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Any problem checking piston-valve clearance this way?

Posted By: Guitar Jones

Any problem checking piston-valve clearance this way? - 05/22/20 01:01 PM

I didn't want to drive the hour to work and then an hour back to get my dial indicator, remove the valve springs and install the checking springs so I thought I'd just stack feeler gauges between the rocker and valve tip and see if the engine stills turns over with no binding at the critical points from 15* BTDC to 15* ATDC. And it does. I have .098 under the exhaust and .087 under the intake. I think I have enough clearance.

Attached picture IMG_20200522_085114.jpg
Posted By: 340Cuda

Re: Any problem checking piston-valve clearance this way? - 05/22/20 01:03 PM

I have never seen it done that way but it seems perfectly valid to me.
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/22/20 01:07 PM

Well I guess if you must know the exact number it would be very time consuming, but if you really only need to know that you have enough clearance then I think this worked.
Posted By: gzig5

Re: Any problem checking piston-valve clearance this way? - 05/22/20 01:07 PM

It should work, but are you sure you would be able to determine a slight interference? Say .005"? I'd be worried about something deflecting and allowing it to continue turning.
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/22/20 01:16 PM

Originally Posted by gzig5
It should work, but are you sure you would be able to determine a slight interference? Say .005"? I'd be worried about something deflecting and allowing it to continue turning.

I suppose I could continue to add a little at a time until it stops turning, but even if it were say .005 off I think I still have sufficient clearance. I've run my race engines much tighter than this without problems. The lifters are shimmed solid and the feeler gauges under the pedelstals are there to get zero lash.
Posted By: markz528

Re: Any problem checking piston-valve clearance this way? - 05/22/20 03:55 PM

I have done it like that in the past but I used height checking springs and pulled all the spark plugs so that I had a better feel. You can bend a valve pretty easy if it hits.

Of course this does not work with hydraulic lifters.
Posted By: pittsburghracer

Re: Any problem checking piston-valve clearance this way? - 05/22/20 04:11 PM

I do every single one of my builds this way and will be doing another one today. I sneak up on my total clearance. If my clearance is running close to minimum I will clay them up and check them that way because doing it the feeler gauge way changes the valve timing a few degrees.
Posted By: fast68plymouth

Re: Any problem checking piston-valve clearance this way? - 05/22/20 04:27 PM

Originally Posted by markz528
I have done it like that in the past but I used height checking springs and pulled all the spark plugs so that I had a better feel. You can bend a valve pretty easy if it hits.

Of course this does not work with hydraulic lifters.


Unless you bottom the lifters out first.
Posted By: gregsdart

Re: Any problem checking piston-valve clearance this way? - 05/22/20 04:33 PM

Do you check for lifter bleed down after you are done? If ther is any then subtract the lash you see at the base circle of each from your measured cleaeance.
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/22/20 05:12 PM

I shimmed a pair of stock rollers solid then shimmed under the pedestal to get zero lash. This also told me what the preload on the lifter would be. It' a tad light at .048 and .043. Hughes says .080 on these lifters so longer pushrods may be needed.
And yes, I had all the plugs out so I could feel it better.
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/22/20 10:57 PM

Well it runs, didnt bang any valves. Lifters are noisy though I figured they would be. Ordered some longer pushrods but it runs good and everything works as it should. I dkn't think I can continue to run the 87 octane crap in it anymore as it diesled a little on shut off. Might get some colder plugs for it. It has some Bosch E3's in it now of unknown heat range.
Posted By: dvw

Re: Any problem checking piston-valve clearance this way? - 05/23/20 12:04 PM

The only issue I see with this method is if the radial clearance was very close. Running clearance heated up could be too close?
Doug
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/23/20 12:18 PM

The pistons don't have valve reliefs, they are flat with a slight dish so not a problem on this engine but most valve reliefs are usually spec'd for what ever size valve they fit or for stock size valves.
Posted By: 440Jim

Re: Any problem checking piston-valve clearance this way? - 05/23/20 01:45 PM

Originally Posted by Guitar Jones
I shimmed a pair of stock rollers solid then shimmed under the pedestal to get zero lash. This also told me what the preload on the lifter would be. It' a tad light at .048 and .043. Hughes says .080 on these lifters so longer pushrods may be needed.
And yes, I had all the plugs out so I could feel it better.
Wow, removed lifters and shimmed, removed rockers and shimmed, etc.
I would have driven to work and back to get the dial indicator. The time spent taking the motor apart and putting it back to together correctly is worth considering.

That said, you are close and should be OK, just don't float the valves with RPM.
Posted By: Guitar Jones

Re: Any problem checking piston-valve clearance this way? - 05/23/20 06:29 PM

Originally Posted by 440Jim
Originally Posted by Guitar Jones
I shimmed a pair of stock rollers solid then shimmed under the pedestal to get zero lash. This also told me what the preload on the lifter would be. It' a tad light at .048 and .043. Hughes says .080 on these lifters so longer pushrods may be needed.
And yes, I had all the plugs out so I could feel it better.
Wow, removed lifters and shimmed, removed rockers and shimmed, etc.
I would have driven to work and back to get the dial indicator. The time spent taking the motor apart and putting it back to together correctly is worth considering.

That said, you are close and should be OK, just don't float the valves with RPM.

Lol, it was already apart except I had already bolted the heads back on thinking I was going to use a smaller cam, but the bigger cam showed up Friday and the smaller one did not and probably won't until Tuesday or Wednesday. I really needed to get this truck running so I figured I'd give it a try. Didn't really have anything better to do and the drive to work is excruciating even at 4 in the morning so...But it runs great, I can't complain, but probably will anyway. laugh2
Posted By: dvw

Re: Any problem checking piston-valve clearance this way? - 05/24/20 11:34 AM

Originally Posted by Guitar Jones
The pistons don't have valve reliefs, they are flat with a slight dish so not a problem on this engine but most valve reliefs are usually spec'd for what ever size valve they fit or for stock size valves.

But not all. If its a custom piston the configuration could be tight in this area. In your case this method wouldn't worry me. But I wouldn't use this method ( or dial indicator either) as gospel. Especially if cam timing may be moved around.
Doug
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