The V8 Owners Forum -

Hi all,

I know this topic has been discussed before, but Im seriously considering a winter project based around a 3900 spare short engine using chevy or ford parts.

A lot of you guys have experience of this and it has got me thinking
The car is lightweight and I think I could sacrifice some torque for traction and extra revs.
What US parts can be used with the rover to build a 7000+rpm screamer?

Piston type, size
rod type, length etc?

I know machining would be needed but just to get some ideas.

Has this opened up a can of worms or is there a typical combination of parts which you guys use regularly/reliably

Steve

If you're going to rev that much it'll be worth using an xbolt block to be honest.

Hi Steve,

Good question and a reasonably simple answer.

With the 3.9L stroke of 2.8" divided by 2 = 1.4" + 6" Chevy rods and a set of Keith Black Hypereutectic pistons with comp height of 1.561" job done.

Well there will be a bit of work to make it fit but mainly only to the rods which will need narrowing at the big ends and require a custom set of shells and boring the block to 3.736". will increase capacity to 4022cc.

Pistons http://kb-silvolite.com/performance.php ... ls&P_id=42

If you want higher compression they do a flat top with 5cc cut outs but not compatable with Rover valve position

Bones (Richard) had a set of I think Scat Chevy 6" rods for sale.

If you are looking to use 7000RPM you may want to consider using a mains girdle plate to tie the bottom end together.

Regards,

Kevin

depends on what cc your after, and the how much dosh you got, i read of someone using chevy ford and buick parts for 4.8. but if your going to use the 3.9 crank then i think the above post has answered it , rich (and yes i still got the scat rods for sale)

Ok cheers guys,
I understand the need for cross bolting and or/a girdle plate at high RPM.

Where would I get custom shells from Kevin?

Are domed pistons an option or not, and what about stronger/alternative cranks or would they only be made from unobtanium?

I wouldnt really want much more CCs Rich, just something that pulls harder and longer . I know it would need to breathe well but im just looking at the short engine options at the moment.

Steve

Perhaps for 7000+rpm it would be worth taking a look at the top end.... very stiff valve springs would be needed to prevent valve float at that speed. Therefore it might be worth considering roller rockers, especially as they might save a bit of weight which will reduce the load on the valvetrain.

A lightweight flywheel etc would also help the engine rev and should be ok if its a lightweight car.

Now I stand to be corrected on the above so please let me know if you think I am talking bol**cks!

makes sense to me!

Got roller rockers HD springs and billet flywheel already, although taking some weight off it could well be beneficial.

Got my quotes mixed up there!!

There are many obstacles to getting hi revs out of the Rover but one of the main ones is the size of the valves that you can use. The rover also dosen't like revving a big stroke either. An edelbrock inlet will curtail any attemps to rev the nuts off it too. The easiest way to build a revvy rover: 3.9 block, big valve heads st3 etc., solid cam M248+, roller rockers, single plane inlet, big carb, good headers. If you can make anything that moves or goes round weigh a little less then so much the better..

HairbearTE wrote:There are many obstacles to getting hi revs out of the Rover but one of the main ones is the size of the valves that you can use. The rover also dosen't like revving a big stroke either. An edelbrock inlet will curtail any attemps to rev the nuts off it too. The easiest way to build a revvy rover: 3.9 block, big valve heads st3 etc., solid cam M248+, roller rockers, single plane inlet, big carb, good headers. If you can make anything that moves or goes round weigh a little less then so much the better..

Haha I am not sure I know ANY engines that like reving a big stroke! But yeah weight is important.

Also, check parts such as clutchs, as I know that while most of AP racings clutch covers are rated to 9000 rpm for the rover, there is one 240dia that is only rated to 6000. Though I am sure you'd be putting a good clutch in etc so shouldnt be a problem...

Cerametallic as you'd have to engage it at quite a high rpm?

HairbearTE wrote:There are many obstacles to getting hi revs out of the Rover but one of the main ones is the size of the valves that you can use. The rover also dosen't like revving a big stroke either. An edelbrock inlet will curtail any attemps to rev the nuts off it too. The easiest way to build a revvy rover: 3.9 block, big valve heads st3 etc., solid cam M248+, roller rockers, single plane inlet, big carb, good headers. If you can make anything that moves or goes round weigh a little less then so much the better..

Ok, so can the stroke be changed? Presumably you would need a shorter throw crank and even longer rods or higher compression height pistons?
Pardon the ignorance but I havent got my head round this yet. If it is possible what are the part options?
I know there are stroker kits but they mainly increase capacity not revs, is that right?

The larger the bore relative to the stroke, the higher the potential power output of the engine due to the increased potential for higher revving. The Rover 3.9 is about as good as it gets on the Rover in terms of a short stroke and big bore. I wouldn't bother trying to shorten the stroke, as what power you would gain in increased revving, you would loose in power due to displacement.

crayefish wrote:The larger the bore relative to the stroke, the higher the potential power output of the engine due to the increased potential for higher revving. The Rover 3.9 is about as good as it gets on the Rover in terms of a short stroke and big bore. I wouldn't bother trying to shorten the stroke, as what power you would gain in increased revving, you would loose in power due to displacement.

Got it now, thanks

HairbearTE wrote:There are many obstacles to getting hi revs out of the Rover but one of the main ones is the size of the valves that you can use. The rover also dosen't like revving a big stroke either. An edelbrock inlet will curtail any attemps to rev the nuts off it too. The easiest way to build a revvy rover: 3.9 block, big valve heads st3 etc., solid cam M248+, roller rockers, single plane inlet, big carb, good headers. If you can make anything that moves or goes round weigh a little less then so much the better..

I have always been curious to know how Traco made to build their Olds long stroke 4.4 engine based on 215 block.
I remember also RS could rev their 4.3 stroker kit up 7000RPM but I know they used an full counterweight crank and 1.72 rod/stroke ratio.

Wotland wrote: I remember also RS could rev their 4.3 stroker kit up 7000RPM but I know they used an full counterweight crank and 1.72 rod/stroke ratio.

Now that is impressive! I wonder what the serice interval was for it....

It's possible to get big engines with big strokes to rev very high, but then you end up with ally rods etc and they have to be checked/replaced every few thousand miles... not great for a daily driver. Works well fr drag engines though

You use ally rods to cussion the crank against loads of nitros, big boost or nitromethane, not for high revs, if you have the dosh you use titanium rods for high revs. True top fuel drag engines use ally rods but not because you rev them. As was said above your issue with trying to rev the Rover is getting it to breathe, you can put together a bottom end that will take 7500+ revs and substitute valve gear that will take it, the heads however will not let it make any real power up there without being very heavily modified or being repalced wiith aftermarket ones.
Mike