tr7triumph.com

Finally got around to removing them old waxstat adjusters,
replaced them with the penny,(not as easy as people say)
refitted them and set the mixture to level with the carb bridge,then back 2 turns on both,
checked that they were moving on choke action,not leaking etc,
fired her up,now backfiring through the exhaust,
gave up,washed up,and seriously considering burning her to the ground on the fifth of november,
just about losing my patience on this "car" now,
why oh why didnt i buy a dolly sprint......
wise cracks will really be appreciated,
so why all of a sudden is it backfiring,was a little lumpy before but no backfire

Your frustration is understandable, but not many on here will appreciate - or agree - with your sentiments.

I respectfully suggest you'll have much the same set of problems with the Dolly, should you decide to buy one.

My advice is to persevere - and use the strength of the Forum. Do you belong to any TR-related Clubs? They may have monthly meetings in your area with willing members who'd love the opportunity to tinker...

Maxwell


2.0 TR7 FHC \ Current
1.8 Mazda MX5 \ Current

Frustration is a syndrome we all know well.

First things first, can we please edit the title of this topic to something less vulgar?

Second, Jiffy, I spent 5 full hours Tuesday afternoon trying to get the right rear angled brake line fitting into the hole. Somehow it mysteriously caught and threaded as I was about to rip it all off with a hack saw to make a new brake line. That night and the next day my bones went on strike from any physical activity. I full well understand your mental state. Please get a good nights sleep to let your subconscious deal with the problem.

Thirdly, I suggest more research be done on your problem before grabbing the tools again. I can't help but wonder if part or the whole of the issue isn't ignition based?

Mildred Hargis

Backfiring from the exhaust indicates unburned petrol meeting oxygen in the exhaust system, & with the elevated temperature there encounted, burning quite quickly, IE exploding.

Perhaps you now have a rich mixture introducing unburnt petrol, or something you have done is allowing oxygen into the exhaust. I always look for the cause of a new problem in what ever I have just changed.

Have fun finding it, & remember, if you weren't doing this, you would probably be sitting in front of a TV, growing fat.

Hasbeen

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Mildred</i>



First things first, can we please edit the title of this topic to something less vulgar?

Mildred Hargis
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Quite right Mildred, spelling the word "ASS" is quite vulgar, much better to use the more civilsed "ARSE" spelling


"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

80'Triumph TR7, 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
'98 MG-F, 69'Ford F250.
76' Ford F100

If you set the jet level with the carb bridge then the mix should ok to start with. Did you then do a complete carb set up?

I have being playing with some waxstats but not fitted them, I would use two 1 pennies and the small silver cylinder that sat ontop of the wax capsule to get the jet to sit at the same height as before.



Pete
1981 Carmelian Red 2 litre DHC.
Polybush, KYB shocks, electric fan, electric windows and electronic ignition roller bearing struts and anti-dive kit - otherwise standard
1979 Pageant Blue Spitfire 1500 - some restoration in progress.

JIffy, if you buy your Dolly Sprint you will find you get the same carbs with the same issues unless they are properly set up. There is something else going on that you need to sort out.

Russ

1980 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

Why on earth did you remove the waxstats - mine work perfectly well. Was there something wrong with them?? But since you have - as others have suggested - you can't just blindly set carbs like that and walk away. You do have to set them up correctly - lifting the pistons and listening at the inlets with a rubber tube. And yes - Dolly has the same carbs......and even more quirks/problems.......

Getting the jets at the same height below the bridge can be difficult as it is almost impossible to tell when the jet is level with the bridge to start with. If you have a vernier caliper with a depth gauge, remove the bells and slides then set the jets .125" below the bridge so you have a good starting point. Backfiring through the exhaust indicates a rich mixture, and backfiring through the carbies indicates a lean mixture. Check the dashpots are filled...ATF seems to work well in our relatively warm climate.

TR7 Convertible
Sprint Motor
MegaSquirt EFI

I'm not doubting the idea - but I have never been able to understand WHY a weak mixture causes a backfire through the carb.....can anyone explain?

Hi,

A lean mixture can POSS cause a intake backfire due too, the mixture will burn at a slower rate and even to the point, especially if a lot of valve overlap due to cam spec, on acceleration it can still be burning during exhaust cycle and as the inlet valve opens to help purge the cylinder it can then burn in the intake manifold.

Another cause of back firing in the inlet manifold can be over advanced ignition timimg where the spark ignites the mixture before the inlet valve closes and the burn can escape into the inlet manifold with a 'pop' !

Cheers John


LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty Now with an overdrive conversion

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6, BUILT NOT BROUGHT !!!!

I'm sure John is right, but the only times I have had backfiring through the carb was,

1/ When a car that had sat for 3 years had so much rust on an inlet valve stem it was sticking open to some extent.

2/ My current 7 when bought had the No 2 inlet valve shimmed so it was held 24 thou open, when It should be closed. I don't know if it had run much like that, but I was pleasantly surprised when the valve was not burnt out.

With the air filters removed to try to tune the thing, we discovered it was also flooding so badly, [due to 4 PSI fuel pressure we found later], that petrol was dripping out of the carb throat, when we started it.

When it backfired, it ignited this petrol, & blew a sheet of flames some feet. Never a dull moment with a nice TR7 for company.

Hasbeen

Thanks lads - pretty much what I was thinking.