B.O.R. Missed Oportunities ?

[ag1234]

All these years, have we discussed the Ausie Rover 4.5L/ engine/head ? 10 deg. valve inclination with stud mounted rockers. This
  may allow for moderate canting of the valves ?  AIR., this is a square motor with 3.5" bore/stroke, with .687" raised deck ?

 Intake manifolds in general.: At the bottom of most inlet bores you'll find a SHARP edge ! This is not to enhance flow, only lazy.
  How to fix ? . Start with largest diameter " dovetail cutter", that will fit down the bores. Finish with ball rotary file and reverse sanding
  cones.
 
  Why venturi valve seats ? When Ford was developing heads for the 7L. GT40 engine, for  better torque off the turns. they
   used venturi style seat areas, for increased port velocity, They thought this would limit top-end power but actually increased it,
   throughout the range. This could be obtained in other heads with custom valve seats. By stepping the OD. of a taller seat,
   you achieve a correct venturi ratio, height to cross section reduction.
                                                                                                                    Onward, Art.

[MGBV8]

Are you speaking of the Rover 4.4L?  Only square Rover V8 that I am aware of.  Never seen one.  Can't be a lot of them.

[ag1234]

A little larger at running temp.

[Dan Jones]

Art is talking about the Australian 4.4L V8 used in the Leyland P76.  It's related to the Rover V8 but has a taller deck height and correspondingly wider intake manifold, along with other differences (cylinder heads, crank bolt circle, pilot bushing, motor mounts, etc.)  It had a 3.5" bore and 3.5" stroke.  There's nothing magic about a "square" engine but the 3.5" stroke could be used in a Rover V8.

[BlownMGB-V8]

I think it's a cast iron crank and the Buick 350's high alloy nodular iron crank with 3.85 stroke might be a better choice for a larger motor. The 3.5" bore is nothing to get excited about and the taller deck is no help really. At that deck height the 300 block with it's 3.75" bore is better. A .050" overbore with that crank gives a 5.7L displacement. Just about right for the MGB.

On all the BOPR/SBB engines the power is in the heads. That is why turbo and super charging was so successful with those engines even at low boost. It also explains the ongoing popularity of porting despite the expense. The TA heads with 230cfm intake flow out of the box are a mighty improvement and competitive with porting as a path to power despite the high cost, and they can be further ported to get flow up into the 260 numbers. That's competitive with current LS technology IIRC. Dan, I'm sure you could offer us further insight on that as it's sort of your hobby. What would you say to a question about the dollar to HP ratio of big valves vs porting vs new heads vs new heads + porting? Are they at all competitive with each other, or does the cost just skyrocket?

My approach has followed the factory track first with turbo and then with supercharging, and finally with the new heads and supercharging. That still leaves porting the new heads but I doubt I'll ever do that.

Jim

[ag1234]

Dan, any flow reports for the 4.4  head ? Seems like moderate canting of the valves should help. Any long-term use reports on a 3.85" stroke with a short rod ratio ?
                                                                              Art.