4.6 engine information

C

Chips

Member
I have just got my hands on a range rover p38 4.6 engine and would like to rebuild it and fit it into my 3500s.
I have a 5 speed LT77 gearbox fitted at the moment so should cope with the extra power and torque.
I would like to keep it on HIF carbs. I no not ideal and will restrict power output but I like the simple things in life.
Has anyone run a 4.6 on HIF carbs ? and how did they get on.
 
I believe our esteemed friend Ron roves around Australia with a 4.6 on HIFs in his saffron yellow P6. Username SydneyRoverP6.
 
I have a 2" HS8 set up available if you fancy playing with those.
Fitted to my 4.6 yielded 236 bhp, dyno sheet available.
Includes, worked manifold, carbs, electric fuel cut off valve to provide cold start enrichment, extended elbows to connect to... modified filter can with two new Montego filters, selection of needles, fitted with new main jets. Good economy. Bolts right up to stock throttle linkage. Clears bonnet.
 
As per this thread: SU Carbs for 4.6 litre ?

Yes, just re-jet the carbs and all will be ok.
I started with the following setup, on a slightly tuned 4.6l:

  • Twin SU HIF6 on (almost) std manifold.
  • float level 60 thou
  • BBW .100in Jet Needle
  • yellow graded 8oz springs
  • Poppet valveless butterflies available from SUcarb.co.uk, Throttle disc kit WZX 1321
It was a little lean at higher revs, but this allows thinning the needle to suit. The engine is smooth, pulls cleanly and strong.
Gavin.
 
Reading this with interest, so my current 3.5 block is at the mechanics, if they cant remove the broken 'easy~out' tool from the broken head bolt then the block will be my new big paper weight, So I'm looking at various options & see 4.6 'good' 2nd hand P38 engines on fleabay for around £700~£1k on average. If I go this route then I'll only need the block & heads, so can I use my P6 timing chain cover (with uprated oil pump kit form real steel), my sump cover & I'll use my original manifold and HIF6 carbs which I have just rebuilt.
Saying all that is the 4 ltr P38 just as good option or even the 3.9 ltr. I have new timing chain kit, all new gaskets, will get new cam n lifters too.

If my current block can be fixed the great but I'm looking at £2k for rebuild , being early high compression then new pistons are £700,, needs re~bore, new shells, new rings, both side needs skimming ect.

Cheers Damian.
 
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If your mechanics manage to get the bolt rump and easy-snap out, and you are then able to use your original block, why can't you re-use the early high comp pistons?
If you opted for a bigger lump from a P38 Rangie, wouldn't you want to use the matching crank, rods'n'pistons that came in it? Surely the pistons from the 3.5 wouldn't fit, being smaller?
Sorry I haven't helped you with your enquiry, just heaped more questions on top.
 
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The 4.6 will give you some grunt ok. My 4.0L is basically the same engine with a different throw crank. I have an SD1 timing cover so you could use the P6 one with an oil pump upgrade kit, I use the P6 sump and oil pick up, so that works, exhaust and inlet manifolds both fit, but you will need to use some different needles in the carbs.
 
Hi guys, all info is appreciated :) The pistons are shot so if its having a re-bore, all new bearings, polished crank, skimmed heads etc then new pitons & rings makes sense. If however the bolt cannot be removed then a good second hand 3.9, 4.0 or 4.6 block was an option but as a complete engine, I I then would then use my 3.5 parts as Quattro advises. I have faith in the enginnering company, they have been in business for 125yrs & are very good, they based here in Somerset in Bridgewater & are called Hamlins, www.hamlinsengineering.co.uk. Fingers N everything else crossed !
 
Hello Chips,

I have a suspicion that the 4.6 produces more torque than the LT77 is designed to handle. The 4.6 in my Rover was fitted in 2007, and since then has travelled over 200,000 miles (322,000km). To fit into the P6B, either a P6B or SD1 timing cover, you can use either a P6B or later oil pump front cover, Lucas 35D8 distributor regraphed as the 4.6 requires less overall advance compared to the 3.5, 28 degrees as opposed to 36 degrees. You can comfortably set the timing to 10 or 12 degrees at 600rpm. Is your engine low comp or high comp? Owing to the way the engines produce their torque, the low comps are preferrable with auto transmissions, the high comps with manual transmissions.

The P6B sump and oil pick up are required, a spacer for the crankshaft pulley as the 4.6 crank has a longer nose. A true roller double row timing chain is vastly superior to the Morse type, so do avoid the latter. SU HIF6 carburettors are perfectly fine for all types of driving, BBW needles and yellow grade springs. Be aware that these needles are still too lean at various points, so ideally they should be polished by someone that knows how to do it, whilst the car is running on a rolling road. If that is not feasible, just try the BBW and one or two richer needles and see how they go. It is trial and error as you're doing something that was not offered by the factory, a custom order in fact! Adjust the float depths to 60 thou and fit solid butterfly valves, don't use those with poppet valves. The original P6B air canister will need replacing as the 4.6 requires from memory 30% more airflow. The nose that allows air to pass through is much too small, so are the standard air filters. You will need significantly larger ones if your engine is to breathe as it should.

There is a dowel on the rear of the crankshaft that from memory requires removal so as to fit the P6B flex plate. P6B exhasut manifolds will bolt straight up to the 10 bolt heads which are to be used with composite gaskets. Use a tin inlet manifold gasket.

Ron.
 
Hi Ron, Many thanks for the great information! some very useful tips . I'm still in 'lingo' with my block, if they can get the broken bolt & with the broken 'easy-out' tool then I'll stick with it as it'll be brand new and is the early high compression version. If not then I'll be looking out for a good condition replacement short block, ideally just the block, there are quite a few 3.9's on eBay advertised as good running engines before removal so I may go that route for ease & just to get the car running again. Many thanks thanks again, Damian
 
I'm in the process of installing a brand new Top hat 4.6 short motor with timing gear into my RR. I got it in south Australia for $3950.00 AUS plus shipping. He assembles them from bought in parts from UK. Makes me think you need to shop around more for your parts...they sound very pricey in comparison. Try JP pistons. Note the cranks are externally balanced so you need to keep the harmonic balancer (to which the weights are welded) or get the lot (balancer to flywheel/clutch) re balanced.
 
Hi Ron

What have you done to your air filters ?
I was thinking of using montego filters and enlarging the snorkel on the air box.
I don't no if it would be better to use a air box and filters from a sd1 if they flow more air.
Thanks Paul.
 
Hi Paul,

The air filter box that I am using is from the U.K home market SD1, which was very different to the version that came on the engine for the Australian market. It features a significantly larger air intake conduit to make up for the air flow volume loss due to the cold air snorkel that was fitted over it. I use K & N air filters that I was able to buy directly from K & N in the USA, as at the time they were not available in Australia. I removed the original air filter retention brackets thus permitting fitment of the larger filters.

Ron.
DamianZ28 said:
Hi Ron, Many thanks for the great information! some very useful tips . I'm still in 'lingo' with my block, if they can get the broken bolt & with the broken 'easy-out' tool then I'll stick with it as it'll be brand new and is the early high compression version. If not then I'll be looking out for a good condition replacement short block, ideally just the block, there are quite a few 3.9's on eBay advertised as good running engines before removal so I may go that route for ease & just to get the car running again. Many thanks thanks again, Damian
Click to expand...

Pleasure Damian, glad that you found it helpful!

20190626_103940[1].jpg
 
Ron, Why do you recommend a tin gasket on the valley cover in a 4.6? Any reaction to Hammills suggestion to reduce oil flow to the rockers by partly plugging the supply hole in the head?
thanks
 
Hi JP,

When my 4.6 was being assembled, the workshop manager ( a Rover man his whole working life - almost 40 years in 2021) advised not to use them, alignment issue at the time. Other owners that I had spoken with at Rover Owner's days when we were talking engines, offered their experiences with composite inlet manifold gaskets. Bolt holes not lining up being a common complaint, and waste of money, should have stayed with tin. Maybe these are just isolated occurences and everyone else has no issues. Not having used one I am not offereing my own personal experience, but when people sing from the same songbook, that usually means the advice is worth listening to.

Unless there is an alternative path for the oil to flow, partly plugging a supply gallery won't achieve anything viable. If we assume that the oil within this part of the engine is essentially homogeneous and isotropic (uniform density with physical properties equivalent in all directions), partially plugging a hole only serves to increase the velocity of the flow as it exits the restriction. The law of conservation of mass tells us simply that V1A1 = V2A2. If we set up a control volume around the location of interest, the flow entering the volume must equal the flow exiting the volume, unless as I say there is an alternative path. If there is, then partially blocking the feed will make a difference. If there is no alternative path, then it makes no difference in terms of the total flow within a given time. Where it become more tricky is when we consider viscosity and the impact that this will have, and how increasing the velocity at the point of exiting the restriction will increase turbulence within the flow. Oil like water is a Newtonian fluid where the shear stress of the fluid is directly proportional to the velocity gradient.

Ron.
 
FWIW I think the composite valley gasket is a night and day improvement over the tin. I am used to fettling the holes as I have always fitted skimmed heads. I fettle the port holes as well.

I am struggling with the science mentioned above for restricting the oil flow. I am thinking of a kitchen sink tap as a basic example. There is no alternative path, the tap is either open or closed. If the tap is half opened the flow of water is reduced from the full open position thus reducing the flow. Would not the same apply if one was to reduce the flow of oil by reducing the orifice size that it was flowing through ?
 
cobraboy said:
FWIW I think the composite valley gasket is a night and day improvement over the tin. I am used to fettling the holes as I have always fitted skimmed heads. I fettle the port holes as well.

I am struggling with the science mentioned above for restricting the oil flow. I am thinking of a kitchen sink tap as a basic example. There is no alternative path, the tap is either open or closed. If the tap is half opened the flow of water is reduced from the full open position thus reducing the flow. Would not the same apply if one was to reduce the flow of oil by reducing the orifice size that it was flowing through ?
Click to expand...

If you think of a tap as being a valve. The cross sectional area of the pipe is the same either side of the valve. If you partially close the valve, the velocity of the flow before the valve will be the same as the velocity after the valve, if it were not, the velocity of the flow leaving the tap would increase. Think of a hose which is flowing at a given velocity. Place your finger across the end of the hose, what do you notice? The velocity increases as the cross sectional area is diminished by your finger. The total volume of water travelling before the exiting the hose and that leaving the hose are the same. No matter how bizzare things might seem, always remember that the laws of physics will always be true (except when approaching a Black hole, but that is another story).

Ron.
 
Ron, The reason Hammill gave was to increase oil pressure where it was needed more - the crank and camshaft bearings - your alternate path. Also, I think velocity of flow is not the same as the rate of volume flow - gals/min involves the pipe cross section, and has nothing to do with pressure . with the finger over the hose end, the spray velocity goes up, but so does the pressure, and the flow rate goes down. To Cobraboy's example I add the difference in oil pressure in a worn engine (large clearances), versus that on close fitted new engine - smaller orifices for the oil to exit the system.
As an aside, what happens when you push kero through a steel pipe too fast?
How did Bernoulli predict the gas turbine engine?
 
Ron
Thanks for persevering. Yes I understand the velocity before and after the 'valve' or restriction must be the same, this is true of the restriction placed in the oil way, it reduces the flow after the restriction, which it does before also, so you are limiting the flow down that whole passage, which is the aim in order to conserve flow to other parts of the engine.
 
jp928 said:
Ron, The reason Hammill gave was to increase oil pressure where it was needed more - the crank and camshaft bearings - your alternate path. Also, I think velocity of flow is not the same as the rate of volume flow - gals/min involves the pipe cross section, and has nothing to do with pressure . with the finger over the hose end, the spray velocity goes up, but so does the pressure, and the flow rate goes down. To Cobraboy's example I add the difference in oil pressure in a worn engine (large clearances), versus that on close fitted new engine - smaller orifices for the oil to exit the system.
As an aside, what happens when you push kero through a steel pipe too fast?
How did Bernoulli predict the gas turbine engine?
Click to expand...

You are correct JP, velocity of flow and rate of flow are indeed not the same. The units of velocity are LT^-1 whilst the units of flow are L^3T^-1. Pressure and velocity are related but not as you indicated. An increase in axial velocity does indeed see an increase in axial pressure, but that is not the pressure that matters in an engine or indeed in a human being, it is radial pressure exerted circumferentially. When velocity increases, radial pressure decreases. Velocity, flow and cross sectional area are related by Q = VA where Q is flow rate, V= velocity and A=cross sectional area. This is a simplistic equation which ignores friction and viscosity, but it provides a view of their relationship.

Hmmm, pushing kero through a steel pipe too fast? Well kero is a hydrocarbon, so obviously flammable, at high velocity the ratio of inertial to viscous forces will result in turbulence, so a smooth boundary layer is unlikely, the generation of heat from friction will likely see it ignite. Unless there is a minimum pressure (radial pressure) that it needs to be exposed to in order to prevent a change of state?

Ron.
 
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