Base Circle and Overlap question
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Cruiser
Joined: Sep 2012
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From: Canada
Base Circle and Overlap question
So the way I'm going to find base circle and install my push rods would be to put the opposite cam in overlap (both lifters moving at the same time). Then install both push rods on the opposite cam as that cam should now be on base circle. That seems to be the way most people do it.
A friend today told me that the better way to do it is to put your finger down onto the intake lifter and turn the trans until the lifter was at it's lowest point. He then installs the push rod on that intake side. Before moving to the exhaust side of that cam he does the same thing on the opposite cam (intake side). Then he moves to the exhaust sides of both cams. He said that was just the way he was taught and the guy who taught him told him it was a more reliable way to do it but he didn't know what the reason was.
Would like to know your opinions on the matter and what you do personally.
A friend today told me that the better way to do it is to put your finger down onto the intake lifter and turn the trans until the lifter was at it's lowest point. He then installs the push rod on that intake side. Before moving to the exhaust side of that cam he does the same thing on the opposite cam (intake side). Then he moves to the exhaust sides of both cams. He said that was just the way he was taught and the guy who taught him told him it was a more reliable way to do it but he didn't know what the reason was.
Would like to know your opinions on the matter and what you do personally.
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Joined: Sep 2009
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From: deland,florida
100`s of ways to skin a cat.its a lot eaisier just to find TDC,with both valves closed & do both in that cyl,wait for bleed down & do the same in the other cyl.since shovel days,p/rod adjustment is one thing that has been over complicated many times
Tourer
Joined: Jan 2012
Posts: 373
Likes: 90
From: australia
If its your first time installing pushrods, finding tdc,, finding base circle,, etc,, some advice can be confusing from people that can do it in there sleep...
You have the theory right,, why not remove, (or leave off), the cam cover,,, get a torch and look in the cam chest, and physically see pushrods on base circle !!!!!! Use same method , if you are cutting pushrods also .... The first time you will be more confident with the install ....
You have the theory right,, why not remove, (or leave off), the cam cover,,, get a torch and look in the cam chest, and physically see pushrods on base circle !!!!!! Use same method , if you are cutting pushrods also .... The first time you will be more confident with the install ....
Tourer
Joined: Jul 2014
Posts: 426
Likes: 157
From: Lake Wales, Fl
+1 on NtrainDave's method - The way I learned- a few years ago - on solid lifter Panheads was to watch the front intake pushrod go up then back down - Intake stroke - bring that piston up to TDC - compression stroke - both front cyl valves are now closed- I stick a srewdriver in the sparkplug hole to feel the piston get it as close as you can to TDC- it won't be exact. Adjust the front pushrods, use the lifter mfg specs on how far to go. do the math,( how many threads per in are your pushrods?) Walk away - have a cup of coffee - relax - when you can spin the front pushrods easily between your fingers repeat the process on the rear cyl. They important thing is to follow the same steps in the same order each time you do it - less chance of an error. - Eastcoast Jim
Last edited by Eastcoast Jim; Jun 30, 2016 at 08:04 AM.
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Cruiser
Joined: Sep 2012
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From: Canada
So if I was installing the pushrods on the rear cam, and I put the front cam on overlap is that the same as TDC? I read a fair amount of posts about feeling the air from the spk plg hole and using a straw in the hole to watch its lift etc., but without actually seeing it done on a video or something it's not 100% clear.
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Joined: Mar 2012
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From: Centennial, CO
As you rotate the engine with the rear wheel, watch the pushrods move up and down. When they get to TDC, the pushrods will stop moving at the same time, MOMENTARILY. This is TDC. Rotate the engine a couple times to see the whole thing in action. It will become clear to you what we are talking about.
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Cruiser
Joined: Sep 2012
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From: Canada
thanks QC. I'll try that later. The push rods are out already but I can use a couple of magnetic tipped grabber rods that I have instead by dropping them down onto the lifters. So when both rods stop moving at the same time TDC is achieved and the push rods are installed on that same cam/cylinder. Is that correct?