16 replies to this topic

[dansnyderECE2010]

So, I cleaned my carb, adjusted my valve clearances (first time doing that), gapped my sparkplugs, and tossed everything back together with a new air filter.  Now, when I start the car, it idles rough below 1100rpm and when I have it steady around there, I give it throttle and air pops back through the carb and the car loses power (stalls out if I'm not careful).  I'm thinking I may have screwed up my valve clearances and now my valves aren't sealing properly...  Thoughts anyone?

[Dusky]

How did you set the valve clearance?

It is more probably that your carb needs adjusting

[bowen25]

Oil in the dashpot?

[Carlos W]

Wrongly set Tappets maybe?

What did you use to guide you through the process?

[dklawson]

The symptoms you are describing sound like classic fuel starvation (barely idle, won't rev, backfire through the carb, and no change to the timing settings).  If you made any changes to the mixture, that could be your problem.  Which carb do you have and what dis you do with it during cleaning?

 

That said, you had the spark plugs out.  Double check that you have put the wires back on them in the correct order.  The firing order is 1-3-4-2 with the plug wires arranged counterclockwise around the distributor cap and cylinder #1 is at the water pump end of the block.

[dansnyderECE2010]

Hey everyone, thanks for the responses.  I checked the firing order and all was well, that was my first concern.  I haven't touched the tappets yet after gapping to .3mm using the rules of 9's.  I considered the fact that I only had problems when giving it a brisk push of the throttle.  Seemed fine when I depressed the throttle slowly.  I sorted through my carb to make sure I didn;t forget anything and I made the decision to add some more oil to the dash-pot.  Turns out that this took ar of the problem ( I think ).  I had originally put half an inch or so worth of 5w30 to the dash-pot.  I realized that this probably didn't allow much oil to sit above the plunger within and decided to fill the thing up with about 1/2" of air at the top.  This makes more sense as the oil can then resist movement of the needle.  Now I'm back to my same old rich mixture for some reason...

 

As a side note, when I blow into the float valve with the fuel reservoir inverted (from the carb), should I be able to get air through if I blow hard on it?  I was able to, figured I'd ask..

[dklawson]

If you invert the float valve assembly you should not be able to blow through the inlet hose connection.  If you were able to blow through, check the tip of the valve for witness marks and replace if you see any.  If there are no witness marks. make sure the valve is not binding up in the hole it goes into.  The Viton tipped valves available as replacements work very well and are what I use whenever I have to replace float valves.

[minimender]

Make sure you put all the pipes back in the right places, sounds like you might have air getting in somewhere, crank breather pipe maybe

[dansnyderECE2010]

Well, I notice my breather pipe has no hose clamps on it although I imagine that's because this line isn't under pressure.  Not hard to add if that sounds like a problem to anyone.  A thought, my vacuum line was pretty hard to take off and even harder to get on, what would be the result of a leak in that?

[Gremlin]

Well, I notice my breather pipe has no hose clamps on it although I imagine that's because this line isn't under pressure.  Not hard to add if that sounds like a problem to anyone.  A thought, my vacuum line was pretty hard to take off and even harder to get on, what would be the result of a leak in that?

The same as if you get an air leak anywhere downstream of the jet and needle

[jaydee]

5w30 is too thin, if you need a thin oil try saw oil otherwise 3 in 1 is good

[dansnyderECE2010]

I'll pick up some 3 in 1 next time I'm at the store, thanks.

 

I took a look at my needle valve and it seems to be working properly.  Blowing pretty hard when inverted and can't get air through.  I took a look at the actual needle valve and I don't see any scoring or irregularities on the needle.  I did noticed that (the car isn't starting right now) when I opened up the fuel reservoir on the carb there was gas coming out so the level was at least at the height of the seal.  I realize the reservoir may not be perfectly level but it was coming out as soon as I loosened one of the three retaining screws.  Does that sound normal or was the level too high?  What level should I expect?  I assume if the level is too high that means my needle valve is not operating properly...  Maybe there's some sort of adjustment needed...  Thoughts?

[dklawson]

When the float valve is sealing properly, the level in the bowl is typically about 2/3 full.  If the level is above that it means that fuel is probably flowing through the jet directly into the carb rather than being sucked out of the jet by vacuum.  Basically, running way too rich or flooding.

 

You said that you were not able to blow through the fuel hose inlet with the float bowl lid inverted.  That says the needle should be closing.  Adjustment of the valve closure point is controlled a couple of different ways.  The older floats have metal arms on them.  The metal arms are "bent" to set the float height as described in the service manual.  If you don't have a manual, go to the Burlen web site and look through the tech articles on SU HS carbs.  The information should be there. 

 

If you have the later, one-piece plastic float the procedure for setting the float height is not typically described at all.  There is/are fiber washers between the float valve body and the float bowl lid.  You change the number and thickness of the fiber washers until you get the jet height set properly.  Properly in this case is determined more or less by trial and error.  You have to set the height where you think it is "right", then put the bowl lid on the carb and crank the engine to fill the float bowl.  With the suction chamber removed from the carb you should be able to see the fuel in the jet 1/8" or more down from the jet's top surface.  This is all approximate.

 

Regarding dashpot oil... that is a topic unto itself.  People run everything from WD-40 up to 90W gear oil in the dashpots as they see fit based on how they want their engine to perform.  Three-In-One Oil comes in two types.  The red bottle is typically a straight 30W oil, the blue bottle is 20W.  The factory oil from Burlen is a straight 20W. 

[dansnyderECE2010]

Interesting..  So a bud of mine gave me his replacement needle and I compared it to mine.  Turns out there's a pretty substantial groove on mine.  I tossed the new one in.  Haven't tested it but I expect it to work better.  The gap between the reservoir housing and the float when inverted is definitely withing tolerance according to the haynes manual.

 

As for oil, I have some decently heavy engine oil for the car already so I suppose I could use that.  Lighter oil means richer on acceleration or....? 

[KernowCooper]

Lighter oil is weaker on acceleration, thicker oil more restriction on the slide lifting which = less air and drawing fuel from the jet