VALVE CLEARANCE

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vitamindart

vitamindart

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ok, with all the rocker talk lately. it has me wondering if, I did put a set of 1.6's in my slant.
would I have enough valve clearance? cam is currently a 465 lift, would end up 496 with a 1.6 rocker. head was only given a slight shave, block on the other hand was given a bigger cut.
we cut .120 off the block. pistons were still a good .030-.060 in the hole ( if I remember correctly ) just wondering if I would have to pull the head to check the clearance or ?
 
Two ways to find out:
1. pull the head, put clay on top of the piston, replace the head, slowly spin the engine around a few times, remove head, measure valve impressions in the clay.
2. Just fire up the engine as is, after warm up, pull the head and look for bent valves and/or depressions in the pistons.
jus sayin....
 
You can take off the valve spring make sure you are at TDC and measure how far the valve drops till it hits the piston, then you will know for sure.
 
hmm, I didn't think of that Charlie. these were cut for different seals when the larger valves and ported. I guess I might be pulling the head.
 
If the guides were cut for positive seals, they were probably shortened, also. You might be OK, but you should check to be sure.
 
brian6pac said:
You can take off the valve spring make sure you are at TDC and measure how far the valve drops till it hits the piston, then you will know for sure.
Click to expand...
Actually that is not a good check. If there is not enough clearance, the intake valve would hit the piston, somewhere after TDC, and the exhaust would hit somewhere before TDC (or vice versa, I forget which)
Checking Piston-to-Valve Clearance, the Right Way!
This is the way I do it, except I start checking about 25 degrees before, and keep checking all the way to the point where the clearance gets larger. A lot depends on the cam, and where it is degreed.
 
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thanks Charlie, they were cut. might be a good reason for me to pull the head and verify the tdc mark I have always questions was off on this new balancer. would kill two birds with one stone. if I have enough clearance I could use the steel shim gasket I have and bump the compression a little while i'm at it.
 
While the head is off to check TDC, and V/P clearance, I would highly recommend you degree the cam, if not already done.
PS: You can do the checks, without removing the head if you so desire. You will need to remove at least 2 valve springs, however.
 
Keep in m ind, it's not the lift that gets you in trouble. It's the duration. Not the how much the valve is open, but when.
 
yeah, I have run into that before with my big block the .600 lift cam had clearance issues but the .705 lift cleared by a mile. looks like a head R & R will be in my future if I go this route.
 
RustyRatRod said:
Well, the "when" kinda covers that. lol
Click to expand...

Since I disagree I will explain. When is timing events, so 6 degrees BTDC or what ever. How fast is ramp rates. Like a 500 velocity and a 700 velocity since the 700 is more that is faster, so that also has to be taken into account. LOL.
 
dart19666 said:
Since I disagree I will explain. When is timing events, so 6 degrees BTDC or what ever. How fast is ramp rates. Like a 500 velocity and a 700 velocity since the 700 is more that is faster, so that also has to be taken into account. LOL.
Click to expand...

Ok let me put it this way. If one lobe ram is quicker than the other, it might get there WHEN the piston is still up. How fast the ram is affects everything.

If you disagree with that, you need help.
 
I only design cams lobes for a living and there is a big difference between when and fast. But Instead of picking apart what and how you said something to prove who is right who is wrong.......................................................

I NEED HELP. ha ha ha ha ha
 
dart19666 said:
I only design cams lobes for a living and there is a big difference between when and fast. But Instead of picking apart what and how you said something to prove who is right who is wrong.......................................................

I NEED HELP. ha ha ha ha ha
Click to expand...

If as a camshaft designer you cannot see that the ramp speed affects everything to do with WHEN the valve opens, then you need a new job.
 
RustyRatRod said:
If as a camshaft designer you cannot see that the ramp speed affects everything to do with WHEN the valve opens, then you need a new job.
Click to expand...

Or just dont talk to less than par people who do not understand simple physics. LOL Ramp speed is how fast..........WHEN "as you put it" is duration. Two different things. ha ha ha ha.
 
dart19666 said:
Or just dont talk to less than par people who do not understand simple physics. LOL Ramp speed is how fast..........WHEN "as you put it" is duration. Two different things. ha ha ha ha.
Click to expand...

Ok. A pitcher pitches a fastball. Then a slowball. Which one gets there first? That's WHEN. Sure, duration is how long the valve is open. But if you compare a slow ramp to a fast one, the fast one will get TO that duration FIRST.

Lesson over. Now go back to designing cams.
 
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