FM 246P piston

[Royce]

Does anyone have the cc volume of the valve pockets on this piston?.. I am building a 360 horse 352 and am having a tough time getting the spec compression.  The piston sits down in the hole .053  Even after decking the block .030. I think there is still a .015 shim gasket available otherwise I will go with the .020. Not ideal..

[gt350hr]

   -6.2 cc's according to my notes.

[frnkeore]

Are you using the 6.54 rod?

[price5113]

I remember the reliefs coming in around 8cc's back years ago when I ran a set, and yes the comp height with those pistons makes for terrible 'quench"..........

[427John]

These pistons must be for the later low compression 352's,the original's had no valve reliefs.Frnkeore brings up a good question,with the .030 deck and still being .050 down,would lead you to believe that you have the shorter 390 rods,even being rebuilder pistons they normally only drop .020 or so.The original 352 rods will have a B9AE or C0AE casting number,my buddies early 360hp engine originally had the early B9AE narrow beam rods,he was concerned about the strength of the narrow beam rods and used late 352/360 C7TE wide beam rods when he rebuilt it.

[Royce]

I ended up with a C7 Rod probably a 360.. The original CO rod was .040 shorter than that!  I know it is common practice for mfg to add compression height on stock replacement pistons.. I guess to be safe after a meathead sbc builder gets his hands on an FE.  LOL  I think I will spit the diff on valve relief volume and go 7 cc.. I have yet too CC the heads.  I think I can get my compression but quench won't be ideal..

[frnkeore]

Does anyone have the cc volume of the valve pockets on this piston?.. I am building a 360 horse 352 and am having a tough time getting the spec compression.  The piston sits down in the hole .053  Even after decking the block .030. I think there is still a .015 shim gasket available otherwise I will go with the .020. Not ideal..

Edit:
From the data that I have, the original low compression 352's, compression height, is 1.825, giving a Deck clearance of .055. The HC, CH is 1.866 and no valve relief, giving a nominal deck clearance of .014. My 361 Edsel pistons with 6.54 rods, have a measured CH of 1.872, .008 deck clearance and no valve relief.

Factory HC 352, is 10.2 CR, Edsel, 10.5, either account for the top ring space.

Speed Pro’s, 361, 6.488 rod, FT piston, Summit Racing Part Number: SLP-H994 has a CH of 1.882 in. Ford's original FT piston, was 1.902.

The 361, Speed Pro @ 1.882, gives nominal, deck clearance of .002 above the block, with a 6.54 rod.

A lot of time, the CH is reduced to compensate for the increased CR that the over bore gives.

[427John]

They also lower CH to accommodate any decking the block may need.Lowering CH has to be the worst way to adjust CR dishing the piston would be much better but it must be a more expensive method.I didn't realize there was that much difference in CH on the different versions of 352 pistons,I knew there was an export version of the 352 but didn't think they would drop the piston that much..Ford did that with 360's too,they used 390 pistons both the flattop with 4 VR and the dished ones, some even came thru with 410 pistons,I believe thats why some of the 360's were so prone to pinging.

[Barry_R]

Most of the cast replacement Sealed Power pistons were originally designed for large volume rebuilders such as Jasper or AER.  They reduced compression height by +/-.020 to allow those companies to mill blocks and decks without needing to dedicate time (= cost) to individually fit each engine.  When you are rebuilding literally hundreds of engines each day its far easier to just cut every block .010 as it moves through the shop, and if its been rebuilt once or twice in the past you could find your way into trouble otherwise.  Some incremental reduction in performance was never a concern because the new replacement engine was always an improvement over the broken or worn out one coming out.

[Royce]

CH of my cast replacement pistons is 1.77   Factory spec is 1.844  The factory compression distance is .036. That is a lot of real estate to make up to get to the factory 10.5 compression ratio

[My427stang]

CH of my cast replacement pistons is 1.77   Factory spec is 1.844  The factory compression distance is .036. That is a lot of real estate to make up to get to the factory 10.5 compression ratio

If you are 1.77, put 390 rods and crank in there for 10.150 rotating assembly, with a .030 deck assuming you started at 10.170, you'll be .010 tall, add a Felpro 8554 and quench will be nice.  Not sure where compression will be not knowing heads and pistons, but will be a stout little stocker 390 bottom end

[Royce]

I would if that is what I was going for... My objective is to build a 352/360 hp as close as possible to factory specs, then test it to see if it really makes 360 horse  with original parts..Then it goes back in a 60 Starliner original 352/360

[427John]

When my buddy rebuilt his 360 horse engine he used a set of ancient NOS Jahns cast pistons I found at a swap meet they were flat top with no valve reliefs and he was very happy with how they worked out.The original pistons that came out of it had been knurled back in the early 60's by a perfect circle knurling machine that leaves a PC logo in the knurling on the skirts,we thought they were pretty cool.The old Jahns pistons were probably heavy as sledgehammers but he was happy and it balanced out OK.Have you done any tricks to the D heads?If you go with the larger valves you may be able to lose a couple of CC's with those.

[My427stang]

CH of my cast replacement pistons is 1.77   Factory spec is 1.844  The factory compression distance is .036. That is a lot of real estate to make up to get to the factory 10.5 compression ratio

I would if that is what I was going for... My objective is to build a 352/360 hp as close as possible to factory specs, then test it to see if it really makes 360 horse  with original parts..Then it goes back in a 60 Starliner original 352/360

Makes perfect sense, and fun project, I drifted off forgetting what this plan was.....  Are you considering a custom piston to get where you need to be? 

[frnkeore]

Nothing seems to add up:

1.75 + 6.54 + 1.77 = 10.06

 10.14 (decked .030)
-10.06
-----------
000.08

Was the block decked prior to your build?

I think I would be temped to have a set of custom pistons made with the original 1.844 CH and have .006, deck clearance.