cams

[estutjaweh]

search down again...no surprise there!

I've just been offered a good used set of pistons, rods and crank to convert the 4.0 engine to 4.6. A few questions to this:

Do I need to source a 4.6l ECU or is the only difference the chip in which case I can just use my 4.0l EUC and upgrade the chip.
Cams. Fast road cam for good torque and acceleration/throttle responce. I don't care all that much for top speed. What recommendations do you have?


Further info, presently the rest of the engine internals are standard (I thought it best to upgrade capacity first) so apart form air intake and cooling, the engine is still 'as is' from the factory.

[QBee]

ECU - I have been told very firmly this morning by my TVR expert that there is no such thing as a 4 litre ECU or a 4.6 litre ECU or a 5 litre ECU. The bible says that the 5 litre ECU is set up differently to allow for the greater airflow through the engine. You may need to get a different chip for the ECU if you use a different cam.

Cams - I have just been choosing what cam for my car for fast road use and fun track day use (ie fun driving, not trying to break lap records). The choice seems to be between the TVR885 cam and the Stealth cam. I don't have a clue, sorry, if you can just keep your 4 litre cam. There are other cams available, with different torque characteristics.

You need an expert, and i am not one. I didn't even know you could convert a 4 litre to a 4.6.....

[KateV8]

You need to be careful what is possible with the block you are starting from, and this brings to light the age-old confusion between 3.9 and 4.0l blocks which others on here know far more about than I do. I sent my complete engine to J Eales last year for the same conversion and finished up with a brand new block, necessary because the 4.6 crank bearings were too large for the journals in my existing engine. As far as I know it's this whole crossbolted/non crossbolted scenario but don't go away and somebody will be along to advise...

[Mr Supercharged]

You are right, the size is 2.3" on the intermediate and pre serp engines and 2.5" on the cross bolted (4.0 / 4.6) motors. It is possible to use an intermediate block with a larger crank if you line bore it I believe, but best to get the right block to start off with.

[phazed]

If you do go own the 4.6 route, I have an ECU that was altered by Austec racing to suit my tweaked 4.6.

[blitzracing]

The basic ECU is the same across all engine sizes- the only thing that changes is the Fuel Map chip that plugs in, so you just need a 4.6 chip.

[wuckfitracing]

As previous post says beware crank journals will have to be line bored to take 4.6 crank if it is a non cross bolted 3.9 engine. I know I did it. Still works out to be quite astrong block though.