Sva Using 40's

[colivent]

i inserted a couple of stainless steel brilo pads in side the exhaust, with a crome trim for the exhaust and cut a peice of perforated plate to fit inside the trim. this stops the pads from coming out help in place with a small screw. after sva take trim off and rev engine to get pads out. better to insert pads just outside sva centre (cuts down on the revs meaning car wont reach more than 60mph)

[Guest WHEELNUT]

Not too certain about the validity of some of the suggestions on this problem.I wuold expect an engine that has been cammed up and fitted with 40's to be a bit lumpy at idle,also advancing the timing will probably improve the idle but when driving, won't it "pink" alot? Regarding the hydrocarbons,remember hc's are unburnt fuel, the thought crossed my mind that this engine may have undergone surgery prior to fitment, a good run in may help. the best advice I have seen was get it to a rolling road! or swap the carb. will be interested to know how yuo get on.

[Guest WHEELNUT]

had a few more thoughts about the suggestions and one idea has me confused. If you put a pinto ignition system on an engine analyser,i.e. on an oscilloscope , the secondary ignition pattern shows the level of kv being produced to fire the plug. if a lead goes doen i.e. open circuit as the old carbon leads do, the you get a trace showing increased kv. the same occurs if you get worn out plugs only not as dramatic. the way I understand it is the bigger the gap the more kv required to fire the plug? I do agree that if compression is raised this does also increase the kv required but disagree with closing the plug gap to increase kv's. If I'm wrong , please will someone give me the correct theory behind this.

[Guest Steve Allen]

Malcolm

Hired a trailor today and took the car to a rolling road garage in Huddersfield (Car Craft) Had a really good feeling about the chap who owned it, Who assured me he can get the levels down to pass. It looks as if i have a problem with one of the 40's so it may mean new ones or change to a cheaper single carb, He also has a lot of old spares so that may be an option. He new webers like the back of his hand and has got only 3 years to retire. People like this are so hard to find as the younger mechanics just want to plug a device into your managment system to find out whats wrong. Will let you know what he comes up with.

Steve

[Guest Mark P]

I know it's a bit late as you have hired a trailer, but, you can drive the car as long as it is insured and booked in to a place to have work done on it, I was unsure about this when I was getting mine ready for the SVA so I popped down to the local cop shop and asked. The amount of work I was having done before the SVA was unreal

 

Mark

[IanS]

Replying to Wheelnut.

 

The breakdown voltage of a spark plug is proportional to the plug gap. Double the gap double the volts required. All other things being the same.

The breakdown volts are inversly proportional to the presure in the cylinder at the time, in other words close the throttle and get a low manifold presure and you require not many volts, Floor it giving atmospheric presure in the manifold and a high presure at the spark and you need lots of volts to make a spark.

 

On looser fitting engines (read worn rings or valve stem seals) and the low presure sucks oil into the cylinder, This coats the plug and often stops the spark.

 

Ian

[Guest JohnS]

I realise that you are worried about the SVA but when it comes to the MOT remember that being a kit car the Mot emmisions test is as per a pre 1975 car eg. visual smoke test, even a smokie pinto will pass that

 

John

[Guest graham dockerill]

John your wrong, the visual test for cars with a engine newer than 1975 was withdrawn in April 03. See totalkitcar site, article 252.shtml .

[Guest mark kingston]

mine passed the sva with twin webber 45s fitted..... i just used a cheapo halfords sold emmision tester prior to the test to check out the levels and all was ok...

regards

mark kingston

[Guest WHEELNUT]

I read the above reply about sparks and stuff and the gist is, if I've understood it is that my earlier post was roughly right.please confirm?

[IanS]

Wheelnut yes I only tried to expand a bit on what you said.