406 Build from He//

[GA445]

After being scammed by a quote reputable FE guru with a Dyno Time-only cracked block motor, I located a 406 cross-bolt main and started building. Survival Motor Sports heads, Diamond 41302 pistons, comp cams 33-244-4 solid cam 244-244,540 lift. The engine is 30 over and the crank is a 1U cut 10, Harlen Sharp rocker assembly with end stands. Here is the problem after assembly by my engine guy, who is a FE guy, the valves are hitting the pistons. Double-checked everything. What am I missing??

[JimNolan]

Where in the h-ll did you find a cross bolted 406. I'd make sure it had a HP on the side of the block. To your question: The answer is simple, you get gigantic head gaskets, cut valve reliefs in your pistons, get other pistons or get a cam with less lift. That's the only options I see. I ran a FE with a .031" quench for years but it only had a .500" valve lift.

[GA445]

All your responses are valid, I was looking to see if I missed anything, and will be looking for cam options come Monday, the motor is stamped HP. 

[GerryP]

It depends upon how bad it is.  Advancing or retarding the cam can change piston to valve clearance. 

Cam advanced:  intake valve to piston clearance is reduced, exhaust valve to piston clearance is increased

Cam retarded:  intake valve to piston clearance increased, exhaust valve to piston clearance reduced

Obviously, if the pistons don't have the valve relief in the correct position or the reliefs are for a smaller valve, no cam advance or retard is going to fix that.  You really need to know where the valve is contacting the piston to know how to fix it.

[Jb427]

What did your engine Builder say? When you asked him what you should do? did they tell you anything? besides there is not enough piston to valve clearance

[jayb]

+1 on what GerryP said.  Double check your cam timing, make sure it is right.  If it is, pull a head and put clay in a couple of the cylinders.  Find out if the issue is valves missing the reliefs in the pistons, or if it really is P-V clearance.  I don't know of any .540 lift cams that will cause a piston to valve clearance issue...

[67xr7cat]

So things are not adding up right here.  That cam is Comps 270S which is 224/224 @ .050 and with a 1.76 rocker ratio has a gross valve lift of .551", so after lash  you should have a net lift of .529".  Your piston has a CH of 1.755 which with a standard length rod should be used with a 3.78" stroke crank which would be stock for a 406.  That piston should have plenty of valve clearance with that cam.

Now here is what is not adding up.  You say the crank is a !U which is a 428 crank with a 3.98" stroke.  Unless your rod is .100" shorter than stock you would need to take .100" off the top of that piston, otherwise it would be sticking out of the block a good bit!  If they cut .100" off the piston and did not re-cut the valve notches I can see a possible problem.  Now if that is what was done first find a new shop.  As to fixing it you could cut the valve reliefs deeper.  A shop can flycut them in a mill or Isky sells a tool that you use with your cylinder head and you can cut them without removing the pistons from the block.

Just one thing you will need to find out how much can be cut from that piston. If the pistons are out you can measure the crown thickness.  If not I'd call Diamond and ask them.  Hope this helps.

[hbstang]

+1 on what 67xr7 cat said.also make sure pistons are not in up side down! it happens.