View Full Version : Line Boring - Is this needed when main bolts are replaced with studs?

10-10-03, 10:09 PM
Is this absolutely necessary?

I know when rod bolts are replaced the big ends should be closed and honed, however is this needed when the main caps have their bolts replaced?

Engine is a 2jz.

mopar lover
11-10-03, 10:37 AM
Big ends need to be resized because 99% of the time to remove and replace the rod bolts requires a press or the force of a hammer.

Also line boring is only required when the main caps are replaced. If you wanted to do it you would get it line honed. A lot of people have just replaced the main bolts with main studs and assembled it. It isn't critical, but if you are unsure torque up your main caps and measure them.

11-10-03, 12:30 PM
Originally posted by mopar lover
Big ends need to be resized because 99% of the time to remove and replace the rod bolts requires a press or the force of a hammer.

Also line boring is only required when the main caps are replaced. If you wanted to do it you would get it line honed. A lot of people have just replaced the main bolts with main studs and assembled it. It isn't critical, but if you are unsure torque up your main caps and measure them.

Wot he said. :) Usually you wouldn't bother unless you are rectifying a problem, as the main caps are aligned by dowels or the machining in the block, and not the bolts. So unless you've replaced a cap, or you think the block is out of true (such as irregular bearing wear) then it's probably a waste of time and money.

11-10-03, 03:10 PM
The rod bolts on the 2j simply undo - nothing needs to be pressed/hammered out - however the big end will be getting resized.


I guess i'll have to just check the clearances when I fit the studs and speak with my machinist.

Jim - no irregular bearing wear that I can see, all bearings are in very good condition.

Thanks for the replies :)

11-10-03, 03:59 PM
FFS Jon, leave the farken thing alone willya?!?!?!? :rolleyes: :p

12-10-03, 09:01 PM
Can't help myself :)

13-10-03, 10:47 AM
how old is the motor?? if it has done some kays get it line bored just for peice of mind, especially if you are going to pull some more power out of her. if you have just spent the money and put new studs in, spend the extra $100 and get it line bored.



13-10-03, 11:42 AM
It was built in mid 94 - however I'm not sure on the kms done, it'd be lucky to have 20 or 30,000kms on it - It's extremely clean internally, and the bearings are mint, as are the turbos and such.

I don't want to mess with too many things, more so because it becomes 1 thing after another as it's becoming now :)

18-10-03, 01:26 PM
The reason the rod big ends need to be resized (and the reason they _may_ be hard to get apart) is that with long enough, or frequent enough trips into higher rpms (than the rods can handle indefinitely) they start to oval out. If you get it in a reasonable time, you then have to remachine them to correct it. On a high rpm serious race effort, more likely it'd be time to replace them. If you get new rod bolts (and even the best rod bolts in the world have a set limit to the times they can be undone and retensioned/stretched before they _won't_ be safe to re-use. Many stock rod bolts are best not reused period.

The reason for getting them resized when new bolts are fitted is because the change of bolts itself will produce a slightly different distortion to the rod big end - and they must be done accordingly.

WIth regard the the main caps - the choice as to whether or not to align hone is answered by torqueing them up and measuring the main tunnels for concentricity and diameter. If they aren't round, it could be a drama on a race engine, if they aren't the right diameter, they won't produce the appropriate radial tension/bearing crush. Last but not least, they need to actually be in line.

ON some 'dino' engines - they run somewhat larger bearing clearances - and it seems that they can get away with a little less attention here - for anything short of drag or circuit race competition (you'd be unlucky to ever see a drama on a streeter)

Here's something that even 90% of the people who might recommend main tunnel reszing won't tell you - and will possibly cause you no end of grief. Unless it's just a 0.0001-0.0002 " out (1 - 2 ten thousandths) the way they have to do it is to machine the block where the caps sit, and also machine the main cap parting face. SO they squeeze together closer and then a new circle can be machined through the main tunnel. This process actually ends up relocating the crankshaft a little higher. Probably only 5thou - maybe a little less possibly more. Now unless you then use a dial indicator, and check the crank alignment with the trans input shaft (or similar on an auto - sometimes you measure the front pump recess/seating face on autos) and use new offset dowls (the steel 'pins' that line the gearbox up as you bolt it in. - basically special ones that have a 5 (or whatever is needed) thou offset in the middle - like a step - you are up shit creek.

If you don't do this, you'll end up breaking flexplates, possibly the front pump on the trans, the convertor 'snout' or on a manual genrerally the input shaft carrier bearing and smaller spigot bearing (where the mainshaft slots in the back of the 3/4 cluster (that'll make sense to someone)

In a roundabout way this comes up with hemis, and it was only 'discovered' when someone casually discussed the problems of main tunnel line boring, and trans flexplate and convertor failure.. MOst hemi 6s didn't have a torqueflite pattern. So people weld and drill the trans case to fit them. But they don't always take time to ensure it's perfectly aligned. It's lead some to try and profit from it pretending there is some sort of witchcraft about hemi transmissions, and only their option will work rather than them being honest and letting on that there is a practical and logical fix....

If you want a ballpark of what constitutes acceptable alignment - I'd personally want it to be _less_ than 1 thou out - as close to zero as possible.

One other thing - unless it's really not up to scratch - I'd really strongly urge leaving it. Unless you go to a very good machinist (and I'd guess that it wouldn't be a problem in this country to find one whereever you live, just don't make the mistake that any and all reconditioners are safe to entrust this work to) - unless they do it right, the result will actually be far more problematic than the current engine condition..

John McKenzie

19-10-03, 08:41 PM
i second that notion , leave it be.
bear in mind that the stock bolts are torque-to-yield and should be replaced rather than reused.

20-10-03, 06:23 PM
I third it.

The caps should register in the block and are not aligned by the studs.

You can have all sorts of bother depending in the engine. Timing chains/valve timing can also be an issue too.

24-10-03, 07:50 PM
Thanks for all the replies :)

I understand the concept as to why the big end needs to be resized when rod bolts are replaced (and in the case of the 2jz, they are a TTY bolt, thus the condom bolt - use once then chuck).

I'm replacing the head bolts with ARP Studs, the main bolts with ARP studs and the rod bolts with ARP bolts.

The rods will be resized, as per the original post however jmac has posted a far more indepth reason to the rod bolts and main caps/bolts, kind of off topic to the original thread, but it makes alot of sense - an excellent post as per all your other posts, thankyou Mr Mckenzie :).

Pete - I am replacing all the important fasteners with ARP hardware and I know all the rod/head/main bolts are TTY thus the original thread of replacing the main bolts with studs ;),


The question was if the main bolts are replaced with studs, is a line hone/bore required - I've installed the above hardware and checked all the tolerences and it looks to be ok with them fitted, will speak to themachinist and see what his final word is on the matter.



24-10-03, 08:04 PM
arp studs throughout ... you must be shooting for some serious hp over whats achievable with a stock motor :)

24-10-03, 08:48 PM
Money dictates all unfortunetly, but they're a throw away bolt from the factory, so it's cheap insurance at the end of the day.

tossing up whether to go GT40 or GT42/45...that's the deciding factor :)

25-10-03, 01:10 AM
The question was if main studs were installed - would it require line honing.

I (think) I answered - but it may have gotten lost in the 'waffling on' included in my post sorry.

short answer - I'd be bloody amazed it if was neccesary, but to be sure measure.

extended reason - firstly bare and then a second time after install bearings, torque main caps to spec (or the revised spec as per ARP instructions - which are included if they deem it necessary to run a different spec with the studs - if in _any_ doubt contact them and they will advise - they do know what's what) and _measure_ the main cap _and_ bearings diameter - to check that they are round and uniform. Without measuring no-one can say 100% for sure, but I'd bet a lot that it will be a-ok as is.

On rods, some tricks are sometimes used (some are ok, some are in my opinion retarded, and actually end up increasing stress on the rod cap - the last thing you need - in this case cutting the rod parting faces slightly diagonally so that when they clamp down it tries to squeeze) to increse the clamping or bearing crush.

Thing to remeber - the rods are (by necessity) relatively light - too heavy and you lose power, and also it adds to bearing stress. And then there is also physical space considerations. Main caps on the other hand - don't have to move - let alone at 7000rpm (which actually means 14,000 'trips' one up one down) or so. They are hooked a a huge structure - the block - so as a result they can by and large 'hold' their shape a little easier than a rod cap. Fitting new rod bolts can distort the rod - just removing the old ones, and squeezing new ones in, let alone the extra clamping often available (even at the same tension) due to superior bolt composition and design (even the underside of the nut affects things), not to mention that the original bolts - even the ones that aren't torque to yield, will likely have lost some elasticity over time.

If it did require it it would more likely be because they were cast or machined _wrong_ in the first place. In this day and age it's highly doubtful. Apparently 202 holden main tunnels aren't perfect - one of them is a fraction off. In normal driving - never an issue - but according to the guy who was one of the key figures in the development of the XU-1, it was enough that they corrected it (the xu1 202 blocks have other differences too, but that was one of them)

So add all that up - unless the engines have inherent main tunnel misalignment from the factory, it's unlikely at best. The structure involved has far less possibility of distorting by a country mile. Then there's the fact that at big power levels, the main web area may give _a fraction_ anyway - as evidenced by the use of main stud girdles in high rpm/output race engines. Which means on a streeter they'd possibly flex a fraction under load - and this flex would be different with each cylinders combustion event doing a 'mexican wave' - so the fact they are perfectly lined up - or arent - on the engine stand, it doesn't totally represent the 'as running' condition. The primary issue (within reason) is not the alignment, it's bearing shape and size - which on main caps isn't altered as much - not nearly - by different fasteners.

John McKenzie

25-10-03, 10:20 AM
Awesome info John - That's exactly answer I was looking for :)

I have done some measurements with a telescoping gauge (borrowed from work and calibrated a few months ago) and each of the caps diameter are within spec both with and without the bearings installed.

I've also installed the crank and it rotates nicely - feels the same as it was prior to removing it originally. I will be getting some plastigage to double check the bearing to journal clearances before final assembly though - It's just a case of getting a hold of the stuff!