4.6 Crank....

[neal1980]

Hi,

I have a 1996 4.0, I have been given a 4.6 bottom end. I want to fit the crank. Will this be a direct fit to my current rods?

Do i need to change anything else?

Thanks

Neal

[GreenV8S]

I rather doubt it. I think the main and big end bearings are a different size, obviously the stroke is different so you will need a shorter rod or piston. If you're going to mix and match components then you really need to get advice from somebody who knows these engines inside out.

[900T-R]

Isn't a later 4.6 bottom end (they're all crossbolted, right?) a straight swap, and if it is would the end result - given the obvious remapping - be worth having (this is assuming the short engine that you've been given is a good'un or at least provides a good base for a simple rebuild/reconditioning)?

I have seen a handful of 4,6 litre converted 4.0 Chimaeras so far, and on the face of it, it looks like a relatively easy route to breath new life into an older/high mile steed...

[neal1980]

I have the rods as well and a whole box full of stuff. The liner got pulled down a few mm. can this be repaired so i can use the 4.6 engine or best to transfer everything from it.

Thanks Guys

[tahiti450]

Peter is exactly right, unless you have a full knowledge of the various and many detail changes in spec across the long production life of the RV8, you could run into all sorts of issues. If you enjoy technical stuff, buy Des Hammill's book , "Power tuning the rover V8 engine", and if you want the full story also David Hardcastle's books on the RV8. I have always (from the age of 10, so 33 years!) been very interested in the RV8 but until i read the above volumes i never realised the myriad differences across the range.
For starters the 4.6 engines are, or should all be, 38A engines with red graded blocks (referring to the measured thickness of aluminium behind the liners) with cross-bolted bottom ends and the larger journal cranks. As with alle engines the crank and rods should really be treated as a set unless you are going to have the whole lot rebalanced etc. Liner slip is fairly common on these engines, worse on certain blocks than others and particularly where the engine has been run at high water temps (which apparently is why this was a big problem on range rovers running 90+ C temps but less so for cooler running TVRs ). Also it may be associated with cracking of the cylinder wall behind the liner. The only remedy for this, if the block is salvagable, is to remove all liners and fit special top-hat liners and so on and so forth....
So basically it aint straight forward.

[Boosted Ls1]

Your 4.6 parts will fit into the 4.0 block. I'd hone the 4.0 bores first and make sure the 4.6 rings aren't gummed up. Then run it in for a few miles.

Boosted.

[v8 racing]

not realy sure on which block the liner has sliped? if the 4.6 bottom end is complete and good just use the whole thing, the crank will fit in either block, the 4.0 rods are longer so you will need the 4.6 rods, the 4.0 pistons have a smaller dish and are heavier than the 4,6 ones but can be used if you balance the assembly and open the chambers in your heads slightly to get the compresion right

[tahiti450]

Boosted Ls1 said:

Your 4.6 parts will fit into the 4.0 block. I'd hone the 4.0 bores first and make sure the 4.6 rings aren't gummed up. Then run it in for a few miles. Boosted.

This is likely to be true, but if your engine has the 38A block and is one of the "interim" spec engines including 4.0 (3.9) from 94 to 98 then it would be machined for the small journal / short nose crank. Apparently all the pukka 38A engines (4.0 and 4.6 destined for series II Ranger Rovers - from which I believe most of TVRs supply came) have the large journal / long nose crank and are all cross bolted (together with 10 (rather than 14) bolt heads and blocks and stretch bolts). More confusion arises however, as from previous threads it appears that few if any 4.0 TVRs are crossbolted, suggesting that these may be the interim block as above - yet most / all 450s are crossbolted as would be expected with these engines based on the 4.6 series II RR unit. Hope that makes some sense, but no doubt someone will tell me this is all wrong shortly....

>> Edited by tahiti450 on Saturday 18th March 01:03

[wheeljack888]

Tahiti's right, all is not as it seems. I'm going through the upgrade route and have finally sorted myself out with a off-car 4.6 build which is progressing very slowly. I too have a 1996 4.0 litre and it's the weird interim spec. It has:

Long-nose but small journals crank (2.3" mains and 2.0" crankpins).
Long-nose crank for serpentine drive and crank-driven oil pump.
Old style 143.76mm 3.9 rods and the old 3.9 deep pistons that look like they're from a diesel.
The block is a cross-bolted casting but not machined to be cross-bolted.
The heads are 28cc chamber 10 bolt fixings.

I suppose if you wanted to you could line-bore your existing block to accept the large journal crank and machine the cross-bolt tappings. But for probably a little more money you could repair the 4.0/4.6 block with top-hat liners (V8racing's place does it) and then sell on your TVR short-engine. The other thing is that the 4.0 litre TVR heads aren't ported and are standard size valves. Probably OK for a 4.6 Range Rover which only revs to 4750rpm but a little restrictive on a TVR.

Cheers

Phil

[v8 racing]

I think where the confusion lies is that an interim engine should not be called a 4.0, it is still the 3.9, the only true 4.0 ltrs are the factory cross bolted ones with the large journal crank, although they are the same cc, i guess it probably stems from tvr calling there cars 400's!! but if you went to labdrover and asked for a 4.0 short engine there will only be the listing for the cross bolted engines