Edelbrock 500 on RV8 4.6

[desertrover]

Hello,
years ago, when I switched from Holley to Edelbrock, I had the Edelbrock st up in a workshop by a specialist for US cars.
As I now changed the heads, the cam and converted my dizzy from dual point to unilite, I thought it might be a good idea to have the Edelbrock jets and needles/spring kit ( 1486 ) as the Landy goes on an overlandtrip to Kenya from the 27th of december.
Today the kit arrived.
So I was nosy and opened the carb to see what set up the specialist has done, because the set up Rpi ( when I bought the carb ) told me would be best didn´t work.
I just took out the needles and springs and what?
The specialist used different springs and needles on the primes.
one side was ( as Rpi told me ) 65X52, the other side was 57x49.
The springs are different also. I didn´t check the jets until now.
The q is: Is that normal to use different needles and springs?
I would say "no".
What do you mean?!
Many thanx.
Btw: The car was ok for the last years.
Cheers
Stephan

[sidecar]

What they have done to your carb in my humble opinion is complete rubbish! The 65-52 needle is standard and was too rich on cruise on my 4.6, and on my old 3.5 and on every other 3.5 that I've worked on. The spec of your engine will be different from mine so that might have an effect but if I was a betting man I'd say that the standard 65 is still too rich.

Regardless of the spec of the engine both sides of the carb should be setup the same, the other needle is mega rich assuming that both sides of the carb have the same jets fitted. (if not that's still bad!)

A good starting point if every other setting is standard is 67-55. This is a touch lean on the power step for max BHP but not too lean to do any harm. I've modified a set of needles so that they are 67-52 along with fitting 107 secondary jets. My motor is stage III so needs to run fairly rich when my foot is on the floor to keep everything nice and cool. I think that there is a 68-52 needle but that might be too lean on cruise.

Pete

[kiwicar]

Don't know about the details of jet sizes but both sides should be the same on a V8, especially if it is to go on a dual plane manifold. Might be different on a straight 6 if the manifold has the carb off set but on a V8 both the same.
Mike

[desertrover]

So today I switched to the advised 67X65, I just have to check what jets are in the carb. Standard is .86, but I think .83 are fitted because the car has some probs to get running without flooring the throttle to much.
When I try to get off as I´m used to the engine goes done but not off.

What doe the numbers say: 65X52 or 67x55.
One is the thickness of the needle ( the firts # ) but the second?
and is it in inches?
I know how to translate inches to the metric system. But are the #s inches or a edelbrock specific thing?

[sidecar]

So today I switched to the advised 67X65, I just have to check what jets are in the carb. Standard is .86, but I think .83 are fitted because the car has some probs to get running without flooring the throttle to much.
When I try to get off as I´m used to the engine goes done but not off.

What doe the numbers say: 65X52 or 67x55.
One is the thickness of the needle ( the firts # ) but the second?
and is it in inches?
I know how to translate inches to the metric system. But are the #s inches or a edelbrock specific thing?

The needle that I suggested was 67-55 not 67-65! (I don't think that there is a 67-65)

Anyway both of the numbers are the diameter of the needle in thou of an inch. The smaller number is the power step and is at the tip of the needle, the bigger number is the diameter further up the needle and is the cruise step.

If you have those needles fitted and 83 primary jets it will be too lean to run properly. Don't be fooled by a small change in jet or needle size, it makes a big difference to the mixture. By the way the jet will have 383 or 386 on it etc, the 3 just means that the jet is for a 500 carb, the 83 or 86 is the diameter of the hole in the jet. The numbers are REALLY difficult to read! If you are running 83 jets and the needles that I suggested you will be at point "10" on the edelbrock chart, this is very lean. Point "6" is what I suggested. (even going to point "11" maybe too lean)

You really MUST take the carb apart and find out what primary and secondary jets are fitted, if you don't you won't have a clue what the mixture is. Remove the air filter stud before you take the top of the carb as it will rip the gasket.


I was helping a guy on the Cobra forum, he just could not be bothered to pull the carb apart and when he tried the needles that I sent to him they did not work....it was a total waste of time!

The edelbrock website has a chart that allows you to compare one needle/jet combination with another but it does have one or two errors in it! You could do it yourself, work out the area of the jet and the area of the needle, subtract the needle area from the jet area and what's left is the size of the ring shaped hole that the fuel can flow through. Remember that the needle has two sizes, one is for cruise at high manifold vacuum, the other is the power step when the vacuum in the manifold drops. You can also mess about with the seconadry jet to change the mixture when the secondary chokes start to open and for WOT.


Here is a calculator thingy to help compare jet and needle combinations:-

http://www.302w.com/Edelbrock-Carbureto ... lator.aspx

Regards,

Pete

[desertrover]

Hi Pete,
many thanx, I checked the jets and they were .83 . I´m now changing to .86 .
I have the Edelbrock chart.
The Rpi suggestion was "11" and that was not drivable very well.
You´re right, was a mistake of mine, I used 67x55 needles.

My engine specs are:
4.6l with 4.6 heads ( chambers 26cc ), the heads I´ve ported and polished myself to gasketsize and behind the valves I cleaned and ported/polished them very well.
Valves are standard size, valve guides are also standard, springs are Piper and the lifters also.
Cam is a piper 270/108.
This is an older one I bought new on ebay.
I think the timing is the same as the newer specs ( 28 64 64 28 ), duration is 272° but the lift is a bit more at .445".

[sidecar]

Hi Pete,
many thanx, I checked the jets and they were .83 . I´m now changing to .86 .
I have the Edelbrock chart.
The Rpi suggestion was "11" and that was not drivable very well.
You´re right, was a mistake of mine, I used 67x55 needles.

My engine specs are:
4.6l with 4.6 heads ( chambers 26cc ), the heads I´ve ported and polished myself to gasketsize and behind the valves I cleaned and ported/polished them very well.
Valves are standard size, valve guides are also standard, springs are Piper and the lifters also.
Cam is a piper 270/108.
This is an older one I bought new on ebay.
I think the timing is the same as the newer specs ( 28 64 64 28 ), duration is 272° but the lift is a bit more at .445".

I'm sure that you'l find setting 6 is a good base start at least.

Also set the pilot screws up to maybe 2+3/4 which will be way too rich, then wind one of them in slowly, the revs may pick up a little but at some point they will just start to drop again. Stop turning the screw in and open the screw 1/4 of a turn. Do the same "turn in slowly procedure" with the other screw then open it back out 1/4 of a turn. My screws are both 2 turns open.

If your manifold is a 360 jobbie then you have to treat both screws as one screw, do the same procedure as above but turn in each screw 1/8 of a turn at a time then do the same with the other screw. Keep hopping back from one screw to the other going in 1/8 of a turn at a time until the motor just starts to slow, then wind both screws out 1/4 of a turn.

My motor is stage III, I went a bit further with my carb, the needles are 67-52, you can not buy these needles, I modified a set to make them. I also run 107 secondaries. You will need a lambda probe if you want to fine tune your carb to that degree, either that or a rolling road!


Pete

[desertrover]

Many thanx Pete,
I changed the jets to .86 and it runs fine now.
I´ve got a Edelbrock manifold. so that´s not a 360° I think.
I left the secondaries as they were. Perhaps I will go a little richer and try that for acceleration and offroad use, where in some situations a quick step on the accelarator can get you there

[desertrover]

I hope it´s now a littler mor "economique"

[sidecar]

I hope it´s now a littler mor "economique"

It will be!

[desertrover]

Hi Pete,
another q!
How did you alter your needles?
I mean the 67x55 to 67x52? Sanding paper or machining.
My car runs just fine, but accelerationwise it´s a bit worse than it was.
OK I didn´t change the sec jets, they are the standard ones, I ordered some bigger pairs to try.
A change in springs just alters the reaction of the engine, as I understand right.

[sidecar]

Hi Pete,
another q!
How did you alter your needles?
I mean the 67x55 to 67x52? Sanding paper or machining.
My car runs just fine, but accelerationwise it´s a bit worse than it was.
OK I didn´t change the sec jets, they are the standard ones, I ordered some bigger pairs to try.
A change in springs just alters the reaction of the engine, as I understand right.

If you have access to a lathe and the chuck allows you can put the needles in it in such away that the 90 degree bend is poking out of the back of the chuck then it is dead easy. Just spin the needle at quite a fast rate and hold a steel ruler which has a layer of 600 wet and dry wrapped round it up against the thinner bit of the needle. Gradually thin the needle down to whatever size you want. A "52" needle is 52 thou. You can polish the needle with a bit of metal polish to finish the job.

I do not have a lathe so I found some thin brass tube (The stuff that you get in model shops) it was nearly the right diameter I "swaged" it out with the shank of a pop rivit with a point ground onto one end. I then cut the needle in two about 10mm below the 90 degree bend. I could then spin the pointy bit in my pillar drill and do the thinning down that way. Finally using the brass tube (about 10mm long) I could make a sleeve and solder the two bits of the needle back together!

I think that there is a 68-52 needle, the 68 bit might be just too lean on cruise but you could thin that down to 67 thus making a 67-52.

This is the one big problem with these needles, you can never find a setting that suits both cruise and power... well I could not anyway!

The secondaries seem a lot less sensitive than the primaries, I went up in size quite a lot before my lambda probe noticed the difference. The jets in my secondaries are not even ment for the 500 carb, they are 407's which are 107 thou in size. Repower sell them, they are only a couple of quid for a set so you could buy a few different sizes.

I never had much luck with the springs, I never notice the difference, you could just say that the 4.6 lump will probably make more vacuum than say a 3.5 so it might need slighty stiffer springs to get it onto the powerstep soon enough. I just stuck the silver springs in!

HTH,

Pete

[desertrover]

Now I calculated all the possible jet spring combs to have the fuel "flow".
Results:

Sidecar:
.086 jets with 67x55 needles: cruise 2,95 mm² flow/ power 4,43 mm² flow

Rpi:
.083 jets with 65x52 needles: cruise 2,7 mm²/ power 4,24 mm²

"twisted setup of my "tuner"":
one side
.083 jets with 65x52 needles
other side
.083 jets with 57x49 needles: cruise 3,2 mm²/ power 4,4 mm²

These figures are the sums of the two venturis on stage 1!

As you can see, Rpi is the leanest in power and cruise, so can´t be to rich at cruise as said above.
As you can see, the set up of my tuner is the same( sidecar ) in power, but too rich in cruise.

[jefferybond]

The Rpi suggestion was "11" and that was not drivable very well.
You´re right, was a mistake of mine, I used 67x55 needles.

I used RPi's suggested settings initially on my 3.5, and it also didn't work well - too lean. In fact I had to richer than the stock setting to get it right.

I think the requirements of every engine are different when you consider exhaust manifolds, CR, cams, air filters etc, so when RPi claim to know the best settings purely based on engine size I don't believe them!

Jeff

[sidecar]

The Rpi suggestion was "11" and that was not drivable very well.
You´re right, was a mistake of mine, I used 67x55 needles.

I used RPi's suggested settings initially on my 3.5, and it also didn't work well - too lean. In fact I had to richer than the stock setting to get it right.

I think the requirements of every engine are different when you consider exhaust manifolds, CR, cams, air filters etc, so when RPi claim to know the best settings purely based on engine size I don't believe them!

Jeff

Yep, I agree the RPI settings are no good!