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ag1234
Arthur Gertz

(136 posts)

Registered:
03/29/2023 08:26PM

Main British Car:


B.O.R. Missed Oportunities ?
Posted by: ag1234
Date: December 16, 2024 10:21AM

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
Carl Floyd
Kingsport, TN
(4571 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: B.O.R. Missed Oportunities ?
Posted by: MGBV8
Date: December 16, 2024 11:36AM

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.



Edited 1 time(s). Last edit at 12/16/2024 11:37AM by MGBV8.


ag1234
Arthur Gertz

(136 posts)

Registered:
03/29/2023 08:26PM

Main British Car:


Re: B.O.R. Missed Oportunities ?
Posted by: ag1234
Date: December 16, 2024 11:19PM

A little larger at running temp.


Dan Jones
Dan Jones
St. Louis, Missouri
(308 posts)

Registered:
07/21/2008 03:32PM

Main British Car:
1980 Triumph TR8 3.5L Rover V8

Re: B.O.R. Missed Oportunities ?
Posted by: Dan Jones
Date: December 18, 2024 08:05PM

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
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6508 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: B.O.R. Missed Oportunities ?
Posted by: BlownMGB-V8
Date: December 19, 2024 11:14AM

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
Arthur Gertz

(136 posts)

Registered:
03/29/2023 08:26PM

Main British Car:


Re: B.O.R. Missed Oportunities ?
Posted by: ag1234
Date: December 20, 2024 04:40PM

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.


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