ripley Posted February 8, 2006 Share Posted February 8, 2006 Ive just been offered a fully rebuilt 4.0litre TVR Bottomend with 3.9 R/R Heads & EFI, uprated cam, steelrockers etc for a very good price, but was wondering if there is any difference between the 4.0TVR bottomend & a 3.9 R/R bottomend ie is it crossdrilled or is it just a normal 3.9 called a 4.0 just to sound good?? Quote Link to comment Share on other sites More sharing options...
pugwash Posted February 8, 2006 Share Posted February 8, 2006 Ive just been offered a fully rebuilt 4.0litre TVR Bottomend with 3.9 R/R Heads & EFI, uprated cam, steelrockers etc for a very good price, but was wondering if there is any difference between the 4.0TVR bottomend & a 3.9 R/R bottomend ie is it crossdrilled or is it just a normal 3.9 called a 4.0 just to sound good?? I'm not an expert, so if i get contradicted don't get surprised. i uprated my engine from 3.9 to 4.0. The actual CC of the engine didn't change! Everything else did change though- so the engine was way way better! Do you mean is the engine Crossbolted? you can see this for yourself if they get a piccy to you- you are looking for a range of 5? blt holes on the side of the block just above the sump- bolts which screw into the bearing caps (these are the bits that hold the crank into the block- could be called something else) and keep the crank nice and tight so at high revs things don't get out of line and blow the engine up. If you are using the engine in a landy then crossbolting the block would be almost totally pointless (unless you are comp safarying). I have a cross bolt block which isn't cross bolted for that very reason. Most imporant thing i would ask is whether the liners have been swapped for top hat versions so that the thing can't slip it's liners any more or have porosity problems! If the bottom end has been rebuilt ask what tolerances it has been balanced to- assuming the rotatinng assembly has been balanced- if it has then you will get a much smoother engine which will be more efficient and rev much more highly! Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted February 8, 2006 Share Posted February 8, 2006 Hi Graham, Ok Cam and Valve timing is more "Extreme" ie 'cammier', and the fueling map on the ECU is different, (but this can be chnaged with a E Prom), the Flywheel is lighter and other than that it just minor changes. the 4.0 is not as much chnaged as the bigger units Nige Quote Link to comment Share on other sites More sharing options...
MogLite Posted February 8, 2006 Share Posted February 8, 2006 ISTR a 3.9 Classic is 3950cc as is a 4.0 P38a !! So watch out for those marketing types !! Quote Link to comment Share on other sites More sharing options...
BogMonster Posted February 8, 2006 Share Posted February 8, 2006 (edited) The old 3.9 used to be quoted as 3947cc, the "4.0" is quoted as 3950cc. Methinks they just rounded it up and it's actually the same engine.... Edited to say I was bored so did some sums... and they are both wrong! The figures quoted in the WSM for a Discovery II V8 are Bore 94.00mm Stroke 71.04mm So... Swept area of each piston = pi x radius squared = 47 x 47 x 3.141592653589 (just to be precise ) = 6939.778 sq mm x 71.04mm gives you 493001.8 cubic mm x 8 cylinders gives you 3944015mm3 which is a whisker over 3944cc. I wonder if I could sue Land Rover for misrepresenting what they were selling me? - now I think about it, it does seem a bit short on power compared to what I was expecting Edited February 8, 2006 by BogBuster Quote Link to comment Share on other sites More sharing options...
ripley Posted February 8, 2006 Author Share Posted February 8, 2006 Hi Graham,Ok Cam and Valve timing is more "Extreme" ie 'cammier', and the fueling map on the ECU is different, (but this can be chnaged with a E Prom), the Flywheel is lighter and other than that it just minor changes. the 4.0 is not as much chnaged as the bigger units Nige thanks for replys, I think its running a standard rangie flywheel that just been balanced, is it worth having a flywheel thats lightned on an auto, surely it cant be that affective. The engine is currently in a auto classic rangie thats come in as an uneconomical repair, im looking at all the receipts tommorrow, so i'll know whats actually been done to it then, i believe all the mapping etc is done as apperntly the output figure was just under 240bhp/260lbft, dont know how true this is, not really looking for that much but it'll be there if needed, will ask about the liners though, ive already got a fully rebuilt 3.5 efi that i havent used but this lump(comes with a free R/R) is just to good a bargin not to snap up Graham Quote Link to comment Share on other sites More sharing options...
Mark90 Posted February 9, 2006 Share Posted February 9, 2006 The old 3.9 used to be quoted as 3947cc, the "4.0" is quoted as 3950cc. Methinks they just rounded it up and it's actually the same engine....Edited to say I was bored so did some sums... and they are both wrong! The figures quoted in the WSM for a Discovery II V8 are Bore 94.00mm Stroke 71.04mm So... Swept area of each piston = pi x radius squared = 47 x 47 x 3.141592653589 (just to be precise ) = 6939.778 sq mm x 71.04mm gives you 493001.8 cubic mm x 8 cylinders gives you 3944015mm3 which is a whisker over 3944cc. I wonder if I could sue Land Rover for misrepresenting what they were selling me? - now I think about it, it does seem a bit short on power compared to what I was expecting Plus the recess in the heads Quote Link to comment Share on other sites More sharing options...
BogMonster Posted February 9, 2006 Share Posted February 9, 2006 Plus the recess in the heads Don't think so, because the CC should be "displacement" which should be the amount the pistons move in the bores, the bit in the heads doesn't get displaced anywhere. Anyway if the bit in the heads is only about 1cc per cyl that would make the compression ratio about 500 to 1 which it isn't think that is right anyway Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted February 9, 2006 Share Posted February 9, 2006 Mr Buster is correct for the way the Europeans (and Japanese, from that) measure engines, considering only swept volume. However, our "Hellyeah" cousins in the USA use the biggest number they can find, and that includes the total enclosed volume. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted February 9, 2006 Share Posted February 9, 2006 Mr Buster is correct for the way the Europeans (and Japanese, from that) measure engines, considering only swept volume. However, our "Hellyeah" cousins in the USA use the biggest number they can find, and that includes the total enclosed volume. So what you are saying is that it's a bit like English spelling, our cousins over the water get it nearly right but not quite... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 9, 2006 Share Posted February 9, 2006 What about the volume down the side of the piston to the first ring? Sad fact of the day - the 3.9 was "renamed" 4.0 for the US market to keep up with the J**p Cherokee which was 4.0. I would advise against lightening the flywheel in an off-roader, my truck had an SD1 flywheel and it was a PITFA off-road, very easy to stall considering it was a 3.9. Or even a 4.0 Hopefully the 4.6 and RR flywheel should sort that, so if I stall it's my own bad driving Also, what I know of TVR engines is that they're bolted together in a shed in blackpool using whatever bits they can find and never make the power that TVR claim they should. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 9, 2006 Share Posted February 9, 2006 Sad fact of the day - the 3.9 was "renamed" 4.0 for the US market to keep up with the J**p Cherokee which was 4.0. There were quite a few other changes from 3.9 to 4.0 - a completely redesigned intake manifold for starters - I've read the 'badge engineering' was at least partly to differentiate that from the earlier engine. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted February 9, 2006 Share Posted February 9, 2006 Graham, Flywheel (lets stick with a mnaul box for the mo for example) are a special world, horses for courses and all that. A Comp safari racer - will spend most of its time high up the rev range, where the max power is, needs to get there asap, as such racers will often have huge amounts machined off the flywheels to allow the engine to "Rev" quickly. Balancing just lets it rev a bit better and without shaking itself apart as quickly, prob is when these racers then hit at 60 mph some thick mud the rev and power comes off very quickly, as it affects the grunt the engine has. HEAVY flywheels means the engine doesn't really wnat to rev, it will, but has to be given time, and it does it sort of begrudgingly, and won't seem as quick on acceleration, but, when you hit the deep gooo at a few hundred rpm it will allow progress and will seem to have bags of grunt and bottom ebnd power.... I am not an expert on autos, but I beluive the torque plates can equally be tweaked in weight, along with the torque convertors, basically you cannot have it both ways, and for what your arfter you wnat loads of bottom end grunt. The last part of this equaltion is shear power, ie a smart car engine with a 1 ton flywheel aint going to give you anything like the grunt of a 5.2V8 tunned to the eyebrows but with a hewavy flywheel, yes a lightened balanced 5.2V8 will see it off into the weeds, but the heavier flywheel version will still make a 3.9 std unit look pants ! Hence why I love mine, wish it was just better around water HTH and makes sense Nige Quote Link to comment Share on other sites More sharing options...
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