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What timing marks with camshaft installed 4 degrees retarded?
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What timing marks with camshaft installed 4 degrees retarded?
I installed my cam 4 degrees retarded for a bit more top end. The 383 will make enough low power.
I'm mocking up the timing cover and balancer and with the crank and cam sprockets lined up, the balancer mark is about 2 degrees off, which makes sense since the cam instructions said buy installing it -4 degrees will only give 2 actual degrees.
But when i set my ignition timing how do I compensate for this? Do I need to?
The balancer hasn't been fully installed so it might line up slightly different.
Re: What timing marks with camshaft installed 4 degrees retarded?
The balancer (and its timing mark) should indicate the absolute position of the crankshaft. This is independent of the camshaft, and thus cam timing would have no effect it. Install the balancer to indicate actual crank TDC.
You can worry about (and experiment with) ignition timing later, and as much as you like.
Re: What timing marks with camshaft installed 4 degrees retarded?
I would suggest you find TDC with a dial indicator on a piston or a piston stop or something. Using the timing sprockets adds an additional layer of uncertainty and error.
Don't forget: when you build the motor "dot to dot" (the way we usually build em, because it's easiest to see there: crank sprocket dot at 12:00, cam sprocket dot at 6:00) you are NOT at #1 firing. It is actually #6 firing. You are at THE OTHER instance of #1 (& #6) TDC, where the exh valve is just closing and the int valve is just opening, at the end of the exh stroke and the beginning of the int stroke. From that position, rotate the crank EXACTLY one full turn, at which time the crank dot will be back to 12:00 and both #1 & #6 will be back to TDC, and the cam dot will ALSO be at 12:00. THAT will be #1 firing.
A motor with the cam retarded will usually want more "static" (low RPM) timing advance than otherwise. That's just a general Rule of Thumb though, by no means definitive or universal. Experiment to find the best setting for your particular combo. It will depend heavily on the particular cam you have, the compression ratio, the gearing, and the converter.
Re: What timing marks with camshaft installed 4 degrees retarded?
In my opinion, it would indeed be best to find true TDC and set the timing tab to indicate that correctly. I presume that someone in Shanghai, or Jalisco, or Cleveland, or Malaysia broached the keyway in the balancer hub off by a couple degrees, milled the groove in the outer shell a couple degrees off, assembled the balancer ring a couple degrees off, or stamped the timing tab a bit off what should have actually been, or some combination of those random errors. Typical ISO quality. It is now your job to correct all of that variation and mark the indicator for true zero.
The bigger problem might be in setting the timing. You're gonna have to calculate whether the base timing advance is 8° Canadian or 8° U.S. Then when the exchange rate fluctuates, you'll get to do it all over again.
Re: What timing marks with camshaft installed 4 degrees retarded?
Find True TDC using a piston stop and then correct the timing tab mounted location.
When you "retarded the camshaft" did you actually degree it in to determine true valve open close events or just wing it with a multi keyway crank timing gear?
The only real way to determine what cam phasing position is going to work best is to try, then TEST different installed positions.. Most all street cars are
undergeared so midrange torque is more important than a big top end.
I like to correct the timing tab for correct TDC and mount a balacer timing tape on the balacer.
Then hard mark various timing bench points such as 36 deg BTC for WOT full power timing.
And also 46 and 50 deg btc as full vac advance timing benchmarks.
Last oem crank balancer and oem timing cover timing tab I check was off by 4 degrees.
Re: What timing marks with camshaft installed 4 degrees retarded?
Originally Posted by F-BIRD'88
Find True TDC using a piston stop and then correct the timing tab mounted location.
When you "retarded the camshaft" did you actually degree it in to determine true valve open close events or just wing it with a multi keyway crank timing gear?
The only real way to determine what cam phasing position is going to work best is to try, then TEST different installed positions.. Most all street cars are
undergeared so midrange torque is more important than a big top end.
I like to correct the timing tab for correct TDC and mount a balacer timing tape on the balacer.
Then hard mark various timing bench points such as 36 deg BTC for WOT full power timing.
And also 46 and 50 deg btc as full vac advance timing benchmarks.
Last oem crank balancer and oem timing cover timing tab I check was off by 4 degrees.
Re: What timing marks with camshaft installed 4 degrees retarded?
Like everyone else said, piston stop and degree wheel to find true TDC. Never believe what the timing marks say.
Cam timing and ignition timing are two different things. Many cams already have valve timing advanced for better street driving. Installing your camshaft 4* retarded just means the valves will be opening/closing 4* later. Advancing a cam moves the powerband lower, retarding moves the power band higher. This has nothing to do with ignition timing which is what you see on the timing pointer. These are always highly inaccurate.
Many, many, many years ago I was adjusting my timing on my race engine. Advance it a couple of degrees and make a pass. Engine kept running better until I was around 44 degrees advanced. Ended up putting a degree wheel and a piston stop on the engine. Timing marks were off 6* so what I thought was 44 was actually 38. To repair it at the time, I bought an adjustable timing pointer so that the pointer was directly in line with the balancer mark when the piston was directly at TDC. Again, a degree wheel and piston stop are required.
Most camshafts can easily be advance or retarded 4* but if you're using a very aggressive camshaft, piston to valve clearance needs to be checked because the valves will be opening or closing at a different time. This usually means camshaft is installed, a thin layer of modeling clay is placed on top of the pistons in the valve pockets and the head is installed, After all the pushrods are installed and valves are adjusted, the engine is rotated 2 revolutions then the heads are pulled back off to see how deep of an imprint the valves left in the clay.
Building an engine and assembling an engine are 2 different things. Building it properly means the engine comes apart a few times to check a lot of clearances. Assembling just means you put a bunch of parts together and hope for the best.
Re: What timing marks with camshaft installed 4 degrees retarded?
Actually, if you use these parts as is, you already have a really good reference mark for TDC.
Paint a line on the timing tab and over the notch in the balancer and forget about the stamped numbers in the tab.
Re: What timing marks with camshaft installed 4 degrees retarded?
Originally Posted by NoEmissions84TA
Actually, if you use these parts as is, you already have a really good reference mark for TDC.
Paint a line on the timing tab and over the notch in the balancer and forget about the stamped numbers in the tab.
I guess the first problem is as sofakingdom pointed out, that when the crank gear and cam gear are dot to dot, it isn't even at TDC on #1. I will use a piston stop and find TDC. Maybe with some luck it will actually line up with the 0 mark.
Re: What timing marks with camshaft installed 4 degrees retarded?
NO that is NOT what I pointed out.
What I DID point out was, that since these are 4-STROKE engines, there are 2 INSTANCES of TDC for each cylinder during one complete engine cycle. In the case of #1, the FIRING instance of TDC, the one that occurs at the end of the compression stroke as that cyl fires and changes over to the beginning of the power stroke, occurs when the dots are both at 12:00. The OTHER instance of TDC, at the end of the exhaust stroke and beginning of the intake stroke, occurs when the dots are together. #1 & #6 come to TDC at the same time (as do the other 3 pairs of cyls that are 4 cyls apart in the firing order: 8 & 5, 4 & 7, and 3 & 2), 90 degrees apart from its neighbor pairs in the order, but ONLY ONE of each pair is at the firing point at each of those instances. The other is at the exh/int changeover.
We build motors at #1 & #6 TDC, but at #6 firing which is dot-to-dot, because it's easy to see and get the mechanicals right. But even though #1 is at TDC then, that's NOT #1 firing!!!! It's #6 firing, and #1 exh/int crossover. Once the sprockets & chain are correctly timed to each other at that instance of #1 TDC, the engine can be brought to #1 firing by rotating the crank exactly one full turn. Then, #1 and #6 will both be back at TDC once again, except that this time, the engine will be #1 firing and #6 exh/int.
Re: What timing marks with camshaft installed 4 degrees retarded?
Originally Posted by sofakingdom
NO that is NOT what I pointed out.
What I DID point out was, that since these are 4-STROKE engines, there are 2 INSTANCES of TDC for each cylinder during one complete engine cycle. In the case of #1, the FIRING instance of TDC, the one that occurs at the end of the compression stroke as that cyl fires and changes over to the beginning of the power stroke, occurs when the dots are both at 12:00. The OTHER instance of TDC, at the end of the exhaust stroke and beginning of the intake stroke, occurs when the dots are together. #1 & #6 come to TDC at the same time (as do the other 3 pairs of cyls that are 4 cyls apart in the firing order: 8 & 5, 4 & 7, and 3 & 2), 90 degrees apart from its neighbor pairs in the order, but ONLY ONE of each pair is at the firing point at each of those instances. The other is at the exh/int changeover.
We build motors at #1 & #6 TDC, but at #6 firing which is dot-to-dot, because it's easy to see and get the mechanicals right. But even though #1 is at TDC then, that's NOT #1 firing!!!! It's #6 firing, and #1 exh/int crossover. Once the sprockets & chain are correctly timed to each other at that instance of #1 TDC, the engine can be brought to #1 firing by rotating the crank exactly one full turn. Then, #1 and #6 will both be back at TDC once again, except that this time, the engine will be #1 firing and #6 exh/int.
Capische much yet?
I got what you said. I worded my response wrong. I will find #1 TDC firing.
06-08-2021, 08:52 PM
