Failed SVA!-help

[Dax SC]

Took the Cobra in to Shrewsbury SVA Test Station on Saturday. It failed on 17 items, mostly due to radius test-all these were easily sorted. Three items which need attention are:-

Mirrors-I only had a drivers side mirror and centre rear view mirror. I have used the Dax SVA mirror mounted on the lower pillar. Can anyone recommend a set of wing mirrors that will allow me to see over the rear wings? i.e they need to be mounted quite high-possible a GD set?

Exhaust hydrocarbon level-the limit here is 1200 Hc. The left bank put out 244 Hc, but the right bank was 2612 HC-off the scale!! The engine is new, only done 40 miles and has not been adjusted from the factory. I am running a 800cfm Edelbrock carb. I don't know my way around the carb, but I do have the Edelbrock manual-presumably I need to adjust the two mixture screws at the front-any suggestions, as I can't understand why the two banks would give widely differnt readings!

Exhaust Decibel level-came out at 105dbA-limit is 101dba. Ok I know I need to repak the exhausts. I am using chicken wire and lagging at the moment-any suggestions as an alternative!

Thanks guys for any help-I want to try to get this fixed for a re-test this week.

Mark Smith
Dax 383 Chevy Stroker/Tremec TKO
Telford Shropshire

[kdavies3]

Hi Mark,
there are two idle screws on the carb onr for each side on the front lower flange, you should adjust these on the tester at your local garage or workshop, as a rule of thumb as you increase the CO mixture HC will fall, but too lean and hi HC will occurr. But remember that you have to pass the CO test too.

Why don't you use a pillar mounted mirror on both sides. I did and passed OK. I've now put them in the body.

As for the exhaust I suggest that you phone Dax they may be able to lend you a pair of restrictor plates to fit inside the end cans.
It will sound crap and won't perform but will pass the noise limit.

It sounds like your engine is the same as mine ish.


http://animatedgif.net/flags/-flags-uncat/Wales.gif

Kev Davies
Dax, 383ci Chevy Stroker, Tremec TKO
South Wales

[SimonP]

Mark,
Before adjusting the carb, check all the spark plugs on the right bank - one may have fouled. Unburnt fuel is pure HC, so this could be the cause of your high reading, especially if the CO is correct or low.
If fouled, clean it by gently heating the tip with a blowlamp (hold it with a spark plug socket and extension bar) to burn off the fuel/oil deposits, or use a spark plug cleaner, but NEVER a wire brush.
Sometimes having the ignition leads tied together in a bunch can cause cross-firing and plug fouling. Use separator "combs" to space the leads apart if this is the case.

Re-starting after cleaning the fouled plug, the engine should run smoother, with a faster idle. Re-adjust idle stop screw to obtain correct idle speed.

The plug MAY foul again (straight away), if there is any quantity of unburnt fuel in the cylinder. You will probably get some exhaust smoke for a couple of seconds as any excess burns off.

I can't see it being carb related, as the right-hand side of the carb does not just feed the right bank - look at the inlet tract arrangement of the manifold.

Basic carb adjustment:
A good starting point is to screw both mixture screws fully in (don't force) then set them both 2 and a half turns out.

Check also that you don't have any vacuum leaks. Look where your vac advance is connected to the carb. There will be a similar stub on the other half of the carb - this should have a rubber blanking cap over it. (both should be blanked if you're not running vac.advance)

Does this help you?
Simon.

[dave]

>Took the Cobra in to Shrewsbury SVA Test Station on Saturday.
> It failed on 17 items, mostly due to radius test-all these
>were easily sorted. Three items which need attention are:-
>
>Mirrors-I only had a drivers side mirror and centre rear view
>mirror. I have used the Dax SVA mirror mounted on the lower
>pillar. Can anyone recommend a set of wing mirrors that will
>allow me to see over the rear wings? i.e they need to be
>mounted quite high-possible a GD set?

The Dax side mirror on the off side and the plastic headded centre mirror should be more than enough. I mount the drivers mirror through the lower screen support screw and this acheives full rearward view.


>Exhaust Decibel level-came out at 105dbA-limit is 101dba. Ok
>I know I need to repak the exhausts. I am using chicken wire
>and lagging at the moment-any suggestions as an alternative!
>

What revs did you give as Max power? I know it's a little late now but i claim max power at 4000 so they test at 3000RPM.
Also do you have the Dax exhaust system?

Any probs Mark, give me a call. 07785 702005
:tu

[graham]

nail on the head. I put 4500rpm and so the test around 3350 and that makes a heck of a difference. I am struggling to pass the noise test. They failed it on .5 of a decibel too much. I can only now resubmit the car for full sva albeit enter a lower value for max engine rpm. Have tried extra silencing at the beginning of the silence plus mesh and steel wool but still too noisy. Have now put restritor plates clipped at the exit (with more stuffing) purely for the test and seems quieter so will have another go next week.

Its a nightmare this sva.

Graham

Mirrors (used high up AK mirror and centre mirror high up on centre stay)

Good luck

Graham

[Dax SC]

Thanks for the advice guys.

Dave-I think I have mounted the wing mirror too low on the pillar. I'll do as you suggested and use one of the existing pre drilled holes in the pillar. Presumably I need to remove the pillar and countersing it from the other side, fix on the mirror and re attatch the pillar?

Kev/Simon-thinking about it, my problem cannot be carb related as you suggested. I think you must be right Simon in that one cylinder is not combusting and chucking out unburnt fuel. I need to get hold of an angled spark plug wrench and pull the plugs.

Graham/Dave-I've got hold of a load of glass-pak from Demon Tweeks to repak the silencers. Hopefully this will do the trick. The system is custom made by Roger at Shinybitz so I can't contact Dax for help!

Another problem that occurred on my drive back from the test was that my brakes came on permanently. The headers run really close to the servo/brake lines, so I guess the heat generated expanded the brake fluid. I'm using standard dot 4 fluid at the moment. Anyway I've now sheilded the brake lines with heat shield tubing, made a heat shield out of aluminium sandwich heat shielding material betwen the servo and headers, and changed the brake fluid for Castrol SRF Racing brake fluid which as a 500F wet boiling point (Dot 4 compatible). I hope this works!

Thanks again guys.

P.S. Kev, I think my engine/gearbox set up is exactly the same as yours as supplied by The Engine Factory in the States, although I did specify a slightly milder cam for 'touring'. Goes like hell and scares the crap outta me!!

Mark Smith
Dax 383 Chevy Stroker/Tremec TKO
Telford Shropshire