Rover v8 4.6 rolling road tuners Suffolk

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V8dax2017
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Rover v8 4.6 rolling road tuners Suffolk

Post by V8dax2017 »

Can anyone recommend a v8 rolling road engine tuners near Suffolk? I have been after having my carb professionally set up for a while now just not sure where.

Thanks Sam



sidecar
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by sidecar »

V8dax2017 wrote:
Mon Apr 09, 2018 9:54 am
Can anyone recommend a v8 rolling road engine tuners near Suffolk? I have been after having my carb professionally set up for a while now just not sure where.

Thanks Sam

What carb is it? If its an Edelbrock then be aware that hardly any rolling road operators know how to set this type of carb up. They are happy to take your money though and then thrash your are on the rollers, they then declare that your carb is running just fine!

I like the Edelbrock carb, I'm just a cynical old git these days!

V8dax2017
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by V8dax2017 »

It is an Edelbrock yes, I will bare that in mind thank you very much.

James 33
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by James 33 »

Rpi engineering in Norfolk would be your best bet. They supply the Edelbrock carb and specialise in the Rover V8.

sidecar
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by sidecar »

James 33 wrote:
Thu Apr 12, 2018 4:56 pm
Rpi engineering in Norfolk would be your best bet. They supply the Edelbrock carb and specialise in the Rover V8.
Sorry to disagree but they know F-all about the carb even though they sell it! I have seen the results of the jet and rod combination that they recommend, it usually runs the engine so lean on cruise that it is barely driveable. I have spoken to RPI and have told them that their setup does not work but they just tried to flog me their 'fix everything' ignition amp!

I have done loads of work on these carbs, I have made my own rods and I am now modifying the standard primary boosters so that they are annular boosters similar to the ones that they fit to their AVS2 carbs. I am still testing my new boosters but they do seem to be very good although the carb needs totally re-calibrating with these boosters

I really don't like offering carb setups over the web but if you are using an Edelbrock Performer manifold then you could try 83 jets with 65-47 rods. This setup is 16% leaner than the stock setup on cruise and is virtually as per the stock setup on the acceleration circuit. My setup used one-off rods and was 17% leaner on cruise and as per stock on acceleration. (So both setups are virtually the same). I would use the silver piston springs and the secondary jets will need be around 80 to 83. If you are running a manifold other than the Edelbrock Performer then I have no idea if the setup that I have given you will be any good. If you are running a dual port manifold on a 4.6 then you will get very poor performance with that setup.

The stock 500 carb setup is way too rich for any RV8, you are wise to get this sorted ASAP as the bore wash from the rich mixture will kill the piston rings.
Last edited by sidecar on Thu Apr 12, 2018 7:58 pm, edited 1 time in total.

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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by sidecar »

I posted up the stuff below on the Edelbrock forum, it will give you a good idea about setting these carbs up, it mentions a spreadsheet that I use to compare jet and rod combinations with any other setup or against the stock setup, if anyone wants the spreadsheet they can PM me their email address and I'll send it to you! (I worked out all the stuff below because I got fed up of going to rolling roads and sussing out that the bloke knew nothing about these carbs, you are better off buying a lambda probe and setting up the carb yourself in my opinion)


Setting up a Edelbrock Performer Carb.
Ver 1.6


Checks that should be made before doing anything else:-

1. Check that the fuel pressure is no more than 6 PSI
2. Check that the fuel flow is capable of proving enough fuel for WOT by using the following formula. BHP = (Fuel flow in CC per min/4.7).
Measure the flow for 30 seconds then times it by 2. Divide the figure by 4.7, the resulting number is the max BHP that could be made using the maximum amount of fuel that the fuel pump can deliver. You need the pump to be able to deliver 50% more fuel than is required. If 1 litre is required then the pump must deliver 1.5 litres per minute. By the way 1 litre of fuel per minute could make 212 BHP (1000/4.7) but I would want the pump to be able to deliver 1.5 litres for a 212 BHP engine.

3. Check that the air filter setup is suitable, there needs to be enough clearance between the top of the carb and the underside of the filter lid, the length of air filter stud gives an indication of the clearance. 50mm clearance being the minimum required. If the air filter stud is 25mm tall then the lid must be way too close to the top of the carb!
4. Check that there is some sort of throttle stop, the carb must not be acting as the throttle stop as it will be damaged or the cable will break.
5. Check that the rubber bungs on the carb vacuum take off points are in good condition.
6. Check that the throttle return springs are setup correctly, a poor setup will wear out the carb or kill someone!
7. Check that the ignition system and in particular the vac advance is set correctly.
8. Take the top off the carb and make sure that the float bowls are clean, check the float heights. You can raise the floats 2-3mm above the standard 10.5mm, this will lower the level of the fuel in the float bowls, it increases what is known as the spill height which helps stop fuel surge when cornering and braking. Really you should clean out the carb if it looks dodgy! (Including the idle screw circuits and booster air vents and jets, the vents DO get blocked and when they do it totally messes up the function of the carb). Make a note of the rods and the jets in the primaries AND secondaries, also note the colour of the piston springs! Refit the top of the carb then fit the pistons, piston rods, and springs, do not try and refit the top of the carb with the rods already in place as it is impossible to get them to go through the primary jets.

A very quick guide on how the actual carburettor functions:-

The carb has a set of primary venturis and secondary venturis, the secondaries only start to operate when the primaries are half open, as the primaries go through the second half of their opening phase the secondaries open so that both the primaries and secondaries are full open at the same point in time. (Full throttle). The secondaries also have an air valve above them that opens independently from the throttle linkage, the vacuum in the carb opens the air valve, the idea behind the valve is to allow the engine itself to have some control over the functions of the secondary venturis. Do not remove the air valve in the belief that it restricts the air flow because you will end up with a lean bog that is so large the engine will actually quit running completely!

The primary venturis are fed by the primary jets but the actual fuel flow that the jets can deliver is also controlled by the piston rods, basically the rod has two diameters which can be measured in thousands of an inch, the jet number is also thousands of an inch. A 3 series jet may have a number such as 386 stamped on it, this jet has a diameter of 86 thou. A 4 series jet is a jet over 100 thou in diameter, a 413 jet is 113 thou in diameter. Jets increment in size by 3 thou, the smallest jet is a 77, the biggest is 113. Some ‘odd’ jets exit that don’t follow the increment by 3 rule, these are jets that have been fitted to carbs at the factory, a 100 jet is an example of such a jet. The piston rods have two numbers stamped on them, these are the two diameters in thou of an inch, a 65-52 rod has a thick (cruise) diameter of 65 thou and an acceleration or power mode circuit diameter of 52 thou.

The fuel flow to the primary boosters is controlled by the cross sectional area of the ring shaped hole or annulus that is formed by the hole in the jet with the piston rod poking through the jet. You can now see that it is quite possible to have a smaller cross sectional area even if you increase the size of the jet if you then use a much thicker piston rod, this would actually lean the carburation off.

You can also see that it is now possible to compare one jet and rod combination against another combination just by comparing the two cross section areas of each combination. An Excel spreadsheet can be used to do this sort of calculation, the spreadsheet can give you a percentage change for a jet and rod combination compared to the standard factory setup. One thing that an Excel spreadsheet won’t do is take into account the ‘wall area’ of the annulus and this could actually have an effect on the fuel flow. You could use a very large jet and a very large rod which will give you a very thin section annulus with a lot of wall area and cross sectional area, it could have the same cross sectional area as a much smaller jet with a very small rod which gives you an annulus with less wall area. The two annulus’s could have the same cross sectional area but the one with less wall area will flow more fuel. Having said all that I’m not sure that the Edelbrock calibration charts take this into account, they do seem to have errors in them and they miss out some perfectly good jet and rod combinations.


Using the above information you can compare any jet and rod combination against the stock setup to work out whether you are going richer on leaner than the stock setup on both the cruise and acceleration circuits of the carb. The other thing to note is that the primary side of the carb has two modes of operation which are controlled by the vacuum in the manifold. When the vacuum is high the engine can only be under a light load, it must just be cruising along with the throttle just cracked open, under these conditions the Air Fuel Ratio (AFR) can be leaned off to increase MPG and reduce bore wash, plug fouling and pollution. The pistons in the carb are pulled down into their low position due to the high vacuum, they actually compress the springs that are trying to push them up, the rods are connected to the pistons so they are also pulled down which pushes the thicker part of the rods into the primary jets, this reduces the cross sectional area of the annulus which then reduces the fuel flow to the primary boosters and therefore leans off the AFR.


When more load is placed on the engine such as during acceleration a richer mixture is required, the vacuum in the manifold is reduced and as long as the correct piston springs have been fitted the springs will now push the pistons up into their high position, now just the tip of the rods are poking into the jets and because the tips have a smaller diameter than the thicker part of the rods the fuel flow will increase which causes the AFR to be richer.

The obvious problem!....One annoying problem with the way that the carb works is that you can end up in a situation where you need to adjust just one of the two circuits controlled by the piston rods, either the cruise or acceleration circuit needs changing and you need to do this without making a percentage change to the other circuit but you cannot find a jet and rod combination that will allow you do this! I have been faced with this situation many times which is why I made a tool that allows me to spin a piston rod in my lathe, I then use VERY fine abrasive paper (wet and dry) along with WD40 in order to reduce the diameter of the part of the rod that needs changing. You must use a good quality imperial micrometer to measure the diameter of the rods, I don’t think that a digital vernier gauge is good enough for this type of work. If I modify a rod I always then use a small needle file to file off the numbers that are stamped on the rod as they no longer give any useful information!

Air Fuel Ratios (AFR):-
The air fuel ratios for petrol (gas) fall into quite a narrow range for 4 stroke engines and the ratios a broadly speaking the same across all 4 stroke engines. (Accept lean burn engines)

The idle circuit…This is one area where the AFR can differ from engine to engine, it can be affected by the duration of the camshaft and the design of the exhaust amongst other things. Luckily it is easy to find out what your engine requires just by listening to the way that the engine responds as you turn the two fuel screws at the front of the carb. The actual AFR figure is not important in this case, the idea is to adjust the carb just to give the engine the AFR that it runs best with when idling. Turning the screws out richens the mixture, turning them in leans off the mixture.

The cruise circuit…
This figure can also differ from engine to engine, a lot depends on the combustion chamber design and the ignition system. Many other factors will also have an effect on the AFR that the engine can effectively run with but at the end of the day your engine is your engine so you just have to work with what you’ve got. The magic figure that people like to talk about is an AFR of 14.7:1 but really this is of no use to anyone, you should aim to run the engine as lean as possible when the car is just cruising along and placing very little load on the engine, hopefully you can obtain a figure that is leaner than 14.7:1. The engine will soon let you know if you have gone too lean as the throttle response will become poor, the car may not even be drivable because it will have big lean bog flat spots, the engine will stumble.

The acceleration (power mode) circuit… The AFR when accelerating on the primary side of the carb only needs to be around 12-12.5:1. You do need an exhaust gas analyser in order to be able to set this circuit up, without one you have no way of setting up this circuit or the WOT circuit.

The Wide Open Throttle (WOT) circuit… The AFR at high RPM and WOT needs to be around 12.8-13:1. When setting up this AFR you must not go leaner than 13:1, the shape of the graph for BHP verses AFR is not symmetrical at all, if you run the engine a little rich you may lose one or two percent of the potential BHP that your engine could make but if you run the engine just a touch too lean you could lose ten times as much BHP as running it a little rich. Remember that 14:1 is still technically a rich mixture because it is richer than the ‘magic’ 14.7:1 but it is too lean to make good BHP at WOT


Setting up each of the circuits of the carburettor.

First phase, the idle circuit
Start the engine and let it fully warm up. Stop the engine and wind in each idle mixture screw, make a note of the turns. Then wind them both out to some arbitrary figure which is more than the figures that you noted, maybe wind them out three and a half turns. Start the engine then slowly wind in each screw ¼ of a turn at a time swapping from one screw to the other, listen to how the engine responds, it may well speed up as the mixture strength gets near what the engine wants, at some point the ‘bark’ will just start to drop from the exhaust, the engine may well slow down a few RPM and may rock on its engine mounts, at this point wind each screw out ¼ of a turn. Edelbrock suggest screwing each screw in until the engine drops 20 RPM and leaving the screw in that position, I think that my method will end up with the screws more or less in the same position as Edelbrocks setup method anyway. Set the idle speed then kill the engine. Wind each screw in and note the turns before resetting them back to their final position, if one is in ¼ more than the other then bring it out so they are both at the higher figure. The AFR may well be 12-13.5:1, it could be leaner but the figure does not really matter, the engine has ‘told’ you what it wanted, you just had to listen!


Second phase, the cruise circuit
Connect a vacuum gauge to the non-timed port of the carb which is the lower of the two small vacuum take off points, if the ignition vac canister is connected to this port you will need a tee piece. Fit an exhaust gas analyser (lambda probe) to the exhaust pipe of the car with a suitable AFR gauge inside the car.
Take the car for a drive, find a flat road, it must be flat, not going up-hill or down, drive at a steady throttle at around 50 MPH, try to keep the throttle in a steady position, the vacuum gauge is very useful here because it is very sensitive to changes in the throttle position, try to keep the vacuum level as high as possible whilst maintaining a steady 50 MPH. Do not drive too slowly because you could end up driving the car on the transition slots of the carb which is not the correct circuit for this test. Make a note of the vacuum level in the manifold during this test, it may well be around 15-17 inHg, make a note of the AFR, if it is richer than 14.5:1 then you should consider trying a leaner cruise setup. If the AFR is around 16:1 then it may well be too lean. If you are lucky you can just change the rods which means that you don’t need to take the top off the carb, if the AFR was 14.5:1 you would fit a rod that had a bigger cruise diameter but be aware that a 1 of 2 thou increase in diameter could be quite a large percentage change in the annulus cross sectional area. If you cannot find a suitable rod then you need to use the spreadsheet to compare other jet and rod combinations, you could end up fitting a bigger jet and bigger rod which still actually leans the cruise AFR off. You should keep testing leaner and leaner cruise circuit settings until the engine response goes bad then go a fraction richer on this circuit. Note that the Edelbrock calibration charts seem to have step changes of around 4% but I have found that it is possible to hone in on the actual setting down to within around 2%. This is only possible by using an Excel spreadsheet, the Edelbrock charts are not ‘fine-tuned’ enough for this and they do not list every jet and rod combination anyway!


Third phase, the acceleration circuit
Restrict how much the carb can open by some suitable means such as a block of wood under the accelerator pedal so that the primaries are open as far as they can before the secondaries start to open. (The primaries will be half open). You may want to disconnect the accelerator pump arm whilst setting this up so that you don’t flood the engine. It can take a while to sort this out, the primaries must be open as far as possible but the secondaries must not be open at all. Do not fall into the trap of just disconnecting the secondaries linkage as this will allow the primaries to full open without the secondaries opening at all, this is a situation that under normal circumstances the carb would never been in. Connect the accelerator pump arm back up once the ‘restrictor’ has been sorted out.
Drive the car on a suitable road which could have an incline and accelerate as hard as possible just using the primary side of the carb, the throttle stop will prevent the secondaries opening at all, the higher the gear that the transmission is in the better as this gives you more time to take the readings from the vac gauge and the AFR gauge. As you floor the throttle try to take a vacuum reading with the first second of the throttle hitting the stopper, the reason for this is that the vacuum level then might start to rise as the RPM rises, note this reading then take another reading after 2-3 second of acceleration. Hopefully all of the readings fall within a fairly narrow range, let’s say 3 to 5 inHg. (Having someone to take these readings really helps!). The highest reading in our case is 5 inHg which means that you need to fit piston springs that will lift the pistons at 1 to 2 inHg more than the highest reading that you saw, in this case we will need to fit springs the lift the pistons at 6 to 7 inHg. This will ensure that the pistons are fully lifted when you are accelerating the car as hard as possible on the primary side of the carb. If during this test you discover that the springs needed changing then you must make the change and run the test again before you attempt to take an AFR reading. The pistons should not be lifted when the carb is operating in cruise mode, the vac reading that you noted down during the cruise test should be a lot higher than springs rated figures. (Edelbrock list the vacuum levels that the different springs operate at). Note that I believe that the carb should be divided up in to two areas, the primary side and the secondary side, the primary jets and rods effect the AFR’s for that side of the carb and that is why during the acceleration test only the primary side of the carb should be used, the acceleration part of the rod can only be used to make changes to the AFR on the primary side of the carb. During this test it is no good guessing at where half throttle is which is why you must use a throttle stop.
I actually think that even though Edelbrock don’t state that you should setup this circuit when running on the primary side of the carb only if you look at the pistons springs they supply the vacuum levels that the springs operate in all seem to be in the sort of vacuum range that would exist in the manifold when running on the primary side of the carb only. If the secondaries start to operate then the vacuum level drops very quickly to the point where even the weakest spring that they offer would lift the pistons which makes all the other springs redundant. In order to make changes to the acceleration circuit you need to follow the same process for making changes to the cruise circuit but focusing in on the smaller diameter of the rod (The tip of the rod). Fitting a rod with a smaller tip will richen the AFR when the carb is running in ‘power mode’. The Excel spreadsheet allows you to compare one power mode setup against the standard setup and against any other setup. The AFR figure that you are aiming for is between 12:1 and 12.5:1.
The problem that I described earlier can now rear its ugly head, you could end up in a situation where you have found a good setting for the cruise circuit, let’s say 15% leaner than the carbs stock setup but you need the acceleration circuit to be 10% richer than the stock setup but you cannot find a jet and rod combination that gives these figures, if this is the case for you then modifying rods is the only way to get around this. You need to be careful when modifying rods, one thou can make or break a rod, I have setup cars where the cruise part of the rod was 69 thou of an inch and the car was perfectly drivable, fitting a 70 thou rod made the car un-drivable! With the jet that was being used a 1 thou diameter change of the rod actually changed the annulus area by 5% which a quite a lot! In other words in no good guessing at this stuff use a good micrometer and make a note of all of the changes that you try.


Fourth phase, WOT
Remove the throttle stop, set the pedal so that the carb does fully open BUT make sure that the carb and the throttle cable is not being stressed due to incorrect adjustment.
Use a flat or inclined road and open the throttle fully, you also need the revs to be up in the top ¼ of the rev range so up over 4 thousand RPM at least, the higher the RPM the better, make a note of the AFR. If the engine is not running in the 12.8-13:1 AFR range then change the secondary jets and repeat the test, I have found that this adjustment is fairly coarse, I usually go up or down two sizes in order to be able to see any changes to the AFR at WOT. If you don’t like the idea of doing this test on a road then this is where a rolling road could be useful, I don’t think that rolling roads can help when setting up the cruise circuit though because most of them cannot place a steady load on the engine. Also I am not advocating breaking any speed limits during this test, if during this test you feel that you would break the speed limit for the road that you are using then you need to find some other means of carrying out the test!
The primary side of the carb in power mode does of course contribute to the fuel flow at wide open throttle (WOT) but the AFR for WOT is adjusted using the secondary jets which is why it is important to setup the primary side of the carb first.


Fifth phase, acceleration pump
Personally I think that the pump is quite a crude device, I’d try and set it up so that it pumps the minimum amount of fuel it can without there being a lean bog when you boot the throttle in a reasonably high gear. Try flooring the throttle in 3rd gear from 2-3kRPM, feel for a bog and use the exhaust gas analyser to determine whether it was a rich or lean bog. Adjust the accelerator pump to correct the problem. One thing to note is that the higher the vac level is during cruise the more fuel the accelerator pump has to deliver in order to stop a lean bog, this is down to the fact that at high vac levels the fuel that is travelling down the inlet runners will tend to boil into a vapour, this is fine for cruise conditions but when the throttle is floored the vac level drops, the ‘boiled’ fuel condenses out of the air stream and sticks to the runner walls causing a lean bog. The higher the vac level the more the fuel boils into a vapour. (Fuel in the form of a vapour is good for economy running but it is not good for making BHP, fuel that it well atomized is good for BHP!)

V8dax2017
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by V8dax2017 »

Thanks for replies, to be honest I won't be going to Rpi again after all the trouble I had with the clutch they supplied. I am running a edelbrock performer manifold Top dog and have got a jetting kit in the garage for the carb. I have just booked it in with atspeed racing in Essex as they seem to have a great reputation with these carbs but will print off what you have sent. Much appreciated

Sam

stevieturbo
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by stevieturbo »

Dave Walker of CCC and Emerald fame isnt that far away ?

Maybe give him a call ?
9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by scudderfish »

stevieturbo wrote:
Thu Apr 12, 2018 10:12 pm
Dave Walker of CCC and Emerald fame isnt that far away ?

Maybe give him a call ?
I thought he was only interested in doing his own ECUs.

sidecar
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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by sidecar »

The problem that I found when using a rolling road (apart from the operator not knowing anything about these carbs) is that most rolling roads are inertia dynos which means that they can not hold the engine at a steady load, this means that it is not possible to set the cruise circuit up because it is not possible to replicate the load that the engine is under at say 50 MPH. The roller/dyno operator tend to just floor the throttle, check the AFR for WOT and will make a change in the carb for the WOT setting only. On a road car this is not good enough because the car will spend much more time being driven with the throttle just cracked open so the cruise circuit is an important circuit to get right. I'm not saying that they are all like this but the three that I used were, in the end I thought it is better to buy a lambda probe and set the carb up myself. It can take most of a day to set the carb up especially if I have to modify a set of rods. Between my mate and I we have just about every rod and jet that you can get for these carbs but we still end up modifying a set of rods most of the time. (I am very fussy about the AFR's though, using the Edlebrocks calibrations charts would not allow you to be as fussy as me!) AJMHO!

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Re: Rover v8 4.6 rolling road tuners Suffolk

Post by stevieturbo »

scudderfish wrote:
Fri Apr 13, 2018 6:08 am
stevieturbo wrote:
Thu Apr 12, 2018 10:12 pm
Dave Walker of CCC and Emerald fame isnt that far away ?

Maybe give him a call ?
I thought he was only interested in doing his own ECUs.
Can't do any harm to call and ask ? He might well be.
9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

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