That must be why the crank gears have the extra keeways for adjustment.
Question on cam timing when you're ONE tooth off....
- Thread starter Kern Dog
- Start date
Yes, they are for degreeing in the cam
- Local time
- 10:08 AM
- Joined
- Apr 13, 2012
- Messages
- 40,198
- Reaction score
- 149,361
- Location
- Granite Bay CA
This question was inspired by an episode of Engine Masters where they had a low compression Motorhome 440 and were testing the power with the cam advanced and retarded. They had it advanced almost 10 degrees and it lost a bunch of power.
The 318 in this Duster....
May have been the original engine to the car. All 318 2 barrel engines had relatively low compression and a HP peak around 4400-4600 rpms. It's a fuzzy memory but I thought the cam sprocket was retarded at least a tooth on the cam sprocket. Traditionally, retarding a cam moves the power peak later in the RPM scale and lessens power at low RPMs. The problem is/was, an engine with heads as meager as most 318s have will not flow enough air at higher RPMs to take advantage of the delayed power peak.
I have timing sets out in the shed but it has been wet and windy here....I haven't been out back in a couple days.
I was also curious if all manufacturers built their timing sets with a standard number of teeth on their sprockets or if each one could have chosen a number that differed from others as long as the tooth count on the cam sprocket was double of the crank sprocket.
Knowing that I could have been over 14 degrees retarded sure sheds light on the subject! Thank you.
The 318 in this Duster....
May have been the original engine to the car. All 318 2 barrel engines had relatively low compression and a HP peak around 4400-4600 rpms. It's a fuzzy memory but I thought the cam sprocket was retarded at least a tooth on the cam sprocket. Traditionally, retarding a cam moves the power peak later in the RPM scale and lessens power at low RPMs. The problem is/was, an engine with heads as meager as most 318s have will not flow enough air at higher RPMs to take advantage of the delayed power peak.
I have timing sets out in the shed but it has been wet and windy here....I haven't been out back in a couple days.
I was also curious if all manufacturers built their timing sets with a standard number of teeth on their sprockets or if each one could have chosen a number that differed from others as long as the tooth count on the cam sprocket was double of the crank sprocket.
Knowing that I could have been over 14 degrees retarded sure sheds light on the subject! Thank you.
You could have fixed the Duster's power problem with one of these.
Well why did you ask the question????
I had a chain jump on my 84 gran fury la 318. Of course it did it cold when the temperature was single digits outside.
My neighbour pushed it up my hill so I could get it partway in my barn.
Messed with it for at least an hour before I figured out the problem.
I had to Advance the timing a bunch to get it started. It had barely any power until you got around 60 then it was modest at best.
I drove it a couple weeks until it jumped again.
Certainly could have fixed it but it had 157 k on it and it was probably 12 years old so rust was growing rapidly.
I junked it and later regretted it.
I bought it from an old Jewish man named George Pfeiffer who survived a concentration camp.
My neighbour pushed it up my hill so I could get it partway in my barn.
Messed with it for at least an hour before I figured out the problem.
I had to Advance the timing a bunch to get it started. It had barely any power until you got around 60 then it was modest at best.
I drove it a couple weeks until it jumped again.
Certainly could have fixed it but it had 157 k on it and it was probably 12 years old so rust was growing rapidly.
I junked it and later regretted it.
I bought it from an old Jewish man named George Pfeiffer who survived a concentration camp.
- Local time
- 10:08 AM
- Joined
- Apr 13, 2012
- Messages
- 40,198
- Reaction score
- 149,361
- Location
- Granite Bay CA
I found a notebook where I wrote about the work that I was doing with the car.
In there, I wrote that the cam sprocket was 3 teeth off advanced. That technically is 1 1/2 teeth at the crank, right?
The Engine Masters TV episode where they ran the 440 on a dyno showed a power loss with the cam advanced 10 degrees. Being advanced the 3 cam sprocket teeth is what then...almost 22 degrees? The only reason the valves never hit pistons in this low compression 318 was because the pistons probably sat .80 in the hole and because 318 cams had a paltry .373 of lift.
The timing set was not stock, so someone either made a mistake or stupidly thought that advancing the cam timing this much made sense??
In there, I wrote that the cam sprocket was 3 teeth off advanced. That technically is 1 1/2 teeth at the crank, right?
The Engine Masters TV episode where they ran the 440 on a dyno showed a power loss with the cam advanced 10 degrees. Being advanced the 3 cam sprocket teeth is what then...almost 22 degrees? The only reason the valves never hit pistons in this low compression 318 was because the pistons probably sat .80 in the hole and because 318 cams had a paltry .373 of lift.
The timing set was not stock, so someone either made a mistake or stupidly thought that advancing the cam timing this much made sense??
When you were writing it your notebook years ago you probably didn't have a good handle about checking cam timing. I'm guessing you weren't 3 teeth advanced. It was probably a fiber top gear and I don't recall how many teeth they had. People break timing belts and chains in lower performance engines all the time and the valves don't hit the pistons so those engines don't have to worry. But don't try that in 426 Hemi with high compression and a high lift camshaft or you will have a bad day.
The short block that was used for my racecar was used. Before disassembling it I decided to mock up the cam and heads to be used. Wanted to make sure it had enough piston to valve clearance. Slid the cam in and set the Jessel belt drive dot to dot. Ran into an issue before the head or the degree wheel were ever attached. The crank would only rotate 3/4 turn. It didn't take long to find the problem. A rod was hitting the cam. Now what? Thought about it. This cam had less duration than the one that had been used previously. A few calls netted the answer. Apparently my Jessel cam pulley was marked wrong. The dot was 3 teeth off. Had to make a new mark. Then adjust the cam timing with the adjustable inner and outer cam pulley.
Doug
Doug
- Local time
- 10:08 AM
- Joined
- Apr 13, 2012
- Messages
- 40,198
- Reaction score
- 149,361
- Location
- Granite Bay CA
This was an aftermarket timing set with steel sprockets.
Similar threads
