db's 66 Belvedere ***FOR SALE***

[Dave999]

so if we assume no button
and a chain that runs straight and is decent and not stretched

that leaves 4 things

1) its always been like that and it isn't causing a problem
2) the cam has been ground with its lobes in the wrong place, nigh on impossible to do cos the cam blanks dictate where they are
3) the boss on the end of the cam is too fat or too thin
4) the drive on the end of the crank has moved forward. it can't move back i don't think and in theory it can't move forward as it is pressed by the snout of the balancer....but it might have done

but in your photos i don't know where the front of the engine is


Yes i'm peculiar in running a button. but it was a factory warranty fix on many hemi 6's to solve oil pump and worn block/cover issues. so most fit something better than a welded on nut with a bolt through it on the timing cover.

cam endfloat.JPG (48.32 KiB) Viewed 1202 times

[db]

Sorry I'm confusing myself... The cam is too far BACK. In this pic you can see the dissy drive.
Is it a problem? Possibly. It inexplicably snapped a pushrod 2 years ago. The same valve has now punched a hole through the lifter. To my thinking if the edge of the adjacent lobe caught under the edge of this lifter it could lift it. Could that explain the damage? It's DEFINITELY been rubbing against it as it's ground the bottom 1/16" edge of the lifter

[Dave999]

so if its too far back obvioulsy it needs to come forward slightly.......Mmmmm...
i think you are going to need to look at the timing set and see whats what.

i run a set with a bearing on the back. the centre of the big sproket is offset to to acomodate a bit more "stuff" bearing etc between it and block when compared with a near flat single row standard sprocket. so it dictates how far back the cam sits for me.

the reason people use these on hemi 6s is that the cam sprokect used to grind its way into the front of the block. resulting in a cam that slopped too far back and too far forward once a single row standard chain streteched a bit.
not of much of a problem with a dual roller chain but, bearing and cam button os belt and braces to avoid a smashed oil pump (none made since 1982) it is still the norm on hemi 6s

this is not a problem i have ever heard of on a v8 motor mind, its a failing that is as far as i know unique to the hemi 6.

when you get in there it could be as easy as the sprocket has an offset, no bearing, looks the same front to back and is currently on backwards

if it has a bearing obviuously that won't be the issue
if its the cam it will have to come out and have a bit taken off the end i guess. pull the whole lot forward a few mm in relation to the sprocket

I'm guessing..........there may be other ways.

are you missing come kind of spacer on the crank behind the crank sprocket....this is where i illustrate that i have no clue about the v8

but i don' think you'll know until the timing cover comes off

Dave

[Blue]

The position of the oil pump causes the cam to walk to the rear on a small block I believe. The position of the cam in the block will be limited by the clearance between the cam plate and the sprocket I would think, need to pull the timing cover and see what's going on in there.

[Pete]

Do you have a cam button? NO - it is a mechanical cam, not a Roller Cam.

Do you have a double row chain YES.

Is the sprocket bolted down YES.

i.e does your cam actually sit in the right place fore/aft. YES.

There is no shim or adjustment on a stock style Cam, unlike the pre-load thrust button on a Roller Cam.

As long as the lifters rotate when the cam rotates you are good to go.

[Blue]

Yes but witness marks on those 2 lifters shows something is clearly amiss.

[db]

Thanks Blue, yes there's no way the cam is right in relation to the lifters.
If the the cam hasn't moved and if there's no play, the best I can think of is to take the cam out and very carefully chamfer the offending lobes so they just clear the adjacent lifters. At least I can be sure I've eliminated any possible future contact.

Is there anything to watch out for in removing and refitting the cam?
I can remove my rad & grille, etc so no I shouldn't need to move the motor, although it's on a motor plate so I'll need to prop it up to remove the plate.
So it's remove rad, grille, alt, water pump, plate, timing gear, etc. Lifters out, dissy out and just slide the cam out the front?
I take it I'll need to mark the cam/ timing gear in relation to the crank.

[Blue]

yes that's pretty much it. The only other thing is to make a handle for the cam long enough to get two hands on that will thread into the end of the cam.
Without a handle it's difficult to get the cam in or out without taking a chunk out of the cam bearings with a lobe.

[db]

Ooh good tip thanks!

[Pete]

I do not think you can chamfer the Lobes - I think you will damage the case hardening on the Cam lobes and then the lifters will eat them for lunch.

[Dave999]

take out the cam
take a slice off the front on a lathe, this avoids having to do anything with the hardened lobes
put retainer and sprocket back on

how does a small block cam retainer work??
have you got the right one?

this is some kind of genius they forgot to add to my motor...hence my preoccupation with other cam retention methods

Dave

[Pete]

Alex Doig built the motor from a Spec supplied by Andy Neal and Ray Barton.

[db]

It sounds gruesome but I'm confident in my bodgery after many years of it
When I say chamfer, I mean to take a tiny amount off the rear edge of the lobe highlighted in green.
The lifter proper to the lobe only contacts the front part between the red lines, well away from my meddling.

It'll be fine

[db]

Right, I'm going in!
Today, thanks to the wonders of the new website, you'll be treated to live reporting as I dismantle the front of my car to get to the cam.

[latil]

Should be good. Is it easier working with car hanging on the wall?