hydro carbons

[marc69]

my project nova failed the mot on several things,

one of them was emmissions, the co was unbeleivably (10% of the limit) clean but the hydrocarbons were 3 times over the limit.

i removed the breather hoses from the carb but is there a problem?

It's a 1.4 but on a pierberg from a 1.3 and the cam is a kent so I'm not sure the valve timing is exactly right?

[Royston]

check ignition timing and that the vacuum advance is working correctly.

My Sport when I took her for test origionally was over on Co @ 9% but the hydrocarbons went off the scale on the machine (10,000+)lol

my timing was fixed at 34 deg OK at 3500 rpm, not tick over:d

[marc69]

thanks, my tickover is 1200 rpm, it's the best I can get it with this cam and it's a bit lumpy. I'll check the ignition timing with a strobe, I did replace the vacuum advance.

10,000+ hydro carbonson your sport was impressive though!

[novasrikev]

clean air filter it worked a treat on my old nova

[marc69]

mine hasnt got one!

[marc69]

the mot tester said something about possibilities of valve seams or piston rings, but would the compression and co still be good if this was the case?

[Royston]

I would certainly check the timing with a light, and check it is advancing OK as the revs increase.

If valve stem seals are leaking you normally get the classic puff of smoke on start up after the car has stood over night.

If valve seats or piston rings are worn/leaking a compression test will help identify.

Has the carb been tuned to suit the camshaft?

What cam is it, (Part No?) if it is really wild might be hard to set up with the limits of the carb (is the carburettor OK)

Has the engine been serviced lately?

If you are running without the air cleaner it might affect how the carb operates (tends to go lean without one) I also think it is madness to run with out one.

If it has run with out an air cleaner for a long time/high mileage, piston rings/liners may well be goosed, comp check will tell you

[marc69]

Thanks, when I say there is no air filter, there is a cobbled together K and N mesh thing but it's not a proper Nova airfilter.

The carb is off a 1.3 but I have the broken 1.4 carb so perhaps swapping the jets may help?

The engine has been serviced with new oil etc.
I've done the timing with the strobe, the vacuum advance is working, I put a new vacuum on the distributor as the old one was goosed.

The car has only run 4 miles since I got it (to the test station and back) as I need my driving licence for work, too big a risk. No idea what the previous owner did with it and the car it came out of?

kent cam NV051, fairly mild

No smoke on start up although there is a little water at the back of the exhaust (carb with no cat)

I don't know how a proper compression test is done, the ony thing I did when i got the car was an old tip from my dad. The engine wouldn't run at all so to check that each cylinder worked, I wedged some foam packing in each hole, turned the started a few turns and then went out to find each numbered bit of foam (thrown out on the floor). From there on I onviously worked to get the cengine going and I am actually quite pleased in that it drove there and back (all 4 miles!) with ease.

What you ,mentioned re the mixture being too weak, would this cause the hydro carbons? if so then the 1.3 jets seem like the culprit.

Sadly there are a few more other items for this MOT, I thought I had done really well with this project.........

[Royston]

Hydro carbons is unburnt fuel, either too rich mixture, bad timing, worn/ damaged engine.

Does it sound even, ie running an all s cylinders, or running off beat?

[marc69]

The car runs fine, idle is a little lumpy, I cannot get it smoother but assumed it is the cam. it revs etc fine

for the test, i'm probably best to leave the 1.3 jets in then, keeping it all lean.

could be a worn engine, if so I probably won't bother getting it repaired as it's only a 1.4 but hopefully it's just been the timing (be it valve or ignition). I've changed these from the test so if it goes in again for a check, I'll see if there is any difference.