Cam offset dowel install help

[grumpyf14d]

I am replacing the cam dowel with an offset dowel and need some help with how to accomplishing the task. I believe it is as simple as:

1. Take a punch and knock out the current dowel from the backside of the cam face.
2. Replace with the new offset dowel making sure the offset part of the dowel is to the right if looking at it from the front of the engine.
3. Drill new holes to elongate the current ones in the cam sprocket.
4. Attach cam sprocket and install the cam into the engine block.

i have searched the threads here and can’t find anything about “how to”. I have looked in Jake’s book to no avail. I am surprised there is nothing documenting this considering most folks choose to run an offset dowel for cam timing. I am also surprised that there aren’t cam sprockets available with the elongated bolt holes to accept the differing offset dowels.

Thanks in advance for your help.

Keith

[BeerBudgetRacing]

https://www.burtonpower.com/parts-by...duct_group=156

will one of the adjustable ones work?

[bob darcey]

In a perfect world it would be that simple--but it isn't. Jake's book gives a cam timing procedure on pages 107 and 108, but it doesn't address the need to elongate the bolt holes--which becomes obvious eventually. I elongate the holes by filing. Cam timing is pretty critical, so consider following Jake's process with a degree wheel to confirm position. Jake's description uses the intake lobe center as the target, but using half-way between opening and closing events (.050" lift valve on the opening ramp and .050" lift from fully closed) gives good results. That "should" be the same result, but there's often some variance. You may also find that the four intake lobes aren't all marching to the same drummer, so you may want to check all four lobes and compromise as required. You do this without an offset button in place; get the sprocket in proper position, then find an offset dowel that fits.

[grumpyf14d]

Bob,
thanks for the info, I hear what you are saying about how to get the timing correct. My follow up question would be; do you use a punch on the backside of the dowel to get it out?

[bob darcey]

The back of the dowel is about two-thirds obscured by the front main journal, so you won't be able to get a straight shot at it with a punch. Sounds (and is) brutal, but you may have to use vice grips if the dowel is tight in the hole. If it's a zero offset dowel, it isn't much good for anything and you do want to avoid marring the bearing journal. Maybe someone has found a better way.

[grumpyf14d]

Yeah, I suspected as much. I hate it when you have to take to vice grips to solve a problem.

[T644HU07]

Jake's book refers to two methods to achieve the necessary offset: an offset dowel in the camshaft and an offset bushing in the sprocket. The engines I've had experience with all used offset bushings. There are two advantages to using this method. 1. You can use the existing dowel. No need to remove it. 2. No need to elongate the holes in the sprocket. Just enlarge the hole in the sprocket and press in the offset bushing. A lot less work.
Offset Bushing.jpg

[bob darcey]

No need to elongate the holes in the sprocket.
Offset Bushing.jpg

That doesn't eliminate the need to elongate the two bolt holes. With either method, the camshaft is being rotated relative to the sprocket, by exactly the same amount; the sprocket holes have to be elongated to get 3-4 crankshaft degrees of retard. Done this about a dozen times and every one required some filing of the holes.

[Sean Gallagher]

It's things like this is why I paid Joe Stimola to build and Dyno my engines.
Drop it in the chasis and good to go for 15+ races.

Just Sayin'