Piston to valve clearance consideration

[Mrbill426]

Although I will be checking it anyway is there any reason to believe I will have piston to valve clearance issues when using these pistons with the custom cam I had ground?
The cam is based on a stock '68 340  with .444"/.453" lift's; 276/284 degree duration's.  Heads are stock rebuilt with hardened inserts and heavier springs; stock ratio rockers and stock length push rods.  Since the pistons are supposed to be stock (but forged) replacements and the cam a stock profile I would think there would be plenty of room.  It's a early 1972 engine with a forged crank.   I do intend to smooth sharp edges on the crowns and check them for equal weight.
Thanks!

[1 Wild R/T]

Should be fine...

[TGGodfrey]

I have a similar measurement on my cam and i run these pistons in my AAR.  Mine stick out of the hole .024 and I am using the felpro 8553 gasket.  Heads measure 67 CC's so they have been lightly milled (cleanup).  I just clayed mine a couple days ago and clearance is more than adequate.  DO NOT take my word for it, double check yours but you will not be wasting your time assembling it.

My cam is an old general Kenetics and Measures 220/225 @ .050 and .450/.450 Lift.

Gasket is verified to compress to .047.  safe to say i could go to a .030 gasket if i wanted.

Terry

Clay is slightly above the piston.

[Chryco Psycho]

I agree you should have lots of room up to .520 lift area at least .

[RUNCHARGER]

Good idea to always check. I have run a 495 lift cam with those pistons no problem. You never know over the years how much the heads have been milled etc. though.

[Mrbill426]

Thanks guys... you all rock; I appreciate the help! 

I assume when using the clay I will need a pair of solid lifters?  What engine would I buy them for to get the right size?? 

[TGGodfrey]

no on the solid.

I use an old lifter, Take it apart, remove the spring and oil washer/valve, then use small 3/16 stainless washers to shim the plunger to the preload i want (.030 in my case).  You could do the same with a new one too.  Small washers are available at menards.

I used check springs when i did these because i was also measuring for pushrods too.  Checker springs just make turning easier but are not necessary for checking clearance.  I can get you a picture of the lifter later if you like.  I could send it to you too as long as you send it back.

Terry

[ek3]

there is the fairly accurate  old quick test.. set the lash/pre- load on a pair of valves and then   place .100"  stack of feeler gauges under the rocker arm and turn it over to see if it is touching anywhere ... the more important factor is in cam timing . the open and close points during overlap is where any clearance issues will be . its not just how much lift but, when it gets there..... 

[Mrbill426]

@TGGodfrey thanks for the info and I do have checker springs; also some old lifters I can take apart.
So, I won't ask you to send yours but appreciate that offer.

no on the solid.

I use an old lifter, Take it apart, remove the spring and oil washer/valve, then use small 3/16 stainless washers to shim the plunger to the preload i want (.030 in my case).  You could do the same with a new one too.  Small washers are available at menards.

I used check springs when i did these because i was also measuring for pushrods too.  Checker springs just make turning easier but are not necessary for checking clearance.  I can get you a picture of the lifter later if you like.  I could send it to you too as long as you send it back.

Terry

[Mrbill426]

@ek3 good point there; thanks 

there is the fairly accurate  old quick test.. set the lash/pre- load on a pair of valves and then   place .100"  stack of feeler gauges under the rocker arm and turn it over to see if it is touching anywhere ... the more important factor is in cam timing . the open and close points during overlap is where any clearance issues will be . its not just how much lift but, when it gets there..... 

[ek3]

you're welcome ! nothing like a little peace of mind !! been there many times !

[jimynick]

If it's together, you can run the particular piston up to it's TDC, check the installed height of the valve stem, remove the retainer and spring and lower the valve until it touches the piston, checking the distance it moves with a dial indicator. Just my 

[Chryco Psycho]

Except that TDC is not usually the tight point , it is more like *8 after TDc when the intake is closest to the piston as the valve chases the piston down the hole

[ek3]

Except that TDC is not usually the tight point , it is more like *8 after TDc when the intake is closest to the piston as the valve chases the piston down the hole

yes. you have  got to check it during the overlap phase.. its about timing and lift..