Four barrel conversion


Well-Known Member
This has been on the cards for a long while, I finally got around to having a crack at it.
Until recently I owned a Ford High Performance Mustang 289 K code, the K code had a unique 4 barrel Autolite 4100 carb, this thing was the mutts nuts, so much nicer than a Holley.
When a friend had one for sale I grabbed it and built it up to be the same as the one fitted to the Mustang, my logic - if it made the Mustang's 4.7 litre go like the wind it would be OK for the 4.6 Rover.
It is not proven yet, but it is fitted and the car seems to like it, finessing the jetting is yet to come, but the hard work of getting the thing sitting on the Rover is done.
Nice and clean inside, valley gasket removed to allow trial fitting of Offy intake and port fettling
I went for a 1" phenolic spacer to improve torque and reduce heat transfer. The spacer is ducted underneath to the brass stub I tapped into the rear for a PCV system.
Manual choke Autolite 4100 on Offy 360.
I made a cable throttle linkage operating off the old auto kick down cable bracketry at the rear of the left cyl head.
K&N Filter and bling to finish off :)

Who knows, a set of downdraught's may be the next step ?


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ooohhh tasty :)

I never did get my weber to run right, it was good, but never spot on :)

Best of luck with it, V8s need a 4 barrel they just look right together



Well-Known Member
Excellent. From what I’ve read with the Edelbrock/Weber 500, no off the shelf needle/jet combo is spot on, close but not perfect for the 4.6. A custom profile is required. I’ve got an AFR gauge going on my build so I can really see what’s going on at different driving conditions and tune accurately.
I like the spacer, I’ve got similar plans but with a thicker one. Any plans to blend/taper the underside?


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First test today, had to return home PDQ, AFR gauge off the scale lean. I had fitted jets for a bog standard Ford 289 thinking they would be close, nope ! car would not pull, better fuelling when the secondaries came in.
So I fitted the jets for the 289 HiPo and bingo car pulled well, only a slight hesitation just off idle. so back again and increased the pump shot by re positioning the lever as the shot looked weak, another run and the slight bog has gone. Pulled a plug and colour good. Need to watch AFR at a very light throttle, may need to go up one jet size on primaries. Car pulls like a train, I would say the HS8 match the Autolite for torque, maybe even have an edge, but car feels stronger at high rpm with no sign of running out of puff.
All this with stock ish 3500s exhaust manifolds, headers will really let it run.
Very pleased with the first runs, well worth all the planning and work.

Jim the Offy has had some work and has been cleaned up, I made sure the ports are ok to the head, the plenum is fairly nice corner wise. It is an old fashioned 360, there are better designs now, but this one likes WOT :)

Thanks Richard
The 4100 is not a true 600 CFM Carb, which is why I picked it for the Rover. A 600 is reckoned to be too much for a stock 289 (4.7 litre), the 4100 reputedly flows around 530 ish CFM so ought to suit the Rover.
I did not want to just go and buy a 500 Weber, that would be too easy :rolleyes:
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