Camshaft timing challenge

Side clearance I would want .005-.015
A stock cam wheel has 52 teeth.
The keyway on the stock crank is not even close too what you picture shows .
IMG_20251102_164932219.jpg
 
The Lunatic crank the key is in inline with the crank pin . As well.
 

Attachments

  • IMG_20251102_170709437.jpg
    IMG_20251102_170709437.jpg
    61.3 KB · Views: 42
Last edited:
Are you rebuilding a previously running engine or assembling a basket case engine?
That file mark on the cam gear suggests custom cam timing, too me .
 
I am rebuilding a running engine.
It is the 2 nd Pure Power i rebuild , on top I helped some other racers on theirs .
All Pure Power 3,250 have the same timing . All of them sit in it the same way .
So it is proven to work , but my inner “Monk” pushes me to understand why it is this way .
I checked , yes the timing mark on my crank gear is way off where it is originally
 
It's highly probable it's a propietary thing .
Doesn't matter where the dots are .
It matters where the valve event's happen .
As you say if it works it's good .
 
I haven't read through all the posts but it appears to me that from your initial post that you are not identifying the true cam timing correctly. The exhaust lobe has to be up (max lift) at the timing marked on the cam. Stock, it will be where the little Dyno logo is engraved.
It sounds like the previous builder has changed the timing on the cam itself and possibly the crank/cam timing gear as well.
Either way, I'm guessing that there is only one way that the cam will install and rotate in the block without hitting the crank. That's going to determine how they originally had it timed/aligned when it has clearance.
Now, as for the "why"... Who knows. Maybe it got them some extra degree of timing that wasn't available by simply moving the adjustable cam gear. I would think you would just have Randy (Dyno Cams) grind the cam to your specs if that were the case. He's done that for me on many occasions when I want something "special" that's not an off the shelf cam.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
36 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
flattop1 said:
@CarlsonMotorsports
Brian should have some input on side clearance. As well as that timing scenario . I believe he is a Engineer and a top Flathead Guru .
Click to expand...
Endplay on the crank?

Minimum .008." I prefer to run them looser than that on stockers where the crank can't be centered in the bore or an aftermarket sleeve has not been installed to the center of the crank. On a custom built (jr drag / open) engine, you should be able to tighten that clearance up considerably.
Tell tale signs of incorrect crank-bore alignment is the scuffing of the side of the rod and/or bearings grabbing the radius.
 
Thanks a lot , yes very valuable info !
I have it a little looser on my build . When I opened the engine the sideplay was at 0,04 inch
I brought it to 0.02 inches .
Prefer having it a little loose .
Yes why they changed everything is a good question .
Currently trying to figure out where to set the ignition .
Most are around 0,500 . Maybe i stick with 0,450 as I dont need the full power for the youngest
 
Samotorsport said:
Thanks a lot , yes very valuable info !
I have it a little looser on my build . When I opened the engine the sideplay was at 0,04 inch
I brought it to 0.02 inches .
Prefer having it a little loose .
Yes why they changed everything is a good question .
Currently trying to figure out where to set the ignition .
Most are around 0,500 . Maybe i stick with 0,450 as I dont need the full power for the youngest
Click to expand...
Stroked crank , on methanol?
 
You must log in or register to reply here.
Back
Top