have core shifts? How so? I've seen HUGE core shifts very commonly, and I don't think I've EVER seen a block that had consistent bore thickness concentric with the bore centerline. One of the reasons we sonic test bore thickness is not just to see if an overbore is doable, but also to determine if we have sufficient thickness to index the bore spacing if required when we bore.
More info on the "myth" of core shift from your testing, please...
More info on the "myth" of core shift from your testing, please...
We have seen many times the 7 cylinders will soinc test fine and there will be one that will that will not be up to spec.
We sonic test all the blocks that come through the door.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
I'm avoiding comment on this thread, but I had to hear more about this - you've proved that GEN I's don't have core shifts? How so? I've seen HUGE core shifts very commonly, and I don't think I've EVER seen a block that had consistent bore thickness concentric with the bore centerline. One of the reasons we sonic test bore thickness is not just to see if an overbore is doable, but also to determine if we have sufficient thickness to index the bore spacing if required when we bore.
More info on the "myth" of core shift from your testing, please...
More info on the "myth" of core shift from your testing, please...
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I have no idea what you mean by "go by coreshift".
Coreshift means that the bore is not cast concentric with the bore centerline - you seem to be using it in reverse. If you mean machining by the bore centerline regardless of differences in bore wall thickness caused by coreshift, I agree that's wrong...which was the point of my post.
At the same time, tweaking the bore centerline to get even bore wall thickness all the way around even if the centerlines are off doesn't make a lot of sense to me...but it's always a compromise on a stock block.
I read the statement "coreshift is a myth" as meaning that all blocks you'd seen were right on with the bore centerlines...which clearly they're not.
'nuff said - just a terminology thing.
Coreshift means that the bore is not cast concentric with the bore centerline - you seem to be using it in reverse. If you mean machining by the bore centerline regardless of differences in bore wall thickness caused by coreshift, I agree that's wrong...which was the point of my post.
At the same time, tweaking the bore centerline to get even bore wall thickness all the way around even if the centerlines are off doesn't make a lot of sense to me...but it's always a compromise on a stock block.
I read the statement "coreshift is a myth" as meaning that all blocks you'd seen were right on with the bore centerlines...which clearly they're not.
'nuff said - just a terminology thing.
Last edited by billla; Sep 23, 2008 at 02:51 PM.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,136
Likes: 8
From: Chichester, UK
Bill, Thank you for your input. 
I know nothing about engine building so everyone's help is most welcome
Took the conrods and pistons off tonight and all is labeled and put away for now.
I will try to take the crankshaft off tommorow.
Thank you
Paul
I know nothing about engine building so everyone's help is most welcome
Took the conrods and pistons off tonight and all is labeled and put away for now.
I will try to take the crankshaft off tommorow.
Thank you
Paul
