Intake Valve sizes & H617CP30 Pistons

[Badsunbird]

Okay Everyone,

Putting together a new 355 sbc and using the H617CP30 .275 dome pistons. My question is does anyone know how big of an intake valve you can run with these pistons without having any clearance issues? (i.e. 2.05, 2.08, 2.10 ect) Getting ready to order new 23° aluminum cylinder heads and would like to know if anyone has any information about this?

[Monza Harry]

The manufacturer should be able to give you the valve relief diameter. May even be in some online catalogue. I don't know what the radial clearance should be but that shouldn't be hard to find out either. The other aspects will be ultimately decided by the Head/Cam/Rocker Combo. I am sure someone here will have that information and will share this. I have read this all and used to know it off the top of my head but that "was a long long time ago" I thought about recording this in a booklet, but I had already forgotten the info and that is why I thought I should record it. Harry http://fme-cat.com/overlays/part-detail ... Num=H617CP 30&partType=Cast Piston&brandId=SD I checked the "JE Pistons website and they recommend a Min. of 0.100 valve to head clearance (longitudinally/or travel) and a radial clearance of 0.050 (that means per side, a valve relief of 2.200" dia. will only fit a 2.100" valve, as a pretty radical SBC example)

[Smiley]

2.100 valves will usually require aftermarket pistons notched for valve clearance
What heads are you looking at ?

[spencerforhire]

There's so many variables that in the end you'll have to do the "lump of clay" test to make sure. Not just the valve diameter variable, but camshaft lift, duration & centerline, deck height, head gasket thickness and even the head(my AFR 227's and others have non-OEM valve spacing) itself can effect piston to valve clearance. Just went through this process myself; I had intended to run 1.6:1 rockers on at least the intakes but ended up downgrading to 1.52:1 all the way around just to keep the clearance safe, especially on the exhaust. I could have advanced the cam a couple of degrees, but it wasn't exactly where I wanted it to begin with and had already made compromises in that area.

[Badsunbird]

Alright, here is what I am working with,

292 duration
244 @ .050
.006 valve timing
110° lobe separation
106° intake centerline
501 valve lift
.334 lobe lift
Exh. closes @ 34° ATDC
Exh. opens @ 77° BBDC
Int. opens @ 37° BBDC
Int. closes @ 74° ATDC

Head gasket is .041 compressed
Using 1.5 Rocker arms
Cylinder heads are going to be 195cc, 72cc com. chamber.
?.?? Int. Valves
1.60 Exh. Valves
Standard sbc deck height.
H617CP30, .275 dome pistons.

Did I forget anything?

[spencerforhire]

Yeah- A lump of clay. lol.
Joking aside, you are probably ok, as you only have .501 lift, 72cc heads and the block is not decked. The piston manufacturer might have some idea as to how deep their valve notches are in comparison to others.

[Smiley]

I would use forged flat top pistons
64 cc chamber heads with 2.02" intakes
clay test before final assembly.

Beware the no name aluminum heads on ebay, they are cheap for a reason.

[Badsunbird]

Well I contacted Federal Mogul the other day and they advised me that you can safely run 2.10 intake valves with these pistons as long as you are running a standard deck height and unmilled cylinder heads without any clearance issues with my cam selection. So I went ahead and ordered my new Pro-filer cylinder heads with the 195 cc intake runners, 72 cc combustion chambers, 2.05/1.60 valves. I think that this should end up being a pretty good set up.
Thanks everyone for all of your input, it's been greatly appreciated!