My 4.6 V8 Rebuild Thread

Thor manifold is supposed to be better for torque. Comes from the design of the inlet tract post plastic and lower manifold . Compare the design to the large volume plenum and lower half of the earlier design.

Ask your guy if he's got any idea of it's possible to swap the MAF (Mass Air Flow) for a MAP (Manifold Absolute Pressure) sensor. The MAF (especially the Thor) are fairly notorious for failing (often intermittently) and causing all sorts of grief. Voice of experience, took me 3 months and an auto rebuild to figure mine out. If he can then I'd be interested in a swap.

Also what air cleaner are you planning on running? If it's the oil bath, then consider that the MAF will also be effected very negatively by any oil film on it (again especially the Thor one). A MAP sensor will be fairly impervious to it. (I'm guessing by age that the 101 may have an oil bath but with the V8 not sure and then you're swapping the inlet system so it'll be different again...)

Excuse the question if you have already answered it. Pedro is onto the same issue in his last post, 4000 rpm for 100 km/h does not sound like a low revving torquey engine's job. Have you considered the need to change diffs or the use of a beefy overdrive?

While the weight of the 101 might be greater than one of the other sheds either 110 or Rangie, the frontal cross sectional area will be the major contributor to drag (Cd will be a factor and 101 will not be good) it is not going to be that different. I would therefore expect that on the flat and into a head wind it will need to rev a little higher than a 4.6 in a Rangie but not as high as the 3.5. Therefore under head wind or high speed climb you may need to drop it a cog in a manual or in an auto drop out of TC lockup to keep from dropping road speed. At lower revs with taller diffs the 4.6 should run quieter and use less fuel.

I don't know if I'm barking up the wrong tree here or if it just a cost constrained build or something to be considered later.

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Originally Posted by slug_burner

Have you considered the need to change diffs or the use of a beefy overdrive?

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All 101 owners have considered these issues - I have a overdrive and a 3.5 will only pull it on the dead flat or downhill. Other options are to change diffs to 4.7s but again this reduces drivability with the 3.5s lack of torque up the rev range and does impact low range abilities. RRC high speed hi range transfer case gears are also available. The 101 has plenty of low end but is lacking in the mid range when you are on the highway - hence a bigger engine providing more torque through increased capacity and a Cam is the way to go. Also a 4.6 will pull the overdrive and hi speed transfer gears in normal driving. Also - while a 101 weighs the same as a Disco or Defender it has to pull 35" tyres as standard. Your point about wind resistance is very valid - it dies in strong headwinds.

Not really wanting the 101 to go a lot faster as there are other design issues that come into play that prevent this. Also while it does just under 4000rpm at 100kph a 101 will rarely see that as a GPS speed and hardly ever in overdrive on the flat as the engine cannot pull it. My 101 has a GPS top speed of 113kph on the flat and about 100kph when in overdrive. It gives about 10% better fuel consumption in overdrive but sometimes worse. At 113kph you do not feel all that safe.

A 4.6 should allow me to cruise at 100kph instead of 85-90kph and more importantly not die on the hills - 50kph up long hills is not usual and my 3.5 runs very sweet and performs well compared to other 101s.

Cheers

Garry

The reason I mentioned it is because I used to have a 202 in my Landie and it just didn't pull the car well at all until the revs were up. It wasn't until years later - and with the 202 replaced with a Land-Rover motor - that I realised that it would have had a car cam in it and that's why it was happy cruising at 90kmh, but a dog to take off with. I should have kept the engine and rebuilt it with the torque lower down. And changed the gearing!

If you have a Thor manifold, I presume you can use it with the GEMS system.
There were some mods regarding the lower manifold bolts (designated "V") on the Thor engine due to manifold leakage.

The Motronic EMS software setup was deliberately designed by the BMW engineers to be complex to preclude it being altered :mad: further, if it is altered more than a set number of times, the ECU locks up and becomes a "brick" ...

However, the GEMS lends itself to improvements, including upgraded Ford injectors (check out the RANGEROVERS.NET forum). There are reports elsewhere that intelligent upgrade of the GEMS could have produced a better outcome than the "turnkey" Motronic system (which became the bane of BMW 318 tuners in European motorsport for reasons mentioned above...)

EDIT: valve lift is a critical issue on these engines: check out the extract of Des Hamill's book on tuning Rover V8 engines in Google books ..it's all there regarding maximum lift before valve guides need machining etc.

Rockers: Are you going to build it with the standard alloy rockers or use the steel ones? (sorry you may have mentioned this previously but I didn't register...) I recently bought a set of the steel ones from Turners in the UK together with their shim kit for adjusting the height of the rocker shaft posts. I'm glad I did...the valves were not seated evenly (>30 thou difference in height of valve stems), machined heads and composite (Elring) gaskets. I needed 32 thou under each post on both heads to bring the lifter preload within specs.

The lifter preload is critical. There are lots of instructions about using welding wire of known diameter as a go/no-go gauge for determining whether the distance between the top surface of the lifter cylinder and the bottom of the retaining spring clip is within spec (20-60 thou) A better way is to use the protruding rail on the end of a digital vernier caliper to measure the "step" distance between the top of the cylinder and the top of the installed lifter , and substract the measured distance from the top of the lifter to the cylinder on a spare lifter of the same type...or measure said distance on each lifter before you install. The difference is the preload. ...If you use a shim, you need to use a factor of 1.55 as the leverage ratio of the rocker arm. So, if the preload is 100 thou for example, a 40 thou shim under the rocker post will reduce the preload by 40 x 1.55 =62 thou, leaving a preload of 38 thou, which is optimum! The Turner shims come in three gauges...16, 32 and 48 thou... You have to use the same gauge on all the posts on the same head else you will break the rocker shaft... alternatively, go for adjustable push rods. If you go this route, you'll need to get your friendly machinist to "check" the holes through which the push rods pass because the adjustables are 5/16"diameter and need extra clearance. Smiths in the USA are the best source of adjustables (apparently)...

Priming oil pump: You can buy a 12mm(1.5mm thread) male stud with a 3/8" barb which screws into the oil pressure switch gallery. You just connect it with polythene tubing to a pump on a cordless drill to prime the oil pump and send oil all through the galleries prior to start up...

PM me if you want to explore this further. I have just completed this exercise and fired the beast up yesterday... I have some spare sets of shims

Thanks for that information - to clarify I have the Gems manifold, plenum etc but not ECU. I have access to a Thor manifold etc but not ECU.

I am intending to use the standard Rover rockers, lifters, springs and valves. No modifications are needed to run the Crow Cam I have ordered.

Cheers

Garry

Hi Garry
I put in an MSII Extra ECU when I changed to a 4.6 in the RRC, worked out really well, no more distributor and MAF and you can tune/adjust just about everything if you want to including AF ratio with a wideband sensor. I think it would go really well with the Thor intake
Nick

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Originally Posted by garrycol

Thanks for that information - to clarify I have the Gems manifold, plenum etc but not ECU. I have access to a Thor manifold etc but not ECU.

I am intending to use the standard Rover rockers, lifters, springs and valves. No modifications are needed to run the Crow Cam I have ordered.

Cheers

Garry

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Just to clarify, the steel rockers are standard spec. The advantage is that where on the standard alloy rocker arms the cups and the pads are separate items and pressed into place, with the steel rockers they are all one piece and are part of the machining of the rocker arm. I've had "new" rockers fail in that the pads dropped out! Karcraft have the steel ones (cast iron) and they're actually a bit cheaper than the aftermarket alloy ones.

also, recommend the Payen metal, not composite, valley gasket. There's a chance of delamination of the composite one. Fitting the metal one with a smear of Loctite 518 on both sides is a better choice (IMHO!)

Thanks - composite head gaskets and tin (not composite) inlet manifold gaskets already acquired.

A question for the mechanics.

Early in this thread you will see I had to have a head bolt hole welded up as a head bolt had stripped the threads and a poorly inserted helicoil had caused two small cracks around the hole. All fixed now and the crack areas reinforced so should be an issue in the future.

However - the head bolt holes are 47mm deep and the thread runs all the way to the bottom on the undamaged holes. In putting the new helicoil in the repairer used a helicoil that is only 20mm long so when I put in the ARP head stud all the torque is only going to be taken by 20mm of thread in the head.

I would have thought this is not enough when the head is torqued down and I am likely to end up where I started with a stripped head bolt hole.

Should the repairer used a 40mm helicoil in this hole??

Thanks

Garry

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Originally Posted by Nick S

Hi Garry
I put in an MSII Extra ECU when I changed to a 4.6 in the RRC, worked out really well, no more distributor and MAF and you can tune/adjust just about everything if you want to including AF ratio with a wideband sensor. I think it would go really well with the Thor intake
Nick

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Thanks - I will go onto the MS forum and ask a few questions.

Cheers

Garry