TDC ?
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TDC ?
I assembled my cams and outer gears this evening and with the cam marks lined up and the outer gear marks lined up, gears aligned and torqued; I noticed that my rear piston was at TDC. I seem to remember that on an automotive engine the #1 cylinder is always at TDC when timing the cam and aligning the timing marks. The crank and cam are at a 2 to 1 ratio. Is the same true on the Twin Cam or do I have to rotate the crank until the front cylinder is at TDC and re-align the cam timing marks? By the way, I haven't put the heads on yet. HELP_________________________
Road Captain
Joined: Feb 2005
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RE: TDC ?
I am assuming you are going back with non adjustable push rods.As long as you have all your marks right when you installed everything into the plate and when you put outer gear/chains onit will not make any differance at this point. When you put it back togeather do one cylinder at a time. Go ahead and install both heads and lower rockerbox covers.Drop both lifters in there bores in one cylinderand then rotate the engine by spinning the rear wheel till both lifters at there lowest point. drop your push rods threw and then install your rockerboxes and torque to spech. Then drop lifters in other cylinder bore and rotate till they both are at there lowest point, rods, rockerboxes ,torque. BTY Same applys if this is a gear drive set up. I hope I understand your question correct.
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RE: TDC ?
Mentor, You are probably right. I think I remember that the rear does fire 1st but can't remember for sure. My reply was that he doesn't have to rotate to TDC to install cams, sprockets and chains as long as punch marks are lined up. I have only done about 5 cam changes so I am far from expert but I couldn't remember having to find TDC on a cam change except when removing rockerboxes. I just reread my 04 Softail manual on cam install and couldn't find anything on TDCto do the job. I may be way off and PLEASE correct me if wrong. I never want to give false info.
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RE: TDC ?
Thanks for the replys; seems that the idiosyncrosies continue on my first TC build. The reason that I noticed TDC is that the heads were off and I could see the pistons location. Today I put the heads on and when I bolted down the rocker support plate, the push rods wouldn't budge. Well, the exhaust would spin with some effort. I rechecked the cam marks and lifter position and put the rocker support back on, same thing. I left it as is to see if the lifter needed to bleed down and haven't been back to check it yet. The only change that I can think of that would make any difference is that I used a .030 Cometic Head gasket. I am not sure if the original gasket was a .040 or .060. I do know that could give me between .010 and ..030 less lifter preload. The cylinders are new to the engine too. The pistons came right to the top of the cylinders so with the .030 Head gasket, I should have a proper squish band. That is all that I have other than I will measuer the pushrods and go from there.
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RE: TDC ?
Well, it's been two days until i could get back to my "95" project and with the rocker assembly snugged down, I can turn the pushrods with my thumb and forefinger with some resistance. The lifters must have bled down so I am putting the front head on and continuing. I am still a little lost as to the bleed down on hydrolic lifters. It seems that they shouldn't pump up more than they do while they are lifting the pushrod during running. They already have .060 of preload built in to adjust them when the cams are on their base circle. I have read a bunch of stuff about lifeters in the last two days and .030 seems to be the ideal amount of preload; measured by scribing the pushrods at max and min. preload. Too much information. Any comments are welcome.
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