Lifter Offset

[SS Killer]

Looking at your drawing, the lifter body could possibly make contact with the cam lobe.

I was really just trying to illustrate my assumptions on the way things line up... I spent maybe a minute on the thing.

So what I'm hearing is that the lifters sit directly on the cam and are not designed to contact the cam in this form?

[RedHeartbeat]

I'd be really surprised if that is how the bores are setup. My assumption would be that the lifter bores are on the same exact centerline as the camshaft. Offsetting the lifters would make grinding a cam a bitch.

[outlaw_king]

we have off set lifters in one of our comp motors the lifters set in the bore just like any other lifter would what is off set is the top of the lifter where the push rod sets. on one side of our motor they are offset all the way to the back on the other side they are offset all the way to the front. we had to do this to clear the intake runners cause we moved them so much.

keep in mind when you offset the lifter you have to off set the rocker arm as well... looks kind of like a dog leg if you will.

[txarkitekt]

I got my measurements from this website I have saved on My Favorites.... Motor Dimensions and Specs. As for that .143 variance, you have to divide that by two cause you are using .143 as what is left over from the bore diameter and lifter diameter. So you have .071" of clearance around the lifter, based on what the specs say. To me, seventy one thousandths of an inch is pretty damn small... I just replaced all the lifters in Alan's truck in Tuesday night and they fit in there decently, but the plastic lifter cups also hold the lifter in place so that it won't wiggle around. And from what I could see, the lifters centerline is aligned at whatever angle to the cams centerline. It looked to me that there was no offset.

[RedHeartbeat]

Damn good thing you're an architect and not a mechanical designer. The slip fit of the lifter bores is closer to .002".

[txarkitekt]

Ok, I am trying to figure out how you got .002". Ok, for math's sake, the area (pi x radius squared) of the cross-sectioned lifter bore is .558 square inches. The lifter itself has a cross-sectioned area of .385 square inches. That leaves us with this buffer area between the lifter and the bore walls of the block at .173 square inches, in cross-section. See pic below:



Now, with those numbers given, lets look at a section through the lifter bore:




So, from looking at the pics and dimensions of it all, what are we left with?

[txarkitekt]

Damn those pictures suck. Let me go back and make some EPS files and import them into PS and then reattach them...

[RedHeartbeat]

I used this handy-dandy little device called an OD micrometer and measured the size of a lifter fresh out of the block. .8415-.8420"

.843-.842 = .001 minimal clearance
.8415-.844 = .0025 maximum clearance

[SS Killer]

Damn those pictures suck. Let me go back and make some EPS files and import them into PS and then reattach them...

You're talking about having more than a 1/16th of an inch slop around the entire lifter.

Take it from a Mechanical/Manufacturing Engineer... that would never work.

[outlaw_king]

are you looking at offset in that the lifter is offset in the bore? that is not the case. the offset comes in where the pushrod hits the lifter. if you look at the top of a lifter the hole is dead center correct? now imagine that hole as far to the left or right as possible. that is how they offset lifters. i will try and bring one saturday to the dyno day to show you what i speak of... if you want me too...

lifters are only going to have .001-.002 clearance between the lifter and the lifter boss. that is why on most race motors people insert bronze guides.