The V8 Owners Forum -

Hello all , I'm after some help I'm collecting parts for a tt conversion over the winter .
At the moment I have a3.9 with cam , holley 390 and offenhousen manifold in a back halved firenza running 10x15 rear. Wheels on a volvo 240 axle .
I'm after building another engine so what's best
3.9 or 4.6 as a starting point . I would have thought cross bolt mains to be better ?
I already have a set of alloy buick 300 heads waiting to be used .
I'm a fabricator so not fussed about making exhaust manifolds was looking at 2 Subaru turbos to use
With these heads I think they will give a very low compression
What pistons will I need will rods and crank be ok
Also do I go blow thu carb or injection and use a mega jolt ?
Any one done one or any help would be great also looking at a sensible hp don't want to keep building more engines , will be used on the track a lot drag racing cheers all Dazza

I would probably say go with a 4.6 if you are building a new engine. Ideally you'd need one with top hat liners. The buick heads are great and do give lower compression, I would say probably upgrade at least the pistons to forged and maybe the rods. Saying that, people have and can do quite high hp on standard internals as long as it's done properly. Fuel injection would probably be better for a high hp turbo installation over carbs, but it depends what your preference is.

Are only certain 4.6 got top hat liners ?
This is all new to me thanks

1stpop wrote:Are only certain 4.6 got top hat liners ?
This is all new to me thanks

It's a well known problem with the 4.6 blocks, and if you are adding forced induction it increases the risk (to any block, actually). Don't have that risk, and fit top hat liners. It's not cheap, but it's the only solid solution to dropped liners. I had a 3.9 resleeved, and two liners dropped and my turbos only put out a little over 300bhp.

Ok thanks , so any 4.6 block can have top hat liners fitted, any idea who does this and at a rough cost ,
Cheers

There are a few places that do them, have a search on google. Cost is usually about a grand.

I used Turner Engineering - which cost about £1500. There are cheaper alternatives.

Chris.

I used David Knight for my top hat installations. Near Northampton.

Perry

Thanks all , will get the block sorted 1st then .

1stpop wrote:Hello all , I'm after some help I'm collecting parts for a tt conversion over the winter .
At the moment I have a3.9 with cam , holley 390 and offenhousen manifold in a back halved firenza running 10x15 rear. Wheels on a volvo 240 axle .
I'm after building another engine so what's best
3.9 or 4.6 as a starting point . I would have thought cross bolt mains to be better ?
I already have a set of alloy buick 300 heads waiting to be used .
I'm a fabricator so not fussed about making exhaust manifolds was looking at 2 Subaru turbos to use
With these heads I think they will give a very low compression
What pistons will I need will rods and crank be ok
Also do I go blow thu carb or injection and use a mega jolt ?
Any one done one or any help would be great also looking at a sensible hp don't want to keep building more engines , will be used on the track a lot drag racing cheers all Dazza

There was a thread here a while back where a guy in the US did a simple blow through turbo kit on an MG or something. Not sure where it is.

Likewise another member did TT his RV8 using a pair of TD04's....again, name, cant remember.

Blow through carb can work, but IMO you'd need to buy a carb off someone to suit the application, trying to find someone to tune a carb will be very difficult.
I'd prefer to use fuel injection, simply because it is far more versatile and gives better all round control. But that'll be an additional expense of course compared to the carb.
Long term, the more you drive the car...the more it will make sense..

Realistically I'd say you're talking in the 500hp range and at that it should be pretty reliable. Over that is possible...but the old Rover really isnt that great.

As for base engine...4.6 is probably best, but again if you already have a good 3.9 I'd struggle to justify hunting down and spending a fortune on a 4.6