4.2 into a 1987 classic with standard 5speed and flapper

So would it work?

I have 2 else rrc and my 1987. Thinking of stripping one lse as parts and was toying with a 1987 4.2 thought😀😀😀😀

block the same

Yes it would work. It's easy! Just take out the 3.5, and put in the 4.2.

If I were you as well I'd keep the hotwire injection with 4.2 and transfer that into the '87 RRC as well rather than run flapper injection on a 4.2. Although unless you have a pile of Lucas 14CUX ECUs, you can't offer yourself an ECU when it runs like a bag of spanners.

the easiest way is to stick a 4-barrel edelbrock carb on there

Actually I disagree. To fit a 4-barrel edelbrock carburettor you would first have to buy the kit. Then when you get all the bits in the post, you then have to take the inlet manifold off the 4.2 and fit the manifold and carburettor.

Or you just leave the engine alone and drop it in, then transfer the hotwire injection wiring loom into the '87.

So yes, if you have a spare £600 or however much this edelbrock carburettor kit costs and you're dead scared of minimal wiring/electronics then yes it would probably be 'easier'.

fight!!!

both right. but efi from 3.5 wont be tuned to 4.2...so can of worms..av to use 4.2 efi sytem, then real easy.

zen said:

fight!!!

both right. but efi from 3.5 wont be tuned to 4.2...so can of worms..av to use 4.2 efi sytem, then real easy.

Click to expand...

I said easiest

Fresh 4.2 with 500 Brock and standard cam makes more
bhp than injected 4.6

griffman said:

I said easiest



Fresh 4.2 with 500 Brock and standard cam makes more

bhp than injected 4.6

Click to expand...

Really? Didn't know that. Thought efi produced more grunt than carbs but I'm no expert

Defo stick with the 4.2 Hotwire injection system (14CUX) one of the best injections systems they used. Very simple to understand and tunable by Mark Adams if you are looking for ultimate bhp however one of Mark Adams chips through RPi engineering will make sure the engine is running spot on if you want to take it to the next level.

Flapper system would run it however you would need to fit an adjustable fuel pressure regulator and crank the fuel pressure up so it was injecting more fuel. Down side to this, there is no lambda feedback so its not self monitoring, and you are putting more stress on already very very old parts.

Yes the 4 barrel webber option is a very nice setup and if you didn't have the 14cux injection system would probably be the best £ for £ option but as you have the 14cux go with it and enjoy.

Sounds like an interesting project, I assume your 3.5 is past it's best? The smaller capacity engine is admittedly the lowest performer but majors on longevity as any of the 94mm bore units are prone to slipped liners. I knew an engineer who stroked (kit from Real Steel) a 3.5 to 4.3 & gained so much grunt that he blew the clutch pack on the auto, but of course the conversion wasn't cheap even though he did all the work himself.

Thanks for the replys.
I tow a big caravan so the extra would be nice also my right foot would feel much happier with the grin I would have on my chops when solo.
I do actually have a stack of flapper ecus and would run LPG most of the time so am in 2 minds on the fuel side.
My 2 else are not in the next weeks so let's see

Hmm LPG, that changes my view a bit.

If your going to be on LPG for 95% of running then it would be quite safe to say leaving flapper injection on isn't going to cause you any great problems and fitting a rising rate adjustable fuel pressure regulator with increased fuel pressure will ensure the engine is running something like right for those odd moments when you do run on petrol.

However, I still personally would invest a little more time in the project and fit the Hotwire system if you have it there as it a far better system than the flapper. And all of your LPG components should fit and work without issue.

I presume you have already upgraded, regularly service your ignition system with the LPG on board then?