Hello New to forum and going paranoid.

Alex · 25 Nov 2019

All of it as in machining cylinder liners out, etc? I thought the was only Hartech who had the capability to do everything inhouse :dont know:

Hertsdriver · 25 Nov 2019

milling out a liner isn't exactly challenging from a machining point of view. Most engineering shops could do it if they are properly directed.

Robert SausageTrousers · 25 Nov 2019

Yeah the head was sent off for machining, and the front bumper sent off to be repainted, but ****** (not sure why we're not allowed to mention their name?) did the rest in house. With a full service, chains etc and all the associated bits and bobs, the bill was just over £10k, with a 2 year or 20k mile warranty.

Alex · 25 Nov 2019

Hertsdriver said:
milling out a liner isn't exactly challenging from a machining point of view. Most engineering shops could do it if they are properly directed.

Not true. I know what these engines are like and what problems Hartech have had to overcome when doing them. It's not as simple as bore those cylinders out to 'x' diameter.

Hertsdriver · 25 Nov 2019

Alex said:
Hertsdriver said:

milling out a liner isn't exactly challenging from a machining point of view. Most engineering shops could do it if they are properly directed.

Click to expand...

Not true. I know what these engines are like and what problems Hartech have had to overcome when doing them. It's not as simple as bore those cylinders out to 'x' diameter.

No, its absolutely true. Milling it out is very straightforward, providing you have the machinery.
Knowing what the 'x' is to mill it out to is the issue, and that is where an engineering shop needs to be properly directed.

Alex · 25 Nov 2019

In a perfect world yes. But that's not the case with these engines. No 2 blocks are the same. In fact - I'd go as far to say they are an Engineering embarrassment. The pitch on the bores (distance between each bore) are all over the place, the heads aren't skimmed flat and sometimes even have a step on them where its been done in 2 passes at different z-axis coordinates. The bores aren't always in line to the positions on the crank, the bore offsets from bank 1 & bank 2 are all over the place......I could go on.

Until you've measured these things to death and spent tens of thousands on proper custom made jigs, fixtures and tooling, forget about it.

Phil 997 · 25 Nov 2019

I am not 100% but seem to remember Hartech telling me that they also improve the flow of oil on their rebuilds , I may be wrong as it was almost a year ago I first talked to them about this and I have had a lot of sleeps since then. :thumb:

Alex · 25 Nov 2019

They do various machining mods to improve oil / water flow for better temperature control of the engine.

Hertsdriver · 25 Nov 2019

Alex said:
In a perfect world yes. But that's not the case with these engines. No 2 blocks are the same. In fact - I'd go as far to say they are an Engineering embarrassment. The pitch on the bores (distance between each bore) are all over the place, the heads aren't skimmed flat and sometimes even have a step on them where its been done in 2 passes at different z-axis coordinates. The bores aren't always in line to the positions on the crank, the bore offsets from bank 1 & bank 2 are all over the place......I could go on.

Until you've measured these things to death and spent tens of thousands on proper custom made jigs, fixtures and tooling, forget about it.

When you mill a bore for a liner, you find the centre point of the current bore, then use that as the datum. The heads have got nothing to do with the bore machining, neither has the position of the crank or anything to do with how poorly made the engine was in the first place. You find the centre, and machine out to the desired size. It really isn't difficult. Knowing the correct size is obviously the important bit, but if you instruct a machine shop to bore out to 'x' mm, thats what they will do.

You can see Hartechs machining in their engine rebuild video on their website, I don't think by looking at it its a cnc machine like a SERDI, it looks like an old school milling machine worked by an experienced engineer (apologies if that isnt correct, its a very short burst of a timelapse video).

The Hartech solution isn't an interference fit as the material is the same as the block (albeit the surface of the bore is Nicasil plated) , and the liner is held in place by their proprietary closed deck design. A more traditional iron or steel liner would require undersized machining and then heating the casting before installing the liner. In my limited experience of 2 stroke engines (go karts, lambrettas) Nicasil as fitted by Hartech is clearly the better long term option, but Baz has already admitted that an Iron or Steel liners can work in this application, depending on how well they are installed, and how correct the tolerances are for heat expansion etc.

Alex · 25 Nov 2019

So you've watched the video.

Trust me, Hartech machine the bores in the correct position they should've originally been in at the right pitch to each other. Just because it may not be a CNC does not mean they don't machine to a set pitch and accuracy from set datums relevant to the crank position. If they didn't, for starters, the flats on the top hats of the liners would interfere and not fit.

And to say the pitch on the crank pins has no relevance to the pitch on the bores

Example - if the pitch on the crank pins is say 100mm and the pitch on the bores is 102mm, by the time you got to the 3rd bore you'd be 6mm out. How's that not relevant? They wouldn't line up with each other.

To pick up each individual bore knowing the pitch on them is out is cowboy engineering and not how I'd do it, Hartech do it or any other decent Engineer would do it.

Hertsdriver · 25 Nov 2019

Alex said:
And to say the pitch on the crank pins has no relevance to the pitch on the bores

I didnt say that though, dont mis-quote me.
I said it had no relation to an engineering firm milling a liner.
They wouldnt have the crank, they would just have the block and the instructions. Which is why the instructions to the firm are the important part. The actual machining is simple work, I dont know why this is worth arguing over as its pretty much indisputable.

Alex · 25 Nov 2019

I didn't twist your words:

Hertsdriver said:
When you mill a bore for a liner, you find the centre point of the current bore, then use that as the datum. The heads have got nothing to do with the bore machining, neither has the position of the crank or anything to do with how poorly made the engine was in the first place.

The pitch on the bores should be right. Some Porsche engines are, some aren't - Fact. Why would you machine them out of line when they should be in line, it's absolute crackers and possibly part reason why they need a rebuild in the 1st place.

This is where the problem lies when places sub out the machining work and they follow errors instead of doing the job properly.

Edit: and to add to what I've said - we know the bores wear more on one side than the other and go out of shape - how do you pick the centre of the bore up when it's like that?

Hertsdriver · 25 Nov 2019

You are twisting things.
I was merely commenting on your insistence that machining a block to accept liners is difficult, it isn't it's easy as a process.
I agree that things you have mentioned and others should absolutely be part of the evaluation of where to perform the machining, but that actual machining itself is a simple task for a machine shop.

Alex · 25 Nov 2019

That may be the case, but once Trevor Reznik down at Renwick St Engineering is dicking about trying to pick a bore up and get's frustrated cos it's all over the place, he says f**** it, gets it somewhere near and bores it out. The machined block goes back to the engine builder, he presses a new liner in, then 12 months down the line it's up at Hartech getting done again.

I can not stress the importance of getting these blocks machined out properly (as Hartech do) to how they should be machined. This is the sole reason they do everything in house - to ensure it is done exactly to how they want it doing - the correct way.

I'm not trying to cause argument, just want people to be aware of what's involved (or not at some outfits) when rebuilding these engines and how important it is to get it right.

Off for me scram :food:

Hertsdriver · 25 Nov 2019

I don't think Baz would call Steve Winters work at JAZ into question, Which is where this started. What you just posted I don't disagree with, but we were talking about 2 specialists that were mentioned, not some random.

Hello New to forum and going paranoid.

Alex

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