Conrods - they won't break, honest....
Discussion
Let me share this insight into TVR engine manufacturing fidelity with you.....
Part of TVR Power’s blueprinting rebuild of the bottom-end of my 4.5 15,000 mile engine (this was the first time it had been opened) was fine balancing. I’d already had a report from Jason after he’d stripped the short motor that everything was ok with little visible wear. Then I got a call from him as he was starting the balancing. There was a problem with a couple Look how much metal isn’t there to hang on to 12T of piston force. of rods, one in particular. There was insufficient metal on one side of the little-end due to the machining that had occurred during its production. He wouldn’t put it back in if it were his engine.
OK - I happened to have a new rod in the garage, I'd send it through... Unfortunately the rods had changed in the last stages of AJP8 production and the ones now available were heavier than those in my engine – by about 80g, which is quite a lot. So you can't replace one or two old rods with new ones as it would totally wreck engine balance. He’d check with the factory if they had any old ones left . I subsequently got a call from Dom @ TVR Power (Jason on his hols). He told me the factory didn’t have any old-style rods and said as there was no history of AJP8 rods snapping it was up to me - if I said refit, he’d do it. I gulped - at the thick end of £100 each a set of new rods would blow a gaping hole in an already sieve-like budget. Ah the joys of engine builds! All the time and effort and money can go up in a puff off smoke the first time the engine starts or is seriously flexed because of the want of one new nut. Been there, done it, got the bag of shrapnel (in the dim distant past, but it still smarts). Daren't risk it – I told him to replace the lot. What would you do?
However I was concerned about the extra weight, as this would add load to the crank, increase vibrations and slow response. I asked Dom to take as much weight as poss off the new rods. Later Jason reported about 40g per rod had been shaved off – and no metal thickness probs. Not bad going, guys.
Got the short-motor back along with a box of old parts. Was gobsmacked with the old rods. Look at the pics!
You can see the little end bores are out of line with the casting.
Look how much metal isn’t there to hang on to 12T of piston force. It must be just luck - or relatively few miles - that there hasn't been a breakage (this engine was pulling 428bhp on Noble's dyno...)
Talk about quality engineering – somebody should to TVR - as somebody in the factory actually hand selected and lovingly put these beauties into my engine in the first place..
I happened to have a new style rod hanging up in the garage (not a shaved one unfortunately) so I could do some compares and take pix. Definitely more meaty. Thicker and with more metal around both ends. Holes in right place too.
Good ol’ TVR they finally learn.... just before they stop production. Grrrr! Doh!
Part of TVR Power’s blueprinting rebuild of the bottom-end of my 4.5 15,000 mile engine (this was the first time it had been opened) was fine balancing. I’d already had a report from Jason after he’d stripped the short motor that everything was ok with little visible wear. Then I got a call from him as he was starting the balancing. There was a problem with a couple Look how much metal isn’t there to hang on to 12T of piston force. of rods, one in particular. There was insufficient metal on one side of the little-end due to the machining that had occurred during its production. He wouldn’t put it back in if it were his engine.
OK - I happened to have a new rod in the garage, I'd send it through... Unfortunately the rods had changed in the last stages of AJP8 production and the ones now available were heavier than those in my engine – by about 80g, which is quite a lot. So you can't replace one or two old rods with new ones as it would totally wreck engine balance. He’d check with the factory if they had any old ones left . I subsequently got a call from Dom @ TVR Power (Jason on his hols). He told me the factory didn’t have any old-style rods and said as there was no history of AJP8 rods snapping it was up to me - if I said refit, he’d do it. I gulped - at the thick end of £100 each a set of new rods would blow a gaping hole in an already sieve-like budget. Ah the joys of engine builds! All the time and effort and money can go up in a puff off smoke the first time the engine starts or is seriously flexed because of the want of one new nut. Been there, done it, got the bag of shrapnel (in the dim distant past, but it still smarts). Daren't risk it – I told him to replace the lot. What would you do?
However I was concerned about the extra weight, as this would add load to the crank, increase vibrations and slow response. I asked Dom to take as much weight as poss off the new rods. Later Jason reported about 40g per rod had been shaved off – and no metal thickness probs. Not bad going, guys.
Got the short-motor back along with a box of old parts. Was gobsmacked with the old rods. Look at the pics!
You can see the little end bores are out of line with the casting. Look how much metal isn’t there to hang on to 12T of piston force. It must be just luck - or relatively few miles - that there hasn't been a breakage (this engine was pulling 428bhp on Noble's dyno...)
Talk about quality engineering – somebody should to TVR - as somebody in the factory actually hand selected and lovingly put these beauties into my engine in the first place..
I happened to have a new style rod hanging up in the garage (not a shaved one unfortunately) so I could do some compares and take pix. Definitely more meaty. Thicker and with more metal around both ends. Holes in right place too.
Good ol’ TVR they finally learn.... just before they stop production. Grrrr! Doh!
[quote=Do CARILLO MAKE TVR RODS as they do a proper job 
[/quote]
Yes they do, they are the ones Auto craft, and I think Austec are selling now.
I don't think they cost that sort of money either, though might be wrong.
that 12t sounds a lot, is that right? sounds like a hell of a lot.
Nick
[/quote] Yes they do, they are the ones Auto craft, and I think Austec are selling now.
I don't think they cost that sort of money either, though might be wrong.
that 12t sounds a lot, is that right? sounds like a hell of a lot.
Nick
I would have thought with no sign of stress, you could be fairly sure they would be okay cos they survived the last five years 
. The stress on the rod is different depending on where you are talking about. I would have thought the most stress is through the bottom of the ring and shaft on the power stroke, and much less on the top. So I wonder if the 12 tonnes is talking about this.
I would probably xray them, but if not sign of stress # I would have put them back on.
I took the rods out of my R1 motorcycle about a year ago, IIRR, the rods were thinner than my finger, and they were good for 10,000 rpm in a one litre engine!!
But I guess you have to be guided by the experts.
. The stress on the rod is different depending on where you are talking about. I would have thought the most stress is through the bottom of the ring and shaft on the power stroke, and much less on the top. So I wonder if the 12 tonnes is talking about this. I would probably xray them, but if not sign of stress # I would have put them back on.
I took the rods out of my R1 motorcycle about a year ago, IIRR, the rods were thinner than my finger, and they were good for 10,000 rpm in a one litre engine!!
But I guess you have to be guided by the experts.
The thing is the engine builder has to be really sure as he's putting his reputation on the line. The last thing he wants is for the engine to go bang shortly after he's built it, so he's going to be extra safe.
On the owners view, if I was already spending a lot on an engine rebuild I'd want it perfect. I spent about an extra 20% on my capri engine over and above the quote because of problems/improvement, but I'd guessed on 25% and had the money available. Mind you - that was planned. It doesn't always help if it's unplanned.
On the owners view, if I was already spending a lot on an engine rebuild I'd want it perfect. I spent about an extra 20% on my capri engine over and above the quote because of problems/improvement, but I'd guessed on 25% and had the money available. Mind you - that was planned. It doesn't always help if it's unplanned.
byker28i said:
The thing is the engine builder has to be really sure as he's putting his reputation on the line. The last thing he wants is for the engine to go bang shortly after he's built it, so he's going to be extra safe.
On the owners view, if I was already spending a lot on an engine rebuild I'd want it perfect. I spent about an extra 20% on my capri engine over and above the quote because of problems/improvement, but I'd guessed on 25% and had the money available. Mind you - that was planned. It doesn't always help if it's unplanned.
On the owners view, if I was already spending a lot on an engine rebuild I'd want it perfect. I spent about an extra 20% on my capri engine over and above the quote because of problems/improvement, but I'd guessed on 25% and had the money available. Mind you - that was planned. It doesn't always help if it's unplanned.
Yep point taken.
It looks like somebody has already been having a go with the grinder on the small end of your old rod , I have never seen one ground on the sides before , very strange ! Does this mean they are going to add weight to your crank to balance the rods ? Does the new rod have a number on it ? David
All totally dependant on the mass of the piston. Worst point for loading would be on the exhaust stroke as this is the time that the piston is unloaded and therefor the point when the piston would want to leave the rod.
Not ideal but as said, if it's survived this long it's pretty unlikely that it's gonna let go now.
Still better to be safe than sorry.
Not ideal but as said, if it's survived this long it's pretty unlikely that it's gonna let go now.
Still better to be safe than sorry.
I understand that the same con rod was used for both the speed 6 and the AJP8.
The S6 has a longer stroke, so the rod is cast with an oval little end.
Rod for the 6 are then bored near the top of the oval (giving a top heavy rod…
Rods for the 8 are bored near the bottom of the oval – and the extra material at the top is ground off.
Pic shows a standard S6 rod (with heavy little end), and the TVRcraft carillo replacement.
The S6 has a longer stroke, so the rod is cast with an oval little end.
Rod for the 6 are then bored near the top of the oval (giving a top heavy rod…
Rods for the 8 are bored near the bottom of the oval – and the extra material at the top is ground off.
Pic shows a standard S6 rod (with heavy little end), and the TVRcraft carillo replacement.
Steve_T said:
Nickccc said:
that 12t sounds a lot, is that right? sounds like a hell of a lot.
Nick
From what I remember Al Melling saying the ball park figure not to exceed for rods in a sports car engine was 2.8 tonnes. 12 sounds a bit out to me.
Steve.
Apologies - I was way out with the 12T - I read my spreadsheet wrong. Peak piston force is about 2.25T @ 7,500
plasticman said:
It looks like somebody has already been having a go with the grinder on the small end of your old rod , I have never seen one ground on the sides before , very strange ! Does this mean they are going to add weight to your crank to balance the rods ? Does the new rod have a number on it ? David
Yes a grinder has been on the old ones. If it wasn't during manufacture then it can only have been for Red Rose conversion by the factory.
The crank self balances as it is flat plane. Extra weight on one crankpin from the heavier rods is counteracted by same extra weight on opposite pin. Its the secondary piston forces that will increase and what I was concerned about. These can't be fully balanced at the crank and the 75deg vee means they are larger than on a 90 deg vee.
No part nos on new rod.
Cheers
cerbhead said:
plasticman said:
It looks like somebody has already been having a go with the grinder on the small end of your old rod , I have never seen one ground on the sides before , very strange ! Does this mean they are going to add weight to your crank to balance the rods ? Does the new rod have a number on it ? David
Yes a grinder has been on the old ones. If it wasn't during manufacture then it can only have been for Red Rose conversion by the factory.
Cheers
This is probably why the engine now needs a rebuild, some monkey at the factory screwed it up. This has no reflection on Dom's staff, they on the whole seem to be a good bunch of people, and Dom in the past has been nothing but excellect with any problem I have had and really helped/sorted me out.
Before you frown on my post, my engine has just had to have £6.5k worth of work, due to crap work at the factory, for, get this, to correct what the former owner paid TVR (factory) £6.5 to be repaired (inc RR conversion). F8ck me, thats £13k on engine work in 3 years!!!! even the RR conversion stuff was not even done properly, and there were places were my journals on the crank had 2 tho gaps not touching the bearings. Now, you would have thought TVR would have spotted this when they rebuilt then engine, wel, apparently not!!!!!!
I wrote to TVR to tell them all that was wrong with my engine, and they didnt even have the coutsey to reply back to me, and yes they did get my mail, I even spoke to TVR, no names mentioned here, and not even, "oh well have a look at it since the engine has only done 3000 miles since we rebuilt it".....................AHhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
If I had been the owner I would have thrown it back at TVR and told them to sort their sh7t out and put it right FOC. As you can tell, stories like this f88king p8ss me off!!!
Mr F
Right I have to stop now or I will go off on one today!!!!!
Mr Freefall - strewth! I didn't want the agro and time that complaining to the factory would involve so just took it on the chin (again).
Let me make clear absolutely no complaints re TVR Power - Dom, Jason and Ray have been excellent and extremely helpful throughout.
Must be a moral in here somewhere about knowing when NOT to manufacture engines.........
. Let me make clear absolutely no complaints re TVR Power - Dom, Jason and Ray have been excellent and extremely helpful throughout.
Must be a moral in here somewhere about knowing when NOT to manufacture engines.........
BCA said:
Ah, I have just worked out who you are... May I ask what went wrong to necessitate the rebuild in the first place?/ what caused the head gasket problem?
You have the advantage of me BCA.....
Basically I had planned to have the engine out as part of the development programme, for major mod of the cooling system, including full ECU temperature control with electric pump – this meant disabling the mechanical pump, which meant engine out and a limited strip.
Unfortunately the leaky head gasket intervened. Overheating on rolling road seems likely to be main culprit, made worse by new exhaust manifolds that restricted rad airflow down the side of the engine. It spent a long session (couple of weeks) getting Emerald calibrated and mapped – it was the first Cerb to be fitted with one so lots of development needed, then another long session remapping for new exhaust manifolds, both followed by l-l-long journeys home. It wasn’t immediately obvious the gasket had gone as the car still ran smoothly and the oil was clean. Although doubts were cast when we couldn’t get it to give more than 390bhp, down on the 428bhp it ran at Noble’s before the Emerald and new manifolds – but that was put down to variation between rolling roads. It was the loss of water that eventually pointed the finger….. On strip-down I found head nuts on one side of heads not as tight as on other (the ones that you need torque adapter to get at). I suspect they were not torqued properly by factory at Red Rose conversion. Funny how it was also on that side of the heads that the leaks occurred on two cylinders……
Fixing the head gasket led to deciding to go with copper head gaskets and wired cylinder liners to ensure the problem didn’t recur. That meant bottom-end strip-down and therefore sensible to do full refurb. As heads were coming off also took opportunity to fully refurb them and do more gasflow mods. Chamber volumes were all over the place (previous thread – the factory again!), which meant more work to do to balance them and lift the CR to 11.2.
Cheers
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