cam base circle/pushrod length ?s HELP!
09-27-2013, 06:45 AM
#1
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cam base circle/pushrod length ?s HELP! How do you find the cams base circle while heads are on? when i installed my cam i lined up cam gear 6 oclock & crank gear at 12 oclock, is that top dead center on #1 cylinder? and will the base circle be at the position i need to measure push rod length?
09-27-2013, 05:07 PM
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So i been reading for days now and im trying to figure out where my cam needs to be to measure for pushrod length, so if the piston is at tdc will the cam base be at the lifters? is there a way to use the timing gears so i know where the base circle is? or am i thinking to much and should just put piston on tdc and measure from there?
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09-27-2013, 11:48 PM
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Well, a lot of the guys frequenting here are looking for answers just like you. Some tech veterans that still come around make take a while to get to your question.
No, just don't just put on TDC and measure for pushrods. 6 o clock and 12 oc clock or 12 o clock and 12 o clock are both TDC.....Anytime the crank is at 12 the number 1 piston is at TDC. The cam's sprocket determines whether its compression or exhaust stroke.
For finding the cam's base circle, this method is simple and works:
If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.
No, just don't just put on TDC and measure for pushrods. 6 o clock and 12 oc clock or 12 o clock and 12 o clock are both TDC.....Anytime the crank is at 12 the number 1 piston is at TDC. The cam's sprocket determines whether its compression or exhaust stroke.
For finding the cam's base circle, this method is simple and works:
If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.
09-28-2013, 09:30 AM
#10
120 views in 16 hrs and not one person can give me a simple answer? i remember when this site was active for tech questions, now it seems if your post doesnt start with,build thread, wow enging blew etc, you dont get much replys!
sorry had to vent! all i need is pushrods and im done with motor, but cant get an answer and my manual isnt helping!
sorry had to vent! all i need is pushrods and im done with motor, but cant get an answer and my manual isnt helping!
Sorry had to vent.
I took a shot at helping you in one of your other posts and hope that gets you moving in the right direction.
09-28-2013, 09:43 AM
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The thing is i only have one pushrod tool, i have no pushrods.how can i determin the valve movement with one rod? Would i have to setup the ex and turn the crank till it starts to open, then unbolt that rocker and put the rod in the intake and measure from there?
Last edited by allan808; 09-28-2013 at 09:49 AM.
09-28-2013, 10:09 AM
#12
Post your measurements in terms of turns of the pushrod checker tool from completely closed position.
09-28-2013, 10:10 AM
#13
You answered your own question. Put your checker in the ex. and rotate the
engine till it's roughly halfway open, then remove and use to measure the in.
When checking the ex. for length set the engine where the in. has met max
lift and just starts to close. You should be using light checking springs or
remove the outers(assuming duals) and just set up the inners for much less
pressure when unbolting the rocker arms so as to not strip out the threads in
the heads. You may end up with 2 different lengths depending on the diff-
erent lobes of your cam but most pick a compromising length between the
two measurements which will have adecuate preload for both.
engine till it's roughly halfway open, then remove and use to measure the in.
When checking the ex. for length set the engine where the in. has met max
lift and just starts to close. You should be using light checking springs or
remove the outers(assuming duals) and just set up the inners for much less
pressure when unbolting the rocker arms so as to not strip out the threads in
the heads. You may end up with 2 different lengths depending on the diff-
erent lobes of your cam but most pick a compromising length between the
two measurements which will have adecuate preload for both.
09-28-2013, 04:39 PM
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You answered your own question. Put your checker in the ex. and rotate the
engine till it's roughly halfway open, then remove and use to measure the in.
When checking the ex. for length set the engine where the in. has met max
lift and just starts to close. You should be using light checking springs or
remove the outers(assuming duals) and just set up the inners for much less
pressure when unbolting the rocker arms so as to not strip out the threads in
the heads. You may end up with 2 different lengths depending on the diff-
erent lobes of your cam but most pick a compromising length between the
two measurements which will have adecuate preload for both.
engine till it's roughly halfway open, then remove and use to measure the in.
When checking the ex. for length set the engine where the in. has met max
lift and just starts to close. You should be using light checking springs or
remove the outers(assuming duals) and just set up the inners for much less
pressure when unbolting the rocker arms so as to not strip out the threads in
the heads. You may end up with 2 different lengths depending on the diff-
erent lobes of your cam but most pick a compromising length between the
two measurements which will have adecuate preload for both.
09-28-2013, 10:51 PM
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leave the rocker off put the push rod on the lifter turn the motor over while you hold the pushrod in place once you feel it go all the way up and down turn it a little past it comes down and you are on the base circle of the cam
09-29-2013, 12:30 AM
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Put your one pushrod (the tool set just short of 7.400") in the intake lifter slot, install the rocker so the pushrod and lifter are in contact, and observe the rocker's movement while you turn the crank. Intake valve closing (pushrod moving downward) shows you are approaching TDC firing. The exhaust lifter will be on base circle for sure, so you can take your measurement as well.
Post your measurements in terms of turns of the pushrod checker tool from completely closed position.
Post your measurements in terms of turns of the pushrod checker tool from completely closed position.
7.400 pushrod, intake 1.6 turns & exhaust 1.7 turns
7.375 pushrod, intake 1.3/8 turns & exhaust 1.45
09-29-2013, 08:07 PM
#19
You're checking where your rocker is riding on the tip of the valve and adjusting the push rod to make it ride closest to the center while you rotate the motor aren't you? Just making sure your doing it right.
09-29-2013, 08:40 PM
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What i did was, on #1 cylinder tdc, i watched as the intake got to full open then measured the exh side. Then turned the engine till exh was full open then measured the intake! is that correct?
