Mains..

need4speed · Post by **need4speed** » Tue Apr 22, 2008 9:58 am

Why is it some engineering shops specify that when you take your block to them for a rebore, you must have the main caps fitted and torqued up?
Some shops say you should and some say you dont. What is the reasoning here?

Post by **katanaman** » Tue Apr 22, 2008 10:04 am

because that is the way the engine runs so if the block moves the bores will be true when built. Torque plates are also a good idea as this simulates the heads being in place. Does it really matter? depends on what your building I suppose and I would say at a guess its much more important to do it on a cross bolt block.

need4speed · Post by **need4speed** » Tue Apr 22, 2008 10:09 am

hmm. sounds like a good idea after your explaination. my next question then is, does anyone have an old used set of main cap bolts they could sell me? I (stupidly) threw mine away as for this engine i intend to use ARP studs which i dont have yet..

ChrisJC · Post by **ChrisJC** » Tue Apr 22, 2008 12:02 pm

katanaman wrote:I would say at a guess its much more important to do it on a cross bolt block.

That is dead right - if you torque down the mains in an x-bolt block and leave out the side bolts, the bearings will be far enough out of true to grip the crankshaft surprisingly tightly!

Chris.

Boosted LS1 · Post by **Boosted LS1** » Tue Apr 22, 2008 9:02 pm

It depends on the type of boring bar they are going to use. Some boring bars are large fixed machines and they may clamp the block down using the mains. Other boring bars are more portable and clamp underneath the block, via an adjacent cylinder. Such as a Van Norman.

I used to use a local company who always wanted the main bearing caps. Now I go elsewhere and they don't need caps.

TVRleigh · Post by **TVRleigh** » Tue Apr 29, 2008 12:32 pm

ChrisJC wrote:
katanaman wrote:I would say at a guess its much more important to do it on a cross bolt block.
That is dead right - if you torque down the mains in an x-bolt block and leave out the side bolts, the bearings will be far enough out of true to grip the crankshaft surprisingly tightly!

Chris.

Would think this would be more true if you re-bore the journal bit. than then piston bores.

Also depends on the engine, I made the mistake of trying the crank to mesure the clearance and did not put in the x-bolts. the crank would still turn, but not spin freely.

stevieturbo · Post by **stevieturbo** » Tue Apr 29, 2008 5:09 pm

ChrisJC wrote:
katanaman wrote:I would say at a guess its much more important to do it on a cross bolt block.
That is dead right - if you torque down the mains in an x-bolt block and leave out the side bolts, the bearings will be far enough out of true to grip the crankshaft surprisingly tightly!

Chris.

Same with my old 4.6. Torque the mains up to spec, and you couldnt turn the crank easily by hand.

Finish it off with the side bolts. And all of a sudden, the crank rotated freely !!! I couldnt believe the difference.

Rover's shitty K-series is another perfect example. Remove the head, and you cant turn the engine over, as the pistons are almost stuck in the bores !!!

davemgb · Post by **davemgb** » Tue Apr 29, 2008 7:40 pm

Rover's shitty K-series is another perfect example. Remove the head, and you cant turn the engine over, as the pistons are almost stuck in the bores !!!

Steve,

You make a valid point then instantly loose the plot over exactly the same issue. The Rover K series is a precision item, the bad reputation has come from self proclaimed 'engineers' who don't understand how it was designed and have made shitty mchanges to the engine.

Shame really that someone at Land Rover didn't remove the outer head bolts on the V8 earlier, but they possible didn't know how to tell the cheif engineer there was a problem with his design.

Dave

stevieturbo · Post by **stevieturbo** » Tue Apr 29, 2008 7:56 pm

Precision item.....well, you could call it that.

Point is, everything should be torqued up where possible, before carrying out any machining work, as so much changes.

I still call them a crap engine. In the same way Toyota's MR2 turbo and GT4's are crap engines too. Not sure which goes through head gaskets faster.

A quality, precision item would not be so unreliable.

Lehto · Post by **Lehto** » Fri May 02, 2008 7:02 pm

stevieturbo wrote:Precision item.....well, you could call it that.

Point is, everything should be torqued up where possible, before carrying out any machining work, as so much changes.

I still call them a crap engine. In the same way Toyota's MR2 turbo and GT4's are crap engines too. Not sure which goes through head gaskets faster.

A quality, precision item would not be so unreliable.

I own a Rover 200 with 1.8L (non-vvc) K-series and I have the reinforced landrover gasket with new oil ladder, etc and I have put a load of kilometres on it and driven long distances pedal to metal.

This is my first post here... some of you might know me from SD1 forum.