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Morgan Carbtune  Rating:  Rating
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 Posted: 05-29-2011 02:54 am
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jarnol123
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Got the Morgan Carbtune and fixed it all up....Problem I have is that I only get movement in the rods for cylinders 3 & 4. 1& 2 don't move at all. I changed the rubber tubes around and they all work on 3 & 3 so it's not the rubber tubes.

Is it possibly an air leak in the front carb (DHLA 45)??

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 Posted: 05-29-2011 05:29 am
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Jensen Healey
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This site may help:

http://groups.yahoo.com/group/S1S2S3owners/files/Dellorto%20jetting/

You need to be a member of Yahoo Groups to log in.

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 Posted: 05-29-2011 08:16 am
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subwoofer
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This sounds to me like the carbs are massively off balance. To get you into the ball park:

- Up the revs by means of the idle stop screw on the rear carb till you see a vacuum signal for all four cylinders, alt. turns the carbtune upside down for low-vacuum mode.

- Make sure all idle air bypass screws are turned all the way in, these are only there to balance the two barrels in a carb to each other.

- Make sure all the parts of the throttle axle assembly are there; spring loaded plunger and screw.

- Balance the front and rear carb by adjusting the screw on the throttle lever until the lowest (reading) vacuum barrel on the front carb matches the lowest vacuum barrel on the rear carb.

- end by bringing the highest vacuum barrel of each pair down to the lowest by opening the idle bypass screw for the high vaccum barrel.

I think your problem is that the carbs are massively off balance, combined with too low revs to get a stable reading.

--
Joachim

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 Posted: 05-29-2011 02:39 pm
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jarnol123
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ok i'll give it a go

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 Posted: 05-30-2011 07:46 pm
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jarnol123
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OK tried all of that...I did the upside down test and whatever I did I couldn't get the two carbs to less than 9cmhg between them. The front carb is hovering around 16-17 and the back one is around 25-26. I tried the balancing screw at every setting and it doesn't make any difference. tried adjusting idle mixtures..no joy there either . I have the bypass screws all the way in on all 4 barrels..

stumped!

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 Posted: 05-30-2011 08:08 pm
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subwoofer
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Hmmmmm. If you look down the barrels, do the butterflies look like they are in the same position? It sounds like the front carb butterfly is offset compared to the rear carb - towards full throttle.

If both barrels of the front carb are roughly equal I think we can rule out a vacuum leak for now, there is something fundamentally wrong with the throttle opening, methinks.

Stupid question: Are both carbs from the same car?

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Joachim

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 Posted: 05-30-2011 10:59 pm
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jarnol123
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front carb butterfly is about 30-35 degrees open ...the rear carb is closed or very nearly closed.

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 Posted: 05-31-2011 04:28 am
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subwoofer
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There's your problem then, and probably the source of all the observed misbehaviour!

Both pairs of butterflies should be very nearly closed at idle, and the whole point of balancing is to make them move in unison.

I guess the linkage on the front carb has been disassembled at some point and not put together correctly. At this hour (6:20am) I can't remember how the linkage is connected to the throttle axle, so I can't tell you exactly how to fix it, but I don't think you need to take the carbs off.

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Joachim

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 Posted: 05-31-2011 01:41 pm
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Brett Gibson JH5 20497
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I's my understanding that the linkage between the carbs has to be disconnected when tuning the carbs, once their in sync then they should act toghter.

Brett

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 Posted: 05-31-2011 02:37 pm
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subwoofer
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Are you sure the linkages are joined correctly? If done wrong, the front carb will have a lot of opening at idle.

This is what it is supposed to look like:



--
Joachim

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 Posted: 05-31-2011 03:29 pm
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Dan (Florida)
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I do believe you are running Stromberg single barrel carbs in which only  2 tubes will work, 1-2, and 3-4.  Furthermore you wont see the butterflyvalves as they are behind the slides. You are only balancing 2 lines

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 Posted: 05-31-2011 06:22 pm
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Esprit2
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Jensen Healey wrote: This site may help:
http://groups.yahoo.com/group/S1S2S3owners/files/Dellorto%20jetting/
You need to be a member of Yahoo Groups to log in.

Ahhh...  that explains it.   I'm the moderator over at S1S2S3Owners,  and I was curious about the sudden influx of subscription requests from Jensen-Healey owners.

No problem.

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 Posted: 06-05-2011 04:41 am
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jarnol123
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one thing i did notice was that when i turn the carbtune upside down and before the engine is switched on the 4 cylinders all read about 16 ....when i get the engine running ...cylinders 3 & 4 go up to about 25 but cylinders 1 & 2 don't move at all no matter what I do.

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 Posted: 06-05-2011 08:22 am
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subwoofer
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You have already identified the reason why there is no vacuum on 1&2, have you located the problem?

My bet is that you didn't get the connection between the linkages right, it can be tricky to get right - I had to have both carbs loose at the same time to get them to join correctly.

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Joachim

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 Posted: 06-05-2011 06:14 pm
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jarnol123
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Ok so I got it so the butterflies all look to be in the same position...problem now is that cylinders 1 &2 go right up to the max on the carbtune and 3&4 seem really low. I guess it's the balancing again right? but the butteflies seem to be in about the same place.

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 Posted: 06-05-2011 07:58 pm
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subwoofer
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You are getting closer!

Since you have it running with all butterflies in the ballpark it is time to go through the balancing procedure. Turn the balancing screw - the one with the yellow gunk on it in the picture - in (clockwise) to bring the vacuum on 1&2 down in relation to 3&4. Small adjustments should make a difference quickly. I don't think you should have to have the carbtune upside down to get a good reading.

It would be so much easier to help if I could stand next to you and the car, but unfortunately you are 7000 miles and 9 hours time difference away... :-)

--
Joachim

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 Posted: 06-05-2011 11:44 pm
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jarnol123
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Ok I have them all lined up pretty much....here's some other interesting stuff...

1. When I pull the throttle lever in between the carbs it seems to stick sometimes and rev up and down for no reason..only slightly...sounds like a vacuum leak somewhere?

2. I think my timing is way in advance...I loosened the distributor but even twisting it doesn't make enough difference..what should the setting be? and also, how do I set the timing properly ( i have a timing light)?

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 Posted: 06-06-2011 04:35 am
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subwoofer
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Good that we are getting somewhere!

1. No reason to suspect a vacuum leak, you would have seen that with the carbtune. Do you have a proper return spring installed from the throttle linkage to the air filters? The springs in the carbs are not strong enough in themselves, this makes for some interesting driving if you don't get the right spring installed (I have tried).

2. Are you still running points? Check them for wear and clearance first - or better yet throw them out and replace with a Pertronix unit. Idle should be somewhere around 10 degrees, 28-29 degrees at max advance.

--
Joachim

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 Posted: 06-06-2011 04:19 pm
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jarnol123
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I'll check the springs but did you replace yours with something else? Ie not stock.
Also, can you walk me through setting the timing? I want to make sure i'm doing it right. I have pertronix ignitor with flamethrower coil and the standard Lucas distributor.

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 Posted: 06-06-2011 06:23 pm
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subwoofer
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I'll try as best as I can to walk you through it, beginning with the return spring. There should be one spring at the back of each carb, but these are not strong enough to pull the throttle cable all the way back, so there must be a third spring, marked with the red arrow in the first picture.



Unless the ignition is less than 2 degrees off, you should leave the nut pointed to by the blue arrow alone, and loosen the distributor clamp (green arrow) just enough that you can turn the distributor. Don't loosen too much, or the distributor will pop out, leaving you fiddling for a while to replace it. It is wise to mark your starting position with a scribe or pencil in case you suddenly get a lot of movement (happens easily). Rotating the top of the distributor towards the cylinders will retard the timing, away will advance it.

I recommend that you stop the engine between adjustments, since over advancing it while running will cause flames to spit out through the carbs - in close proximity to where your face probably is at that exact moment...



These are your timing reference marks. If you have a dumb timing gun like I have (no dial on it), the mark on the crankshaft pulley (red arrow) should line up with the "10" mark (blue arrow) when you point the gun at the pulley and pull the trigger while the engine is idling (inductive pickup clamped around #1 plug wire). Revving it should make it move close to the "30" mark, but not above. If your timing is WAY out (as in not firing at all), marking the notch on the pulley with some brightly coloured nail polish stolen from your wife will make it a lot easier to spot during the flash.

Sorry for the out-of-focus shots, it was the best my phone would let me do today.

--
Joachim

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