The V8 Owners Forum -

Hi guys, beginning shopping list for the engine to put my eventually re-worked 300 heads on. They will go into me and my mates new project locost 7, with a crossover manifold and either DCOE or ITBs. Light and for Only track use, want a real track, sprint and possible strip toy to compliment the landy. But we are having a bit of a debate, 4.0 or 5.0 RV8??? Ultimate power or rev-ability?? With roller rockers and a wild cam would we reap the benefit of the revving 4.0 or is this hardly noticeable besides the ultimate 5 litre (no more). Cost is not the ultimate limiter but it is nice to think the 4.0 set up may be a little cheaper also. what do you think...

Ohhhh - also am thinking of buying some of those really dear 4 prong spark plugs for my 5,0 landy (mega jolt) over the current NGK R (standard). Has anybody noticed any difference in premium plugs?? Or is it just a good set of well gapped regular plugs just as good???

For racing I think those 4 prong plugs are just heat collectors and possibly intended to improve weaker ign systems? Just my thoughts by the way.

I only use NGK now. The range of plugs is great. I never use resistor plugs either as I dont have anything to pick up interference. As long as the heat range is correct for what you are doing NGK's will be fine. Mine have performed well on nitrous and boost with standard ign systems and now the MSD. I may sound biased, but I like to stick with what I know will work from experience and use.

Thanks, yes I thought as much, just hot spots waiting to happen. What about the 4.0 vs 5.0 question. I agreed with my mat that we would go with the consensus.

Wouldn't a 4.6 be cheaper than a 5.0, and you still get a bit more torque over the 4.0? I'm using NGK Iridiums but to be honest they don't seem to make much difference over the ordinary NGKs, but may last longer

In fact, it depends of which 5.0 you intend to use. Factory TVR 500 engine ?

For spark plug, ordinary NGKs make great job.

If we go for 5.0 it would not be a factory tvr setp, would assemble a ood balanced ottom end. If we went for the 4.6 then it would be purely for cost (still possible) but I would have thought the characteristics of the engine would be similar, If we didn't go for 5.0 then we thought that we should go for a different character engine and we wondered if we would actually be better off with a revvy 4.0 than a less so larger capacity in a very lit track car.

I assume you are running edis coil packs ? - they give a decent spark and you dont need to waste money on fancy plugs. You must use resistor versions though.

Eliot wrote:I assume you are running edis coil packs ? - they give a decent spark and you dont need to waste money on fancy plugs. You must use resistor versions though.

Is this because the plugs give off RF interference that will upset the ECU ??

mgbv8 wrote:

Eliot wrote:I assume you are running edis coil packs ? - they give a decent spark and you dont need to waste money on fancy plugs. You must use resistor versions though.

Is this because the plugs give off RF interference that will upset the ECU ??

yes.

Yes I am running EDIS - will keep to NGKs

As the heads are largely the same - would the overall air volume and power be largely the same from a 4.0 (bore diameter also) - but obviously mid range torque will be less - although all dyno runs show the 5.0 and greater engines all produce the most power. Wander which crank is also the most hardy uin stock form (4.0 vs 5.0) obviously all 5.0 cranks are non stock (appart from TVR. Was it the 4.0 that had forged rods as standard or 4.6??

"although all dyno runs show the 5.0 and greater engines all produce the most power."
You wouldn't build one if the dyno sheets didn't show them making more power now would you??
Remember a bigger capacity engine (especially a longer stroke one) can generally take more cam timing than a smaller capacity engine whilst still remaining street drivable. Also simple head porting techniques like "open the ports as big as they will go" work better with a long stroke engine configuration (like most big capacity rovers are!) these two aspects alone will generally lead to the bigger capacity engine showing more power (though pretty well always at a lower VE).
Best regards
Mike

Even the 5.0L TVR cranks weren't standard !
Farndons offset ground them for TVR !
How I know ?
Farndons used the TVR crank drawings to make my 5.0L billet steel crank for me !

THis is a good article by Ray from V8 Developments

http://www.pistonheads.com/gassing/topi ... ices&mid=0

How much was that if you don't mind me asking?? Would love, LOVE, a steel crank. Do you think they would make one from iron for me for a reasonable amount of money??

Surely the only reason anyone would have a billet crank is because a forged one is not available off the shelf for the stroke required? I can't see how a machined crank could ever be as strong as a forged crank unless there was some seriously crappy materials or forging process used making a standard one- when you machine a billet you destroy the grain structure that gives a billet it's strength. If it is well engineered (over-engineered!) I guess you could get over this problem, but a forged one should always be stronger.