Discovery 3.9 v8 - rebuilds, reliability, options….

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resto_d1

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I assume only the 3.9 EFI came in the discovery 1? Not sure if the 3.5 did but 3.9 efi is all I’ve seen…

Say you were to freshly build one, are they reliable or just prone to issues? All I know about the v8s is they can be spiky on temps?

You’ll think I’m nuts but I’m considering fitting a v8 to my current 300tdi D1 project. The 300tdi is in bits at the moment and the plan was to rebuild it with a turners head.

Original plan for my D1 was a shoot bus. My pick-up does all I need so I can’t help considering a v8 build as I’ve never had a v8 and would like to own at least one before they get banned. It would be nice to have a noise that makes me smile again. Not so mad about the power but if it can be upped when building then why not!

Is there much involved with swapping over if I was daft enough to do so? I assume you use the EFI loom from a D1, mounts are probably different too.

@Henry_b any thoughts?
 
Very early ones had the 3.5
They are only prone to issues mostly when neglected, if you keep it well serviced and replace anything iffy before it becomes a problem then they are usually ok
Still seems like a lot of work doing the swap tho, as always complete donor vehicle is the way to go
 
Kev12 said:
Very early ones had the 3.5
They are only prone to issues mostly when neglected, if you keep it well serviced and replace anything iffy before it becomes a problem then they are usually ok
Still seems like a lot of work doing the swap tho, as always complete donor vehicle is the way to go
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Indeed. It’s a consideration and maybe a daft one but I’m still curious
 
I thought they’d be knocking about on eBay and the odd dead d1 would be on there. The v8 engines seem to be fairly costly.
Maybe it is a daft idea and I’ll just buy an old 740 or 50 once it’s built 😂
 
resto_d1 said:
Is there much involved with swapping over if I was daft enough to do so? I assume you use the EFI loom from a D1, mounts are probably different too.
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The V8 is lovely idea for your use.
But.... 🤔.

Donor car would be the easiest way to make sure you have all the bits you need.
Manual or Auto? is that a change from original? The original bell housing will not bolt up to a V8.
The little bits will soon add up to the cost of a donor🫣.

Yes the V8 has a certain lure, We know:oops:.

J
 
resto_d1 said:
Auto. Was going to get a new Ashcroft autobox as the one on there is very tired anyway
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Ask Ashcroft if the auto box could be fitted to the 300tdi after….

Now a 3.9 is good,small amount of electronics but reliable if treated right. Raced the 3.5efi & only thing we done was ruin an ecu and caused over fueling.
 
V8 is a good engine in any guise, the reality of fact is neglect is what kills them and in all seriousness they can take a hammering before they do fail..

the D1 did come with the carb'd 3.5 the early F and G plate cars.

Bear in mind you can fit the sump and front cover of a 3.5/9 on to the 4.6 block that way you have proper low end grunt even in stock form.

rebuilding one isn't difficult and to be fair if done properly you'll have no issues, i'd stud them personally for strength and thats about it..
 
Henry_b said:
V8 is a good engine in any guise, the reality of fact is neglect is what kills them and in all seriousness they can take a hammering before they do fail..

the D1 did come with the carb'd 3.5 the early F and G plate cars.

Bear in mind you can fit the sump and front cover of a 3.5/9 on to the 4.6 block that way you have proper low end grunt even in stock form.

rebuilding one isn't difficult and to be fair if done properly you'll have no issues, i'd stud them personally for strength and thats about it..
Click to expand...

4.6 short engine from what? Still use the 3.5/9 head? There was slipped liners mentioned above. Does that only come if overheated or is there a preventative thing during rebuild that can be done to stop this occurring?

Cheers
 
resto_d1 said:
4.6 short engine from what? Still use the 3.5/9 head? There was slipped liners mentioned above. Does that only come if overheated or is there a preventative thing during rebuild that can be done to stop this occurring?

Cheers
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Top hat liners are a mandatory fit if you want a bulletproof motor all RV8 builders fit them as a matter of course.

Preventing slipped liners, fuelling and cooling are the 2 main killers, too lean a fuel mixture causing excessive heat and a neglected cooling system doing the same.

4.6 short engine from the P38, still can be found quite easily and cheaply 2nd hand or get a rebuilt unit from V8developements.
 
Henry_b said:
Top hat liners are a mandatory fit if you want a bulletproof motor all RV8 builders fit them as a matter of course.

Preventing slipped liners, fuelling and cooling are the 2 main killers, too lean a fuel mixture causing excessive heat and a neglected cooling system doing the same.

4.6 short engine from the P38, still can be found quite easily and cheaply 2nd hand or get a rebuilt unit from V8developements.
Click to expand...
So you could mate a p38 engine block to a 3.9 head and run it off EFI management rather than having to go Thor or gems?
 
Heads are the same 3.5 to 4.6 the only difference was the change to 10bolt heads in 1994 and the very early 3.5's had smaller valves...

Also the latter 4.0 and 4.6 have a stronger bottom end with cross bolted mains, quite a sturdy unit,

And yes you are not limited to motronic (thor) or Lucas (Gems) systems, you can them on a Edelbrock carb if you so wish.. :)
 
resto_d1 said:
Auto. Was going to get a new Ashcroft autobox as the one on there is very tired anyway
Click to expand...

Won’t be a straight ex though as V8 is different bellhousing. So extra surcharge probably.

Diesel to petrol, exhaust system. Lots of little things, donor car here we come.
Henry_b said:
Bear in mind you can fit the sump and front cover of a 3.5/9 on to the 4.6 block that way you have proper low end grunt even in stock form.
Click to expand...
You sure? That’s all that need changing?
Thought cam and a few other things need changing to.

But at the end of the day I wouldn’t discourage anybody from having a V8 in their life :)

J
 
marjon said:
Won’t be a straight ex though as V8 is different bellhousing. So extra surcharge probably.

Diesel to petrol, exhaust system. Lots of little things, donor car here we come.

You sure? That’s all that need changing?
Thought cam and a few other things need changing to.

But at the end of the day I wouldn’t discourage anybody from having a V8 in their life :)

J
Click to expand...

Yeah I think they’re will be extra charge. It’s also changing from edc to non edc which is another expense of it
 
marjon said:
Won’t be a straight ex though as V8 is different bellhousing. So extra surcharge probably.

Diesel to petrol, exhaust system. Lots of little things, donor car here we come.

You sure? That’s all that need changing?
Thought cam and a few other things need changing to.

But at the end of the day I wouldn’t discourage anybody from having a V8 in their life :)

J
Click to expand...
Sump - Oil pickup - front cover - oil pump - from memory, not too difficult.
 
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