I knew the 409s have a Heron head but I don't think I ever saw the deck of one before. What's the purpose of the crescent shaped reliefs in the cylinder walls? And the flats on the intake sides of the pistons provide some squish? How does the combustion chamber work (compare) in general to a standard wedge? How about the ports on these engines? Being 'truck' engines I guess not high flow stuff? Thanks for the photos.
The notch at the top of a truck block drops the compression about a 1/2 point. The stock truck heads are similar to low perf 348 heads in valve size and port size. However, the truck heads have a small combustion chamber as well. The actual combustion chamber is located in the cylinder-compression is changed by changing pistons.
Bore cuts lower the compression on the truck engines without playing with the heads and pistons too much. All the trucks heads are pretty crappy stock. 333 head with the rotators removed will get by. 348/409 likes tight quench. I run mine 28 on the high side rock. 11:1 on pump premium without problems. Runs best with total timing at 34 degrees.
A classic Heron head is flat, but with the combustion chamber contained within a dished depression in the top of the piston. The W-engines don't have a classic Heron head. The heads are flat, but the chamber is formed by the angle of the block deck. The low compression versions have a flattop piston forming a true wedge chamber. The higher compression versions have some squish provided by a very cumbersome and heavy piston. The angled block deck was also found in the Mercury-Edsel-Lincoln V8 introduced about the same time as the W-engine. The angled block deck was found to have more negatives in terms of piston design limitations than advantages from no valve shrouding. Both designs were taken out of production in the early '6os and the Ford OHV8s and BBC which succeeded these featured "porcupine" multiple inclined valve angles with the chamber back in the head. jack vines
Benno, Most of that was in the pistons. The notch in the cylinder drops the compression a little, but might add a little to breathing by unshrouding the valve.
The unshrouding of the valve was something that I always thought was a good thing. I have had guys argue the point with me but you know me I am a total ass when I et something in my head. I personally am always trying to keep a running list of motors inmy head that make good quick blower motors so the lower compression truck motors from the factory are always something that I look for. hey look at your messages I want to pick your brain about something OT.
By the way I never mentioned it and should have cool motor. Anyone who doesn't love a W motor truck block or not has a screw loose.
Nothing wrong with truck blocks. The one with the finned aluminum covers I posted above started as a truck engine. Did lots of changing, but it should hang with a factory QB (HiPo 2X4) engine.
The notch in the block is also there for exhaust valve clearance and if you run oversize valves you can have a clearance problem on a pass block you can ask me how I know.
Wingman9, The painted valve covers were a 1962 only deal on the 400 and 409 hp/409s. In 1963 they went to chromed valvecovers on the HiPo engines. The paint has a green tint to the silver. It's supposed to be the "right" color. It came from Show Cars (409 specialty parts). Benno, The engine is an original 1951 engine with good numbers and matching belly numbers. I spent a ton of money having the original heads "rebuilt" by the best (supposedly) Panhead rebuilder in the country at the time. Trouble is, they were in about as bad a shape when they got back as they were when I sent them. So I went with STD heads. The rocker covers are original (60s/70s) Randy Smith Custom Cycle Engineering parts. I had to buy 2 sets and use 2 front covers to get the full finned covers on both heads. About a month after that, they started selling repops.
LOL if the best panhead builder in the country got those heads I would have done them right for you. Those old heads were hard to work with, a lot of guys used to mill the brass seats out of them and try and put pressed in hard seats, that didn't work well, something about the alloy that they used when they cast the heads. We discovered that screw in seats worked best. @saltflats, I have had to notch a Hypo 409 block to clear the valves before, not nearly as much as a truck block is notched but still had to relieve one before. I am no expert about it and may be totally incorrect but I think that the notch in the truck block had more to do with it then just to lower compression, I think it was something that they did to build low end torque. It is not something tat I could prove and I have never read anything about it being that it is just something that I have grown in my head.
I put together an 11.5 to 1 cr'd .060" over/409 back years ago. It had a NASCAR solid cam in it and a reworked 348 trip intake that I put three big Rochester 2-barrels on.. 2.5" cast-iron exhaust manifolds with Imp exhaust pipes with one flipped 180 degrees and all this bolted right onto my '67 Camaro 350SS's engine bay just like it was stock!! It started off life as a lime truck engine.. I gave $50 for it back then... Chrome valve covers and chrome trip air filter housing.. Sucker ran like a SB on steroids!! pdq67
The Jalopy Journal
