The V8 Owners Forum -

Just got my self a nearly crossbolted 3.9 bottom end into which i want to build a bigger cc engine at some point next year.

Looking around at all the stroker kits v8 tuners seems the best at £1600 for a 4.8 with hypereutectic (is that spelt right?) pistons, decent rods and crank etc but its till alot of money! Is there a proven combo of parts to make up a strong higher cc bottom end yourself?

What about getting a 4.6 crank and turning down the mains to fit my smaller journal block then using the 4.0 pistons to create a high comp 4.6?

Buick 300 bits?

Tvr 5.0 griff bits? I know for a fact the tvr uses machined down 3.9 pistons which would be easy to replicate as i already have some to suit a +20 bore but i don't know what crank or rods are used.

Could these be of use?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... &rd=1&rd=1

check your block actually has enclosed main caps as a lot of the 3.9s didnt, while they had the bosses for the cross bolts they didn't have the right caps meaning you cant cross bolt the block. If you wanted to use the 4.6 crank I would get the block line bored to the right mains size instead of reducing the crank. It will be a stronger job in the end.

katanaman wrote:check your block actually has enclosed main caps as a lot of the 3.9s didnt, while they had the bosses for the cross bolts they didn't have the right caps meaning you cant cross bolt the block. If you wanted to use the 4.6 crank I would get the block line bored to the right mains size instead of reducing the crank. It will be a stronger job in the end.

Devil and the deep blue here, machine the mains out, but then you are reducing the landing area for the mains on a non x bolt block, if you can X bolt the block, by all means bore out the caps and block, but 2 bolt rovers do have a habit of mains walking, Me? I would have the crank up on the lathe by now roughing it out.
Ian .

Well, i'm I'm fairly sure its the early type of interim engine meaning it can't be cross bolted But i'm not too fussed about that, i bought it as i wanted a spare to build another bottom into! I could always glue some bolt heads onto the bosses so i can atleast brag that its a cross bolt block lol!

The bonus with this block though is that is should have the clearance to put a 4.6 crank into it as i understand the early type of 3.9 wouldn't normally clear the bigger crank whereas this block is pretty much the same as a later casting and should clear it. However, if i can go bigger than 4.6 i'd like to!

If its the early style of interim block i've no choice but to turn down the 4.6 crank due to the reasons Ian mentions (thanks dude!)

If i were to go this route and use 4.0 pistons to up the comp ratio do i use the 4.6 rods or the 4.0 rods?

The v8 tuner kit is ok and it's cheap but you say you want to build better. How much better?

I have a custom crank casting from my own patterns. It strokes from 86 to 94mm, takes stock chevrolet rods and they're cheap Buy your own pistons, resleeve to 96mm and you can have a 5.5 rover. The crank will fit an early or late engines and comes with a long nose. It's also fully counterbalanced likesome tvrs. The v8t crank is just a 4.6 item offset ground.

The downside with my cranks is they take ages to get machined but I may have found a solution.

Boosted.

mmmmm tell me more,
i'm collecting another 3.9 bottom end this weekend and want to build a bigger engine also.

My late 3.9 is a non crossbolted block with bosses, the mains are std type not crossbolt type FYI

What more can I say. The rod journals are slightly wider so they accept a chevy rod, 2" or 2.1" depending on how much you grind off and the offset. The mains are 2.5" but can be ground down to 2.3". It has counterweights opposite all the rods. It has a long nose which I can shorten. I get them cast in SG nodular iron and they can be heat treated etc as well.

I'll try to upload a picture of the raw castings.

Boosted.

softdash3.9 wrote:My late 3.9 is a non crossbolted block with bosses, the mains are std type not crossbolt type FYI

Intermediate engine.

Boosted.

Yes, should have stated that

Ok boosted, how much? Plus how much is resleeving blocks these days!!!

These are the raw castings before machining and heat treatment.



A finished item is on my web page, the rover section. If you see a 5.5 rv8 in the UK it's got my crank in it!

Boosted.

Boosted

I WANT ONE OF THOSE !!!

How much you going to sell them for ??

time i started saving,

what work will need to be done to a 3.9 bottom end then mike to go to 5.5????
and price wise too please,

£1100 for the 5.0 crank, wow thats alot of money but i'm guessing this crank is the daddy of rover cranks?

In the 5.0 build what pistons and rods do you reckon to use?

And what sort of rpm limits would a 5.0 litre engine with your crank be safe to?