Degree-ing a roller cam & establishing pushrod length

[simplyconnected]

...Some cam companies 'build-in' their own advance while others do not.

Go through my procedure and you can verify exactly what you have and how far off it is...

Well? What did your degree wheel say?

Somehow I have the distinct feeling you are not using your degree wheel or my procedures, because you never report your results.

Gathering as much technical info as possible is the right thing to do including consulting the cam company. Now that I have given you as much help as I can, ask the cam company to explain their numbers and how they apply to your FE. - Dave

[HighwayThunder]

Degree Wheel results

Did the procedure 4 times. These are the readings...

1. 107.75
2. 106.25 (outlier, made an error)
3. 108.5
4. 108

Tossing out the 2nd result, the average is 108.1.

After changing the crank sprocket keyway, took 2 readings...

1. 104.5
2. 103.5

So, about 104 (consistent with Cloyes spec of a 4 degree difference).

[HighwayThunder]

Talking with Tech Support

I called Comp Cams tech support to discuss my roller cam install. What I learned surprised me.

My cam spec card says that the intake center line (ICL) is at 106 degrees. However, that is the design spec, not the actual manufacturing test results. From my cam’s serial number the support tech looked up the test results, which place the actual ICL for my cam at 107.3 degrees, within their acceptable range of tolerance.

I would have expected tighter tolerances for a computer-controlled manufacturing process, but the truth is that Comp Cams uses humans to grind some of their cams. Yes, my cam was made by a machinist.

The cam was designed to optimize low-end power, good for a street application. So, I’ve decided to go with my original degree wheel ICL results of about 108 degrees.

Cheers,

[HighwayThunder]

Finishing up before buttoning up

The pushrods will be 8.850"

Set adjustable pushrods to that length and checked valve to piston clearances.

Intake valve to piston = 0.271" (Comp Cams minimum is 0.100")

Exhaust valve to piston = 0.178" (Comp Cams minimum is 0.125")

BTW, finding modeling clay can be problematic. I rediscovered Play-Doh, available in Target's toy section for only $2.99.

Cheers,

[simplyconnected]

Comp Cams verified what I posted:

...Just because a number is written doesn't make it so. It costs no more money to verify for yourself, then you will know...

You still haven't determined whether your cam is advanced or retarded with respect to your crankshaft.

Is it possible to get a precise measurement using Play-Doh? I would think it's too spongy. - Dave

[simplyconnected]

I like your picture and all the colors. They show the intake correctly opening before TDC (Top Dead Center).
The graph also shows the intake valve closing BEFORE BDC (Bottom Dead Center) even though your numbers say it doesn't.

Let's throw out all the numbers for a few minutes and absorb this:
Your cam has a TDC as well. Where is it? Does it coincide with your crankshaft TDC? How would you know if your timing chain is off a tooth? Are you using a dial indicator on both #1 cylinder valves?

Let's make this much easier with just a little understanding of how cam and crank timing works.

Look at your firing order: 1-5-4-2-6-3-7-8
You know that the crank needs to rotate twice for each cam revolution so let's break down the firing order more...
1-5-4-2 <-here is the first revolution.
6-3-7-8 <-here is the second revolution

Since it takes two crank revolutions, by looking at the firing order it's easy to see...
When #1 piston is up (TDC) so is #6. The other pistons follow suit (#5 & #3 are up at the same time, 4&7, etc).

Break it down even more... When 1 is up, 4 is down. (this is how we measure stroke). So now we know that pistons go up and down in PAIRS. Let's add a camshaft. Any camshaft.

We know when #1 is firing, #6 is in its exhaust stroke. BOTH pistons are at or near TDC.

Even though your pistons are configured in a "V", when #1 and #6 are at TDC, the crankshaft sprocket keyway is right on top (at 12:00 o'clock).
Is the crankshaft keyway broached in the right place?
Is the crank sprocket broached in the right place?
Is the Cam dowel hole drilled in the right place?
Is the Cam Sprocket dowel hole drilled in the right place?

You said the cam card had values that might differ from reality. Now we have a stack of error that is becoming serious. Look way past cam numbers so you can see the big picture, then we can come back to them.

In a prior post I asked you to rotate the crank until #6 exhaust valve is closing and #6 intake valve is opening. We use this overlap to 'scavenge', meaning, the exhaust gasses are in motion out the exhaust valve. Even though the piston stops at the top, by having both valves open, fresh fuel mixture will purge the combustion chamber of spent gas and replace it with new mixture BEFORE the exhaust valve closes.

This is important. When #6 exh valve is on its way closed AND #6 int valve is opening... right when both rocker arms are dead even, THAT position is the centerline of your camshaft. With the rocker arms level with a straightedge, look at your crank timing marks. They should be dead nuts on TDC.

From here, you can know for certain where the cam really is and then adjust your cam timing with relation to your crankshaft. From here, you can get the dial indicators out and do precise numbers.

You can see that before you start, you need to know where TDC is on your crankshaft, you need to understand the firing order and THEN you can find your cam timing. After setting your cam-to-crank timing, THEN you measure piston-to-valve clearance. This sequence cannot be done any other order or your numbers will be wrong.

Instead of using Play-Doh, touch the valves down to the piston by hand and use a feeler gauge between the valve stem and rocker arm. If clearance is less than .125", either adjust your cam timing or cut valve reliefs into the tops of your pistons.

If any part of this is unclear, call me @ 248-544-8834 - Dave

[HighwayThunder]

Corrected graphic

I deleted the post containing the graphic because I knew it wasn't right. I had to visualize it as a linear timeline to see what was wrong (see attachment).

One can see the intake/exhaust "scavenge" overlap for #1 cylinder at the end of the timeline.

I've corrected the original graphic, which represents a front view of the crankshaft (also attached).

It was my theory that the Ford stock cam timing of 112 degrees ICL wrt crankshaft TDC could be considered a reference point. If so then the Comp Cams' ICL of 107 degrees would be an advance.

I'll run the measurements again using your methods and post results (but it may take a few days).

Cheers,

[HighwayThunder]

Piston to valve clearances

Using the method of measuring between the valve stems and the rocker arm...

Intake: 0.157"
Exhaust: 0.145"

[simplyconnected]

If those numbers were done with the cam/crank timing you will use, go ahead and start your engine.

You already set the pre-load on your lifters correctly which will prevent bent pushrods and these new piston-to-valve clearance numbers will prevent bent valves.

I believe the cause of your problems was not due to bad gas but cam timing and/or pushrod lengths that were incorrect.

Engine building is very precise. If you buy stock parts then you depend on Ford engineers' numbers to be correct. The moment you deviate from stock changes the measurements and tolerances. All must be carefully checked before any attempt to run. Something as simple as a thinner or thicker head gasket changes your lifter preload.

Then, there is the poor guy who overheated his engine... He goes to a dealership and they send one or both heads out to be 'machined straight'. Dealerships don't machine heads, they simply assemble parts sent to them. God help the poor customer.

Did you get a degree wheel reading when your #6 valves were even? - Dave

[HighwayThunder]

Follow-up

Thanks to all for the advice and support. For those interested, the engine starts and runs OK.

However, there's a tapping noise emanating from the valve covers, which is louder on the right side. I removed the covers to locate the source of the tapping. The oiling is good, no bent pushrods, no valve lash.

I suspect that one of the roller lifter retaining bars is tapping against the sheet metal oil baffle that's under the intake manifold. (I noticed that that could happen when I was degreeing the cam. Was mindful of that when I reassembled the top end, but perhaps not careful enough.)

Will let you know.

Cheers,

[simplyconnected]

Do you mean like this?:

Top RH corner of the splash pan is where I bent the baffle away from the lifter actions. I have no noise.

Thanks for the update. Your engine should be an unleashed beast with that cam you got. - Dave

[HighwayThunder]

Oil Baffle Modification

Bending the baffle in the indicated spot did clear the #1 lifter bar, but then I had clearance problems at the #8 position. Truth is, the whole baffle is warped and defies attempts to bend it back to its original shape.

To ensure clearances I installed stand-offs. The stand-offs are 2" tall. Each stand-off is secured with a lock washer, opposing nuts, and sealer. The stand-offs are positioned to contact the "V" in the valley behind/between the lifter sets, so that the stand-offs stay put.

Here are pictures...

[HighwayThunder]

Tuning an engine with an aftermarket cam

The manual for the 390 engine has tables for ignition timing, but that assumes that the engine has a factory cam. My cam is aftermarket (Comp Cams FE XR282HR-10).


Comp Cams tech support could not specify optimal ignition points.


Do the stock timing specs apply to the new cam profile?


If not, is there some way of determining the correct tuning points?


Cheers,

[simplyconnected]

Bending the baffle in the indicated spot did clear the #1 lifter bar, but then I had clearance problems at the #8 position. Truth is, the whole baffle is warped and defies attempts to bend it back to its original shape.

To ensure clearances I installed stand-offs...

If you installed the baffle according to OEM specs, it 'clips-in' under the heads at specific tabs. You should not need standoffs if you followed this procedure. I use the same roller lifters that you have and only had interference as shown earlier.

The manual for the 390 engine has tables for ignition timing, but that assumes that the engine has a factory cam. My cam is aftermarket (Comp Cams FE XR282HR-10).

Comp Cams tech support could not specify optimal ignition points.

Do the stock timing specs apply to the new cam profile?

The Ford manuals only apply to OEM parts. There is no way Ford could possibly anticipate someone would put a 282 degree duration cam in one of their engines.

Your particular cam has very little horsepower at idle speeds. That affects torque converter stall speed (stock converters will bog down the engine) and distributor centrifugal advance (as well as carb settings), etc.

It's very important, whoever works on your Ford engine, understands FE engines. Chevy builders have a difficult time to the point where some quit or overcharge to cover 'learning' costs. So, find an experienced FE engine build shop, one that have done many dozens of FEs. That's why your cam company couldn't help.

Since you have little power at low rpms, your distributor needs to advance much later than stock settings. There are many more considerations like; weight of your car, what fuel you are running, compression ratio, what rpm range you normally run at so you operate in the peak range of torque, etc. When you choose a cam, this should not be a 'blind' consideration but an experienced choice for the service of this engine. - Dave

[stubbie]

Maybe that's a question better asked on the FE Engine Tech Forum.