Opinons sought: P38 4.0 -v- 4.6

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malcolm_durant

malcolm_durant

Active Member
Posts
272
Location
Chatham, Kent
Evening All,

Continuing my slow-burning quest for a P38 with a V8 and I can't help notice the 4.6 doesn't really seem to be any pricier than the 4.0. Even insurance seems likely to be little different to me (I have a full NCB etc etc).

I am wondering from those who have owned both how they would sum up the pro's and con's of the two capacities of V8 when compared to each other.

For example, is there much real world difference in performance, economy, driving experience etc?

Given the size and weight of the car, I'm not too clear if the 35bhp & 40lb/ft advantage the 4.6 has over the 4.0 translates into anything tangible on the road.

Thanks in advance!

Malcolm
 
they are essentially the same car, the only difference apart from the 4.6 usually has a higher spec, is the stroke of the piston!

they both share the same box, how is it stronger? (unless you mean against the manual but i thought the manual was only fitted to the doozel?)
 
Had both, the 4.6 can be less smooth and certainly less fuel efficient. Have two 4.0s, (3 if you count the 3.9 classic) and generally more user friendly. You don't notice the power difference really as they are all big heavy beasts. If you drive any of them for performance expect fuel consumption in the teens if you are lucky, so the slightly less power of the 4.0 is not an issue at normal speeds.

A lot of the 4.6s get converted to gas - some swear by it, others at it believing it can exacerbate overheating.
 
i think getting a good engine is the most important, not the size. theres no point in getting a duff engine as it will have to be replaced, and you can replace the 4.0 with a 4.6!
 
as gav said most important is getting a good engine.. ive had both and theres not a great deal of difference to be honest,,they say the 4.6 has more overheating issues ? but a neglected 4.0 could be worse than a loved 4.6.
in the later ones (1999 on) the engines are pretty much the same, and the 4.0 was done in the higher spec models too.
 
I'm sure I remember reading that the 4.6 is actually more economical than the 4.0...

Just had a quick google check and the figures I found seem to back that up.

Not sure why that would be though unless it's just better suited to the weight than the 4.0

Guy
 
kooky_guy said:
I'm sure I remember reading that the 4.6 is actually more economical than the 4.0...

Just had a quick google check and the figures I found seem to back that up.

Not sure why that would be though unless it's just better suited to the weight than the 4.0

Guy
Click to expand...

When I was looking for a P38 with an LPG conversion in mind, the LPG spcialist advised that a 4.6 would be better as, in his experience, they were more economical than the 4.0. Having bought and converted a 2000 4.6 Vogue, we're getting 19mpg regularly.
 
gavbriggs said:
i stand corrected they are slightly different boxes, it'd be wise for me to research brfore blurting in future!!!
Click to expand...


No worries

I only know due to my project motor having the wrong gearbox for a diesel conversion

Got my knowledge from ashcrofts who were very helpful, apparently they fit some of the 4.6 auto box (ZF4HP24) to the 4.0 & 2.5 auto box (ZF4HP22) for an extra fee as certain bits are stronger


Ashcroft Transmissions

they change the center internals to do with C1/C2 One way clutch
 
My 4.6 Thor seems to return better economy than any 4.0 I have heard about. (It also seems better than many 4.6 GEMS equipped RRs.)

16 mpg in town and 22mpg on the motorway/good A roads.

I'd suggest the additional torque provided by the thor manifold and Bosch management were reasonably large contributors to gaining economy through increased efficiency.
 
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