Edelbrock 500 jets n stuff

[Richard P6]

Been having a play with a calibration kit and a great piece of kit called a Stack wide band Lambda gauge.

I have started off with the carb with 83 jets and 62/52 rods.
This is how I bought the car and this set up gives a 4% leaner than stock (LTS) in cruise and 10.8% LTS in power.

Set up 83 62/52 4% LTS cruise 10.8% LTS Power

This gave me an A/F ratio on a rolling road of up to 14.3 at 3,000 rpm and levelling out at 13.2 at higher revs. Didn't have the gauge then so don't know what it was like in cruise, although it did run ok.

I then tried some 83 jets with 63/47 rods.

Set up 83 63/47 7.9% LTS cruise 0.26% LTS Power

This was a stage leaner in cruise, but a lot richer in power. The car did run better but the mpg went down to 22mpg from 26. So, on went the gauge.

This set up was giving me around 14 on cruise and part throttle acceleration, but when I booted it, it went straight to 10. It may have been richer, but the gauge only reads to 10.

The cruise seemed ok, could be a little leaner, but the power mode had to be leaned down, so I tried: -

Set up 86 67/55 8.3% LTS cruise 6.8% LTS Power

So a little leaner on cruise but a lot leaner on power. This didn’t make a lot of difference. Cruise was still 14 or so, the manual advises 13 at tickover up to 15.3 at 3,000 rpm. Power was still off the scale at 10 but was bouncing up to 11.5 or so.

In desperation to get the power A/F right I tried the RPI set up: -

Set up 83 65/52 16% LTS cruise 10.8% LTS Power

At cruise it runs at 14-15.5 (2,000 rpm) and at WOT runs between 11.5 and 13 so not too bad. Unfortunately it has a very bad lean spot on part throttle. When cruising along, the merest hint of throttle makes the gauge hit 16 (all it reads to) and the car hesitates. I have set the pump to its middle hole, tried it again – no difference. I tried to nearest hole to the carb, lost the clip, spent 4 hours looking for it, taught the local wildlife some new words, and then made one out of a paper clip!!! Still not solved this. Is it too lean on cruise, or is the pump tired, or am I missing something?

The confusing bit is this – why is the 10.8% LTS power set up still running a little rich at WOT, when the same setting when I bought the car, showed it running lean? I have fitted a 3” filter in place of the 2” one, fitted a heat dissipator gasket, removed the angle plate, but not much else.

[JSF55]

Have you tried replacing the jets in the secondaries with something a bit smaller? that will bring the WOT reading down a bit

[sidecar]

Sounds like you are having a lot of fun! I went through a similar set of tests but using an Innovate LC1. At the end of the day I don't think that you can be too critical of what the AFR figures are, you have to find out what suites your engine. Des Hammills book states that you can run a cruise AFR of 15:1 but there is no way that either of the two engines that I've had in my Cobra would run that lean. The RPI setting is too lean on cruise, that is why when you touch the throttle it hesitates.

Basically run the cruise as lean as you can before the engine response becomes bad. When in cruise the lean mixture will not harm the engine as the effective cooling capacity of the radiator is so great it will not allow the engine to over heat. The lean mixture helps MPG, it also cleans up the plugs.

Even in power mode and under acceleration if it's a bit lean I don't think that it would do any harm. (13.5-14:1 being a bit leaner then say the 12.5-13:1 that would give maximum acceleration. 14.5-15:1 being far too lean)

The WOT is a different kettle of fish, you don't want that too lean or you'll hole a piston if you hold it at WOT for long enough.

10:1 is also bad as you will get bore wash.

Here is some stuff that I wrote, please note that I have now gone down on the secondaries but I can't remember what to!

http://how-to-build-a-pilgrim-sumo.wiki ... ing-system

Like JSF55 said I think you are going having start messing about with the secondaries. They start to have an effect as soon as the secondary plates start to open. Their effect gets bigger the more more the secondaries are opened. I'm sure that you know this!

BTW don't use the Edlebrock chart to work out jet changes, it is full of mistakes! (Although I suspect that you already know this to!)

Pete

[Richard P6]

Thank you JSF55. I will get to the secondaries when I have the cruise and power setting right.

Many thanks Sidecar.

I have a copy of Des Hammill's book heading my way but am on holiday for a fortnight so it won't be much use until I get back.

I have read your stuff and found it very useful. In fact using your information I have made up a spread sheet with all of the jets and rods I could find and am using it to find set ups to try. The next one will be: -

Set up 86 jet 68/57 12.6% LTS cruise 11.6% LTS power.

This will richen up the cruise from 16 to 12.6 and lean down the power only a little. Problem is the rods are not included in the calibration kit

I have put new springs in, same type but I had some new orange ones in the kit so used them. I might try to go a stage stronger on these to see if that does anything.

[sidecar]

Thank you JSF55. I will get to the secondaries when I have the cruise and power setting right.

Many thanks Sidecar.

I have a copy of Des Hammill's book heading my way but am on holiday for a fortnight so it won't be much use until I get back.

I have read your stuff and found it very useful. In fact using your information I have made up a spread sheet with all of the jets and rods I could find and am using it to find set ups to try. The next one will be: -

Set up 86 jet 68/57 12.6% LTS cruise 11.6% LTS power.

This will richen up the cruise from 16 to 12.6 and lean down the power only a little. Problem is the rods are not included in the calibration kit

I have put new springs in, same type but I had some new orange ones in the kit so used them. I might try to go a stage stronger on these to see if that does anything.

Hi Richard,

Thanks for the compliments!

I found that a 68 rod was too lean, it is only 1 thou bigger than the 67 that I use but it does make a difference. Having said that you should try anything and everything as your engine is not my engine! Keeping clear notes it the key!

BTW there is a lot of BHP and MPG locked up inside your dizzy, the standard Rover settings are a pile of poo!

Keep up the good work!

Pete

[CastleMGBV8]

Richard,

good advice from Pete whwas very helpful when i recalibrated my Edelbrock 500 on my new 4.35 engine.

Couple of points, A change of step up springs made a big difference on my engine which would not idle below 1500 RPM because of the low vacuum created by the long duration cam I am using and the stage 3 big valve heads probably had some effect.

To check which springs you need, measure the vacuum at idle and this will give you the information so you can select the correct springs and this will have an effect on idle and cruise but not WOT.

Secondly it is important to optimise you ignition set up as if your not burning the fuel efficiently you will not get accurate readings from the wide band.

Kevin.

[sidecar]

Richard,

good advice from Pete whwas very helpful when i recalibrated my Edelbrock 500 on my new 4.35 engine.

Couple of points, A change of step up springs made a big difference on my engine which would not idle below 1500 RPM because of the low vacuum created by the long duration cam I am using and the stage 3 big valve heads probably had some effect.

To check which springs you need, measure the vacuum at idle and this will give you the information so you can select the correct springs and this will have an effect on idle and cruise but not WOT.

Secondly it is important to optimise you ignition set up as if your not burning the fuel efficiently you will not get accurate readings from the wide band.

Kevin.

Hi Kev,

I have not found that the springs make much diffrence on my engine but you are completely right, if they are too strong to ever allow the vac to pull the rods down you will have BAD problems. Half of the carbs function will be lost!

We must have posted at the same time vis the ignition!

Pete

[Richard P6]

My igntion system comprises of a new Rover contactless dizzy from an SD1, (RPI told me it was a new one when they fitted it last September but I think it is one they have had remanuactured, so as good as new), an RPI power amp, magnecor 8mm leads, and NKG BP6ES plugs set at 0.8mm, and connected to the left hand (when looking from the front) port (higher one) on the Eddy. Static timing is presently set at 6 BTDC

There are NO markings on the vacuum unit showing advance figures.

I realise that the ignition side will have an effect but cannot adjust (sort) this, and the secondaries, and the primaries, and everything else at the same time - it is just too confusing.

So I have decided to get the obvious sorted first and have rewired the low tension circuit which made a great difference (it was rigged up with those horrible little blue connector things), junked the Mallory twin point for a new SD1 dizzy which again made a big improvement, then fitted a Mr Gasket 98 heat dissipator and changed the 14 x 2" air filter for a 14 x 3" K&N. I then resited the regulator which now sits well away from those very hot mainfolds and more importantly keeps the incoming and outgoing fuel pipes away from them too.

I am now (slowly cos I don't get much time at present) setting up the primary jets and rods, will look at the secondaries if the cruise and power are ok but WOT is out, then have a good look at the the dizzy and try to set up the advance curve.

I can always go back and tweak the carb afterwards, or put the angle plate back in, or rig up some ducting for the air intake, or whatever needs doing.

Good fun this

[CastleMGBV8]

Pete/Richard,

The spring change to guessed(I do not have vacuum gauge) weakest spring allowed me to get the idle down to 800 RPM from 1500 RPM and with the rod and jet change the drivability was improved enormously.

The engine will now allow it to coast along at 35 MPH in 4th gear approx 1500 RPM and will pull cleanly away without changing down with no hesitation whatsoever, drop it down to second and give it a bootfull and it will accelerate hard with seamless increasing power as the revs rise.

Carb spec is silver step up springs, .086 Jets and .067 x .055 Rods on the primaries with the secondaries currently left stock although some people have changed these to one size smaller at .092. As in normal road use you only use the primaries I was not too concerned about it in the knowledge that at WOT it might be a bit rich, but safe from an A/F ratio point of view.

I still have the mod to do to the Performer manifold, ie drilling the two holes in the thermostat housing area which are apparently a standard design in the Offenhauser and original Buick and Rover manifolds the lack of these causing the thermostat not to open properly.

Kevin.

[JSF55]

Have you set the floats correctly on the carb, not a big job to do and recommended by someone else on here, mine were miles out, so much so that last log i run was all rich, i'll be looking for some dry weather to take it out and make a few changes, time .... i wish i had somemore of it

[CastleMGBV8]

Richard,

6 degrees initial advance is nowhere nearly enough, if you do not want to play around with advance curves at the moment set the initial at 10 degress and permanently disconnect the vacuum and block the port on the carb.

This will get you much closer, but the curve will still be too slow and on all the Lucas dizzys, they do not give full advance to quite late, anything up to 4500 RPM and you really want it all in by around 3000 RPM even in a standard engine.

You will probably get a couple of degrees more than you need at full advance but it will not do any harm as you will be past peak torque.

JSF55 mentioned the float heights and drop which I forgot, this is important to insure correct fuel delivery and a relatively simple job whilst you have the top off changing jets.

Kevin.

[sidecar]

Depending on the dizzy and the engine size you might find that that you can set the dizzy up quite well without having to do too much work.

The book that you have on order gives alot of details on setting up the ignition timing.

If you have a 3.5 lump you can go for 14 static, this really does improve the low RPM performance, on two dizzies that I setup for friends on their 3.5 lumps 14 static gave 36 all in which just dandy! (on a 3.5)

The bob weight springs are far too stiff as standard unless they are knackered, they quite often are! The Real Steel spring kit has suitable springs.

Surprisingly I have written and article on setting up dizzies!

Here it is:-

http://how-to-build-a-pilgrim-sumo.wiki ... by-members

I MUST stress that unless you find true TDC and set the damper pointer up properly you are wasting your time!

Pete

[Richard P6]

I have connected a vacuum gauge and it reads 18 ins/hg at 650rpm.

I set the floats at 11mm a while ago and also the fuel pressure to 5-6 PSI at tickover.

Not quite sure how this helps with the springs, so have put in the pink ones which are rated at 7ins/hg. The hesistation is not as pronounced, almost gone altogther in fact. Might try the silver ones.

Now, I have always been resistant to disconnecting the vacumm, but thought I would give it a go anyway . I set the static to 12 BTDC which was 13 after tightening it up - why does it do that?? and then blanked off the port by putting a bolt (not a set screw ) into the pipe.

Set the idle screws to give 13 on the gauge then set the tickover to 600rpm.

Cruising at a constant speed at 2,000rpm now shows 14.5 to 15, easing down on the power drops momentarily to 16 and then goes to 13.5 to 14, and WOT sits around 11.5.

Just driving around normally the gauge will now and again go right off the scale at either end, i.e. it will sometimes go to 16 for an instant, and other times will go to 10 - is this normal?

I will drive around like this for a while and see how it goes. When I get back from holiday, my company is moving into a 2,000' unit in Sheffield so I will be able to get some timing tape on and map the advance curve - I take it that it is now just a matter of sitting the revs at a certain point and reading the timing marks, then making a graph. I can't do this at the moment as the neighbours can be easily upset by reving a V8 at 5,000rpm

[sidecar]

I have connected a vacuum gauge and it reads 18 ins/hg at 650rpm.

I set the floats at 11mm a while ago and also the fuel pressure to 5-6 PSI at tickover.

Not quite sure how this helps with the springs, so have put in the pink ones which are rated at 7ins/hg. The hesistation is not as pronounced, almost gone altogther in fact. Might try the silver ones.

Now, I have always been resistant to disconnecting the vacumm, but thought I would give it a go anyway . I set the static to 12 BTDC which was 13 after tightening it up - why does it do that?? and then blanked off the port by putting a bolt (not a set screw ) into the pipe.

Set the idle screws to give 13 on the gauge then set the tickover to 600rpm.

Cruising at a constant speed at 2,000rpm now shows 14.5 to 15, easing down on the power drops momentarily to 16 and then goes to 13.5 to 14, and WOT sits around 11.5.

Just driving around normally the gauge will now and again go right off the scale at either end, i.e. it will sometimes go to 16 for an instant, and other times will go to 10 - is this normal?

I will drive around like this for a while and see how it goes. When I get back from holiday, my company is moving into a 2,000' unit in Sheffield so I will be able to get some timing tape on and map the advance curve - I take it that it is now just a matter of sitting the revs at a certain point and reading the timing marks, then making a graph. I can't do this at the moment as the neighbours can be easily upset by reving a V8 at 5,000rpm

My dizzy adds a degree or two when the bolt is tightened, I guess the dizzy is being pushed into the casing a bit more and as the gears are "skew gears" this must cause the extra degee or two.

As you have a lot of vacuum you could try some stiffer rod springs otherwise you may find that the rods stay in cruise mode for too long. To be honest I'd bung in the orange ones. If you have hesitation its because the setup is too lean. The Rover lump is too old a design to be able to burn a 16:1 mixture, it will see that as fresh air!

The flicking to 10:1 might be the accelerator pump dumping its load, they bung in far too much for a smallish V8. If the throttle has not been moved when the gauge flicks to 10:1 then I don't know what the casue is!

I guess your motor is fairly standard, my lump won't run at 600 RPM at all!
(nor will it pull 18 inches of vacuum)


Hopefully you should not have to rev the lump to 5k, rev it until all the advance is in. (vac disconnected), get someone to note what the revs were. You will need some sort of hand signalling agreement when doing the test! If you do have to rev it to 5k then you really should change the bob weight springs to get this down to 2700 RPM. If the mechanical is all in at 5k then losing the vac system may well cause a loss in performance.

Really the vac system just does not work too well with the Eddy carb. (It was Kevin that found this out by researching on the web)



Pete

[Richard P6]

Thank Pete

I'll get hold of a pair of 68/57s and see what they do.

The engine is a 4L cross bolted stage one engine with an Offenhauser dual port manifold, Weber four barrel carburettor, stage one unleaded heads, Piper RP4 high torque cam and followers, steel rockers, Cloyes duplex timing chain and sprockets, lightened and balanced flywheel, high torque gear reduction starter motor. A&P electronic ignition power amp. Magnecor 8mm plug leads. 14 x 3" K&N air filter. Facet red top fuel pump. Malpassi fuel pressure regulator. J&P stainless exhaust manifolds.

I took the vacuum measurement from the lower port on the front of the carb, but usually run the dizzy from the higher one.

The engine is designed as a road engine for pottering about, but will upset the GTi brigade when I want to - it is not used in any form of competition.

Oh well off on my hols -