Help on Valve to piston clearance

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Help on Valve to piston clearance

Post  75truck on July 4th 2017, 12:42 am

Have a 429 zero decked block with cj type pistons with the one intake eyebrow.

First photo shows short block with brass strips that will seperate head from block by .040 (compressed dimension for Victor Reinz head gasket).



Here is head installed on right bank with the dial indicator.

I brought up the #1 piston to TDC and pushed the valve down and measured .425 as the valve hit the piston. I did not install the lifter, pushrod, and rocker yet.

Am I missing something? I have not installed the above items, and put puddy on the piston top and rotated the crank.

                                                                                  In                     Ex
My Bulllit cam card says                     Duration @.50          230                   235
                                                    Lift                        .3235                .325
                                                    Gross Lift                .560                 .562



Is there a good article that addresses the checking of valve clearance for the 429 /460 engine?

Bob
Tucson

75truck

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Re: Help on Valve to piston clearance

Post  rmcomprandy on July 4th 2017, 5:39 pm

75truck wrote:Have a 429 zero decked block with cj type pistons with the one intake eyebrow.

First photo shows short block with brass strips that will seperate head from block by .040 (compressed dimension for Victor Reinz head gasket).



Here is head installed on right bank with the dial indicator.

I brought up the #1 piston to TDC and pushed the valve down and measured .425 as the valve hit the piston. I did not install the lifter, pushrod, and rocker yet.

Am I missing something? I have not installed the above items, and put puddy on the piston top and rotated the crank.

                                                                                  In                     Ex
My Bulllit cam card says                     Duration @.50          230                   235
                                                    Lift                        .3235                .325
                                                    Gross Lift                .560                 .562



Is there a good article that addresses the checking of valve clearance for the 429 /460 engine?

Bob
Tucson

Valve drop at TDC with a head gasket ... that sounds about right with a CJ type piston notch.

Valve lift AT Top Dead Center NOT maximum valve lift, (which occurs somewhere with the piston past half-way down the bore), is probably what you are missing.

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My next step Play Dough

Post  75truck on July 5th 2017, 9:18 am

Ok - thanks a bunch for setting me on the right track.

I'll be spinning my engine with the puddy soon and report the results.

Thanx so much
Bob
Tucson

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Re: Help on Valve to piston clearance

Post  Mark O'Neal on July 6th 2017, 3:07 am

If you're going to compute it you'd need the lift at 5 and 10 before and after split overlap.

But clay is cheaper than a Cam Doctor.

The only cam grinder that could ever supply us those numbers was Harold Brookshire.

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Re: Help on Valve to piston clearance

Post  gt350hr on July 6th 2017, 11:10 am

Intake valve lift at 10*s after TDC ( at the retainer) should be around .128-.130 ( assuming a 110*lsa) so you will have PLENTY of piston to valve. Same for the exhaust. I'm no Harold Brookshire (rip) but I spent a few years in the camshaft industry as well as the piston industry. rmcomprandy  is right the piston is often an inch away from the fully open valve. The "tight spot" is like Mark suggested , usually around 10*s before TDC on exhaust closing and 10*s after on intake opening. Unless the head has been milled most pistons will accept a cam in the 250's at .050 before getting close.

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Checked clearance with clay

Post  75truck on July 9th 2017, 11:59 am

And here's what I got.  Intake valve clearance .246   Exhaust .230

Seems like I have got plenty of clearance.

Thanx all!






Bob
Tucson

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