Just kicking tires, as I'm kinda new to the Y-Block arena, but I'm hoping for some additional insight. When I first got my 55 two yrs ago, I combed the interweb like crazy looking for a 312. Luckily, I didn't find one. What I've learned so far about the Y Block: Seems like an actual 312 isn't the correct route, unless one has a T-Bird or Concourse 312 car that just HAS to have a 312 in it.(although, casting numbers-wise, a judge would aparently need to pull your engine apart to verify it wasn't actually a 312...but I digress) Rather, one is better off with a 292 bored out to 312 specs, with a 312 crank, rods, and (of course, pistons), else a 292 Crank ground off-axis to throw the same stroke as the 312 Crank. This would eliminate the rear main seal issue and the cracked bearing webs, the inherent weak links in a 312 block. Do I have that right? Questions: Crank: Is an off-axis 292 crank with it's decreased m*** better than a 312 crank for revving up quicker, or does that make zero difference in a street car? High Ratio Rocker Arms: Easy enough principal. More Open Valve = more air. Essentially, a poor man's camshaft upgrade. But then I found out that the High Ratio Rockers need to be paired with Shorter Pushrods. Whaaaaa....? Doesnt that kinda defeat the purpose? I' sure things must work out math-wise, but it almost seems like a guy would almost be better off with the Stock Rocker Arms and just set his valve lash to near zero to get the same effect. Why wouldn't you want to use the longer Pushrods with the High Ratio Rockers to maximize the valve opening? Would the Stock (longer) Pushrods w/the High Ratio Rocker Arms drive the Valves into the piston? Connecting Rods: Same story here. Longer Stroke of the 312 CID crank makes total sense. But once again, I found if ya go with the 312 Crank, ya also gotta go with the SHORTER 312 connecting rods. again, whaaat? <scratching head> Jeez, "1 step forward, 2 steps back" seems to be the theme here again. Math obviously wins here as well with Stroke x Piston Area=Volume, but wouldn't one want the extra stroke provided by the longer 292 Connecting rods? Again, why wouldn't one want the Stock Connecting Rods on the stroker crank? Would the longer rods drive the Valves into the piston? Like i said, I think I've read enough to understand that the High Ratio Rocker Arms and the Larger Stroke Crank must be paired with the SHORTER Pushrods and Connecting Rods, but it sure isn't a very intuitive thing. Anything I'm missing? (yeah, I've already read that the dots on the Timing Gears don't line up...because THAT would make too much sense as well. LOL) I'm starting to understand why it's called a "Y" Block, as in YTF???? Thanks
Back in the late 60's when I ran 1/4 mile dirt track we replaced a 312 that went south with a 292 bored .060" over with the ECZ-G heads from the 312 it ran quicker lap times and accelerated quicker off the corners maybe thanks to the slightly shorter stroke. We did have a stroke of luck as we had a set of Gotha Hi-lift rockers very light in weight. A standing joke seems to be "all Y-blocks are a 312".
Your best bet would be to join y blocks forever. Those guys can answer all you questions and then some.
I haven't built a y block in a few years, but here are my comments: 1. As Longroof said, join yblocksforever and also to go eatonbalancing.com for information. 2. Seals - Bear in mind that these were developed in the early 1950's when all manufacturers use rope rear seal. Neoprene seals were later made for the 272/292 because they are were more common but I believe that neoprene are now available for the 312. (Eatons site should have information. 3. Main webbing - This was a potential problem if someone overtorqued the mains during a rebuild, but was not a common problem. I would focus on a 292 not because of seals or webbing, but because there are just a lot more available. 4. Stroking - I wouldn't bother with the expense of stroking a 292 crank. A .060" overbore on a 292 would be around 301 cubic inch and I think the stroked 292 crank can get you up to 318ci, so the stroking advantage would be negligible. Mummert has stroker kits that can go up to 338ci if you provide a 312 crank for offset grinding, but they are costly. 5. Rocker arms - A higher ratio rocker arm increases lift by having a greater distance from the pivot point, so it essentially becomes a longer lever. This typically requires a shorter push rod on any type engine. Hope this helps. James
If a longer push rod or connecting rod goes farther up on the stroke, you have to remember that it is also higher at the bottom of the stroke. So the effective "stroke" is the same. You have to modify what is pushing the rod (cam or crankshaft) to modify the stroke. A 292 connecting rod on a 312 crank would push the piston up above the deck, causing interference with the head.
The extra stroke would be a minimal gain, I would concentrate your funds on the on things that are Y-block weaknesses like getting the Mummert aluminum heads and intake and a matching camshaft. There was a recent facebook post in the y-block group showing some 4 tube equal length headers that should be available soon for car applications.
Try looking here and asking you will probably have to scroll back a ways there was a picture of them in their jig. https://www.facebook.com/groups/fordyblock/
Someone on Yblocksforever had/has a 312 for sale a while back. It might still be available. http://forums.y-blocksforever.com/Topic137495.aspx?Keywords=312#bm139433
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