My 4.6 V8 Rebuild Thread

[slug_burner]

garry,

The amount of power to be made is unlikely to be greatly different for an injected system versus a carburetor system. Power is mostly dependent on how well you can get the air into the cylinders, it is the air that limits how much power you can make. As long as you put excess fuel in, all the air (oxygen) molecules will be consumed. If you are after economy and want to keep your engine in tune longer without having to adjust or service points, fuel metering jets, slop in butterflys etc, then the injection system will do that better than a carburetor system. The injected system utilise multiple forms of feedback to adjust the fuel and deliver the correct amount for the air available. The injected systems also can alter the timing better than vacuum advance and spinning weights.

The injected ECU controlled system will run better for longer and will not waste fuel. The carburetor system will run somewhere thereabouts near enough is good enough and because it is mostly mechanical people have a better chance of fiddling with the system to keep it going at less than optimum tune but it will keep running.

People are a little concerned about electronics because they don't understand it or can't see what is going on and when things go wrong they feel helpless.

This is a good opportunity for you to have a play car on which you can learn about the electronic control and monitoring/feedback systems.

We all have our own drivers that lead us to do things and we also have limitations whether they be financial or time limited it doesn't matter we all make our choices. Good luck with whatever choice you make for your engine build.

[101RRS]

You have covered most of the things that are going through my mind. If I can get either a Thor or Gems manifold, injectors etc for a reasonable price I will go that route - if not then it is carbies.

Cheers

garry

[101RRS]

I have assumed that 4.0 and later 4.6 heads are the same - I should have confirmed that assumption earlier but didn't.

So are they the same and if not how are they different. Also how are they different to 3.9 and 3.5 heads?

Thanks

Garry

[slug_burner]

The head volume will differ for a given compression ratio due to the different swept volume of the engine.

[101RRS]

The head volume will differ for a given compression ratio due to the different swept volume of the engine.

In unmodified Rover engines the compression ratio is determined by the volume of the bowl in the top of the pistons and the stroke so if the heads are the same there should be no difference in compression ratio for a particular piston stroke combination if different standard heads are used.

Cheers

Garry

[PLR]

I have assumed that 4.0 and later 4.6 heads are the same - I should have confirmed that assumption earlier but didn't.

So are they the same and if not how are they different. Also how are they different to 3.9 and 3.5 heads?

Thanks

Garry

10 bolt 3.9 /4.0 / 4.6 same thing , suit comp gasket , smaller combustion chambers .

14 bolt 3.5 /3.9 1976 on basic same suit tin gasket , flat washer type stem seal , last 3.9 uses same stem seals as 10 bolts .

Earlier 14 bolt pre 1976 use same tin gasket , no stem seals , have smaller dia valve heads , same as used in Rover cars also same size valve heads as 10 bolt Leyland P76 and Terrier Trucks .

The easiest way of knowing what is what is that they all have id numbers like blocks .

[101RRS]

Thanks - I have 4.0 heads as the engine is a top hatted 4.0 - now with a 4.6 crank and conrods.

From what you have indicated - 4.0 heads are the same as 4.6 heads.

Cheers

Garry

[101RRS]

Another maybe basic question. Will I need to install a surge tank with either a Thor or Gems injection system? Do standard fuel injected RR and Discos have a surge tank and if so where is it installed??

Thanks

Garry

[bee utey]

Another maybe basic question. Will I need to install a surge tank with either a Thor or Gems injection system? Do standard fuel injected RR and Discos have a surge tank and if so where is it installed??

Thanks

Garry

Standard RR EFI pumps live in a plastic tub which installs in the tank through a big ring so they have their own swirl pot (surge tank?) built in. If you have an external pump in mind, look online, the ricer boys have all the blingy bits you'll need. Anything that can feed a snail powered Nismo will feed your V8.

Be aware that GEMS inlet manifolds are hardly different from D1/RRC 3.9 ones and have the fuel pressure regulator at the fuel rail. D1 may be easier to obtain. THOR systems have the fuel pressure regulator built into the pump assembly and a single line to the engine. You may have to fit your own external regulator to make it work on the truck. I believe you may be able to use the earlier injectors, rail and regulator in conjunction with the THOR manifold.

Just out of curiosity, are you putting gas back on this engine? Vapour injected gas would go well with your planned level of complexity.

[Kevin B]

the ricer boys have all the blingy bits you'll need.