In the current buildup of Larry70GS's 470, we are going to be running 3 different camshafts, to test the effect of lobe designs and centerlines, as well as one of the first hyd roller cam profiles.
I thought that it would be a good idea to do a little show and tell on cam degreeing, so I took a whole bunch of pictures.
First off, the reason for degreeing the cam in your engine, is twofold. We need to located the camshaft correctly in relation to the crank and pistons, as well as verify that he cam was ground correctly, within reason. It's not unusual to find variation from the cam card in the actual specs, but you hope they are close.
Let's take a look at the three different cams:
Two hydraulic flat tappet designs. The TA 413 nearest in the pic, a Lunati grind from their "Voodoo" line in the middle, and the TA roller.
The TA 413 has a conventional lobe profile, and is built on a slightly reduced dimension lobe base circle.
The Lunati cam uses their more agressive lobes, and has more lobe lift than the TA cam, so it requires a greater reduction of base circle, as well as clearances ground for the lifters on the core itself.
These are both cast iron cores.
The TA roller cam is built off a 1050A Steel billet material, and it's easy to see the design difference in the lobes, that's possible once you add a roller to the bottom of the lifter.
The roller cam also has some unique features- because you have to control the end play of the cam, the nose is counterbored for a cam bumper, and an oil hole feeds oil to that bumper assembly, from the number one cam lobe.
Also, a different fuel pump eccentric is used, much bigger than the traditional Buick one.
Also notice the small hole behind the distributor drive gear- this hole, along with oil leaking from around the cam bumper, is used to provide additional oiling to the all important cam/distributor gear mesh. As with most engines, the distributor gear also drives the oil pump, but our BBB's have the oil pump hanging off the front of the motor, so oiling from splash lubrication can be inadaquate in some situations.
Preparation for cam degreeing:
This is going to apply to new builds, those of you changing cams in your car should get the jist of what we are doing here, but your going to have to work harder with it in the car. You can also do this with the heads on, but that's outside the scope of this discussion. For our purposes, we will assume you are assembling a new engine.
You want to degree your cam, after you have installed the following parts in the block, and I do them in this order:
Complete block prepped and finished with all plugs installed- It's best to have the block all finish prepped, so when you degree the cam, it doesn't have to come out again, for any reason- this prevents mistakes in putting the timing chain back on.
Camshaft installed, all but number 1 lobes lubricated- most builders install the camshaft first, as it's easy to guide it thru the bearings from the bottom, before the crank is installed. Leave the lube off the lobes for number one cylinder, so there is no possibility of it affecting your readings.
Crankshaft installed, Number 1 piston and rod assembly installed.- This is the minimum requirement for assembly to degree the cam. Leaving the other 7 pistons and rods on the bench make it much easier for you to rotate the engine.
Fitting the timing chain
What?... don't you just take it out of the box?
No... While it would be nice to live in a perfect world, the reality is that you need to check the fits of both the cam and crank gear, on your parts. A little fitting here will make you experience with cam degreeing much better.
I use this Rollmaster 9 keyway timing chain on just about every build I do, save for rare ultra "budget" build. For two reasons- First, the 9 keyways will allow you to dial the cam in as close as possible, and secondly, you can buy this chain with larger gears, to account for a closer cam to crank dimension, after the block is line honed. All my complete builds are line hone, it's a manditory machining operation on a 40 year old block, that has gone thru thousands of heat cycles. I can't recall the last time I used a standard dimension chain set, I most often use the .005 shorter set.
So.. let's do a test fit on your cam first with the upper gear..
Vary rarely have I had an issue here, as the cam gear nearly always fits nicely on the cam. It's important to have it be a nice fit, but to allow the cam to move freely in the gear- due to the design placement of the fuel pump eccentric, when you actually put the chain on, you have to rotate the cam to get the chain/gear up over the cam. Then you rotate the cam to align the holes.
fuel pump eccentric pointing to the side, to fit the gear over the cam, with the chain engauged with the crank gear.
Then the cam is rotated with the timing chain "snapped" in place, to align the holes to bolt the gear on, while having the alignment marks between the upper and lower gears in the correct location.
More than likely, with the rollmaster set, you will have to do a little fitting of the lower gear. They typically come out of the box with slight press fit on the crank.. test it first.. and then fit it to the crank- two options here- if you remember, and have your parts when the engine is being machined, bring the bottom gear with you, and have your machinist hone it slightly. If you don't have that option, you can work the ID carefully with some crocus cloth, or fine wet-dry sandpaper, to reduce it's id. If you have a die grinder and some 120 grid cartridge rolls, you can use them too. but be careful, you don't want to get it loose, your after a nice, positive slip fit here.
Now that you have your gear fit, let's take a peek at it. Lay it out on top of the lengend that comes with it, to identify and correctly mark the slots and teeth.
Now, I etch the legend onto the gear, to insure accurate alignment. Let me tell you, this is the number one problem with folks using this set. For each different keyway, you use the corresponding different tooth to line the upper dot on the chain with. If you put it on the 4* advance keyway, and then use the "dot" to line up the upper and lower gears, your going to get gibberish numbers in your degreeing.
The dot is only used with the keyway with the dot, and then we used the corresponding tooth with each different keyway.
If you don't have an etching tool, you can use a white or yellow fine felt tip pen to mark the gear.. but mark it, it will save you time in the process.
A word on the cam bolts- Buick used a reduced thickness head cam bolt, on factory applications, to insure fuel pump arm to bolt clearance. This timing chain set is wider, and you have to move the fuel pump forward to achieve arm to chain clearance, so you can use standard dimension heads on the cam. Personally, I like button head allen bolts, to assure clearance, as well as positive engaugement of my tools for installation and removal.
If your using a factory replacement type single timing chain, you have to use the thin head cam bolts, or these button head allen bolts.
OK, now put the lower gear on the crank, in the zero position (dot).
Notice that the alignment dot for the tooth is not straight up.. but slightly rotated counterclockwise.. reach under the motor and grab the number one counterweight on the crank, and rotate it to get the dot straight up, so your sure you align the upper and lower gears properly.
The correct tooth for alignment, after roating the crank slightly. This is the "zero" setting.
Install the timing chain and line the cam and crank gear dots up, tighten it up just past finger tight with the bolts, and your set to start the degreeing process.