4.3 conversion
Discussion
hi, can anyone help? i want to upgrade my 4.0 engine to a 4.3BV. I know the difference in capacity is due to a change in the stroke, raised to 77mm for 4.3l.
My question is how is that 77mm achieved? Did TVR Power alter the length of the con rods? or altered the throw of the crank? or altered the position of the little end in the piston itself? Or a permutation of one or more of the above?
Thanks
My question is how is that 77mm achieved? Did TVR Power alter the length of the con rods? or altered the throw of the crank? or altered the position of the little end in the piston itself? Or a permutation of one or more of the above?
Thanks
TVR didn't do any of that, LR did it as the 430 is based on the LR 4.2 not 3.9 engine.
TVR just enhanced the balancing and machined valve cut outs in the pistons. Most of the work would be making BV heads, new larger seats, valve stem work, lots of porting and of course larger valves. Neither forget the work in matching inlet & exhaust manifolds to the heads.
TVR just enhanced the balancing and machined valve cut outs in the pistons. Most of the work would be making BV heads, new larger seats, valve stem work, lots of porting and of course larger valves. Neither forget the work in matching inlet & exhaust manifolds to the heads.
It's just a 4.2 assembly.
Everyone seems to ignore the simple fact that there are (& always have been) @ 5 grades of bore in Rover engines, & if you use the largest E tolerance bores & pistons you get these minor differences in capacity. You will also often see these small capacity differences quoted in different places and wonder who is right/wrong, but they are enough to affect the 'rounding' nomenclature.
IIRC LR is 4275cc TVR is 4280cc, LR round down to 4200, TVR round to nearest for 4300 (but it does also help to differentiate them from the std LR lump which is reasonable as they have plenty of work done on top of the base!)
Everyone seems to ignore the simple fact that there are (& always have been) @ 5 grades of bore in Rover engines, & if you use the largest E tolerance bores & pistons you get these minor differences in capacity. You will also often see these small capacity differences quoted in different places and wonder who is right/wrong, but they are enough to affect the 'rounding' nomenclature.
IIRC LR is 4275cc TVR is 4280cc, LR round down to 4200, TVR round to nearest for 4300 (but it does also help to differentiate them from the std LR lump which is reasonable as they have plenty of work done on top of the base!)
spend said:
It's just a 4.2 assembly.
IIRC LR is 4275cc TVR is 4280cc, LR round down to 4200, TVR round to nearest for 4300 (but it does also help to differentiate them from the std LR lump which is reasonable as they have plenty of work done on top of the base!)
Ah ha, thanks for that spend. Didn't the reverse happen for the Chimaera 450 blocks tho'? There was a 4.6 RR so TVR rounded down to 450 to differentiate? (my pure guesswork tho').IIRC LR is 4275cc TVR is 4280cc, LR round down to 4200, TVR round to nearest for 4300 (but it does also help to differentiate them from the std LR lump which is reasonable as they have plenty of work done on top of the base!)
I don't think you'd get quite as far with boring an RV8 engine on the 71.1 mm stroke, 96 mm being about the outer practical limit (which I'm sure would require rather more stringent castings selection than is normally the case in a series production environment) which IIRC gives closer to 4.1 litres capacity.
At 94 x 77 mm the LR 4.2/TVR 4.3 still is very much a short stroke engine, anyway...
At 94 x 77 mm the LR 4.2/TVR 4.3 still is very much a short stroke engine, anyway...
TVR 450 = LR 4.6
carsy said:
yes so you did i must pay more attention 
I suppose what i meant was, were the rods OR pistons taken from the 3.9.
From what you say i`m guessing not and the 4.2 had its own unique rods and pistons.
FFS!I suppose what i meant was, were the rods OR pistons taken from the 3.9.
From what you say i`m guessing not and the 4.2 had its own unique rods and pistons.
3.9 & 4.2 have different cranks.
3.9 & 4.2 have different pistons.
3.9 & 4.2 have same length rods
Dave calm down. See we get there in the end.
So they share the same rods, thank you. Thats all i was enquiring about out of curiosity. Sorry if i didnt get my point across clearly enough in the first place.
Silly me, i thought this place was for asking such questions and helping others out. Obviously not.
So they share the same rods, thank you. Thats all i was enquiring about out of curiosity. Sorry if i didnt get my point across clearly enough in the first place.
Silly me, i thought this place was for asking such questions and helping others out. Obviously not.
well, that certainly got heated! seen as i started the thread, i will respond appropriately. Spend, it is you who needs to read the question. Your initial response did not answer my question, only to go on about the obvious description of what the BV stands for.
Until Carsey asked the question again, did you reply the answer i requested in the first place, that the Rods are the same but the stroke increase to 77mm is due to a different throw on the crank aka the 4.2 standard LR one. Thankyou.
However, my question hasnt been completely answered. Spend says that the pistons are different also, however, how are they different? As per my original question, do they have a different little end position which adds to the different throw of the crank to make 4.2/4.3 from 4.0?? or is the difference purely in the crown design (CR etc)
Yes, if anyone has a 4.2/4.3 crank for a seriously cheap price, i may be interested in acquiring it. These are, if only std 4.2 LR ones, easily acquired from most breakers.
Until Carsey asked the question again, did you reply the answer i requested in the first place, that the Rods are the same but the stroke increase to 77mm is due to a different throw on the crank aka the 4.2 standard LR one. Thankyou.
However, my question hasnt been completely answered. Spend says that the pistons are different also, however, how are they different? As per my original question, do they have a different little end position which adds to the different throw of the crank to make 4.2/4.3 from 4.0?? or is the difference purely in the crown design (CR etc)
Yes, if anyone has a 4.2/4.3 crank for a seriously cheap price, i may be interested in acquiring it. These are, if only std 4.2 LR ones, easily acquired from most breakers.
The 4.2 std pistons have a shorter distance from pin to crown than the 3.9 to keep the piston from leaving the block at tdc. Also they have a deeper dish in the piston to give the 8.13 cr. Maybe tvr used the standard pistons and machined them down and decked the block to suit, perhaps someone in the know could shed some light on that.
Yes I do have std 4.2 cranks rods and pistons as stated above pm me an offer if you are interested.
Janes
Yes I do have std 4.2 cranks rods and pistons as stated above pm me an offer if you are interested.
Janes
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