Merits of longer con rods in a 5 Ltr lump?
Discussion
So why did TVR use such short con-rods and give us an undesirable ratio and con rod angles etc?? but can it be improved on without breaking the bank?
I'm sure it must be possable to keep the existing crank (but get it internaly balanced) and get con-rods that are say 10mm longer... and pistons where the pin is further up the piston (as they appear low on the 5 LTR) to overcome some of the piston wobble and side loading the 500's see?... It would give an engine with better torque and be better reving... and should be achievable for £1500??...
May be also putting propper small end bearings in the rods / pistons??
Anyone done anything like this... and what are the advantages / dissadvantages??
I'm sure it must be possable to keep the existing crank (but get it internaly balanced) and get con-rods that are say 10mm longer... and pistons where the pin is further up the piston (as they appear low on the 5 LTR) to overcome some of the piston wobble and side loading the 500's see?... It would give an engine with better torque and be better reving... and should be achievable for £1500??...
May be also putting propper small end bearings in the rods / pistons??
Anyone done anything like this... and what are the advantages / dissadvantages??
No dissadvatage at all, only reason tvr did this is like any other manufactuer cost!!, to get a set of hyperutectic pistons made and rings at a sensible price you are looking at around £400 a set, down side is you would need to order around 200 sets!!, forged pistons you are looking at around £1000 a set for a quality item, off the shelf 4.2 range rover pistons where a discounted price compared to others, nothing stopping you using a set of custom forged pistons and a set of h beam chevy rods and maching the sides down to suit.
Depending on your stroke you can buy budget 'fuelli' rods from the US. I built a 5.4 using these. Can't for the life remember which chev they were for but 327 rings a bell if ever there was such an engine. I matched them to some TRW off the shelf pistons? It was twenty years ago so things are hazy lol.
Using Chevy 5.85" to 6.125" rods and various specs of Chevy pistons forged/cast etc(305 I think amongst others) can be used on the small RV8 journal crankshafts to up displacement 
Boosted SBC 327ci rods would be right 2" journals etc (but need additional machining) 
Boosted SBC 327ci rods would be right 2" journals etc (but need additional machining) Edited by Simon says on Wednesday 4th July 22:03
Simon says said:
Using Chevy 5.85" to 6.125" rods and various specs of Chevy pistons forged/cast etc(305 I think amongst others) can be used on the small RV8 journal crankshafts to up displacement Boosted SBC 327ci would be right
Down side to this is you need to find a chevy piston with the right dish in the piston, most chevy pistons are either flat or domed, which would make our c/r well into the 12's and 13's, but yes the 305 and 327 are the ones to look for. Boosted SBC 327ci would be right 
v8 racing said:
Simon says said:
Using Chevy 5.85" to 6.125" rods and various specs of Chevy pistons forged/cast etc(305 I think amongst others) can be used on the small RV8 journal crankshafts to up displacement Boosted SBC 327ci would be right
Down side to this is you need to find a chevy piston with the right dish in the piston, most chevy pistons are either flat or domed, which would make our c/r well into the 12's and 13's, but yes the 305 and 327 are the ones to look for. Boosted SBC 327ci would be right I seem to remember reading there being a catch and I think you just reminded me 
nothing is ever straight forward when playing around with displacements I guess 
the SB305 is not a favourite with the Yanks rather than the usual SB302/327/350's considered more of a truck engine if memory serves with don't help for piston choice I presume Edited by Simon says on Wednesday 4th July 22:22
all the chevy's where built with massive chamber heads, good for running roller cams etc.. but trying to find a chevy piston with a decent size dish for c/r is almost impossible, the nearest i have got is a forged 305 that was made for a turbo application, -15cc in the dish, even these are too high!!
v8 racing said:
all the chevy's where built with massive chamber heads, good for running roller cams etc.. but trying to find a chevy piston with a decent size dish for c/r is almost impossible, the nearest i have got is a forged 305 that was made for a turbo application, -15cc in the dish, even these are too high!!
Bloody hell, certainly not an easy solution then? Its real shame we dont have the same coverage of go-faster-bits as the Yanks do with their V8's. or more to the point shame the Yanks are not such a big fan of the RV8 would make your job easier i would imagine. TVR Beaver said:
So we are either talking special pistons at £1K or special rods at £1K??.....
Could deeper dished ones exist in the US?
That would be top end speed shop stuff Could deeper dished ones exist in the US?
and the parts needed for one of these mongrul anglo/american conversions are def not that expensive parts wise.If you liner to 96mm you have options with 2.3 pinto pistons which come with flat tops or a 'D' shaped dish which can be machined circular to net about 21cc iirc. Quite a few people produce those.
Thing is, these mods have all been tried by a few on here to reduce the costs but by the time the machining's been done etc it's not commercially viable. In fact it presents hassle and some risk. Diy is an option if you spend hours on research but in reality it's better to just buy the correct parts. I used TRW pistons a few times and they were pretty decent plus cheap and 'off the shelf'.
Thing is, these mods have all been tried by a few on here to reduce the costs but by the time the machining's been done etc it's not commercially viable. In fact it presents hassle and some risk. Diy is an option if you spend hours on research but in reality it's better to just buy the correct parts. I used TRW pistons a few times and they were pretty decent plus cheap and 'off the shelf'.
v8 racing said:
all the chevy's where built with massive chamber heads, good for running roller cams etc.. but trying to find a chevy piston with a decent size dish for c/r is almost impossible, the nearest i have got is a forged 305 that was made for a turbo application, -15cc in the dish, even these are too high!!
The 500 piston (So I'm told) is a machined down std 'something', so could a chevy piston not be made to work with a little fettling...bit off the top here, bit of the bottom there...std chevy (thinned) rod with a 2" big end......
)virgil said:
The 500 piston (So I'm told) is a machined down std 'something', so could a chevy piston not be made to work with a little fettling...bit off the top here, bit of the bottom there...std chevy (thinned) rod with a 2" big end......
The smallest chevy bore diameter still means overboring the rover by a small amount so that's the first compromise. Next is you'll find the pin height is wrong as is the pin diameter and you'll have to decide whether to press fit the larger diameter pin into a honed out rod end. Then you'll find issues with bowl volume and compression. Finally, not only do you have to thin the rods, you have to trim the bearings and champher them so that they don't foul the crank. Simplzzz and a lot of work.It's probably best to get fuelli rods and custom pistons if you want to change rod angle and do it properly. BTW what is the current rod angle?
virgil said:
The 500 piston (So I'm told) is a machined down std 'something', so could a chevy piston not be made to work with a little fettling...bit off the top here, bit of the bottom there...std chevy (thinned) rod with a 2" big end......
The 500 is a fettled 4.2 piston,basically no, like mike has said the smallest bore chevy piston is 95.4 mm, you cant bore the rover block to this without fitting new liners, also as i mentioned the chevy pistons are designed to run with chevy heads, and most pistons are flat topped, so the compresion will be massive, keith black do a piston which a lot of company's use as a stroker piston, you have to machine the bowl out and bore to 95.96mm, but they are a cheap piston around £250 a set, probably fine for the purpose they are made for but once machined very weak, and i would never use them again.
As a diy job, the chepeast way to get a set of nice rods and pistons in a 500 tiv motor would be, a set of 5850 chevy 327 rods, h beams would be, by the time import duties and machine the width down and re tag them for the bearings around £700, a set of 8 custom pistons rings and pins £1000, full internal balance £250, so thats £1950 as a do it yourself kit, there are lots of diy type options out there on forums from using buick 350 cranks to make 5.8 litre engines toyota pistons and lots more
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