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Thoughts on this 4.6 cylinder/piston


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Hi, thought this thread would get more exposure here on the  'International forum', can be moved if a mod wants.

The knowledgable folk at Defender2 have been giving me some pointers regarding my possible 300Tdi to V8 conversion. However I know there are some V8 gurus here also and my recent posts on D2 haven't been replied to yet.

I bought this complete ebay engine a few weeks ago, a 4.6 from a 1997 GEMS p38. A reputable seller with 100% feedback who said that engine ran very well/lovely.

Although the price was such that the engine could be dropped straight in, when it arrived I proceeded to strip it down because if it was to be replacing my 300Tdi, it may as well be refreshed to make it as worthwhile as possible. I was happy with the wear conditions of various bits, anyway when I removed the heads I saw that the piston of cylinder 5 had the classic 'steam cleaned' appearance.

The liner of cylinder 5 seems very much so to be flush with the top of the block, certainly more than cylinder 8's liner where the drop is noticeable (piston 8 looks normal). The head gaskets look pretty much perfect also. I'm therefore a bit puzzled why piston 5 has this appearance. Could it be possible/likely for there to be a crack elsewhere (inlet manifold maybe) allowing water to get in, or could a crack in the block still be getting through to cylinder 5?

In getting top hat liners, what's there to stop cracks in the block from getting worse and worse and causing problems in another way?

Also pictured is some damage to one of the tappet bores, thoughts?

It looks like the engine/block must have been a LR warranty exchange, going by the plaque? The works seems to have been done in around 2000/2001 as suggested by a few date stamps.

The water pump certainly looks very recent also.

 

Thanks for your views.

 

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I would expect it to be cleaner if steam cleaned, to be honest - are you sure it is not just oil contamination or maybe a leaky injector?

Top hat liners mean the gasket fire rings seal on the lipped section of the liner, so if anything did leak round, it won't get into the combustion chamber, and if it tried to go anywhere else well there is still gasket in the way.

 

 

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Despite what the seller might say, I personally would NEVER install an unknown (to me) Rover V8 nowadays without stripping it first.  They are all getting on a bit now, and EVERY one I have ever had has one problem or another. In my experience you will always need a new camshaft and followers as a minimum.

Liners do NOT have to drop to give problems. If you look at your photo, you will see a small black line on the outer edge of the liner at the 7 'o' clock position, inline with the head bolt hole. This is where the water will be coming up when the engine is at working temperature. The cleaning of the pistons biased toward that flaw, so IMO there is a problem.

Liners that have moved do not necessarily give problems. Its the cracks behind them that is the problem.

Only way to check for sure, is to pressure test it with the block hot. If it leaks, it is either scrap or have it top hatted. It will cure the problem permanently, its a well known and easy fix, but its whether you want to pay for it. However, I would be more concerned about the tappet bore. I am not sure if it can be sleeved.

Its not worth buying another block or engine if you want a 4.6, which more like as not will have something wrong in the same way, you may as well fix what you have. 

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The liner in the last photo has certainly slipped.  Given the reputation later engines have for slipped liners, I’d be looking at having all of them replaced with top hat liners, to head off future problems.  If you can remove that slipped liner first, it’d give you an idea of whether the block is worth the cost of doing that.  Hopefully, the rest of it is good to be reused with little more than new shells and seals.

That tapper bore looks reparable.  It can be over bored and sleeved, or tug welded and rebored.  I’m not that familiar with V8s - is that bore for a hydraulic tapper, needing a good seal, or is it just for a n operating rod with no seal?  If the latter, I’d just nib the bur and leave it- as it is a gouge, not a crack.

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4 hours ago, Snagger said:

That tapper bore looks reparable.  It can be over bored and sleeved, or tug welded and rebored.  I’m not that familiar with V8s - is that bore for a hydraulic tapper, needing a good seal, or is it just for a n operating rod with no seal?  If the latter, I’d just nib the bur and leave it- as it is a gouge, not a crack.

Not a good seal as such, just a nice sliding fit.

On closer inspection, I agree that it it a gouge. I have never seen that before myself, but yes, deburr it and run it as is.

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Nice to hear the suggestions, thanks. I knew there was a risk involved with getting a 4.6, and was expecting to have to spend, to make the conversion look 'right' and perform properly. Of course, somewhat annoyingly, if I wish to put the v8 up for sale in its bits it'll never be worth as much with this now uncovered fault. I wonder if the recent looking water pump is a result of the formation of this possible crack in the block. 😆

With the engine striped it would be foolish not to get top hats, although I did rather like Bowie's thoughts, I agree it probably is block cracking, and even if not, still would make sense to get top hat liners for the future's sake of the block. I was indeed intending to get a new camshaft, tappets, followers, timing gear at the very least.

That said, with the added cost of requiring top hat liners, I've reminded myself that a Turner rebuilt 300Tdi with a performance cylinder head would now be similar in price if not less expensive (and give a great deal less head scratching) and keep the vehicle original, not that my 300 needs rebuilding yet, but a 'bit' more power perhaps would make the difference I'm looking for. 

Although I have a soft spot for the V8, I wonder how it will run on e10 fuel?

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This is the problem with them. On the face of it, it seems a nice easy inexpensive conversion, but by the time you have bought Top hat liners, camshaft, rings, shells, possibly rockers and shafts, then the carb and manifold, gearbox clutch exhaust etc etc. Then you might want to go to aftermarket injection and ignition, it comes to a LOT of money. (There, I have talked myself out of it too !)

I wouldnt worry too much about originality, no one else seems to ! As long as its revertable its not a problem.

I wouldnt bother with a "performance" upgrade on the Tdi either.

Why not consider a BMW M57 diesel ? Will cost far less, and you can use it straight out of the Donor with not much worry, use its own ECU with not too much trouble, and you can get WAY more power and torque than ANY Rover V8, reliability (as long as you dont go stupid) and probably more economy as well. Loads of info out there on it.

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Sorry I didn’t catch the auto-bugger changes of tappet to tapper and tig to tug.  It looks like you understood, anyway.

Previously, I’d have said to keep the Tdi, but the venom against diesel isn’t going to get any less.  If you can get reasonable cost per mile from the V8, I’d go that way now as you’d face less city restrictions and it’ll be a nicer drive.  I can see fuel duty levels climbing as they try to force ICE vehicles off the road, and I suspect it’ll do so faster with diesels.  I’d love to be able to predict the reality, but I think it’s plausible that politicians will ensure running a diesel becomes more prohibitively expensive than a petrol.

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  • 3 weeks later...
Posted (edited)

After replacing the intercooler/turbo/inlet hoses and a very slight tweak about 10 degrees clockwise on the boost pin/diaphragm assembly, the 90 has more or less reclaimed the power I felt it had begun to lose over the last few years. In 4th, 50mph is as high as I'd let to get to, then in 5th it can boost from 55-70 without 'too much' bother, and  well it should, as it's also a rag top. It doesn't feel too slouchy. 

I could then get a gas flowed head, uprated intercooler (and therefore adjust boost/fuelling a bit more) and a VGT turbo from allisport. Also a Roamerdrive, and spend money on perfecting the steering and suspension/bushings, and this would still be a few thousand less than the V8 conversion I've calculated would cost. No matter how  much quicker the V8 is, cornering will still slow the Defender down.

So I must ask, after reading practically every 'v8 vs Tdi/Td5' thread on every forum inadvertently twice over, really how much better will a refreshed/part rebuilt 4.6 be over the 300Tdi after it would've had this fettling? It's interesting to hear that some North American NAS Defender owners mention diesels as being 'cooler', talk about the grass being greener...

I'm not adverse to getting the v8 top hatted/rebuilt and installed, just that it would be big shame if it doesn't offer the performance I'm thinking it might. With factory 300Tdi 90 ratios, and a 4.6, I'd hope I could smoothly (huge emphasis on 'smooth'!) pull away from junctions in 2nd and rev to a decent speed to avoid drivers behind from thinking I'm taking forever to get moving, which does seem to be an issue with the 300, until I get into 4th. 

Edited by rednaxela
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A standard 300TDi outputs 264Nm of torque, let's say a fettled one would do 300Nm, a standard 4.6 is 380Nm, with a torquey cam in it should see a bit extra too.

It'll happily give oodles of torque from low RPM, and rev to 5500+. The difference should be well noticeable. It'll never be a rocketship, but it has a good amount of power with a good amount of torque, especially with a manual.

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As Elbekko says...... It will never be a rocketship, but then no one ever has enough performance ! Remember it is not a sports car.

I am no fan of the Rover V8, even though I have had many over the years. But there is no comparison, the V8 is smoother, and QUIETER (unless you have a stupid exhaust) and much quicker than a 300Tdi will ever be, and the faster you go, the better it is, and altogether much nicer to drive. I would prefer Auto myself, but each to his own !

Tuning the Tdi will reduce the difference in fuel consumption, and you are reducing reliability with a high level of tune.

Disadvantages of the V8 are it makes the cab hot (nice in winter though) the fuel consumption, although its not that bad driven "normally", and you will have to change the camshaft and followers every month :ph34r:

Also, aftermarket engine management worries me greatly (Look at the problems ThreePointFive has had) and puts me off doing it. Lots of great help on here, but I still think you need to be a genius IMO to do it, which I am not.

But other than that, there is no contest IMO

 

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205r16 tyres.

I would opt to use the full megasquirt MS2 kit as it seems to be the most 'plug and play' I've found, and I have some hope that off the bat it'd afford the engine a suitable state of tune, as I'd need to bed in the camshaft for 20 mins on the first start, wouldn't I! 😄 😕

The Defender is a second car yet it hugely earns its keep. It's not the familiar case where someone has chosen a 90/110 as their only vehicle and can't come to terms with the lack of performance compared to their previous 'normal' car.

Therefore, it only covers a few thousand miles per year, so, the running costs shouldn't really come into the equation. I'll accept that there will be a noticeable power increase over a well tweaked 300Tdi (I'm not saying that the alterations I might to do mine would get as far as being considered 'well tweaked'), perhaps the best difference would be not the max. attainable speed, but I presume the smoother rate of acceleration and less of a tendency to get 'stuck' at a certain speed (without giving it a further jab of the throttle) on the way up to 70mph.

 

 

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I found my 3.5 wanted to do 3,200 RPM at 70 on 205 tyres. Great for surprising acceleration off the line at the lights but not a relaxed number for long distance cruising. And that was with a 1.2 transfer box. Long motorway journeys don't sound like your use case for the vehicle but something to bear in mind.

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22 hours ago, elbekko said:

A standard 300TDi outputs 264Nm of torque, let's say a fettled one would do 300Nm, a standard 4.6 is 380Nm, with a torquey cam in it should see a bit extra too.

It'll happily give oodles of torque from low RPM, and rev to 5500+. The difference should be well noticeable. It'll never be a rocketship, but it has a good amount of power with a good amount of torque, especially with a manual.

The spread is the difference - the V8 makes relaxed torque from idle to 5k, the TD you have to keep on boost and row the gearstick. Most noticeable on a long climb at one of our play sites - the TDi's all need a run-up and a load of welly (and smoke) and if they bog down or drop off boost they fail and come back down. The V8 you just trundle up, if it bogs down you just apply a bit more right foot and onwards you go with no drama.

For trucks that don't do huge miles the V8 is a lot more civilised and dare I say reliable - and if you drive at TDi speeds you can hit 20mpg or more.

On 8/20/2021 at 11:55 AM, rednaxela said:

I'm not adverse to getting the v8 top hatted/rebuilt and installed, just that it would be big shame if it doesn't offer the performance I'm thinking it might. With factory 300Tdi 90 ratios, and a 4.6, I'd hope I could smoothly (huge emphasis on 'smooth'!) pull away from junctions in 2nd and rev to a decent speed to avoid drivers behind from thinking I'm taking forever to get moving, which does seem to be an issue with the 300, until I get into 4th. 

Our ambulance is a 3-ton brick even by Defender standards and I'm usually pulling away in 2nd, cruising at 130kph with the roamerdrive in (so ~2250rpm) and on a recent trip in a slower convoy (as in, trucker speeds) it managed a good 22mpg. One of my pet hates is being the one holding up a line of traffic, which doesn't happen in the ambulance until about 90mph in the outside lane where various portions of the drivetrain are rotating faster than they're really happy with.

If it was a normal 90 or 110 I'd probably forgo the roamerdrive and just sling a 1.2 transfer box in as there's plenty of torque, it just feels a bit nicer on the clutch to have the lower 1st gear available for the odd steep hill start.

Having driven it up various mountain passes from Trollsteigen to the Alps I'm very happy with the fact I don't have to row the gearstick or cause a traffic jam - we were actually catching up with people in cars and even some of the bikers :lol:

@rednaxelaIf you're local to Basingstoke you're welcome to come over for a spin in the ambulance :P or indeed the 109 if it's road-worthy at the time :ph34r:

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No ones really spoken yet but why aren't you considering a Td5?... with either a slightly longer geared R380 or popping on an overdrive, especially in a 90 they're pretty pokey engines.

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Thanks FF, but too far. Maybe your blog will suffice 😁

I wouldn't consider a Td5 because I don't particularly want to change to another Defender. I've put a lot of work into mine. I wouldn't convert one in either because it would be sacrilege to throw out a 300Tdi when there are plenty of good Td5 vehicles always coming up for sale.

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On 8/21/2021 at 12:45 PM, Maverik said:

No ones really spoken yet but why aren't you considering a Td5?... with either a slightly longer geared R380 or popping on an overdrive, especially in a 90 they're pretty pokey engines.

Everything I've seen about TD5's is just a little disappointing though -  you have as much or more electrickery as a V8, less power, and not enough MPG to feel worthwhile. At least the TDi's seem to manage significantly more MPG than the V8's in return for being awful :lol:

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2 hours ago, FridgeFreezer said:

Everything I've seen about TD5's is just a little disappointing though -  you have as much or more electrickery as a V8, less power, and not enough MPG to feel worthwhile. At least the TDi's seem to manage significantly more MPG than the V8's in return for being awful :lol:

Less is more, Fridge 😁

Mo

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