Stroking my 3.9

[Tree Trimmer]

Doesn't sound too impressive does it? Anyway, I read Des Hammils book. Pretty good stuff, needless to say I'll be re-reading it many times. It almost made me not to want to build any rover v8, including mine. But here is what I have decided. Since my block is a interim block, capable of being cross bolted, I think I will have my block re-linered with rimmed sleeves. This is of course if the block is still in good shape in all the trouble spots after tearing it down.

I might be wrong but I don't think I can buy a used cross-bolted block to rebuild for what it would cost to do the work to my block. And even if I were to find a red 4.6 block there is no guarantee that I won't have some sort of liner problem. It seems putting the rimmed sleeves in would be more insurance against block problems.

I am thinking in the range of 4.4 to 4.8. I need a little more info on parts but at least I know I can get a crank from JE Dev. if I can't find many other options. I'm sure I could have one made in the states but would be afraid the balance might not be right for the rover engine. I'd like a cam like the LE1 which keeps a lot of the torque lower in the rev range. The guy building my engine said a roller cam would last a long time, don't know exactly where to find one for my needs.

I got lots of good advice and information about this topic a couple of weeks ago. After doing more research I'm still on this crazy mission. Is this making any sense or am I just fooling myself?

[HSV Rangie]

http://www.triumphroverspares.com.au/ht ... tparts.htm

look here if not done so already.

Michael

[peter r]

G`day T T ,

No makes perfect sense to me but then , last week i bought another 4.0ltr crossbolted block that has a shifted liner and no carbon on 1 piston .

I pretty much did the same thing after reading the book and decided i like playing with them so i`ll take it as it comes .

I read on a pommie site where the book was discussed and the feeling was that the failure rate for the 3.9 was nowhere near as great as the book suggests , but of coarse most stuff on the net is iffy at the best of times .

On the same site there was discussion on crossbolting 3.9s and they suggested that although the block had the capacity for it there was something about the caps that made it impractical and as i haven`t seen inside an interim it`s only as good as a rumour .

The 4.0 in our 85 RR came with a comp ratio of 8.23:1 , it uses composite gaskets but with a fair amount of material removed from the head surfaces ( partly because unlike yours ours has the larger combustion chambers ) it now has a ratio somewhere around 10:1 but it runs on LPG 99.9% of the time though is able to run on petrol as well . I used a locally ground cam which i possibly should have advanced a bit because it starts around 1300 rpm .
When i was looking at cams ( awhile back now ) if i remember they quoted 1600rpm start but when i looked at there figures and compaired with many others and rovers , the figs said lower than 1600 so took a punt , which i`m happy with but as said maybe a bit of advance .
I consider cams to be too complicated and personal to recommend any particular 1 .

It`s been running now for just on 2 yrs and nothing i`ve done to it has effected it`s reliability , it does run a much lower thermostat and doesn`t have torque to yeild head bolts . The timing is at 16 degs and because lpg runs much hotter than petrol and with the higher comp ratio i consider if it was going to do something it would have by now .

Though i think i would have worries with the same engine in std form in a P38A but not in a 38a i think they would work/last as long as any .

And as for a 3.9 with stepped liners and sealed top and bottom i can`t see how you could go wrong , specially since it won`t matter what goes on in the middle .

All the best , peter .

[walker]

What sort of cost is involved in having the block relined with rimmed sleeves?

[andrew e]

would this be any help to anyone?

http://www.outerlimits4x4.com/PHP_Modul ... hp?t=70337

Andrew

[Tree Trimmer]

What sort of cost is involved in having the block relined with rimmed sleeves?

No firm quotes but estimating $600-800.

[Tree Trimmer]

Thanks Michael for the link. Thanks also Peter, I just can't help second guessing myself on this engine thing. Maybe I'm going overboard but if I spend the money to get the engine to do what I want it to, I want to be as sure as possible that it will be around for a lot of miles to justify the cost. This is equally as important a reason for building with the very best components as performance. Another reason I keep asking for advice is that for 5 years now I have had a vision of what I want to do to my disco, and I don't want that to cause a bad judgment call.

Thanks again,
Tim

[Rotazuk]

Hi
Looking at stroking the 3.9 also , more one of those things I will do when it needs a bit of work . Looking at using a p76 crank , in the 3.9 should go to somewhere like 4.8 or 4.9 .
I came across a web page about a year ago that listed all the different heads and all the different pistons etc and there resulting compression ratio . Damed if I can find it now . Grrr

Will follow this and see how you go

Cheers

Chris