Predator 420 Timing and Valve springs

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LaithSaah

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Hello!

So I'm finally doing it. I am building my Predator 420 with almost everything. I have a billet flywheel and 65lb dual valve springs that are causing me problems. I think the flywheel problem is pretty simple. I want to figure out the timing of the stock flywheel so I can make sure I don't detonate at the wrong time and throw a rod. Is there any documentation about this? I can't seem to find it after a quick search. In terms of the valve springs, they don't seat nicely in the 420 head and had closer to a 70lb compression force compared to the advertised 65. does that matter? I got them in, but I don't want to start my engine have the springs stack, and ruin my new chrome moly push rods. any advice would help!

Thank you!
Laith Saah
 
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panchothedog

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Pretty sure on the big engines ( like yours ) the ARC billet flywheels the timing is the same as the stock ones. 24 degrees BTDC. Hard to mess up the timing when installing the flywheel. Put the key in the slot on the crankshaft, and line up the slot on the flywheel with the key. It will be right. If you are trying to get more performance most folks would install a 4 or 6 degree offset key. Not sure what exactly " not seated nicely " about the valve springs means. On the small engines, it is recommended that you machine the valve spring perch area in order to run dual valve springs. I have only built one big block engine, and on that one I used the 50 lb. single springs. They seem to fit fine and the engine runs like a champ.
If you have the chrome Molly push rods, I wouldn't think 5lbs. of extra spring pressure would be a lot to worry about.
 
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Rat

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LaithSaah said:
. I want to figure out the timing of the stock flywheel so I can make sure I don't detonate at the wrong time and throw a rod.
Click to expand...
If you're wanting to check it's exact position relative to the keyway (any flywheel stock or aftermarket) to have a BTDC reference point, the coil fires when the trailing edge of the magnet is aligned to the leading edge on the trailing leg of the coil frame... all of course is relative to the flywheel rotation direction. This is the static timing reference point you need to compare to the piston TDC to get your ignition °BTDC
 
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