3.5L Rover V8 - Crankshaft Main and Big End pin diameters
Discussion
I confirm those journal sizes from my Glacier Bearings catalogue.
Mains shells are indeed available down to minus 40 thou but big ends can go down as far as minus 60 from for example King Bearings.
http://www.king-bearings.com/cat/
You need to use that site with IE though. It doesn't work with Firefox.
BTW people tend to think that the stated journal size range indicates shagged (below lower limit) and unshagged (above it). It doesn't. It's simply the tolerance range for the original factory grind. A brand new crank can theoretically come out of the factory right at bottom limit and still be fine when it's worn a good bit below that. For a cooking road motor you're unlikely to have an oil pressure issue with good shells and a decent oil pump until the journals are at least 1 thou under bottom limit. In fact many race engine builders would go that low on a regrind as a matter of course to try and minimise bearing friction (which I disagree with as it happens as stated in a recent thread).
Having said that you rarely see a journal that badly worn without the rest of the motor also being shagged. In fact with modern oils you rarely see any crank wear at all unless there's been an actual lubrication failure at extreme mileage or due to oil surge in competition use.
As an aside, many years ago I tried a new crank grinder chappy on the recommendation of a friend and took him an MGB crank for a race motor. I was only having it ground in the first place because it was about half a thou under bottom limit and I build my engines tight but to be honest I could just as easily have left it alone if I wasn't so bloody pedantic. A few days later I went to pick it up, got it back to the workshop, dug out the mikes and found the bloody thing was indeed now 10 thou down on both mains and big ends but both were a full 1 thou under their bottom limits! The bloody thing was actually worse than before I'd had it ground.
I stormed back up there with my own mikes and calibration pieces and when I checked his knackered old mike it was reading a thou large which meant he was grinding every bloody crank he did a thou small and had been doing so for god knows how long. I mean how much bloody trouble is it to get a calibration piece out every now and then and check your mike is still set correctly when you're claiming to be a precision engineer? I do it before every critical job never mind once a decade if you're lucky like this guy.
So severe bollo*kings were issued, I recalibrated his mike myself and told him the thing had better be exactly at the specified top limit as I'd asked for originally when I came back to pick it up after he'd ground it again down to the next 20 thou undersize. To be fair it was spot on but I imagine he sweated a bit over that one rather than cock it up a second time at which point we'd have been rapidly running out of undersize shells to work with.
However the point is he'd been sending out cranks a thou under bottom limit for ages and never had a comeback which means A) very few people have their own mikes and B) most non critical engines run quite happily like that without showing an oil pressure problem.
It also shows that if you want a job done properly either do it yourself or at the very least be able to check what someone else has done for you. Crank grinding is the only major op I can't do in house because it ain't worth buying a £10,000 crank grinder that will only get used once in a blue moon but trying to get someone else to grind a crank properly is not as easy as you'd assume. If I get within half a thou of the size I've told someone to work to it's a minor miracle. Most engine reconditioners are little more than butchers pretending to be precision engineers in my experience. In fact crank grinding is one of the things they actually do tolerably well compared to valve seat cutting which very few of them have a clue about but that's another story.
Dave Baker
Puma Race Engines
Mains shells are indeed available down to minus 40 thou but big ends can go down as far as minus 60 from for example King Bearings.
http://www.king-bearings.com/cat/
You need to use that site with IE though. It doesn't work with Firefox.
BTW people tend to think that the stated journal size range indicates shagged (below lower limit) and unshagged (above it). It doesn't. It's simply the tolerance range for the original factory grind. A brand new crank can theoretically come out of the factory right at bottom limit and still be fine when it's worn a good bit below that. For a cooking road motor you're unlikely to have an oil pressure issue with good shells and a decent oil pump until the journals are at least 1 thou under bottom limit. In fact many race engine builders would go that low on a regrind as a matter of course to try and minimise bearing friction (which I disagree with as it happens as stated in a recent thread).
Having said that you rarely see a journal that badly worn without the rest of the motor also being shagged. In fact with modern oils you rarely see any crank wear at all unless there's been an actual lubrication failure at extreme mileage or due to oil surge in competition use.
As an aside, many years ago I tried a new crank grinder chappy on the recommendation of a friend and took him an MGB crank for a race motor. I was only having it ground in the first place because it was about half a thou under bottom limit and I build my engines tight but to be honest I could just as easily have left it alone if I wasn't so bloody pedantic. A few days later I went to pick it up, got it back to the workshop, dug out the mikes and found the bloody thing was indeed now 10 thou down on both mains and big ends but both were a full 1 thou under their bottom limits! The bloody thing was actually worse than before I'd had it ground.
I stormed back up there with my own mikes and calibration pieces and when I checked his knackered old mike it was reading a thou large which meant he was grinding every bloody crank he did a thou small and had been doing so for god knows how long. I mean how much bloody trouble is it to get a calibration piece out every now and then and check your mike is still set correctly when you're claiming to be a precision engineer? I do it before every critical job never mind once a decade if you're lucky like this guy.
So severe bollo*kings were issued, I recalibrated his mike myself and told him the thing had better be exactly at the specified top limit as I'd asked for originally when I came back to pick it up after he'd ground it again down to the next 20 thou undersize. To be fair it was spot on but I imagine he sweated a bit over that one rather than cock it up a second time at which point we'd have been rapidly running out of undersize shells to work with.
However the point is he'd been sending out cranks a thou under bottom limit for ages and never had a comeback which means A) very few people have their own mikes and B) most non critical engines run quite happily like that without showing an oil pressure problem.
It also shows that if you want a job done properly either do it yourself or at the very least be able to check what someone else has done for you. Crank grinding is the only major op I can't do in house because it ain't worth buying a £10,000 crank grinder that will only get used once in a blue moon but trying to get someone else to grind a crank properly is not as easy as you'd assume. If I get within half a thou of the size I've told someone to work to it's a minor miracle. Most engine reconditioners are little more than butchers pretending to be precision engineers in my experience. In fact crank grinding is one of the things they actually do tolerably well compared to valve seat cutting which very few of them have a clue about but that's another story.
Dave Baker
Puma Race Engines
Edited by Pumaracing on Monday 27th April 19:05
Edited by Pumaracing on Monday 27th April 20:03
You could have got away with the MGB crank.... Less than 002" on a B' race motor and everybody seems to run into bearing trouble, even with vandervells.
The only guy's who grind cranks right are people who make them.... Arrow are fantastic! engine re-con people seem to have the worst mic's but seem to get half decent results. i have invested £???? (4 figure sum) on Mitutoyo mic's... It's still the user who's usally wrong!
When I have valve shims ground, I sent my own mic.
Of course bearing quality is often she*te these days, so even if the crank is ground correctly, even tight.. the clearance ends up large.
The only guy's who grind cranks right are people who make them.... Arrow are fantastic! engine re-con people seem to have the worst mic's but seem to get half decent results. i have invested £???? (4 figure sum) on Mitutoyo mic's... It's still the user who's usally wrong!
When I have valve shims ground, I sent my own mic.
Of course bearing quality is often she*te these days, so even if the crank is ground correctly, even tight.. the clearance ends up large.
Well crank grinding is essentially a very simple operation which the machine is designed to do properly provided it's not completely knackered and all the operator has to do is have accurately calibrated micrometers and a modicum of common sense. Sure it's still possible for them to cock it up either on size or surface finish but it's rare to get a job back that isn't at least functional for a cooking engine even if not as top notch as you might want for a race one. I'd say most engine reconditioners also do a tolerable job of boring and honing.
Skimming heads and blocks starts to show real differences in quality of finish though depending on the equipment and operator skill. I've seen finishes anything from so fine you can see your face in the job down to rough as a badger's arse if it's been done at too fast a feed or with a grinding wheel that needs redressing. Modern engines and gaskets require very fine surface finishes and most blown gasket problems are the fault of the finish the reconditioner managed to achieve rather than any defect in the gasket or the bolts. If you feel any ridges with your fingernail it's far too rough.
Valve seat cutting is a whole different ball game though. It's not just the issue of whether the seats get cut truly concentric to the valve guide so they actually lap in and seal properly it's also that there are no fixed standards to work to for seat width, seat diameter and angles of top and bottom cut so what you get back from each person tends to be a function of the equipment they use and the seat cutters they have in stock. They might all be called three angle seats but whether they flow well or not is in the lap of the gods. I've spent hundreds of hours on the flow bench testing seat widths and angles to find out what works best in different types of head and I can say for an absolute certainty that most seat cutting jobs you might have done will be nowhere near ideal for good flow and power.
That's even assuming they use a decent tungsten carbide seat cutting system with 3 angle cutters rather than some antiquated Black and Decker stone grinding system which plenty of places still use. Back in the day when all cylinder heads were cast iron and valve stems were very thick like the 8mm or 9mm stems which were standard on things like Pintos and MGBs you could just about manage with a stone grinding system. Nowadays however stems are getting thinner and thinner which means the seat cutter, which relies on the rigidity of the pilot it runs on to get good concentricity, have a harder job. 5mm stems are not uncommon on multivalve engines and bike engines can have even smaller ones. Seat inserts are also very hard these days to cope with unleaded fuel so they are harder for any system to cut accurately without chatter or tearing.
Even an expensive carbide cutting system is no panacea for all possible problems. The most common system nowadays is Serdi but I have a friend with one which I've used myself and it's a bugger for cutting off centre or generating chatter on the seat finish. It's extremely sensitive to clearance between the valve guide and the pilot so any guide wear at all stops it working properly even if that wear is miniscule and not really worth reconditioning. It also doesn't like heads where the end of the guide is a long way from the seat, especially ported heads where the guide has maybe been cut off flush with the port instead of sticking further out as normal.
Most standard heads have a seat diameter which is 1mm or so smaller than the diameter of the valve head. That's also what most reconditioners are used to doing simply because A) that's what they usually see and B) they don't have flow benches or any idea of what a perfect valve seat geometry looks like. For best flow the seat in the head MUST be the full size of the head of the valve or you're wasting some of that valve size. Choosing top and bottom cut angles and lengths is then also very critical. Most places have very small range of cutters, perhaps a 1mm wide, a 1.5mm and a 2mm which will all have a 60 degree bottom angle and a 20 or 30 degree top one. Firstly those are not universally ideal angles for any seat and which width they choose is another lottery.
It should be apparent that an ideal seat width ought to be a function of the valve size. For example if 4% of the head diameter is what you need for best flow then a 30mm valve will require a 1.2mm wide seat and a 40mm diameter valve will require a 1.6mm one. These are not nice round numbers which they'll have a cutter for. A 1.5mm cutter might be tolerably close for a 40mm valve but do you use the 1mm cutter or the 1.5mm one for a 30mm valve? Neither will be right.
So for all those reasons seat cutting is the biggest variable you're ever going to see in engine reconditioning or race engine prep. Most seats don't even begin to flow well and far too many don't even seal properly. Getting the seats and adjacent areas perfect can account for nearly 50% of the flow and power gains you can get from a ported race head. Very few people know how to find that 50%.
Skimming heads and blocks starts to show real differences in quality of finish though depending on the equipment and operator skill. I've seen finishes anything from so fine you can see your face in the job down to rough as a badger's arse if it's been done at too fast a feed or with a grinding wheel that needs redressing. Modern engines and gaskets require very fine surface finishes and most blown gasket problems are the fault of the finish the reconditioner managed to achieve rather than any defect in the gasket or the bolts. If you feel any ridges with your fingernail it's far too rough.
Valve seat cutting is a whole different ball game though. It's not just the issue of whether the seats get cut truly concentric to the valve guide so they actually lap in and seal properly it's also that there are no fixed standards to work to for seat width, seat diameter and angles of top and bottom cut so what you get back from each person tends to be a function of the equipment they use and the seat cutters they have in stock. They might all be called three angle seats but whether they flow well or not is in the lap of the gods. I've spent hundreds of hours on the flow bench testing seat widths and angles to find out what works best in different types of head and I can say for an absolute certainty that most seat cutting jobs you might have done will be nowhere near ideal for good flow and power.
That's even assuming they use a decent tungsten carbide seat cutting system with 3 angle cutters rather than some antiquated Black and Decker stone grinding system which plenty of places still use. Back in the day when all cylinder heads were cast iron and valve stems were very thick like the 8mm or 9mm stems which were standard on things like Pintos and MGBs you could just about manage with a stone grinding system. Nowadays however stems are getting thinner and thinner which means the seat cutter, which relies on the rigidity of the pilot it runs on to get good concentricity, have a harder job. 5mm stems are not uncommon on multivalve engines and bike engines can have even smaller ones. Seat inserts are also very hard these days to cope with unleaded fuel so they are harder for any system to cut accurately without chatter or tearing.
Even an expensive carbide cutting system is no panacea for all possible problems. The most common system nowadays is Serdi but I have a friend with one which I've used myself and it's a bugger for cutting off centre or generating chatter on the seat finish. It's extremely sensitive to clearance between the valve guide and the pilot so any guide wear at all stops it working properly even if that wear is miniscule and not really worth reconditioning. It also doesn't like heads where the end of the guide is a long way from the seat, especially ported heads where the guide has maybe been cut off flush with the port instead of sticking further out as normal.
Most standard heads have a seat diameter which is 1mm or so smaller than the diameter of the valve head. That's also what most reconditioners are used to doing simply because A) that's what they usually see and B) they don't have flow benches or any idea of what a perfect valve seat geometry looks like. For best flow the seat in the head MUST be the full size of the head of the valve or you're wasting some of that valve size. Choosing top and bottom cut angles and lengths is then also very critical. Most places have very small range of cutters, perhaps a 1mm wide, a 1.5mm and a 2mm which will all have a 60 degree bottom angle and a 20 or 30 degree top one. Firstly those are not universally ideal angles for any seat and which width they choose is another lottery.
It should be apparent that an ideal seat width ought to be a function of the valve size. For example if 4% of the head diameter is what you need for best flow then a 30mm valve will require a 1.2mm wide seat and a 40mm diameter valve will require a 1.6mm one. These are not nice round numbers which they'll have a cutter for. A 1.5mm cutter might be tolerably close for a 40mm valve but do you use the 1mm cutter or the 1.5mm one for a 30mm valve? Neither will be right.
So for all those reasons seat cutting is the biggest variable you're ever going to see in engine reconditioning or race engine prep. Most seats don't even begin to flow well and far too many don't even seal properly. Getting the seats and adjacent areas perfect can account for nearly 50% of the flow and power gains you can get from a ported race head. Very few people know how to find that 50%.
It's nice to see a true pro on here!
We have a Serdi type cutter at work... The bigger the valve, the bigger the problem. Try 2.1" Aston Martin valves. It constantly cuts off center, and chatters like crazy on hardened inserts.... Great for re-cutting old seats that are well well past their best, and you are only ment to be doing a bottom end job!
can't stand valve seat work, getting all the heights the same is a total PITA. People tell me you can't beat a B&D grinder, with a nacked stone!
We have a Serdi type cutter at work... The bigger the valve, the bigger the problem. Try 2.1" Aston Martin valves. It constantly cuts off center, and chatters like crazy on hardened inserts.... Great for re-cutting old seats that are well well past their best, and you are only ment to be doing a bottom end job!
can't stand valve seat work, getting all the heights the same is a total PITA. People tell me you can't beat a B&D grinder, with a nacked stone!
fatjon said:
I am sitting here looking at a set of standard rover v8 mains and they are 2.4995" to 2.5"
I can say with some confidence they are correct as I have fitted half of them!
Jon
Which seeing as you therefore clearly have a later 4.0 or 4.6 large journal block is neither surprising nor relevant to the OP's 3500.I can say with some confidence they are correct as I have fitted half of them!
Jon
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