3.9V8 to 4.6V8

[101RRS]

From reading a lot of threads concerning converting 3.9s/4.0s to a 4.6, at the macro level I understand I need a 4.6 crank, conrods and pistons (are these last two needed - if so why can't the 3.9s conrods and pistons be used?)

Where would be the best place (cheapest of course) to source these bits new - always on the look for second hand but they seem to only come up rarely.

Also where is the best place (cheapest) to get top hat liners.

Thanks

Garry

[bee utey]

A 4.0/4.6 has bigger main bearings than a 3.5/3.9. So the 4.6 crank will not fit into a 3.9 block The reason you need different rods/pistons is that with extra stroke the old ones would stick out of the bore at TDC. You need to get a whole 4.6 short motor. The only long stroke conversion that will fit the 3.5 is the rare 4.2 crank/rod/piston set. I don't know how it would go with the 3.9 piston bore size.

[CSK]

It might be worth visiting "RPi Engineering - Specialised Rover Engines" (http://www.v8engines.com) for lost of info on Rover V8s, conversions etc.

[101RRS]

So the 4.6 crank will not fit into a 3.9 block

I understood the 3.9 and the early 4.6 out of the P38 were the same block - the higher graded blocks became 4.6s and the lower graded blocks became 3.9s.

Garry

[PhilipA]

Not 3.9 but 4.0.

Name changed reputedly to match Jeep in advertising but a 4.0 has the same bottom end layout as a 4.6 but shorter stroke.

Crank, rods, pistons, are different to a 3.9
Regards Philip A

[101RRS]

Ok - so I have misunderstood.

So the original basic engine design line ended with the 3.9. A new block design (well heavily modified) was introduced with the 4.6 in about 95 which was produced concurrent with the different 3.9 blocks until late 98 when all V8 engines had the same same blocks with different strokes resulting in the new 4.0 (same actual capacity as the 3.9 but different block/induction) and the old 4.6.

Thanks for clearing that up as I might have looked at getting a 4.6 crank etc only to find it would not go into my 3.9. I assume 4.2 cranks etc are rare and as expensive as hens teeth.

How does the P76 4.4 compare to both the 4.2 and the 4.6?

Thanks

Garry

[steve_35]

There is a complete p76 motor for sale on ebay

4.4 V8 Range Rover Land Rover, P76 Leyland Engine Motor - eBay Engine Parts, Engines, Components, Car Parts, Accessories, Cars, Bikes, Boats. (end time 15-Aug-10 14:37:24 AEST) (http://cgi.ebay.com.au/4-4-V8-Range-Rover-Land-Rover-P76-Leyland-Engine-Motor-/160465833521?pt=AU_Car_Parts_Accessories)

[bee utey]

The P76 motor is physically wider (about 25mm) as the Australian engineers used longer rods to maintain smoothness. Crankshaft main bearings and flywheel mounting flange are different. Inlet manifold is a 2 barrel downdraft type. The inlet manifold off a Rover can be used with spacer plates but is prone to vacuum leaks around the spacers. Plenty of P76 motors have been fitted to early Range Rovers etc but they are getting harder to get parts for. My engine shop can no longer source main bearings for them. ACL made them last in 2004 but I suspect that is the end of them. The P76 heads lack the mountings used on the Rovers for alternators and a/c brackets. Using the Rover heads involves using hollow pushrods as the P76 does not run pressure fed rocker shafts.
Really the most reliable conversion is a proper 4.6 rebuilt to best practice etc, then just bolt your bits on to it.

[blackbuttdisco]

I know of a complete P76 with auto gearbox for sale in Melbourne.

[Siska]

For your 3.9 you could look for a Buick 300 crank. Takes a little bit of work and a few specialized parts, but will stroke a 3.9 to around 4.8.

Here is a couple of links I've found about it.

Affordable Aluminum Buick / Rover Stroker Motor, by Kurt Schley (http://www.britishv8.org/Articles/Affordable-Stroker-V8.htm)

And a company that supplies all of the parts that you will need,

D&D Fabrications: Engineering & Fabrication Services (http://www.aluminumv8.com/index.htm)

I've spoken to Mark from D&D and he is a really helpful guy and really knows his stuff. I'm in the process of ordering some parts for the engine I'm building for my Disco.

[101RRS]

For your 3.9 you could look for a Buick 300 crank. Takes a little bit of work and a few specialized parts, but will stroke a 3.9 to around 4.8.

Here is a couple of links I've found about it.

Affordable Aluminum Buick / Rover Stroker Motor, by Kurt Schley (http://www.britishv8.org/Articles/Affordable-Stroker-V8.htm)

And a company that supplies all of the parts that you will need,

D&D Fabrications: Engineering & Fabrication Services (http://www.aluminumv8.com/index.htm)

I've spoken to Mark from D&D and he is a really helpful guy and really knows his stuff. I'm in the process of ordering some parts for the engine I'm building for my Disco.

Thanks for that, though the first link while it talks about the 3.9, it seems to be discussing stroking a 4.0 and 4.6.

I was also hoping for something local - I think I need to reconsider what to do with the 3.9 - maybe a straight rebuild making it higher compression and doing some head and cam shaft work.

Cheers

Garry

[clubagreenie]

On the top hat question, TR Spares in Syd had a 4.0 top hat rebuilt short motor for $3500- at christmas.

[Traco]

The 3.9 is smoother than the 4.6 due to its bore / stroke combination, and it's not quite so prone to cracking as the later 4.0 litre D2 blocks.

A 3.9 can provide reasonable performance, especially as you say when fitted with hc psitons, maybe tin gaskets and a high torque cam like the Real Steel Cyclone specially developed for 3.9 hotwire engines.

But in a heavy 4x4 it's torque that really matters and it's here that there's no substitute for capacity. However I wouldn't risk fitting a second hand 4.6 due to the all too common perosity problem - either a new hc short engine, or better still a top hatted seasoned block is ideal, but then the costs go up considerably.

[bee utey]

From realsteel.co.uk:

305cu in/5l STROKER CRANKSHAFT- 4998cc
DW49951Stroker crank-cast 3.9/4.2 blocks £854.81
This crank has a stroke of 3.508”. Used with our forged stroker pistons, the capacity will increase to 4998cc. Crank must be used with our conrods, as the big end journals are wider than standard. Nitrided & crossdrilled. Long nose. Small diameter mains for 3.9/4.2 cylinder blocks. 2” big end journals. Weight = 19.6k. Made in England.

Real Steel's Rover V8 stroker kit will increase your engines horsepower and torque. The kit has been tested, and it is awesome! Crankshaft - a nodular iron crankshaft crossdrilled & nitrided, with increased stroke (3.508") Available for small main [3.9/4.2 block] and large main [4.0/4.6 block]. Con-rods - 6" steel “I” beam conrods are used, these are very strong, & give a better rod to stroke ratio. Pistons - Forged, high compression, 3.720"
pistons are strong and lightweight. Larger 0.927 gudgeon pins are used.
Fitting - Some grinding will be required, to enable the reciprocating components to clear the inside of the block. A small area of the sump will need to be panelled out to avoid the second conrod from the front of the engine hitting the sump during rotation. Rotate the engine completely to check that nothing is touching internally. A minimum of .060” clearance is required. Be careful not to grind through the “raised” oil gallery “tunnel”.


:)All the stroker stuff is on this site.:)