Valve relief question

[ksquared]

I'm stopped on my 428 engine build with a problem. The valves are too big for the piston notches. Way too big as my picture shows. I marked the piston top for the valve center and then set a divider to the radius of the valves. I hope you can see just how much of a problem I have. The intake valves are 2.2" and the exhausts are 1.712". Pistons are good old TRW forged from the 70's? This is a bit beyond my experience. I understand about cutting larger notches & I'm aware of the Isky tool. But this seems like lot. And the scratch arcs are the valve edges, not the extra clearance needed around the valves. It almost looks like I'd have to notch the cylinder around the intake valve.  Suggestions?

[Tom Gahman]

I think the valve notches should be on the top of the piston.

[blykins]

I'm stopped on my 428 engine build with a problem. The valves are too big for the piston notches. Way too big as my picture shows. I marked the piston top for the valve center and then set a divider to the radius of the valves. I hope you can see just how much of a problem I have. The intake valves are 2.2" and the exhausts are 1.712". Pistons are good old TRW forged from the 70's? This is a bit beyond my experience. I understand about cutting larger notches & I'm aware of the Isky tool. But this seems like lot. And the scratch arcs are the valve edges, not the extra clearance needed around the valves. It almost looks like I'd have to notch the cylinder around the intake valve.  Suggestions?

Certainly plausible.  Here are a set of custom Diamond pistons for a 4.350" bore FE using TFS heads that have 2.190"/1.625" valves.  You can see how far up the valve reliefs go.



You're working with a much smaller bore and pistons that were never intended to see anything larger than a 2.090" valve.

[blykins]

Here are some Racetec pistons for a 428 build.  The reliefs are symmetrical, but you can see their size.   



Recognize that if the valve were flat against the face of the piston, you would need to cut the whole circle out of the piston, but valves come in at an angle towards the piston.  You will not need to do anything to the cylinders as the valve relief will only see the leading edge of the valve coming in. 

The way you have marked the outline is correct.  Center punch the centerline of the valve, then swing your arc around. 

[allrightmike]

Since the valves closest proximity to the piston occurs one side or the other of TDC would it not be best to establish the valve centerline reletive to the piston at that closest point?

[jayb]

It could be that your picture is deceiving, but it doesn't look to me like your punch marks for the valve centers are in the correct place.  They don't appear to be at the center of the valve reliefs that are already in the pistons.  How did you mark the center?

Also, what heads are you using?  If you are using stock 428 heads, with 2.000" valve spacing, you will have less of an issue with clearance to the cylinder wall than if you used Edelbrock heads (2.050" spacing) or 427 heads (2.100" spacing). 

One other thing I just noticed is that even with the stock 2.09" valves, using your marks the valves would still hit the piston tops.  I'm pretty sure you marked the center in the wrong place, or at least used the wrong radius to make your scribe mark.  Difference in radius between your valves and stock valves is only about 0.050".

Edited to correct the valve spacing dimensions - Jay

[ksquared]

The heads are FElony. The tool used to find the valve centers is an old valve modified. See picture. Brent, I did exactly what you suggested. The arcs are what I got. Jay, I don't see how I could have made any errors. The "punch" was in the valve guide and the head bolted to the block. I will admit that just because I can't see an error doesn't mean one wasn't made. Assuming my method is correct, it looks like I have two options: BIGGER notches or different pistons. I do have the original iron CJ heads but you know how it is when you want mo'power.  This is the only thing holding up my engine build. This kind of machine work is beyond my ability at home. I suppose I could take the engine to a machinist but this looks like an involved/expensive task whit no assurance that such a big cut won't compromise the pistons.

[64PI]

Good idea making a punch out of an old valve stem.... Crazy question.... Do you have the head dowels in place?

[jayb]

Try scribing a line using a 1.045" radius.  That would be the same as a stock valve.  If you miss the valve relief with that, then a stock valve won't fit, and that means there is something wrong with your method, because those pistons should work if they are 428 pistons.  They look just like a set I used to have.

Using the modified valve as a punch is the right way to center mark the relief.  Also you might check with Barry to find out what the valve spacing is on his heads.

You could also try using the same method with your 428CJ heads, and see where the mark ends up...

[ksquared]

Yes the dowels are in place. You are right about the original heads. I'll try them. Will be interesting. I'll also try the 1.045" radius. Just thinking... if the valves are at different locations in the chamber, maybe the 2.09 valves wouldn't clear either. I thought I read somewhere that the FElony heads have different (wider) valve positions so that the larger valve will fit. I might have imagined that. I'll check with Barry.

[FErocious]

It could be that your picture is deceiving, but it doesn't look to me like your punch marks for the valve centers are in the correct place.  They don't appear to be at the center of the valve reliefs that are already in the pistons.  How did you mark the center?

Also, what heads are you using?  If you are using stock 428 heads, with 2.100" valve spacing, you will have less of an issue with clearance to the cylinder wall than if you used Edelbrock heads (2.150" spacing) or 427 heads (2.200" spacing). 

One other thing I just noticed is that even with the stock 2.09" valves, using your marks the valves would still hit the piston tops.  I'm pretty sure you marked the center in the wrong place, or at least used the wrong radius to make your scribe mark.  Difference in radius between your valves and stock valves is only about 0.050".

By memory, the OEM STD LR/CJ valve spacing is 1.990", Edelbrock is at 2.045" and 427 OEM at 2.100".

[jayb]

Oops, you are correct, I was off by a tenth.  Actually I have measured 2.00" for standard FE, 2.05" for Edelbrock, and 2.100" for 427.  So much for trusting my memory 

[Tommy-T]

Something doesn't look quite right, but I've never had a pair of Felony heads.

I'd put some checking springs, I use stock rocker arm spacer springs, on #1 cylinder. Then I'd put the piston on #1 at tdc. Put some clay, silly putty, play dough on the valve reliefs of the piston. At the very least, put some wheel bearing grease on the edge of the valve...anything that'll leave a trace. Set the cylinder head on the block without a head gasket. Then gently push the valves down until they hit the piston.
Remove the cylinder head and see where the valves actually touch the piston. I'm all for math and geometry, but sometimes it's just easier to see where things are by actually putting them in the environment where they are going to live.

I have the exact same piston in my Frankenstein 428. With C3AE-D low riser heads and 2.09/1.65 valves they clear fine. Realizing the aftermarket FE heads all have different than Ford spacing and valve sizes, who knows until you check.

[ksquared]

Thanks all. Will check tonight. At work now... As for the clay method, I saw no point as the valves hit the pistons with heads in place with gaskets using check springs.

[ksquared]

Tommy, I think I'll try what you suggest just to confirm my "analysis". Maybe a little dykem blue might help