First Time Engine Rebuild

[bmcecosse]

It's only the exhaust valves that are sunk - so packing the rocker pillars is not really an option, or then it will be wrong for the inlets. The valve stem tips could be ground down - but I'm not sure of the hardening (if any) on the valve tips. Remember also - whatever amount the valves are sunk - then an equal amount of packing (ie a nice flat washer of same thickness) should be placed under the exhaust valve springs.

[edd_barker]

All temperature jokes greatly appreciated!

Phil, I was expecting to just fit a set of the sintered rockers, I know they're not great, but I'm hoping they will do for a road going car. I hadn't heard of having to do any drilling before, I'll re-read Vizard. Will my sintered rockers negate the need for this?

I won't know how much the valves have been sunk by on the recon head, unless they can remember. Can I just measure up the gap from valve face to head surface and work backwards?

RE the push rods, how do I work out what length of those I need, 1275 ones?

Thanks,

Edd

[philthehill]

If you fit a full sintered rocker assy the tapped pillar is the second one so you should be alright.
See the link below from ESM. The tapped pillar is No: 2 pillar from the right.
http://morrisminorspares.co.uk/shop/pop ... 43841fb918
It is only when you fit the early rocker assy to the later heads or fit a later rocker shaft (which are the only ones available now) do you require to consider moving and drilling the pillars.
The sintered rockers are more than adequate for a road going car.
My own engine if fitted with a 1.5 ratio full roller rocker assy but I have tried several variations of rockers over the years.
The 1098cc push rods will be suitable for use with a 940 head fitted to a 1098cc engine.
Phil

[edd_barker]

Phil,

Thanks for that photo, immediately makes it clear what you are talking about, I see exactly what you mean. I'll inspect the set of rockers I have to ensure the 2nd one is tapped, I'm certain it will be, as the lobes are all much wider. They look a tiny bit worn though.

I'll post pics of the push rods, might need some work to reshape, or I'll buy new ones. Expecting to buy new cam followers.

Cheers, thanks again everyone for all your help and advice.

Edd

[philthehill]

Edd
Not sure what you mean about "some work to re-shape" as the push rods in standard form are more than adequate?
A photo will be most helpful.
Phil

[edd_barker]

I'm thinking there was some wear, but I could be confusing myself with the rocker tips. I'll inspect when I can next get in the garage and post pictures.

Cheers,

Edd

[bmcecosse]

Short push rods are fine - and they don't 'wear' - if they are bent - throw them away - they must be dead straight. The rocker shaft may be worn - the rockers are usually fine. Pull one to the side to look at the shaft under the rocker. But these sintered rockers put an offset load on the valve stems - worse than any 'geometry' problems. A nice set of the pressed steel rockers is a better bet - and you can then spend some happy time carefully aligning them with the valve stems..

[edd_barker]

Hi all,

Just to keep those interested updated, I've now heard back from the engineers. The cylinder head I provided them had a depth of .280 between exhaust valves and face, however it was quite badly corroded, so the amount they'd have to skim off meant that for this purpose, it's no good. I am on the hunt for another!

They're commencing all the rest of the overhaul work. Crank just needs a polish, block is being rebored to .060 oversize with all new parts as required. Also fitting a new flywheel ring gear for me as the old one was in tatters!

I'll let you all know how it goes when everything arrives back for rebuild.

Cheers,

Edd

[bmcecosse]

Well done - keep the news coming...

[edd_barker]

Interesting chat with the insurers today, I'm on the MMOC Footman James scheme, they require any swapped engine to be 'fitted professionally', I didn't ask if this applied to other parts but I've swapped the brakes myself! Has anyone else had any experience of this, or are with a more realistic insurer? My renewal is due in a couple of weeks so a good time to switch.

Thanks,

Edd

#EDIT# - They've now told me it just has to go through an MOT when required, as a 1959 Minor this is never, but I do put it through as a matter of 'better safe than sorry'.

[liammonty]

That sounds like utter nonsense, and I wouldn't be surprised if you end up being told something different by someone else at FJ. How would you ever prove it had been 'fitted professionally' if it had been done by a previous owner?! I suspect you will be told to speak to Dave Youngs of Footman James who seems to be the only member of staff who consistently knows what the arrangement is with the MMOC. I was previously insured with them and changed my series II engine from 803 to 948, and the was no requirement for proof of professional fitment. Ultimately, rising costs and poor customer service led me to leave FJ, and insuring my classics has been much less traumatic since I did.

[bmcecosse]

And many will recommend RH Insurance for great service and reasonable cost - with Roadside and Recovery included..

[edd_barker]

Hi all,

Just to ask what thickness an unskimmed 12G940 should be? Thickness of whole head. Got one lined up that's 70mm/2.756 inches. Looks good...

Carb wise, I'm after a HIF38 but they're expensive, any other options?

My spare engine didn't come with a tappet cover where the breather is, what's the best option to source? My current engine has the downward facing pipe, and then rocker breather running to air filter. It only leaks on motorway runs, when it leaks a lot. Should I look at rocker/tappet breather to carb vacuum?

Thanks,

Edd

[ianmack]

When insurers talk of things like a replacement engine needing to be fitted professionally you need to be clear with them what exactly you are doing. Someone in their office may have no idea of the difference between fitting a Rover v8 and just fitting a later a series and treats them all the same. Someone I knew years ago fitted a 948 in an s2 and was told by insurers to get an engineers report. When he explained fully that this was simply a later Minor engine all was well.

[bmcecosse]

Just swap the engine number to the new engine - job done. Who cares! Your 940 head is unskimmed - just as it left the factory. Yes - you need to connect breathers to the carb suction. Better to source a cam follower cover with an upward 'can' take off.

[edd_barker]

Morning all!

Been a fair old wait for this one, my lowly engine was at the back of 48 other A-Series being prepared for a Heritage racing season. The block has been completely overhauled, although I am now sending it back for pocketing....After much discussion I have decided to go down this route. The mini place where I got my HIF38 builds them all the time as the class they race in is restricted to 1098 block but any head, so they all go 12G940, and they all pocket the block. Obviously there is a cost involved, but the rocker geometry will be preserved, no making up of washers etc. They also said that they had never had a problem with excessive heat at the top ring on a race engine, so my road-engine should be OK. Yes the block can never go back to standard head, but with everything reconditioned it should run so well that I (hopefully) never want to change it back! I am paying £100 to have the engine dry assembled with cam etc to work out how much pocketing is required, and then pocketed to necessary clearance. Sounded fair to me. At the very least, I will have done it differently and we will all then have more options to compare to when discussing this conversion! Its a shame I've already had the block faced, but that will teach me for not listening the first time.

Today's question is...The head I have offered up for reconditioning has passed its crack test, but has pretty bad corrosion on the head face, raised rust etc. So it will require more of a skim than usual. Is this likely to raise the compression ratio by too much? I am just getting them to measure if it has been skimmed in the past, but I don't think it has. Are there any magic numbers I can measure to? Maximum skim before CR too high?

My better condition unskimmed head is in Manchester, which I swapped for a 're-con' head, but this turned out to be a donkey, valve guides not changed etc, so I am taking it back but a bit of a faff to drive up there. I would love to use the rusty head as it cost me a tenner and then I can sell the others, but I must confess to not having the greatest understanding of CR etc so I don't want to mess things up! It would be nice to have this engine fitted before the summer!

Looking forward to hearing from you all,


Edd

EDIT - The machine shop have already overhauled the head! The guy misread the ticket, so at least I don't have to take it if I don't want it. The head was unskimmed previously, but had 40 thou taken off the face in the skim. Is this head likely to be suitable on a 1098 block, pocketed for valve clearance, overbored to +040. It sounds like I am going to have to work out CR properly as I don't currently understand it all. Back to Vizard for me!

Thanks,

Edd

[edd_barker]

If anyone can let me know the CC of a 1098 block over bored to +040 that would be great, I can't find it on google.

It will eventually have small pockets in, which will of course affect the volume. This is getting complicated!

The shop are CC'ing the head for me now so I can work out my ratios and see if this will be a suitable road engine. If not then I am not paying for the head.

Cheers!

Edd

[bmcecosse]

I am completely against the block pocketing - I did it 50 years ago on a race engine - and yes it is fine there when the engine will be stripped and rebuilt regularly with new rings. As for £100 to dry assemble etc - you are being taken for a complete ride there! The amount to either 'pocket' or 'sink' is determined only from the cylinder head (assuming standard cam and rockers) - it's very simple - you need 300 thou from exhaust valve face to head face. If not -then sink the valves till you DO have 300 thou. Save the £100.... The 940 head is already at the limit of CR when put on a 1098 engine - so NO skimming is possible -maybe 5 thou to clean the face, something like that - but certainly not 40 thou. Indeed - to an extent it relies on the 'sinking' of the exhaust valve to drop the CR slightly to make sure there won't be pinking or detonation. So the head that has been skimmed will be fine on a 1275, but not on a 1098. You need an unmolested 940 head - measure the gap, and sink the valves IF necessary. On a well used 940 the valves may already have sunk enough by themselves, so nothing for you to do!
Now you mention +40 bore - that makes the CR even higher - the tiny cut-outs won't drop the CR enough - just sink the valves - it WORKS! The money you seem to be willing to throw at this 1098 engine (via the 'machine shop' ) would have been much better invested in a decent 1275. The '940 head on a 1098' conversion is intended as a 'cheap as chips' mod to get a bit more power for very little money!

[edd_barker]

Hi BMC,

Thanks for the reply. I understand your opinion RE block pocketing. I am wanting to go for a fully reconditioned unleaded head, hence my persistence with the machine shop. I know that it can be done with bigger gaps and just sinking the valves, but my aim has always been to build an engine as best as is possible, without worrying (to an extent) how much it costs. I would like everything to be reconditioned, which block-side it currently is.

As soon as I get the CC of the head I will post it here and hopefully someone can help me work out the compression ratio, then I can go from there.

Many thanks,

Edd

EDIT - Yes you are correct I should have gone for a 1275 from the start! The power of hindsight. I am just trying to make the best of the situation I am currently in. Yes I have probably spent a lot more money than required. It is difficult when you are new to a subject and are being given advice in completely opposite directions, some from the internet, some from people stood in front of you. Mistakes are inevitably made that may seem foolish to those more experienced. All I can do is try and move forward!

[philthehill]

Edd

Glad to hear that all is going well.

An unskimmed head is 2.75" in height top face to bottom face.

The swept cubic capacity of a 1098cc engine over bored to plus 0.040" and using standard pistons is 1132cc.

As regards your head the most important dimension is the cc of the combustion chamber.
A standard 12G202 combustion chamber has a volume cc of 26.1cc - a 12G940 head has a volume of 21.4cc.
You should therefore aim for at least a total 26.1cc combustion chamber including the volume of the pocketing which when done becomes part of the combustion chamber.
If you have Vizards book section 9 , Fig 9.13 will explain all.

Phil