Bongo Fury

francophile1947 wrote:

mikeonb4c wrote:But I would be interested to hear that those with direct or general technical knowledge on subjects like this have to say about labour saving costs in not having to transfer valve gear etc.

Based on labour rates when I was in the trade, I suspect that there wouldn't be much difference. It can take a long time to swap all the parts over, especially grinding in the valves to match the new head. I think a complete new head is a good idea, but a different story if you can do the work yourself.

That should give N&G some cheer then as it ought to mean the job costs about the same either way. Plus a complete new head is, as you say, a good idea

haydn callow wrote:I think your right....Make sure the garage you go to knows Bongos......If they replace the head make sure they "true up" the top of the block before fitting a new head.

How would the garage "true up" the block in situ Haydn?

Same way as Simon Jones did his and I did a Morris 1100 30 years ago...If I remember right I got hold of a engineering "flat plate" and some very fine emery and some "blue" stuff. This showed up any "low" points and it was just a case of "polishing away. I think Simon did his with a bit of marble.I think I may have used some grinding paste as well but not sure about that...Whatever I did worked co's I do remember getting it "clean" all over (no blue)

dandywarhol wrote:

haydn callow wrote:I think your right....Make sure the garage you go to knows Bongos......If they replace the head make sure they "true up" the top of the block before fitting a new head.

How would the garage "true up" the block in situ Haydn?

When you say truing up the block alan, do you mean just making sure the mating face is clean enough to make a true seal with the new head gasket?

If somebody suggested skimming the block, i think i'd be inclined to bin it.

I'm not that fond of having a head skimmed really,any more than 6thou milled off is asking for trouble with a raising of the compression ratio,and other complications... I realize that different thickness gaskets can be used to compensate for the C/R but...

What do you reckon to the practice of smearing cam sealent along a scratched block face?

Haydn's method is ideal for cleaning up the surfaces - but not to actually machine it flat - thats why I was asking.

A lot of diesels have the combustion chamber in the piston crown, not the head (the head is flat) so skimming it won't change the compression ratio BDC. I'm not sure if the Bongo engine is one of them - anyone confirm???

The different thickness gaskets are to ensure the pistons don't hit the head - its called piston protrudence or deck height...............

haydn callow wrote:Same way as Simon Jones did his and I did a Morris 1100 30 years ago...If I remember right I got hold of a engineering "flat plate" and some very fine emery and some "blue" stuff. This showed up any "low" points and it was just a case of "polishing away. I think Simon did his with a bit of marble.I think I may have used some grinding paste as well but not sure about that...Whatever I did worked co's I do remember getting it "clean" all over (no blue)

Well that destroyed the surface plates accuracy. Emery 'dust' and grinding paste works wonders in the bores and sump.

Now I'm confused Alan. I'd have thought that whether the head interior was flat or domed, skimming it would reduce the internal volume in the combustion chamber.

I speak from a zero understanding of how these things work though so I'm not challenging the facts, just trying to understand them.

TGP - given that leaving any abrasive material in the bores would be 'unhelpful', could it not simply be blown or flushed out with a reasonable degree of confidence that piston and oil scraper rings would not allow a significant amount of the offensive material to evade removal by getting beyond them?

mikeonb4c wrote:Now I'm confused Alan. I'd have thought that whether the head interior was flat or domed, skimming it would reduce the internal volume in the combustion chamber.

I speak from a zero understanding of how these things work though so I'm not challenging the facts, just trying to understand them.

TGP - given that leaving any abrasive material in the bores would be 'unhelpful', could it not simply be blown or flushed out with a reasonable degree of confidence that piston and oil scraper rings would not allow a significant amount of the offensive material to evade removal by getting beyond them?

Ok Mike, in engineering terms there is...........no............NO.............ARE YOU JOKING.
Think about why you dont run without an air filter.
The particles in abrasive and grinding paste are smaller than the expansion gap of the piston rings. How will you get it out of the oilways in the block?

This isnt a you will blow your engine now problem, just it wont last as long.
Would you put a blob of grinding paste in when you do an oil change?...........Nuff said?

The method I've used (similar to Haydns) is to attach a sheet of emery paper to a portable surface table and with WD40 or similar, clean the block surface up. Cast iron blocks take a helluva lot of rubbing to remove metal - so it only cleans up the surface. "Trueing" up the surface means machining it IMO.

If the combustion chamber is purely in the piston crown then skimming the head surface won't make a difference to the compression ratio because you're not altering the combustion chamber - unless you machine it so much that the valves are sticking out

I'm pretty sure the Bongo has a flat head as it's indirect injection.

The "deck height" is the measurement the pistons protrude out of the cylinder block - it's imperative this measurement is checked if changing the pistons because a suitable head gasket will need to be fitted to allow the pistons to clear the head/valves. The gasket thicknesss is sometimes identified by notches cut into an outside face of the gasket.

I've known keen amateurs to have the head skimmed and fit a thicker gasket to "compensate" for what they've had removed from the flat surfaced head all they're doing is reduce the compression ratio and wonder why the newly rebuilt engine is less keen to to start than before like I say, keen amateurs - and they pay trained mechanics peanuts

Why do peeps assume everyone else is daft..Before any cleaning up is done it stands to reason that all oilways/coolantways cylinder bores are well protected from the ingress of crud....the "flat plate" was a old one from the REME stores...(you can do that sort of thing in the mob if you have mates)

http://www.arrowheadradiator.com/preven ... ilures.htm

This is well worth a read

haydn callow wrote:http://www.arrowheadradiator.com/preven ... ilures.htm

This is well worth a read

This was indeed WELL worth a read. Compulsory for anyone who has had an overheating episode I think. Interesting to be reminded that loss of EGR can cause engines to run hotter. And it reminds me why fitting an engine block temp gauge might be a good idea on an ageing Bongo, as it may provide early warning of progressive loss of efficiency in the cooling system due to a number of ageing factors.

Engine Block Temp Gauge !!! as most of you will know I can supply the TM-2 digital Temp gauge / Alarm. whilst this is a super "top end" product it is a little expensive..Some of you may know that we have had a Thermal switch on trial on 3 Bongos which sets off the low coolant alarm when the engine temp reaches 110 oC. The problem has been that whilst it works it takes ages to reset it'self after "alarming co's the temp has to drop 20 oC for it to reset.
We now have ..almost ready...a fully "user" ajustable High temp alarm which, although it does not have a digital readout does everything else the TM-2 will do. It has a sensor which will be bolted to the Cylinder head and a small unit to mount near the driver which has a Hi Temp adjuster knob.
This will be available as a stand alone unit and also as a combined Low Coolant/Hi Temp alarm.
If ever the head temp exceeds the "user" preset temp the alarm will sound and this unit will reset after a temp drop of only 2 oC.
I will let you know when we have a couple to test and then when they are available.

Will that be any different to what the Mason alarm does Haydn?

It takes the temperature from the head via the original sensor and sounds a user set alarm - the manufacturers sensors themselves seem pretty reliable - just the damping which causes some problems.

dandywarhol wrote:Will that be any different to what the Mason alarm does Haydn?

It takes the temperature from the head via the original sensor and sounds a user set alarm - the manufacturers sensors themselves seem pretty reliable - just the damping which causes some problems.

I'd assumed the original Mazda sensor relied on immersion in the coolant and took the temperature at that point whereas the one Haydn is talking about would bolt to the engine block. But have I got that wrong?

Expensive though it is, I like the idea of the TM2 as (sad git that I am) I would be able to observe the general health of the engine cooling by observing explict temp readouts in similar conditions over time. So I might find myself being able to say 'Funny, we used to get up this hill after a similar drive with temp gauge not exceeding X, but now it is Y. I wonder if the cooling fans aren't switching on'. Etc. etc.