SAAB V4 Forum
SAAB V4 Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Technical
 General Technical
 FoMoCo carb mixture
 New Topic  Reply to Topic 
 Printer Friendly 
Next Page
AuthorPrevious Topic Topic Next Topic
Page  of 2

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 19 Sep 2018 :  11:45:26 Show Profile Visit green96v4's Homepage Reply with Quote
I maybe barking up the wrong tree, so apologies if this is a dumb question....

Ever since getting my 71 back on the road last year, whenever I drive it I stink of exhaust fumes afterwards (like I've been mowing the lawn all day). I often joke to classic owners at car shows and get the "knowing nod" so I'm not sure if it's just the crappy fuel that's available on this side of the pond, or the lead replacement additive I use (Millers VSP) but friends and family have also complained about how rich the car smells, so I'm wondering if I can lean it out or if anyone else has tips or tricks

I don't remember the car smelling this fumey when I had it as my daily driver (in the early 1990's) but I've always tried to rationalize it that we were all probably "nose blind" to pre catalytic converter/leaded petrol air!!!

If I can play with the mixture setting, I'm presuming no 5 in the diagram is the mixture adjustment, but can't really find anything in the manuals I have about which way to turn the screw (my carburetor is slightly different as my 71 is a manual choke, but this was the closest image I could find

We used to import Mini Coopers over to Canada and the 1990MY had an SU carb, it was easy to get it through the emissions test here as we could lean it right out (they have a 2 speed idle test here) Lean it out until it stalled, turn the screw back a quarter turn and take it for an eTest - job done!!

Thanks in advance!



Iain G
V4 Fan

United Kingdom
111 Posts

Posted - 19 Sep 2018 :  13:32:23 Show Profile Reply with Quote
Is fuel peeing-out of the carb over-flow? Then your float valve might be stuck? Or you need to fit a fuel pressure regulator.
Do your plugs' electrodes look black? Then you might need a tune-up.
You could try using a (Gunsons?) Colour-Tune.
Otherwise I suggest the following procedure.
1. Remove idling fuel jet, clean jet and hole with carb cleaner and replace
2. Screw idle mixture screw all the way in gently and count number of turns then remove it, clean screw and hole with carb cleaner and replace same number of turns position
3. Get the engine going and warmed-up
4. Reduce idle speed by screwing-out idle speed screw so engine just about starts to grumble - this makes it more sensitive to your idle mixture adjustments you are going to do next
5. Now screw-in (as you are looking to lean-off) or screw-out the idle mixture screw 1/4 or 1/2 turns at a time until the engine runs smoothest.
6. Increase idle speed back to where it should be (900 rpm-ish) so engine gets smoother and repeat (5.) for final adjustments.
NB rev the engine to 2000 rpm+ after each adjustment and let the engine settle before next adjustment.
Idle mixture position should be in the range 1 to 3 turns out. If it is more then indicates idle fuel jet is too small or blocked if it is less and/or you can't stall the engine by screwing-in idle mixture screw all the way then could be a variety of problems.
See how you go first.

Iain G
Go to Top of Page

Iain G
V4 Fan

United Kingdom
111 Posts

Posted - 19 Sep 2018 :  13:41:48 Show Profile Reply with Quote
........is starting the choke open all the way when disengaged?
Is the air filter clean and unobstructed?


Iain G
Go to Top of Page

RhysN
V4 Fanatic

United Kingdom
278 Posts

Posted - 19 Sep 2018 :  19:30:21 Show Profile Send RhysN an AOL message Reply with Quote
If my response is a bit off topic, please say.
My new acquisition has a dodgy FoMoCo carb. Am I better to;
a; ditch it in favour of a single choke Weber (new for close on 200)
b; wait for a twin choke manifold (I know I shouldn't have sold mine) and shell out for a new carb to suit (Which one please?)
Go to Top of Page

Borstlap
V4 Fanatic

Norway
279 Posts

Posted - 19 Sep 2018 :  19:52:31 Show Profile Reply with Quote
I'd go for option b if I were you, changing to a Weber 32/36 DGV or DGAV if you want an automatic choke.

Alex
Go to Top of Page

melle
V4 Guru

United Kingdom
2851 Posts

Posted - 19 Sep 2018 :  22:06:00 Show Profile Visit melle's Homepage Reply with Quote
I have manifolds if you need another one Rhys. Fast Road Cars do DGVs for 179.

www.saabv4.com
Go to Top of Page

RhysN
V4 Fanatic

United Kingdom
278 Posts

Posted - 20 Sep 2018 :  07:29:21 Show Profile Send RhysN an AOL message Reply with Quote
Thanks Melle, look for an email
Go to Top of Page

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 20 Sep 2018 :  09:48:24 Show Profile Visit green96v4's Homepage Reply with Quote
thanks Iain, great suggestion (and I love step-by-step!!)

just to answer your questions:
Choke is open all the way
Fuel isn't coming out of the overflow pipe
Float is set correctly
Air filter is brand new
Carb was completely overhauled so (should be) working
Haven't whipped out a plug yet to see how they look - may go and do that now!

So screwing in leans the mixture?
Go to Top of Page

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 20 Sep 2018 :  12:05:45 Show Profile Visit green96v4's Homepage Reply with Quote
hmmmm yes a little "carbon" - going to follow Iain's advice and see if it helps, otherwise I'm going to be emailing Melle for a manifold and convincing the wife Santa needs to bring me a present with Weber stamped on it!



Go to Top of Page

melle
V4 Guru

United Kingdom
2851 Posts

Posted - 20 Sep 2018 :  17:05:18 Show Profile Visit melle's Homepage Reply with Quote
Ooof, that is a lot of soot on the plug. Did you have the carb rebuilt, or did you rebuild it yourself? The last time I worked on a FoMoCo is well over a decade ago, but from what I remember I had a bunch and all had worn spindles/ air leaks. Most V4s I've seen up close ran way too rich anyway.

www.saabv4.com
Go to Top of Page

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 20 Sep 2018 :  18:19:07 Show Profile Visit green96v4's Homepage Reply with Quote
Melle - did it all myself, I had all the external components re-plated and the case polished and I then rebuilt it with new gaskets/diaphram/springs etc.

Perhaps it's time to look at a Weber. I've always wanted to keep the car relatively "stock" (ie the standard air filter) I've seen other posts on the forum about a comparable single choke Weber, but I'll have to do my research on exactly which one it is (or be convinced by forum members to go with the twin choke and an intake manifold upgrade!)
Go to Top of Page

melle
V4 Guru

United Kingdom
2851 Posts

Posted - 20 Sep 2018 :  18:42:36 Show Profile Visit melle's Homepage Reply with Quote
Before jumping onto the carb, I would first focus on the ignition system; many "carb" issues are nothing to do with carbs. I would start by visually inspecting the colour and strength of the spark. Only if the ignition turns out to be healthy I would move on to the carb. Not sure if you use the car over the winter, but why not take the current carb off and give it a good inspection at your leisure when the cold sets in, before spending money on a new parts?

The 34ICH is the off-the-shelf Weber to go for if you want to stick with a single choke carb. I have no experience with them, but I believe they're rather good carbs.

www.saabv4.com
Go to Top of Page

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 21 Sep 2018 :  10:03:28 Show Profile Visit green96v4's Homepage Reply with Quote
Thanks Melle - I'm using an Accuspark Electronic Ignition

Question - I have a spark plug tester (the one that you put between the plug and ignition lead and has a transparent plastic housing, so you can "see" the spark) - is there a more scientific way to test colour and strength?

With the amount of salt on the roads here in winter, I take it off the road and tinker with it, so this might become this winter's project!!!
Go to Top of Page

Derek
V4 Guru

United Kingdom
1874 Posts

Posted - 21 Sep 2018 :  12:04:58 Show Profile Reply with Quote
Getting an emissions print out of the car as it is now would be useful. When I put my car in for the MOT after it had been off the road for a couple of years I set it up to be a bit lean, just in case. That gave figures that would have passed better than a new car and the tester had to richen it up quite a bit. Yes, it did run better. That was with a FoMoCo. I later had problems with cutting out. That turned out to be down to flooding due to a leaky float sinking and causing overflow when freewheeling. Search here for details. Photobucket pics may or may not show. My '76 model had a late carb the same as the Souvenir with different float settings than the one shown in Haynes and I had tweaked it back to the Haynes numbers which caused a leak at the hinge. Beware if you are adjusting the float but check it carefully for leaks. Sink in very hot water and watch for bubbles. A high float setting may cause richness. Late carbs also used a different main jet.
Go to Top of Page

green96v4
V4 Fanatic

Canada
458 Posts

Posted - 21 Sep 2018 :  13:12:44 Show Profile Visit green96v4's Homepage Reply with Quote
Thanks Derek
I did set the float up to Haynes Manual specs when I first got mine back on the road (before that it was p*ssing fuel out of the overflow and left me stranded a mile from my house, I think it was basically flooded, but got it going again and then made my adjustments when back home)

I'm going to go through the steps Iain listed and I could then go and get an eTest, see if leaning it out will work, but my fear is what Melle (and most with an opinion on FoMoCo carbs) are talking about, this thing is junk and I should be getting a Weber on it!

The FoMoCo will make a nice desk ornament though!
Go to Top of Page

melle
V4 Guru

United Kingdom
2851 Posts

Posted - 21 Sep 2018 :  17:19:57 Show Profile Visit melle's Homepage Reply with Quote
The particular zamak alloy the FoMoCos are made out of was probably well up to the job back in the day, but after 40-50 years it's way past the life span it was designed for of course. It's the same with the Solex 32TDID twin choke carbs, which have a bad reputation. I believe they were good carbs when new, but after decades of use they're worn out around the spindles and warped as a result of going through thousands of heat cycles. I believe that if a brand new FoMoCo would be a available, it would be a perfectly acceptable replacement for an old FoMoCo.

Retrofit Webers are a whole different ballgame. They are designed with performance in mind and they're much more tunable than carbs designed for production cars. No wonder, the latter should hardly need any tuning and as soon as you start messing with rest of the engine, you want a different carb anyway. Retrofit carbs are usually much more complex, hence way more expensive than carbs for production cars originally were. However, if you use a Weber for a few decades it'll develop the same issues as FoMoCos and Solexes, plenty of proof in my carburettor spares boxes!

Matt, the spark plug tester you're using works just fine. If it's a red one though, I would prefer to just ground the plugs on the block and let them spark so you can gauge the colour of the spark. Definitely worth cleaning the plugs, checking the gaps and making sure all HT lead connections are tight. Electronic ignition, of any sort, unfortunately doesn't safeguard you against ignition failures. Plenty enough that can still go wrong: hair cracks in distributor caps and rotors, coils that go bad, excessive play in the dizzy shaft etc.

www.saabv4.com
Go to Top of Page
Page  of 2Previous Topic Topic Next Topic 
Next Page
 New Topic  Reply to Topic 
 Printer Friendly 
Jump To: 
Snitz Forums 2000
SAAB V4 Forum© 2000-04 Snitz CommunicationsGo To Top Of Page