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[ V8 Engine Fitting Information ]
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[ General Engine Problems ]
[ General Information ]

FAQsGeneral V8 Engine Problems FAQs

Dimensions of the Rover V8 engine fully dressed, and weighing in a 230KG all up.

engine dimensions

With the Rover V8, it is never, 'how many miles they have done',

but how they did them, this is a typical low miles engine, It is not uncommen to see such contamination on a ten year or older engine, that has covered typically less than 50K miles, & has had only factory specified interval oil changes, but please dont let this put you off,
on the other side, a V8 that does a thousand miles a week would last perhaps 200K miles and still be in great shape.

{short description of image}
You can stop them getting like this, if you catch them soon enough, "So Take a look inside"
How to tell the condition of your engine..
How can I tell if my camshaft or tappets are worn?
Checking Tappet Pre-Load
Beware fitting new tappets only.
Camshaft changes (serpentine type).
Oil pump Priming .
Engine overheating problems?
Engine Overheating Problems 3.9 and 4.2 only (pre 96). & 4.0 - 4.6 post 96?
Why should I be careful buying a "used 3.9 or 4.2"? Adjusting end float, mains bearings..

Simple Setting up issues

Before it's final demise, the owner said, Well it runs very well, but its lacking some power and the economy is not so good ?.

How can I tell the condition of my engine. by looking inside?.

A good look inside the rocker covers through the oil hole will help me determine the internal condition (and the minimum parts you will need for a successful job.
if your are unsure. it will be in one of the following categories.

Silver Alloy surfaces.?. Sounds Like a new engine
Brown tarnished.?.Very low mileage Dark brown.? perhaps higher mileage but well cared for.
Black ?.Getting poor, a full rebuild/replacement should be considered.
Black Coated & becoming dense ,? Very poor condition, A rebuild is normally required
Black and a "very" sludgy ? Dead on its feet.

You can be sure this method is a reliable way to determine, What you have, and What you should do. "See the picture above, there is a lot about like this one, and worse. !!!.

How can I tell if my Camshaft and Tappets worn?

It is easy to tell if a cam is worn out, without removing the engine or the need for close inspection.
When the tappets become worn, (Normally 60000 -80000 miles) The Tappet base becomes concave (dished) so when the camshaft rotates, through 360 deg. , the tappet will only ride on the edge's of the camshaft, and only making contact in the center when it goes over the (worn to shape) cam lobe. this has the effect of causing the camshaft to be brown in appearance and shiny on the edges. The cam in a Rover V8 is Hydraulic in its design, this means when it is manufactured the lobe is cut at a slight angle so that it rotates the tappets (essential for them to fill with oil) so even when lobes still look to be intact, if the cam is starting to discolor it is well on the way out, it is important to change the cam, before it start to wear away quickly because the metal particles produced will quickly cause further wear in the crank becoming embedded in the white metal bearings and softer aluminum rockers, causing further engine wear and further metal particle's. Replacing the camshaft and tappets before they get bad will greatly extend engine performance and long life as well.

Longer engine Life, Increased engine efficiency, smooth idle and good power, are all "Not" to be expected from cams that look like this (and it is not an uncommon sight) ,
new cam worn cam
Although you can see this cam is showing all the discoloration's as mentioned, The Camshaft lobe's showing are all becoming "rounded on the shoulders", its been bad for quite some time and would have caused considerable harm to the engine already, not to mention the engines performance and efficiency
Camshaft Kit
A range of Camshaft Kits
are available on our
Special offer pages.
Its is clear to see the tappet on the left is already showing signs or becoming worn, the center is dished (concave) the trouble is, the cam and tappets will get a lot worse than this before you can actually hear them, and the gradual, long term wear means you will not notice the power and economy losses either., So check the condition of your engine by the method we describe above, and judge for yourself, if it's worth closer inspection.

Checking Tappet Pre-load
If you are rebuilding any V8 engine It is becoming more and more essential to check tappet re-load as there have been so many variants of the Rover engine components, and the engine itself now spans over 30 years, so you can't normally "assume" anything, So if you want to be sure of how your engine will end up. don't forget this important issue. Tappet pre-load is the distance between the pushrod seat in the lifter and the circlip, when the lifter is on the heel of the cam and the valve is closed. Not setting the lifter pre-load, will cause premature wear, noisy valve gear, and possible engine failure.!!. Or if your lucky "initial complete loss of compression as the valve will not be able to close fully,

The following information assumes that the following components are in good condition - rockers, pushrods, valve guides and valve stems. a clearance of .040" to a maximum of 0.60" must exist between the spring loaded pushrod seat in the top of the lifter, and the underside of the retaining circlip. This check should be made with the valve gear fully assembled, and the lifter empty of oil, positioned on the lowest point, on the back of the camshaft. The simplest way to measure the gap is by using round wire. Use a piece .040" for the low clearance check, and a piece of .060" for the high clearance check. Check all 16 lifters individually.

There are various ways to adjust the pre-load on the Rover V8. normally a decrease off pre load is required and this is achieved by using the "rocker pedestal shim kit" if the opposite applies the it would be achieved by machining the rocker pedestals however in race and higher end applications adjustable pushrods would be used.

Shim Kits, are inexpensive and include all the sizes you are likely to nee. Adjustable pushrods, are 3/8" and will require the guide holes to be elongated or opened out. Adjustable rockers can be used and are available in a pack. It would be wise to check your valve tip heights are all reasonably the same by putting a straight edge across them. Also, we have seen cases where the rocker pedestal mounting points cast into the head, are not parallel to the cylinder head face. This can make it a long tedious operation. Remember to take into account the rocker arm ratio of approximately 1.6. Make sure the shims are properly aligned under the pedestal so as not to block off the oil supply. Do not use shims of different thickness on the same shaft assembly, as breakage may occur.

Beware fitting new tappets only

Chimera After only 30000 miles or so this TVR developed some familiar TVR rattly top end sounds.
A visit to the a (So called) reputable TVR Garage fixed the problem by fitting some new tappets, believing that they may have perhaps failed. and this was the appropriate cure

Tappets do not fail and replacing them without changing the cam, does not work, You will see why below.

We will not print any names, but it was suggested that it is correct & proper to replace tappets only, even on an engine that has only done 30,000 miles, Well with comments like that its no wonder why we can do so much better for our customers.

These three tappets have only done 5000 miles on the engine they had been fitted to. They all tell a story. from left to right its not looking good

Top. Comparing Cams, At 35000 miles and no sign of wear, The Morgan cam is still looking good
Below. This Cam did not take to its new tappets. So it was bad then and worse now.
{short description of image} {short description of image}

The left hand Tappet shows it is completely worn out and after only 5000 miles it was the worst one on the engine. As expected, it corresponded to the Camshaft lobe that was most worn (probably the one that was the cause of the tappet noise in the first instance)
The middle Tappet is also quite dished and this was going to be the next one to become a major issue soon.
The left hand Tappet shows the signs of wear (rounded indentation expanding from the center all other tappets on this engine at only 5000 miles where showing bad signs of wear and the 3 depicted above represent the extremes and average condition of what we found and what you could expect
By possible luck, at the same time as working on this engine we started work on a Morgan +8 which was going through a stage 3 upgrade, its engine had done only 35000 miles and all the tappets where still in perfect order, indeed in better shape (all 16) than the best of the tappets depicted above.

Camshaft changes (serpentine type)

The later type "Serpentine" V8 engines have the Camshaft further retained by a fixing plate, (secured with two bolts).
The issue is that there are still a few upgrade Cams on the market that do not have the added machining to re-use the fixing plate.
Our's included !! (but were working on it.) This however is not actually required, as nothing else has changed with the V8 engine and its 35 year old design to make this retaining plate necessary, indeed the rotating chain would hold the cam true as would the thrust casting that is still present on and all later type timing covers.

Oil pressure wont prime.

Assuming you have packed the pump with Vaseline or grease, you have a strong charged battery and better still the plugs are removed.


The distributor drive gear pin has come out, or the drive is spinning on the camshaft
The pressure Oil relief valve is stuck open in the pump body.
The pump drive gears are not broken
The strainer pipe is not fully tightened due to incorrect bolt. or the gasket is split.
The stainer has a crack or fracture above the oil level line. or perhaps its blocked.

Engine overheating problems?

Normally overheating would be caused by one of the following examples, This however can only be true if there are absolutely no Internal signs of gasket failure, Block cracked (mainly older 3.9's & 4.2's and this fault cannot be seen (see below)) Or external water leaks, We would always recommend head & Block pressure testing, or at least a chemical block
1. Not all temperature gauges are reliable, Try attaching an external gauge to check readings are correct. also make sure you are using adequate Engine cooling fans, We recommend Pacet cooling Fans systems
2. Check the condition of the radiator (if not new) some have been filled with sealer in there life and circulation can be a problem also if the fragile cooling fins are corroded or missing the radiator will struggle to keep the engine cool. also many altered vehicles may have restricted air flow to the radiator, this may sound trivial but is worth considering.
3. The most common problem is caused by Air locks, You need to be sure to remove all air in the system. One of the most common traps is in the heater radiator inside the car; this can be cleared sometimes by flushing it. To do this remove the two pipes that pass through the bulkhead, Get a high pressure garden hose if you use a commercial high pressure washer, you must not force all the pressure through the radiator so hold the spay a few cm. away. What happens is that for many years the water has passed through this radiator, always in the same direction this means that deposits build up inside flushing in both directions will normally reduce the amount of blockage.
4. And most important, if you cant cure or find it don't drive it, overheated engines will cause the oil pressure relief valve to stick open and cause un-reversible and uncompromising damage

Engine Overheating Problems 3.9 and 4.2 only (pre 96)? & 4.0, 4.6 post 96?

Over heating, Starts with water loss. The early 3.9 and 4.2 (pre 95-96) engines where, basically an over-bored 3.5 casting with 4mm extra on the diameter of the liners, this caused a reduced thickness of aluminium between the water jacket and the cylinder bore. The subsequent water loss problem normally starts off as just a water light that appears once a month or so, Then once a week until it becomes a permanent feature, The normal unsuspecting owner, will have by this time paid for heads to be skimmed and gaskets to be changed by which time they have spent a lot of money already. So, although the engine functions fine it is a permanent worry leading towards a Total engine failure.
Many would be excused for thinking that the overheating is caused by running the engine in a Hot climate, or with a radiator problem. or even insufficient cooling fans, or Oil cooler but we can assure you, this is not normally the case.
3.9 & 4.2 The true & main reason these engines run very hot is due to the fuel/air ratio, or fuel mixture, that is controlled by the engine EFi computer, (ECU Chip) from the factory this was designed to run very lean through the mid range, to make altitude driving or mid range emissions (tested in some countries) less of a problem, the upshot of this however is when these engines are used on low quality or low octane fuels or when indeed the engines are upgraded with items even as minor as free flow air filter, or exhaust headers, & Cam/Head upgrades, although all of these are only mild upgrades they will make weak engine run even weaker, and the problem will get closer!!
The solution is simple. (If its not cracked already) fitting our Optimax or Tornado Eprom (ECU Chip) will give your engine the near perfect fuel / air ratio, it deserves thus, lower engine internal temperatures and give, without other modifications to all 15% efficiency [power and economy & also allow the upgrades you have already done, to be beneficial at last, instead, of being detrimental. 3.9 & 4.2 ECU info "Click"
4.0 & 4.6 (New shape)Suffer a similar but normally less dramatic problem, although these engines are much stronger, "The Same" Air/ fuel ratio problem will arise with low octane fuels, you will not normally however suffer cracked blocks, but you will cause the Liner to shift from its seat or cause sticky valve guides (partial seizure) and the solution is much the same as the 3.9 & 4.2 above, an ECU re chip will sort it out and more Gems ECU info "Click"
All cracked engines (blocks) are not normally repairable due to the fact that it will crack behind other liners, even if you could effectively repair the one at fault
If you are undecided about where the problem actually is, then the next job would be to remove the heads if you see nothing then suspect the worst. (The surest way to tell if your engine is suffering from this problem is the fact that you can find nothing obvious wrong) you could have the heads & block pressure tested if you are still not convinced).

Its no coincidence that the Piston on the right. ( No's 7) seems to have been 'steam. cleaned'

Liner problem
This is a sure sign of the cylinder block being cracked somewhere behind it, In many cases such as this one you will also find that the cylinder liner has moved down the bore slightly . The problem with this engine had been wrongly diagnosed by the main agent ( at a cost of £600.00) to a 4 though, warp in the centre of the head.

Want to see more.

Which is, clearly incorrect. But please be sure, This is not a problem caused by the 4.6 engine itself, or indeed any of the smaller V8's , but is caused by the very weak fuel maps they are subjected too With modern, (un-chipped) Std... fuel injection ECU.'s and the resultant very high cylinder temperatures they run!!.

Why should I be careful buying a "used 3.9 or 4.2"?

Buying Used 3.9, 4.0, 4.2 or 4.6 engines. Please be very very sure if you purchase this 'used engine' You get a written warranty From a reputable supplier, However also realize that although they might refund your money, they cannot replace your wasted time and fitting expenses. (one reason why RPi. will not sell used engines)
You can find more (And some the same) on our V8 general information page

Adjusting end float, mains bearings..

All oversize bearings have oversized thrusts, therefore the crank end float must be adjusted on no 3 ( center) end cap. To do this - take 2 pieces of 1000/1200 emery paper and a flat surface ie glass. Rub down thrusts equally on both sides until a clearance of 6-14 thou is achieved.

Setting up and checking for problems.

{short description of image}First remove advance vacuum pipe from intake and check for positive vacuum when throttle is applied.
{short description of image}Check if (fitted) that the vacuum delay module is not blocked.

{short description of image}Check positive vacuum will pull distributor advance whilst also checking vacuum module is not holed. (when sucking the pipe, the base plate of the distributor should rotate anti-clockwise about 15 deg.)
{short description of image}Check condition of rotor arm for signs of damage or arcing, also check cap and clean contacts (better still fit new)
{short description of image}Check rotor for free play, there should be none, both rotationally and side to side.
{short description of image}Check rotor will turn clockwise through about 20 deg. and smartly retract back to it's home position under good spring tension.
{short description of image}Distributor output is known to be weak so upgrading with our Spark amp is recommended. (see below)
{short description of image}Replace plug leads, preferably with Magnecor. Use good quality Plugs such as NGK BP6ES, avoid fancy plugs, as they don't normally last long.

A check list of common simple issues

{short description of image}.Being sure of TDC' appropriation, with regard to crank indicated timing mark is a must.
{short description of image}Plug gap needs to be 0.8mm - 0.9mm.
{short description of image}Don't use resistor plugs and suppressed leads together.
{short description of image}Std. spec. high street leads may not be able to handle the extra spark KV's'.
{short description of image}Check fuel delivery pressure.
{short description of image}Check Carb. float bowl height.
{short description of image}Check no blocked or restrictive fuel filter in line.
{short description of image}Do you have the fuel return hose (to the tank) connected ?.if so it needs restricting.
{short description of image}Try an alternative coil even if your is new?..

. For other Injection related problems & chipping issues , see relative injection pages.
Never under-estimate the quality of Std, O/E, or High street spec. ignition leads.

A typical e-mail "quote"Thank you for helping me sort out my misfire problem with the amplifier. You may recall when we spoke that I said that the misfire was when on LPG when the engine was cold. You recommended fitting Magnacore leads as well, but as I had new Lucas leads fitted I said that I would try them out with the amplifier first. The result is the engine is sweet as a nut when cold and a definite improvement in power and fuel consumption.

I am very pleased with it and will be recommending other gas users I speak to. Yours sincerely Peter Munday

Below are the graphs for 5.0 and 5.3 litre V8 engines that we have recently had dynode. More info soon

Click the graphs for a more detailed (higher res) version

5.0 litre

5.3 litre

This FAQ Q/A Section is solely for information exchange only, and RPi. or its contributors accept no lability for any issues arising from following up on our printed advise, or subsequent cost that may arise from the same,
For our part we do our best to check all information provided and printed is correct to the best of our knowledge. And as V8. specialists for 15 years we don't get it wrong often.

links to other FAQ pages
[ V8 Engine Fitting Information ] [ Rover 3.5, 3.9, 4.2 to 4.6 Conversion ] [ LPG Conversion details ] [ Fuel Injection Section ]
[ Weber 500 & SU Carbs ] [ Mallory Ignition Systems ] [ General Engine Problems ] [ General Information ]

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Prices & stock are subject to change without notice. Information and advice, as always, is free.

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