Iam building a 427, that is 60 over and iam wondring if im going to run into piston to valve clearance problems. The pstons are arais pstons with a 41.5 cc dome. 11.5 with the 781 heads. The cam is the EX284 574-578 lift and a 284 296 advertised duration and a 240 246 duration at .050.
Thanks
Mike

 

Difficult to know but probably not. It's always good to check though.

Valve lift means nothing since the valves are not open when the piston is at TDC. They hit when the piston starts getting near the top and the valve still isn't fully closed. This depends on duration, overlap, LSA etc. Advancing or retarding cam timing can cause PV problems if clearances were already close.

Rule of thumb is you want minimum 0.100" on the intake and 0.125" on the exhaust. You'll need 2 solid lifters set to zero lash to simulate a hydraulic lifter. Unless there's oil pressure, a hydraulic lifter will give a false reading.

What size valves are in the 871 heads? If they haven't been upgraded to the larger 2.19/1.88 then I wouldn't worry about it. How big are the valve reliefs in those pistons. I had LS6 pistons once and had to get them fly cut for a .630 lift cam. The LS6 pistons also didn't like the 781 heads. A very small section on the side of the combustion chamber needed to be ground down so the piston didn't hit the head.

My current engine has JE race pistons with a 50cc dome giving me 13:1 compression with 119cc heads. Solid roller cam has 0.714 lift and I have lots of PV clearance.

 

I have upgraded to the 2.19 1.88 valve. Im not to sure what the valve reliefs are.

http://www.ariaspistons.com/products...ic.pistons.pdf

If you go there it shows what piston i have. Its for the 427 dome top closed chamber

 

11.5:1 compression with 118cc open chamber heads. When you go to put it together, do a test fit in one cylinder. Install piston and rod onto the crank. You don't need the rings on yet. Install a head gasket and head. See if the crank will rotate past TDC. That will tell you if the dome will fit into the combustion chamber or not.

There's a big difference in building an engine and assembling an engine. When built properly, you can expect to take it apart a few times before it's done.

I'm not impressed with Arias piston choices. My bore is 4.320 and I see no pistons available.

 

Well, the short block is already together. And my heads wont be done for a couple weeks, they are at the machine shop. Im just really worried that i will have to have the pistons cut.