Base Circle and Overlap question
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,596
From: san antonio
Forget about overlap and watching lifters, etc. The easiest way is what Kirby and Dave have described. Rotate the motor, plugs out, finger over the plug hole if you want but you will hear the compressed air push out of the cylinder which means the piston is on the compression stroke. If the rocker covers are off, you can see the valves close. If not, a straw in the plug hole will work, just keep bumping the piston up until the straw stops moving; you are at or near TDC on the compression stroke and can adjust the pushrods on that cylinder. If the cam chest cover is off, you can do as markolula suggests and peek in the cam chest with a light and see the lifter on the base circle of heel of the cam lobe.
Trust me, if this is your first time and you don't stick to basics like insuring that the piston in the cylinder you are working on is at TDC on the compression stroke, you will ***** up. Don't over think, this is not that complicated......
Trust me, if this is your first time and you don't stick to basics like insuring that the piston in the cylinder you are working on is at TDC on the compression stroke, you will ***** up. Don't over think, this is not that complicated......
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,596
From: san antonio
Club Member
Joined: Oct 2011
Posts: 11,165
Likes: 2,466
From: Nor Cal
Mberlin74, (you may already know this) but with your questions on "feeling the air from the spk plg hole and using a straw in the hole to watch its lift etc"...Are you aware that there are 2 TDCs per the 4-cycles (aka 4-Strokes)? Only 1 TDC is appropriate
Fraught with Disaster for a Novice ...IMO (maybe Disaster is too strong a word 
)
But for discussion purposes...it would take less engine revolutions to achieve your goal
Take for example, adjusting (Statically) Hyd lifters on a Small Block Chev (when you could do that, it might have changed by now)...a tech isn't going take the time to find TDC (on Comp Stroke) 8 times by rotating the crank at least 16 times
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.
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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.
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.
)But for discussion purposes...it would take less engine revolutions to achieve your goal
Take for example, adjusting (Statically) Hyd lifters on a Small Block Chev (when you could do that, it might have changed by now)...a tech isn't going take the time to find TDC (on Comp Stroke) 8 times by rotating the crank at least 16 times
.
.
.
Last edited by multihdrdr; Jun 30, 2016 at 04:48 PM.
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