What would you do?! Rebuild advice

mk1storm · Post by **mk1storm** » Tue Feb 05, 2008 7:43 am

Right, going around in circles trying to decide what I want to do with the rebuild of my early 3.9l conversion block. Sorry for the long post!

This is the situation - block is 3.5l with an early JE rebuild capacity increase to 3.9l using 93.5mm bores and omega cast pistons (with valve recesses).

My original intention for this engine (before I knew it wasn't a std 3.5l) was to drop it into my kit car and just run it as it was. Seemed to run ok when it was in the range rover donor, although was never able to properly drive it other than around a field a bit. Anyway, decided it was better to strip down and at least put new rings, seals and bearings in. BUT then finding out what it actually is and doing some digging I now know the piston rings for this size piston/bore are £270! So as far as I see it I have 4 possible options:

1) Rebuild with old rings and just replace bearings and seals and hope it's ok.
2) Spend the £270, just hone bores and fit new bearings & seals.
3) Overbore to 94mm and fit standard 3.9l pistons/rings.
4) Forget it and get another 3.9l block.

So come on then, what are your thoughts?!! Depending on the wind direction I decide on one thing and then 5mins later the other!!!!

RoverP6B · Post by **RoverP6B** » Tue Feb 05, 2008 8:00 am

If a job is worth doing, then it is worth doing properly, so on that basis, new rings, pistons, bearings.

Now it is my understanding that using an original 3.5 block and increasing the capacity reduces the structual integrity of the block, where as larger capacity blocks such as the 3.9 litre were designed and constructed with that capacity in mind from the beginning.

Given their availablity, I would be inclined to buy an interim 3.9 litre, manufactured after April 1994, thus having the benefit of being able to cross bolt the block if you wish, as the bearing caps and block are designed with that provision in mind.

Hope that may help,
Ron.

sidecar · Post by **sidecar** » Tue Feb 05, 2008 9:00 am

RoverP6B wrote:If a job is worth doing, then it is worth doing properly, so on that basis, new rings, pistons, bearings.

Now it is my understanding that using an original 3.5 block and increasing the capacity reduces the structual integrity of the block, where as larger capacity blocks such as the 3.9 litre were designed and constructed with that capacity in mind from the beginning.

Given their availablity, I would be inclined to buy an interim 3.9 litre, manufactured after April 1994, thus having the benefit of being able to cross bolt the block if you wish, as the bearing caps and block are designed with that provision in mind.

Hope that may help,
Ron.

You need to be careful about the age of your block if you buy another one.
If it's too new you will have to fit CATs to get through the SVA test.

Regards,

Pete

mk1storm · Post by **mk1storm** » Wed Feb 06, 2008 7:34 am

Measured up the ring gaps for my old piston rings in the bores last night. Coming out at up to 0.9mm... Hmmm think that rules out refitting those then!

Cheers for the comments so far. Yeah I have to be careful about what age block I get and to be honest I'm quite keen to stick with what I've got simply because to some extent it's a known quantity.

So, to rebore to 94mm and use std pistons (which possibly aren't as good) or stick with the 93.5mm Omega's and stump up the price for the rings. I think I'm swaying towards the latter option now.

need4speed · Post by **need4speed** » Wed Feb 06, 2008 7:51 am

£270! For rings! Who told you that......

On another note. Whats all this malarky about if its a late block you need CAT to pass SVA? My mate has late block fitted in his landrover 110 with megasquirt fuel injection and it went through SVA with not a CAT near it...

sidecar · Post by **sidecar** » Wed Feb 06, 2008 8:09 am

need4speed wrote:£270! For rings! Who told you that......

On another note. Whats all this malarky about if its a late block you need CAT to pass SVA? My mate has late block fitted in his landrover 110 with megasquirt fuel injection and it went through SVA with not a CAT near it...

If you can not prove that the engine was made before 31st July 1992 then it will require CATS and fuel injection.

How old was your mates block?

need4speed · Post by **need4speed** » Wed Feb 06, 2008 8:26 am

Not sure of the exact year, but i am sure that it was one of the later 4.6 engines...

CastleMGBV8 · Post by **CastleMGBV8** » Wed Feb 06, 2008 9:26 am

I think this only applies to kit cars and new registrations under SVA testing procedures. The MOT station only check the the cars VIN number and do not seem interested in the engine number at all.

Kevin.

Ian Anderson · Post by **Ian Anderson** » Wed Feb 06, 2008 11:42 am

The rules are
THe emissions are set based on the age of the engine or the car whichever is the older

So an old Landie with a new engine is based on emissions required on date of Landy build

A Kit car with an old Engine is tested based on the emissions for the year of manufacture of the engine

But for the second you have to be able to prove the age of the engine

Ian

sidecar · Post by **sidecar** » Wed Feb 06, 2008 12:06 pm

Ian Anderson wrote:The rules are
THe emissions are set based on the age of the engine or the car whichever is the older

So an old Landie with a new engine is based on emissions required on date of Landy build

A Kit car with an old Engine is tested based on the emissions for the year of manufacture of the engine

But for the second you have to be able to prove the age of the engine

Ian

Fair enough!

russell_ram · Post by **russell_ram** » Wed Feb 06, 2008 1:15 pm

"The rules are
THe emissions are set based on the age of the engine or the car whichever is the older

So an old Landie with a new engine is based on emissions required on date of Landy build

A Kit car with an old Engine is tested based on the emissions for the year of manufacture of the engine "

But only on new registrations (ie kit cars). I can (currently) stick any engine I want into an existing registered vehicle and the emissions rules will be those that applied to the vehicle with it's original engine.

So my pre 93 non cat equipped vehicle has to meet the same emissions what ever engine I fit to it now as it did with it's old engine (even if the engine I fit now was only ever available in cat equipped form).

Russ

mk1storm · Post by **mk1storm** » Wed Feb 06, 2008 1:29 pm

need4speed wrote:£270! For rings! Who told you that......

On another note. Whats all this malarky about if its a late block you need CAT to pass SVA? My mate has late block fitted in his landrover 110 with megasquirt fuel injection and it went through SVA with not a CAT near it...

Actually £270 was more than I was quoted, thought it was that. It was actually £246 as quoted by JE Developments for 93.5mm piston rings.

If you know of anywhere else I can get them cheaper please let me know!!

need4speed · Post by **need4speed** » Wed Feb 06, 2008 2:28 pm

£246! For rings! I take it they are so expensive because they are not the usual 94mm??
You could buy very good 2nd hand crank/rods/pistons/rings for less!

mk1storm · Post by **mk1storm** » Wed Feb 06, 2008 7:05 pm

I guess it is because of the non-standard size yep... Not found anywhere else that does em for less unfortunately.