Bracket Talk
Piston to valve clearance.

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June 17, 2018, 06:42 PM
Mike Frizie
Piston to valve clearance.
What you guys like to see for piston/valve clearance on your BBC? Checking the 582 build today getting .060 intake /.100 exhaust with a .041 head gasket and lash at zero. HMMMM


Michael Frizie
ET 2471
June 17, 2018, 07:37 PM
imakehp
Depends on a few different things but the clearances you have @ zero lash should work in a basic hot rod engine.
If you're checking it cold with aluminum heads you'll have even more at operating temps.


.
Dave



F J B

June 17, 2018, 11:54 PM
Scott Smith
I wouldn't be afraid of .050 on the intake with the lash.
And .080 on the exhaust.

Intake valve chases the piston. It takes a train wreck for it to hit and by that time clearance doesn't matter.

Excessive valve clearance is waisted CCs that could be added compression with less dome. Less dome happier combustion.
June 18, 2018, 10:24 AM
Kenneth
You are good to go!


Abbott Racing Heads
(432) 558-2841
June 18, 2018, 10:40 PM
Ron C.
It depends on how accurate your checking method is.In general that is very safe under normal conditions. I've run as close as .010 on intakes but exhaust I like more cushion.


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John 14:6
"Creekside Racing Ministry"
MFI system, ProCharger Non-intercooled [6.02 @ 229 or 3.91/660' soft tune and killing power above 6K rpm]
Ron Clevenger
June 19, 2018, 11:48 AM
wideopen231
Plenty good especially with steel rods I have run tighter with aluminum rods and never issue and turn them 9500 rpm.




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June 20, 2018, 07:50 AM
00 DEAD ON
As close as possible. Otherwise your leaving HP on the table JMO


Brian Mollison
2013 American Dragster
2020 Sumerduck Dragway VA Top ET Champion
2017 Sumerduck Top ET & SSS Track Champion
2017 MAC Top ET Track Champion
2009 Sumerduck Dragway Va Top ET & IHRA SSS Track Champion
2008 IHRA Division 1 Top ET Bracket Final Runner-up
2007 Colonial Beach Dragway Top ET Track Champion
June 23, 2018, 04:22 PM
Mike Frizie
Ok im lost . Added the lash to the valves and my measurement doesnt change?


Michael Frizie
ET 2471
June 23, 2018, 09:21 PM
imakehp
Obviously that isn't possible so start over and double check your procedure and measurements as you go.
I didn't read this entire post , but did you mention how you're measuring things?


.
Dave



F J B

June 23, 2018, 09:29 PM
Mike Frizie
Using dial indicator and checker springs, measuring at 10 degrees after for tightest measurement on intake, 10 before for exhaust. Exhaust is fine , intake too tight now? Wtf?


Michael Frizie
ET 2471
June 24, 2018, 02:07 AM
imakehp
The 10 before and 10 after is usually pretty fail safe. But maybe try one intake @ 5 and 15 just to confirm 10 IS your closest point. Same on an exhaust.
Make sure your indicator stand isn't flexing/moving as well as your pointer or degree wheel.
If you had to use different retainers with the checker springs make sure the rocker arm isn't hitting the outside of the retainer somewhere and screwing with your measuring.
I always check with zero lash and just keep that in the back of my mind when considering if I have enough clearance. An aluminum head max effort engine doesn't really need more then the valve lash for clearance on the intake when cold.
We used to say we gave up compression if carbon built up in the intake pocket of the piston.
Of course it's kinda easy to get 15-16 to 1 compression with modern heads these days.
One thing to remember though is you have to check every cylinder when running it that close. Even number rockers arms so they stay with their cylinder.
BTW, using checker springs will actually gain you about .005-.015 more clearance once you put on the race springs.
I like to check a cylinder and then check it again to make sure it repeats. Same thing when degreeing a cam.
Good luck...hope you get it telling you the same thing over and over so you can trust what it's telling you...


.
Dave



F J B

June 24, 2018, 06:06 PM
Ron Gusack
I think the best way to check clearance is to not use checker springs because they are so inaccurate, at least they are when I used them.
June 24, 2018, 07:17 PM
rusty
quote:
I think the best way to check clearance is to not use checker springs because they are so inaccurate, at least they are when I used them.

checking springs will not seat the valve properly and very likely not the same each time


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

June 24, 2018, 08:07 PM
Ron Gusack
quote:
Originally posted by rusty:
quote:
I think the best way to check clearance is to not use checker springs because they are so inaccurate, at least they are when I used them.

checking springs will not seat the valve properly and very likely not the same each time

The springs I had were light enough to make it really hard to set lash without opening the valve so I think you're right about them not seating the valve consistently.
June 25, 2018, 05:58 AM
Scott Smith
If your going to use checker springs you have to physically "pull up" on the retainer while zeroing the dial indicator.
And I check clearance through the range to make sure I have the closest spot.