• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

ignition prob i think?!

Share this page

Phishlvr02

Phishlvr02

Freshman Member
Offline
I have a 75 B, at least that is the way it is listed on the paperwork. It has headers and a Weber Downdraft installed. my problem seems to be a points, distribeter, timing issue but it may be the carb. The car cranks and idles fine, although a little fast, but looses power and backfires and genrerally runs like crap after the revs reach about 2500.

I have changed the plugs, wires and points, but the problem seems to be getting worse. I'm not sure what to do next. I'm thinking timing but it has run alot better in the past and I see no reason why the timing has gotten off. THe shaft in the middle of the dist. seems sloppy, I'm afraid that i need a new dist.

Any help will be appreciated.
 
The most likely thing would be that the point gap has closed. Unless of course it doesn't have points any more. Reset it to .015" & give it a try.
D
 
Maybe the main jet(s) are goober'd up. Can you see gas squirt down the throat from the accelerator pump?
 
I took it to mean from the carb... I keep doin' that.

my bad. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
The points are set to 0.015"

The backfire is out the tailpipe.

I'm going to try to time it tomorrow.

It's a '75 anyone know the dynamic advance? Or the vacuum Advance?

Thanks again
 
Too much gas in the chambers, too (likely the cause of the backfire). Needle and seat are first thing to check, float level and if it's plastic, hold it up to a light to make sure there's no gas inside it. If brass, shake it and listen for the 'sloshing'.
 
I'm thinking not enough fuel in chamber.....

The level should be up to the bottom of the little ramp in the front or slightly above it.
(where the fuel goes in)
The DGV is very sensitive to float level.

Fuel filter?
Bad coil?

Will it stumble like crazy at 2500 & then scream like a banshee at WOT?
 
Yes that is it. At WOT or even at around 4500, if you can get there, it gets alot better. But, between 2500 and 4500 it won't hardly run at all.

Float and needle valve seem to operating normally. There was quite a bit of junk in the bottom of the resevoir. Icleaned it out, looked at the jets and tubes, all look good. But, I'm no good at carbs.

I'm really worried about the slop in the dist. shaft. Anyone know how much is too much?


Thanks again for everything!!
 
Hello Phish,

please describe the 'slop', if it is side to side then the distributor could do with replacement, if it is rotational, well that is normal.

Even with a badly worn distributor I would not expect the problems you seem to have. As long as the gap is set correctly and the mechanical advance is working then it should run fairly well.

Too late for you but I cannot understand why so many people on this forum have cars changed from S.U.s or Zeniths for Weber down draught carburettors. To me it is a retrograde modification.

Alec
 
Yep...I hate em....

But the race class I'm in requires em.

I still can't get rid of the little stumble I get coming out of 10 at BeaveRun or the one I get at 13 sometimes at Nelson.
(High G corner)

I have an entire set of jets, tubes and correctors and have been playing around with it for the last 2 years....No luck.
 
A proper Weber has plated air horns and breathes from the SIDE! /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

A good R&R and rebuild is a good 'first step' here. If you had sediment in the thing, there's likely some in the passages of the body as well. A good cleaning would be in order. Aerosol carb cleaner shot thru all ports and passages, jets, checkvalve(s), etc.
 
Cool I'll try to clean out the carb very thoroughly.
I'll get back to you.

And yes the slop in the dist. is side to side. I can set the points and then push on the shaft from the opposite side and open the points up about 25% to 40% more.

Tahnks again for all your help.
 
A cheap fix for the dizzy would be a Pertronics unit....

They aren't so sensitive to rotor wobble.
(You don't need it anyway unless it is MORE than 1/32")

Mine used to be really bad and was pretty much unaffected by my really loose dist bushing after the Pertronics.....

Or you could rebuild it for twice the price....

I'm cheap....Everything I do is cheap except for the things that really matter....

****Disclamer****
Now I have a $$$ MGA engine but....It is a serious PITA

It won't start...It won't idle....And it gets really hot at stop lights
The only thing it wants to do is kill-kill-kill Miatas

****SO****
Drive with the top down, have fun....And don't go all crazy or your wife will leave you....

Note the time stamp.....I just got back from the pub....
We're going to the track tomorrow. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif /bcforum/images/%%GRAEMLIN_URL%%/jester.gif /bcforum/images/%%GRAEMLIN_URL%%/banana.gif VroomVroom /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
Ledges or the one "next door"?
 
Back
Top