Hi Alex

It's a waste of time and money. If the V8 was a high performance engine with high lift long dwell cam and high compression (i.e. 11:1 or 12:1) yes, but it's basically a truck engine with little performance capability so any porting and polishing would render very little performance. You would need a serious race type engine to make progessive gains, 4 valve head, twin sparks, hi comp, special race cam etc, etc but for a Rover V8 it's a marginal gain, if any. You would also need to increase the engine ECU performance and increase fuelling modes, ignition timing, intake breathing etc, my advice is don't bother unless you have a shed load of cash to spare. I really hate watching decent guys throw money down the drain.

I've been there and done all of that on serious race engines but, the big but, it also destroys longevity and reliability.

 

 

I certainly wouldn't recommend paying the big bucks at a machine shop to have it done, but I did notice a difference with my home brew job. Not to be argentative, of course, but I don't think many guys can boast 9.02 second 0-60 times in a D2 on 33s.

I am curious what you said about reliability though. No doubt you know more on the engine building subject; I'll freely admit you're more experienced than I am. I've never heard of port work causing any reliability issues and it certainly hasn't caused me any. I'd love some elaboration on that.

 

Hi Alex

When I talk about longevity and reliability it's more about the total tuning of the engine for performance where everything possible is done on the engine from crankshaft, rods, pistons, heads, ECU, gas flow etc, the whole package. Once the engine is fully tuned to it's near maximum it becomes susceptible to reliability and longevity (and grenading) issues due to racing and high revving performance stresses.

This outfit is good at tuning engines but it costs serious money.

SBD Motorsport, MBE Engine Management System, Vauxhall, Duratec, Hayabusa

In the UK in many cases we attempt to extract the maximum performance from 3.0 litre or smaller engines, a typical 2.0 litre would be around 300 bhp but they do sometimes expire rapidly due to stresses.

 

Hi Collie, yes I have a lot of experience of tuning twin DOHC engines with bucket shimming which is a long and tedious but essential experience. I have very little or virtually no knowledge of pushrod or V8 engines as they tend to be very 'sluggish' in performance terms. All my experience emanates from the now ancient Cosworth Ford BDA and BDX engines and latterly the Vauxhall XE 'Red top' engines. All of these engines were the DB's and real screamers where we used to extract the ultimate from them. I'm big into long tapered roller body direct injection systems with DOHC.

I have much advice when needed from old pals who worked for the now defunct Brabham F1 and also currently McLaren F1.

I still run a Honda 600 CBR F4i with fuel injection and twin DOHC performance which has 'bucket shimming' for the camshafts.

 

A good port and polish job, runners matched, bowls enlarged properly, most certainly makes a noticeable improvement in pushrod V8 performance
Efi tuning/ air/fuel ratio IS very important for a correctly and strong running engine.
However, a port and polish can improve flow on a stock tune, and with no ill side effects.
If you have the time and money, it is always worth doing.
Reliability is not an issue.

 

Ok, that I can understand. Those things only really come I to account y driving around at WOT, though, other than the ECU tuning. Otherwise you're actually helping engine efficiency.

The reason you really see noticable gains on these engines, also, is because Land Rover used the same port sizes as the original 3.5l head castings. That really is the big bottleneck point on a 4.6l engine. That said, I'd also love to do some TB work soon. I've been eyeballing it for about a week now and it's gonna happen before long. I've touched everything else in the system.

Collie, on the rocker adjustment, typically you want half a turn of preload. However these are not adjustable rockers so you can't go by the half a turn rule of thumb. You will want somewhere between .020" and .060" of preload. Luckily hydraulic lifters aren't as picky as old school solid lifters.

 

Alex,

i am going to read up on it, and it's my first time doing this so am a bit confused. Would you be open to getting on the phone with me before I do it, and just talking me through it? I want to make sure I am measuring properly. I have plans long term for the engine so doing it right is really important to me.

 

Sure, shoot me a PM and I'll shoot you my number.

And honestly, if you're only having the heads decked, not milled, then you should still be fine assuming it was fine before dissasembly. I'll still talk you through the process though. There's not a lot to it.

20 to 60 thou (thousanths of an inch) is a pretty wide tolerance which you can have because the hydraulic lifters give you some cushion.

 

I'll PM, and I appreciate it. The thought process for me is that I just do not trust the shop that did my engine/heads did it right or bothered. I don't know how much they took off then, and so I just want to make sure that I am doing it properly. The last thing a guy without a garage wants is to do it twice.