Thanks Everyone for your advice. POAH I hadnt even thought about tuning the 3.5 rather than changing it. Back to the drawing board, I think!
In your experience what are the best enhancements and are there any to stay away from, when tuning the V8?
Thanks Richard
Hi
Presume you are asking about swapping the 4.2 motor in, rather than trying to make a LSE Rangie out of a 110??
The RV8 is an ok engine. Heads limit valve size and ultimately top end power. So you can actually get a 3.5 to make similar PEAK hp to a 4.0 or 4.2 That said the bigger displacement will make ore torque and make more torque across the entire rpm range, so while PEAK figures will be similar a 4.2 will be making more hp all the while no matter what rpms.
Such a swap should be pretty easy, although it's worth thinking how you want to do it. Do you want to convert to EFI or stick with carbs? Something like a Weber 500 carb will offer good performance and arguably easier than EFI for a home builder. The stock EFI setup works ok but is a bit limited, so it might be worth researching alternative setups like Megasquirt and Megaspark.
What transmission are you planning on? Personally I want manual, more fun, faster and better on fuel. A std 110 V8 should have an LT-85, one of Landy's stoutest boxes, but highly tractor like to use and usually noisy.
I'd personally keep an eye out for an LT-77 or an R380. They are essentially the same box, so I don't personally have a bias on either. You will need a different bellhousing though.
As for tuning...... huge topic. It depends what you want, as in what will you use the vehicle for?
Tuning takes two routes really:
1. Freeing up lost hp through restrictions. So better exhaust, intake, state of fuelling etc. Most call these bolt on's. Good gains can be had but not huge numbers.
2. Making more HP. For this you need to know how HP is calculated:
HP = torque x rpm / 5252
This means making the same torque at higher rpms will mean more HP. Or make more torque at the same rpms and more HP.
Sadly how much torque is made is often largely dictated by displacement. Tuning mods will increase this, but not by drastic amounts.
However making more torque higher in the rpms is a lot easier. If you've ever seen a dyno plot curve, what we would aim to do is move the curve to the right of the graph.
This means the usable powerband shifts up the rpm range, more mid and top end power and less bottom end.
What you need to do is find a balance between how much bottom end grunt and top end power you want.
The low CR 3.5 found in Defenders is pretty much junk for n/a tuning. You can spend a fortune and you'll still see low HP. If you want you could crack it open and replace the pistons with higher CR ones. But this is costly.
A 4.2 would be great or a 4.6 but they carry a premium to buy. A 3.9 EFI isn't a bad bet though. With a decent exhaust (and long tube manifolds), cam and some heads you should be able to see around 240hp from one.
Check out V8 Developments website. Real Steel also do some ok cams too. RPI has lots of info, but pricey as a rule.
