The V8 Owners Forum -

Apart from a 100cc what are the differences between 3.9& 4.0 litre land rover V8

V8 Rail wrote:Apart from a 100cc what are the differences between 3.9& 4.0 litre land rover V8

I believe that there is not 100cc difference, they are in fact the same displacement!

The 4.0 has bigger main bearing journals, it might be cross bolted as well. (not sure on the cross bolts)

As already said, they are exactly the same bore & stroke.

The 3.9 is 'old style', i.e. distributor, small mains & big ends
The 4.0 is the later cross-bolt style with no distributor.

There are some factory engines with a combination of the above....

Chris.

In addition to X 2, the blocks are also different.

4.0 litre engines are all fully cross bolted blocks.

The pistons, rods and crankshafts are distinct between the 3.9 and 4.0 litre engines and cannot be mixed.

Ron.

Thanks for the replys I am considering buying a 3.9 or 4.0 litre engine for my sand rail, which is the better engine I have the chance to buy a 4.0 litre engine complete which has a distributor and covered 84000 miles with an auto box can I put the flywheel from my existing 3.5 P5B engine

As originally built by Land Rover for fitment into Discovery or Range Rover, the 4.0 was not fitted with a distributor.

The engine that you have a chance to purchase will thus be running with a different timing cover, which is not a problem.

The flywheel off your P5B will fit straight on, no problem at all.

Ron.

Theres no reason why you cant have the intermediate engine,

3.9 is your cheapest option as it will have a dissy already, if you go down the 4.0 route you will have to find an interim front cover which aren't cheap or particularly easy to find, and of course a dissy to go with it, and all the serp belts and pulleys etc, you cant use V belts on a 4.0 or 4.6 as the water pump spins backwards with the serp belt arrangement.

Power and reliability wise, if you get a good 4.0 block it will technically handle more power than the 3.9 due to the X bolts, however there is unfortunately a much higher chance you will have problems with liners slipping with a 4.0. A 3.9 with ARP's will easily handle over 200bhp before you have problems with the bottom end so unless you are going down the forced induction or nitrous route, X bolts are not a necessity.

TC

topcatproduction wrote:A 3.9 with ARP's will easily handle over 200bhp before you have problems with the bottom end

I hope its a lot over 200hp or my 3.5 might go bang!

crayefish wrote:

topcatproduction wrote:A 3.9 with ARP's will easily handle over 200bhp before you have problems with the bottom end

I hope its a lot over 200hp or my 3.5 might go bang!

Your 3.5 must be a good spec Zander! What is it?

topcatproduction wrote:Your 3.5 must be a good spec Zander! What is it?

10:1 compression
rhoads lifters
real steal typhoon cam - i think... (the one they got 250hp out of on a 3.5)
stage 3 v8 developments heads
quad downdraught dell'ortos 34mm on JE manifolds (IR)
standard crank and conrodss (fully polished)
high volume oil pump
polished lifter galley
billet rocker shaft outposts


well thats the spec.... havent bought the heads or lifters yet though as am short on cash.... its still in the block machining stage waiting for cash!

crayefish wrote: real steal typhoon cam - i think... (the one they got 250hp out of on a 3.5)

Hmm...so they say!

sidecar wrote:

crayefish wrote: real steal typhoon cam - i think... (the one they got 250hp out of on a 3.5)

Hmm...so they say!

Haha yeah! Another company (cant remember the name) also say they have got 265 out of a 3.5 with only a tiny bit more duration, and can provide a dyno graph to prove it. havent asked yet and cant remember the company to hand.

Either way, my engine is better spec so should produce at least 240... and the dell'ortos should produce some good torque!

I like the sound of the quads, though tuning might be expensive

I am hoping it will be a one off thing and then they will stay tuned! Fat chance of that happening though...

The main thing I am worried about is the break-in procedure for the cam... it has to be started and then rev strait to 2000rpm for 20mins. If the carbs arent set up right (though the seller says they have been sincronised) then it might not get to or stay at 2000rpm...