Crossbolting a small journal 5.0
Discussion
I'm thinking about letting a local workshop crossbolt my 5 litre engine, while it is in pieces. The workshop is experienced, but not that familiar with the RV8, a not so common lump here in Sweden. I know that my block has the right casting to be drilled, but not 100% sure about the main caps. See picture, do they look right to you? They sit tight in the block.
Anyone know if the holes are drilled all the way through the cap so that they "meet" the original holes, if you know what I mean?
Anyone know if the holes are drilled all the way through the cap so that they "meet" the original holes, if you know what I mean?
I have heard mixed opinions about x-bolting the 5ltr block. Dom at PowersPerformance advised me that he has experienced more snapped cranks from x-bolted engines, than those without. Apparently, the x-bolting can be too rigid and wont allow the mains to flex with the crank, increasing the strain on the crank and increasing the risk of snapping. John Eales said he didn't think it was necessary either. However, both said that balancing the rotating assembly was more important.
You could do both, but then there's the argument of small vs large journal and whether more meat on the block vs more meat on the crank. Perhaps with the larger journal, there is less block so it needs the extra rigidity from the x-bolting? All V8D use large journal blocks, but I couldn't tell you how necessary this is from my limited mechanical experience. However, based on opinions on PH and from I've been told elsewhere, I would take the opportunity to get the whole assembly dynamically balanced whilst it is out.
You could do both, but then there's the argument of small vs large journal and whether more meat on the block vs more meat on the crank. Perhaps with the larger journal, there is less block so it needs the extra rigidity from the x-bolting? All V8D use large journal blocks, but I couldn't tell you how necessary this is from my limited mechanical experience. However, based on opinions on PH and from I've been told elsewhere, I would take the opportunity to get the whole assembly dynamically balanced whilst it is out.
So the better you hold it, the less chance it has of fracturing?? 
don't quite ring true?.. you don't want the bottom end to flex at all... get it as stiff as you can so yes, cross bolt it... And remember, the bigger the rotating mass, the longer it takes to get it going (and slow it down) so the small units are all very good IMO.
but I agree with the other comments, getting the internals individualy balance is where its at... I was shocked how much they took of and added onto my crank when it was done
so getting that right is step 1.. and then getting a good harmonic damper fitted to take out any of those nasty vibrations / harmonics... in the end its this that does the damage 
BTW Steffo.. yes.. the holes run into the existing main bolt holes...
don't quite ring true?.. you don't want the bottom end to flex at all... get it as stiff as you can so yes, cross bolt it... And remember, the bigger the rotating mass, the longer it takes to get it going (and slow it down) so the small units are all very good IMO.
but I agree with the other comments, getting the internals individualy balance is where its at... I was shocked how much they took of and added onto my crank when it was done
so getting that right is step 1.. and then getting a good harmonic damper fitted to take out any of those nasty vibrations / harmonics... in the end its this that does the damage BTW Steffo.. yes.. the holes run into the existing main bolt holes...
This is very interesting. First I found Chuffmeister's theories quite convincing, especially when referred to such heavy names as PowersPerformance and John Eales. But on the other hand... Well, contradicting opinions can be refreshing, but also confusing. When asking the specialists it's often a matter of can they perform the job or can they not. The people who offer crossbolting for a decent amount of cash say that it's a must-do, and the others... Well, you know what I'm getting at. But I guess it's different in this case.
At least we can all agree on that balancing is a crucial thing. Don't know how bad TVR's standard crank balancing can be, but something tells me that it probably varies quite a bit between engines, to say the least. In an ordinary TVR-ish way, no offense. I will check what an extra dynamic balancing will cost.
But still - crossbolting or not? More opinions on this are welcome. It's not a complicated job and rather cheap to get done, but what feels worrying is to drill and thread in the existing caps. I'm not surprised that workshops ask if I'm sure of what I'm talking about. I mean, if this was not intended by Rover in the first place, if the factory bored caps in some way are different, I'm on thin ice here. Drilling holes in one of the entire engine's most crucial parts can hardly be recommended.
Can some of you guys assure me that the caps are not destroyed by this operation? That they basically are the same part as the factory drilled? Sorry for this niggle...
At least we can all agree on that balancing is a crucial thing. Don't know how bad TVR's standard crank balancing can be, but something tells me that it probably varies quite a bit between engines, to say the least. In an ordinary TVR-ish way, no offense. I will check what an extra dynamic balancing will cost.
But still - crossbolting or not? More opinions on this are welcome. It's not a complicated job and rather cheap to get done, but what feels worrying is to drill and thread in the existing caps. I'm not surprised that workshops ask if I'm sure of what I'm talking about. I mean, if this was not intended by Rover in the first place, if the factory bored caps in some way are different, I'm on thin ice here. Drilling holes in one of the entire engine's most crucial parts can hardly be recommended.
Can some of you guys assure me that the caps are not destroyed by this operation? That they basically are the same part as the factory drilled? Sorry for this niggle...
My 5ltr block and caps are identical to yours and yes they can be cross bolted for not much money like you say. John Eales internally balanced mine for about £180.
As for cross bolting he said it was worth doing but in no way essential. I havent bothered on mine. Interestingly he told me he wasnt a fan of studs on the mains. How far the cap sides are drilled when cross bolting, i`m affraid i cant say sorry.
As for cross bolting he said it was worth doing but in no way essential. I havent bothered on mine. Interestingly he told me he wasnt a fan of studs on the mains. How far the cap sides are drilled when cross bolting, i`m affraid i cant say sorry.
It was a discussion with Mr Eales that made me have mine done... The stiffer you can get it the better .. Ooo ER..... something about watching the bottom end of a Land Rover unit on a test rig and you could actuals see the bottom end flex !!
I know you are drilling into the cap and putting a hole into a stressed component... and if the component itself was under expansion forces alone it would be a problem... But it's not... all it's doing in real terms is holding the bottom of the cap for the crank to run on.. but its also under loads of compression forces by the main bolts... the only issue IMO is if it starts to collapse under the main bold torque... but if you look at the cross sectional area where its drilled, there is still lots of meat left.
Rover did cross bolt units and used these caps.. so where is the problem??..
I know you are drilling into the cap and putting a hole into a stressed component... and if the component itself was under expansion forces alone it would be a problem... But it's not... all it's doing in real terms is holding the bottom of the cap for the crank to run on.. but its also under loads of compression forces by the main bolts... the only issue IMO is if it starts to collapse under the main bold torque... but if you look at the cross sectional area where its drilled, there is still lots of meat left.
Rover did cross bolt units and used these caps.. so where is the problem??..
Edited by TVR Beaver on Friday 8th May 13:10
I'm not completely through with my crossbolting questions, apparantly.
Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
I'm waiting for an answer from V8D on this, but I'd like to hear your opinions too, all you clever TVR-guys. (In Sweden we have a saying; "Flattery won't take you far", or something like that. I'm counting on that it's unfamiliar to you.)
Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
I'm waiting for an answer from V8D on this, but I'd like to hear your opinions too, all you clever TVR-guys. (In Sweden we have a saying; "Flattery won't take you far", or something like that. I'm counting on that it's unfamiliar to you.)
Steffo said:
I'm not completely through with my crossbolting questions, apparantly.
Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
No, not in my opinion. If the mains are correctly torqued before you machine the crossbolts then you'll be fine. The clamp loads applied by the crossbolts are fairly insignificant. If the crank spins freely then all will be fine. I've fitted lots of ARP mains studs to engines in the past and never had to line bore the block despite the much higher clamp loads.Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
Why not do the crossbolting first and then see how the crank feels? Then make your decision? I'd be worried about line boring a block that's part alloy, part steel.
Boosted LS1 said:
Steffo said:
I'm not completely through with my crossbolting questions, apparantly.
Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
No, not in my opinion. If the mains are correctly torqued before you machine the crossbolts then you'll be fine. The clamp loads applied by the crossbolts are fairly insignificant. If the crank spins freely then all will be fine. I've fitted lots of ARP mains studs to engines in the past and never had to line bore the block despite the much higher clamp loads.Just one more: Do you usually need to line hone the block/caps after crossbolting? Suddenly the bill from my workshop grew essentially when this came up.
Why not do the crossbolting first and then see how the crank feels? Then make your decision? I'd be worried about line boring a block that's part alloy, part steel.
and you are only clamping on the sides at low torque to something that is flexable to some extent.. if it's nipping it's not because of the X-bolts ... but it will be fine
Also remember the bearings are very soft.... But what you don't want to do is mix up bearing caps from their original place... I have seen some of the companies you mention and they have lots of spare caps.. if you are fitting these to a block then yes, you'd have to re-hone...
Edited by TVR Beaver on Tuesday 12th May 08:51
Thanks for all your input, extremely valuable to me!
V8D told me that they always check the line bore after crossbolting, but I take it that they scarecely need to do anything about it.
And Quinny, yes, I noticed that the crank wouldn't turn without me grinding off some millimeters in the block. I experienced a couple of seconds of glassy-eyed resignation until I remembered reading about this somewhere.
V8D told me that they always check the line bore after crossbolting, but I take it that they scarecely need to do anything about it.
And Quinny, yes, I noticed that the crank wouldn't turn without me grinding off some millimeters in the block. I experienced a couple of seconds of glassy-eyed resignation until I remembered reading about this somewhere.
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