cats and there emission reductions

[v8 pete]

is there anyone who know or and direct me to a website that can help

im struggling to get the emissions down on my 4.6 v8 in a westfield
at the moment its a about 3co 2400hc co2 9% and lambda od about .9999

its the hydrocarbons that are the problem .im runnng weber 500 carb
and mallory dizzy .

if i fit cats just for the sva test how much will they bring down the hydrocarbons .
i know they wont last long with carb but just need to get through its first test.

need to know if hc is 2400 what will they go down too
regards pete

[katanaman]

I am no expert on cats but generally they need to be used with injection. Carbs don't meter fuel as accurately resulting in rapid demise of cats. They are a bit on the expensive side for that.

[stevieturbo]

is there anyone who know or and direct me to a website that can help

im struggling to get the emissions down on my 4.6 v8 in a westfield
at the moment its a about 3co 2400hc co2 9% and lambda od about .9999

its the hydrocarbons that are the problem .im runnng weber 500 carb
and mallory dizzy .

if i fit cats just for the sva test how much will they bring down the hydrocarbons .
i know they wont last long with carb but just need to get through its first test.

need to know if hc is 2400 what will they go down too
regards pete

Those numbers dont make sense.

2400ppm HCC is crazy high. Thats serious running problems there, unless the camshaft is a total monster. And even then....those emissions are still mental.

Either you have a valve sealing issue, camshaft problem or cam timing, or a serious missfire at idle.
HCC are unburnt fuel getting through, and 2400ppm is MASSIVE, in capital letters.

[v8 pete]

it not a standard cam
if i increase idle it does go down 1000rpm =1500hc ppm

increase revs more and it comes right down

[CastleMGBV8]

Pete.

What cam. if you have very low vacuum at idle the rods in the carb may be lifting into rich mode and you may need to replace with weaker springs which control the rods.

Has the carb been calibrated for the engine and do you have the handbook, if not you can download from the Edelbrock website.

Kevin.

[stevieturbo]

it not a standard cam
if i increase idle it does go down 1000rpm =1500hc ppm

increase revs more and it comes right down

Even still, unless its a big cam, that still sounds quite high.

[v8 pete]

carb had been tuned for engine but 269bhp but it was probaby set up for power not sva. prevous owner of engine .4.6l cam unknown modfied heads

[Tricky]

Pete what you running with the Mallory Ie coil Msd ???
and what cam???

[v8 pete]

mallory with normal coil and ballast resistor .cam unknown

[Tricky]

if its a big cam you will always have problems with emmisions.

i think your problrm is inginton
i dont think the fuel you putting in is being burnt.
You need a bigger spark,

Look at ungrading to Msd unit and matching coil .
Not cheap but well worth it

[v8 pete]

does this make big difference

[stevieturbo]

what plugs and plug gap ?

Is the ignition system in good order ?


Ive a good used Crane Hi6 and coil here. Although the Crane gold box works fine, the tacho output doesnt work.

Although I think your existing dizzy could stil drive that ?

Not 100% convinced a std ignition system would be so bad though to cause sich high emissions though.

[Tricky]

I have just changed to a mallory un-lite msd blaster ss coil and a MSD 6al

i had big problems with running rich at low rpm

been on a rolling road today not far from you and the new ingintion system has sorted it

What the msd does it gives multi spark up to about 3000 rpm which helps burn the mixture thus giving a better burn and that means lower HC"s

i run a 5.2 rover in my TR7

[v8 pete]

mallory dizzy contactless new plugs 7s i believe and good leads 25thou gap

[stevieturbo]

7's sound like very cold plugs ? Have you tried something like a 5 heat range ?