3.5 to a 3.9

garethp6

garethp6

Active Member
hi i got this spare engine that only done 35k from new and i think its a high compresson and i am thinking of boring it out 2 3.9 or 4.0 what parts would be the same would the crank still be ok to use i know the bores would have to be done out bigger please help me out on this 1
 
The v8 uses different sized liners for the 3.5 and 3.9/4.0 engine blocks. A huge expense to remove the 3.5 liners, machine the block out and then drop in the larger liners, much easier just to find a 3.9 block and use that instead. The crankshaft and rods are interchangeable between the 3.5 and 3.9. The 4.0 has the same bore/stroke/capacity as the 3.9, but has different crankshaft, rods and pistons fitted inside, so is not interchangeable, unless heavy machining is done. Hope this helps.

Simon
 
Hello Gareth,

As Simon indicated, boring out your 3.5 to a 3.9 is a total waist of money given the availability of ready 3.9 litre blocks. There is also the fact that the 3.9 litre engines use a different casting, so boring out a 3.5, especially an early P5B or P6B block will weaken the block considerably.

Ron.
 
Why not just step up to a 4.6? theres not a lot to gain in getting a 3.9.

Graeme
 
I'd like to have £6500 to spend on the whole car. Reckon that would make it a good one
Wonder how much TP3500s spent on his , if he doesn't mind being asked
 
SydneyRoverP6B said:
ghce wrote,..
Why not just step up to a 4.6?
Click to expand...

Hello Graeme,

Cost. It is MUCH more expensive to go for a 4.6 than a 3.9.

Ron.
Click to expand...
Seems to be a few 4.6 RR around very cheap, most especially witht he increasing cost of keeping them fueled up, or does the cost come in with the componants required to get the engine under the p6 bonnet?

Graeme
 
ghce wrote,..
Seems to be a few 4.6 RR around very cheap, most especially witht he increasing cost of keeping them fueled up, or does the cost come in with the componants required to get the engine under the p6 bonnet?
Click to expand...

Hello Graeme,

Like most things it is always cheaper to buy a complete item, be it a Range Rover or a bicycle. The cost of individual components will always exceed the cost of the whole.

Ron.
 
thanks guys i will end up going down that road then so a 3.9 is not worth going for just better cheaping the 3.5 just wanted a bit more power out of the old girl
 
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