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View Full Version : HS2's...big ole' flat spot! Maybe I need to just pay someone.



CanyonCarver
09-25-2003, 04:02 AM
First of all, nice to meet all of you! graemlins/patriot.gif

I really hate to say this, but I'm seriously considering paying someone else to take a look at my baby. Assuming all I need is a good tuning, does anyone have a ballpark figure for what it would cost?

I just replaced the single Stromberg with a set of HS2's. The car idles perfectly, but once moving, will only tolerate about 1/4 throttle before it bogs. It still accelerates, just very slowly, with a pulse to the exhaust note. The car never bucks or dies. Thanks to JonB over at triumphspitfire.com, I found that I had the incorrect needles. Ordered a new set, but still no luck with getting the car running right.

Choked, the car has much more power (though still not what it should be), but runs like it's well, choked. This leads me to believe I can rule out any problems w/ the ignition system? I can't seem to find any vacuum leaks, and the bowls are always about 1/3 full when I check them, but I can't think of anything but fuel starvation, or incorrect mixture at this point...

Dashpots are full of ATF. I really want to drive my car before the sun disappears!!

Thanks for any advice you can offer

Josh

Twinkie
09-25-2003, 09:25 AM
So what type of Triumph is it? You still may not have the correct needles in the carbs. It took me a couple of tries to get it right in my Spitfires. Is the idle smooth?

Izual Angel
09-25-2003, 10:51 AM
Just for ****s and grins, I'd check the timing. I've found quite often the timing is responsible for these problems. Maybe check to see that the pump is putting out enough fuel?

piman
09-25-2003, 12:20 PM
Hello CC,
before you pay anyone, remove both dashpots and pistons.
First off you should see fuel just about to the top of the jets, this will confirm your float level is somewhere near. Next, (ensuring the choke is full off) screw the jets until they are flush with the bridge in the carburettor choke tube, then wind them down twelve flats, i.e. two full turns. This is the standard setting for most S.U. carburettors. (By the way it doesn't matter what needle you have in it should idle at this point as all S.U. needles have the same idle dimension.)
Put the dashpots back on and start it up. With the dashpot dampers out or with the air cleaners off, try and rev the engine to check response. Also watch the two pistons, they should both lift together and roughly the same amount, this is a quick check to see if they are reasonably synchronised.
If you still seem to have the same problem check that the mechanical advance is functioning in the ditributor. Also check your plugs for colour, black is too rich and white too weak. (Usually a 'flat' engine will be too weak, and incidentally need more ignition advance.)
Try the above and see what results you get.

Alec graemlins/cheers.gif

CanyonCarver
09-26-2003, 07:41 PM
Twinkie, the car is a 1970 mkIII with the 1300. The car is all stock, so I went ahead and ordered the standard set of needles for that year.

Well, pistons rise equally, and when I check the bowls, they are always about 1/3 full *except* this morning when I pulled the tops off and the front one was very low. I adjusted the float until it was the same as the rear one when at the top of its stroke, started the car, messed with the mixture a little, rechecked the bowls and back to 1/3 full. If the car was starving for fuel, wouldn't these be nearly dry?

How do I know if the vacuum advance is working correctly? I've turned the distributor a little in the clockwise direction, and it doesn't seem to affect how the car runs.

Thanks so much for all your time.

Josh

piman
09-27-2003, 07:09 AM
Hello Josh,

I couldn't say if 1\3rd is the correct level, I much prefer to look at the top of the jet. However, as the float is quite large, it doesn't sound as if there is a fuel level problem. There could be a delivery problem however, check the fuel filter.
The easy way to check the vacuum advance is with a strobe, pull off the vacuum line and you should see the timing vary. It does very little to affect performance though, and is designed to improve economy. (The carburation would be set by the manufacturer to run weak on part throttle and this calls for some extra advance. The higher vacuum of this part throttle running is used to advance the timing via the vacuum advance mechanism.)
You can swing the distributor quite a way and still run, but if all is stock I would set everything as the book. The real advance on the distributor is the mechanical advance and this can seize. You should be able to rotate, by hand, the central spindle of the distributor (leave the rotor arm on) by about 10 to 20 degrees and it should return when you let go.

Alec graemlins/cheers.gif

[ 09-27-2003: Message edited by: piman ]</p>

CanyonCarver
09-27-2003, 10:09 PM
Aha. I knew there was something I forgot to check from your suggestions, and that was the fuel at the jets. I'll go do that right now.

The fuel filter is fortunately transparent, and just in front of the fuel pump. It's not very large, maybe the girth of a quarter, and about 1.5" long. It's always about 1/3 full. Be back shortly to report on the fuel level at the jets. images/icons/smile.gif

CanyonCarver
09-27-2003, 11:22 PM
Ok. No fuel at the jets. I checked before and after running the car.

I'll replace the fuel filter tonight, and if that doesn't do anything, I would assume I should check the fuel pressure with one of those vacuum thingies?

Making progress! I just hope this weather holds out. Tonight would have been so perfect for a drive.

Thanks again for your time, Alec and everyone else.

MDCanaday
09-28-2003, 11:23 AM
After you get gas to the carbs you may still need to put different needles in the carbs. A good friend of mine recently put SU's on his 1500 and then spent weeks trying to get just the right needle for it. Turned out the right needle was never used!!!(in this carb) He tried some needles out of a 1500 mga and WOW.I would suggest you start with the mg needles to save much frustration and bad language.
MD(mad dog)

Twinkie
09-28-2003, 12:56 PM
I had factory sized needles in my spit 1500 with twin HS4s and they were too lean. I had to go up two sizes to get it right. I think variances in sea level will affect what needles you need.
It'd be interesting to see how these cars ran right out of the factory... images/icons/smile.gif

SilentUnicorn
09-28-2003, 01:56 PM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by MDCanaday:
After you get gas to the carbs you may still need to put different needles in the carbs. A good friend of mine recently put SU's on his 1500 and then spent weeks trying to get just the right needle for it. Turned out the right needle was never used!!!(in this carb) He tried some needles out of a 1500 mga and WOW.I would suggest you start with the mg needles to save much frustration and bad language.
MD(mad dog)<hr></blockquote>


..I take that to mean the right needles were in a mga?

mark

CanyonCarver
09-29-2003, 05:08 AM
Great, just when I thought I at least had the needles sorted. So what you're telling me is that it's possible that I have the wrong needles even though this is what they came with from the factory? This could get $$$.
Just measured the preasure from the fuel pump, and it's only at 1 PSI or so. I believe it should be in the region of 2.5. Choking the car still makes it run better under throttle (but still bad). It seems like the thing would stall if it was a problem with the pump...it never stalls, just runs worse under more than 1/3 throttle or so.

I think the car is jealous that I've been driving the 325e to work. That car is no fun I tell ya! (well, I did blow the doors off a Plymouth Voyager earlier today).

Thanks for the help, all. I'm curious if anyone else has a small bearing 1300 with dual HS2's, and what needles they are using. I would imagine that the car would at least run *decently* with the needles they were originally produced with...

piman
09-29-2003, 10:04 AM
Hello Josh,

Just checked my Burlen manual; Mk 3 1300 Spitfire, USA, 67 to 69:- DD needles.(Part number AUD 1531). There is no listing for a 1970 model USA spec. Ensure that the shoulder on the needle is flush with the face of the piston.
When you are checking your fuel pressure, is the engine running? If there is a restriction or the fuel pump is below par, you may get a reasonable pressure at idle but this will drop off significantly if the demand is increased. By the way is the pump electrical or mechanical?, electric pumps are easy to check, just do a flow measurement, you should be looking at about 8 to 10 US gallons per hour
I presume the symptoms you describe are when you are driving on the road? What is the engine response like if you rev the engine with no load,
does it rev up OK then? One other question, is the rev counter reading steady or erratic? if it is erratic you probably have an ignition fault.

Alec graemlins/cheers.gif

CanyonCarver
09-30-2003, 08:53 PM
A friend of mine with the correct tool checked the pressure for me while I was at work. He left a note saying 1 PSI "above idle". I have no idea how much above idle though, so I'll ask him tonight. The fuel pump is mechanical,and I have no idea the age. Whether or not it's the source of the problem, it seems like it's on its last leg...

The symptom is obviously most noticeable under load, but even when revved while stationary, there is a sputter that my ears are now trained to detect.

And maybe this next part will make you all smack your foreheads, but I forgot to mention that the car has no rear silencer (but stock exhaust with the small straight-thru muffler under the passenger area). I was advised that I wouldn't need different needles because of this, but I'm wondering...

Also, I was trusting the book, "The Triumph Spitfire" in its statement that no changes were made between '69 and '70 except the deletion of one carb. I do know that the '69s used the same exhaust manifold, but maybe there is a slight change somewhere else that would require a richer needle?

Maybe I'll try temporarily restricting some airflow and see if that changes anything. That would definately point to lean needles, right?

Your time is greatly appreciated. Spitfire people are the best!!

Dave Russell
09-30-2003, 09:24 PM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by CanyonCarver:
A friend of mine with the correct tool checked the pressure for me while I was at work. He left a note saying 1 PSI "above idle". I have no idea how much above idle though, so I'll ask him tonight. The fuel pump is mechanical,and I have no idea the age. Whether or not it's the source of the problem, it seems like it's on its last leg...
<hr></blockquote>
CC,
It really doesen't matter much what the rpm is. One psi is definitely too low & likely the cause of the problems. Better try another pump.
D

CanyonCarver
09-30-2003, 10:08 PM
Will do. Funny that it ran so well with the single carb.

Nice car by the way. One of my favorites. graemlins/thumbsup.gif

[ 09-30-2003: Message edited by: CanyonCarver ]</p>

CanyonCarver
10-17-2003, 08:23 PM
ARG!! No luck.

So 40 bucks and a lot of finger crossing later, I'm back at square one. Car doesn't like full throttle, and won't run over 4500 RPM, even when standing still. My only consolation is that the old pump wasn't puttig out enough pressure anyway, and probably needed replacing no matter what.

I decided to check for vacuum leaks again, and I think I have some. But here's the part that confuses me: Isn't the engine speed supposed to RISE when starting fluid is sprayed? Mine goes down. When I did this a few weeks ago, I thought the idle was just settling down, as that's how the car has been running-- rev it up, and the idle slowly drops. Anyway, I decided to spray it right into the carb just to see what would happen and the thing nearly died.

With that now established, I seem to have a leak where the intake joins the head......and at one of the throttle shafts. images/icons/frown.gif It doesn't seem that bad though, but I also found some blue fleks of some kind of sealant or something, which means someone else has already been fooling around in that same spot. Pistons seem to rise in unison.

I'm going to get the intake leak sorted out, but have no idea where to start with that leaky shaft.

Thanks all.

speedracer
10-18-2003, 12:57 AM
Josh,

I just re-read your post and based on a similar problem i have been having with my Sprint, had a thought - have you checked that the jets in your SUs are the same size?

The graemlins/crazy.gif who rebuilt my HS6s managed to fit different size jets (3mm at the back, 2.54mm at the front :mad images/icons/smile.gif the result is a car that idle's "ok", misses on light throttle, is good between 2000-4000 full throttle and misses after that!

Hope that helps & best of luck,

speedracer

[ 10-17-2003: Message edited by: speedracer ]</p>

CanyonCarver
10-22-2003, 11:13 PM
Update: (if anyone is still paying attention)

Front carb has correct fuel level (just to the top of the jet, like Alec said) but rear carb's is a good inch + lower than the jet (I assume the jet is what moves up and down, and not the actual rim that is flush with the bridge). I've raised the float as far as it will go, and no luck. I'm assuming this has a good deal to do with my car's behavior. I've noticed that there is a hard fuel line running between the two carbs (over the air cleaners) on other spits. All I have is a rubber line. I doubt this really changes anything, but I thought I'd bring it up.

Still have a slight leak at the intake even though I changed the gasket. No idle change when fluid is sprayed on the shafts, though (yay).

Put the muffler back on, maybe helping a little, as I don't remember being able to floor it below 3k...

*almost forgot, speedracer, the openings in the top of the jets are the same on both carbs. images/icons/smile.gif

So:
*rear fuel level too low
*small leak at intake
*runs much stronger under full choke, but even with choke all the way off, the carbs are rich at idle.

[ 10-22-2003: Message edited by: CanyonCarver ]</p>

Steve
10-22-2003, 11:21 PM
Chech the float...if there is a hole in it that will make it sit low in the chamber. Does the float move freely up and down on its spindle? A sticking float will affect the level too.

CanyonCarver
10-22-2003, 11:26 PM
Float moves freely, and no holes that I can find. No fuel inside the float either.

Just thought of something- Do I adjust the float to be 1/8" away from the rim of the cover when the little spring in the end of the valve is compressed or uncompressed?

Maybe I'll just manually fill that back bowl with gas until the float level is right, and see if it runs differently at least temporarily...

Steve
10-22-2003, 11:38 PM
Not a bad idea.....the flat spot is a definite indication that you are running too lean. Look on the bright side.....at least you have still not spent as much as if you had paid someone.

Steve
10-22-2003, 11:40 PM
A quick thought....what air cleaner are you using? And yes you are right about the float....my brain was in neutral!

[ 10-22-2003: Message edited by: Steve ]</p>

CanyonCarver
10-22-2003, 11:40 PM
Yes! Not to mention I don't have to worry about that fuel pump, and I picked up some new plug wires, a valve cover gasket, and some cool british flag badges while I was at it.

...If the float did have a hole in it, wouldn't it cause the bowl to overfill, rather than underfill?

CanyonCarver
10-22-2003, 11:52 PM
ummm...none. I have the longflo hemispherical ones but I haven't put them on yet. I believe I am supposed to coat these in oil, but how much to use and what type I have no idea. I put them on once to see if it would change anything and no luck. That was a while ago though...

Steve
10-23-2003, 12:01 AM
K&N sell a good air filter oil.....maybe you are getting too much air?

CanyonCarver
10-23-2003, 12:17 AM
Cool. I'm sure I can pick that up at any auto parts store.

I'm sure it would help a little to have them on, but I've got a feeling that the fuel level in the rear carb is the culprit more than anything.

Dave Russell
10-23-2003, 02:02 AM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by CanyonCarver:
I've got a feeling that the fuel level in the rear carb is the culprit more than anything.<hr></blockquote>

Hi CC,
I think you are correct.
--------------------------------------
Just thought of something- Do I adjust the float to be 1/8" away from the rim of the cover when the little spring in the end of the valve is compressed or uncompressed?
--------------------------------------
Spring uncompressed.
D