Rocker Priming: Odd Cam Oil Hole Angle

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nm9stheham

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Just another FWIW note:

We just primed our 340 with a Crane cam, and could not get oil to the rockers despite setting the angles as below (thanks to Tony for this info):
- Turn the motor to 90* before top dead center coming up on #1 compression. The pass. side rockers should get oil.
- Turn the motor to 20* after top dead center just past #6 compression. The drivers side rockers should get oil.

We installed the cam bearings ourselves carefully and shone a light down through the head passages in the block, so we knew we had all that right. And the cam passages were fully drilled through. So after a lot of tries with the crank angles + and - around these prescribed angles, we decided to move the crank to 45-50 degrees before the prescribed points and try at 5 degree increments. At 45 degrees early, BAM-O, oil to the rockers. Same thing on the other side: 45 degrees earlier.

Sooo, with our Crane cam the correct angles for head oiling are:
- Turn the motor to 135* before top dead center coming up on #1 compression. The pass. side rockers should get oil.
- Turn the motor to 25* BEFORE top dead center just past #6 compression. The drivers side rockers should get oil.

Dunno if this is just a Crane thing or other cam makers have this variable. It does not matter in a running engine, just when you want to do pre-oiling checks.
 
I have never wasted the time to check, but I bet crane is not the only one. like u said, it does not matter in a running engine. time is money, why would an aftermarket cam company take the time to drill the holes in the cam to a precise location relative to the key slot? when we prime the engine, we rotate by hand slowly looking for oil flow up top
 
You need to check your angles and note them during assembly if you want to do oiling checks without all the hassle
 
I don't mean to question your skills, nm9, but I kinda think it points to ................cam timing?
LOL........ but hey, with all of that cam timing errors going around, like a bad case of the flu, I will re-verify for sure. We did degree it with a wheel and dial indicator on the lifter, after ID'ing TDC with the dial indicator (heads off). And double-checked with the new timing pointer. I have managed to escape cam timing errors in 25-30 engines, so hopefully will (for this build) remain one of those who 'will eventually mistime a cam'....as opposed to those who 'have mistimed a cam'. It's kinda like riding motorcycles and having wrecks.....I am a member of the 'has had a wreck' crowd....

I shoulda done as Bakerlite suggests..... note the cam oiling hole orientation before installing. This orientation is not a specified paramter by any means, and apparently can be anywhere.
 
With the heads still off, it's easy to do a quick check of split overlap, but it's hard to imagine the cam timing being off 45*. It's much easier to imagine the cam manufacturer having re-indexed the holes.
The good thing is the passage through the cam, is in fact, through the cam, and the top end is being oiled.Maybe not the way Ma wanted it to be. But oiled nontheless..
All-in-all, it's good to know that we should keep an eye out for stuff like that.

I would also be a member of the "had-a-wreck" club.Make that of the "had-several-wrecks" club.
 
That's why the degrees of turning really don't matter. The cam companies will drill holes where-ever they feel like..lol. When they align- the rockers get oiled.
A few extra steps I do when I assemble...
1. Verify the drilled pasages in the cam are at least as big as the holes in the block. (some are smaller even with the same brand of cams) If they are smaller - enlarge them.
2. If higher rpm or extended rpms are expected or with higher spring loads - add .100" chamfers to the cam's bearing journals in the driection of rotation to add time to each oiling event. Make sure to polish all burrs left completely away with fine emery and wash the cam when done.
2. On the back side of the cam bearings with the extra holes (the outer surfaces that contact the block) add some .080-.100" wide chamfers in the direction of rotation to the holes that run up to the heads. he object is only to chamfer the backing - not the babbit material. This ensures more oiling if the oil passages are drilled a little off.
 
Those are some very good ideas, Moper. One reason we installed the cam bearings ourselves was to get these cam bearing holes well aligned and we did a good job. (Easy to make a tool with a long 1/4" threaded rod, some wood discs, and a large flat washer. Just a little extra driving needed on the back one.))

As a side note related to oiling capacity through the cam: we are using (trying out) the AL PRW PQx rockers. The clearance in the shaft holes around the mounting studs that allows oil in from the pedestal is very small compared to the stock hole; the net flow area into the rocker shaft is only 0.1 sq in as opposed to 0.35 sq in for the stock rocker shaft hole, and 0.45 sq in flow area for the hole in the block from the cam bearings. Plus the total oil flow area out of the PRW rocker shafts to the rockers is also only 0.1 sq in. So, lot of flow is not needed as it is restricted; I wrote to PRW and they said that they keep that clearance hole small for oil restriction. (I can only assume that I got good info.)

We are planning to drill some new oil holes in the PRW rockers to shoot oil to the rollers and springs tops and valve tips, based on general comments on this and Dart Vader's experience. So we'll open up the rocker shaft's clearance hole to the pedestal to around 0.2" sq in to support that added flow.
 
The oil to the top end is regulated by the diameter of the hole in the cam. Oil only will flow when the holes line up, which is only for a short time (in rotational degrees). If you either groove the cam, or run pushrod oiling the rocker might become the restriction. Personally I'd want as much oil as possible to get out of that shaft if I'm using the stock rocker shaft oiling.
 
With oil trough pushrods and the correct rockers, you can do away with the shaft oiling.
 
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