Tach And Dwell

[Don Jordan]

Okay - I don't want to start anything controversial but I have a couple of questions that I have heard many answers to. I was looking on the bay for a tach and dwell meter. Some people say that any will work on a 6v car - others say it must be a 6v meter. I am trying to sync my carbs and I would like to know the RPMs. I'm having a tough time getting them together. It doesn't make sense to me but with the car at an idle, linkage disconnected, if I push in (close) the throttle on the front carb the car will die. If I put my hand over the rear carb the idle will slow but not die. The sync tool on the back carb is hovering right in the middle - on the front carb it blasts right to the top. I don't mean to run this in the ground and I know it's probably covered somewhere but I'd appreciate some feed back.

[randroid]

Don,

My T&D meter is a cheapo-cheapo I needed to buy on the fly 30 years ago and I've never replaced it because it's accurate and has never quit. It doesn't care what voltage you're using nor does it give a whit about the polarity (hook the red wire to the hot side). Maybe in my next life I'll spend more money on one and worry about it more, lol. The vacuum meter is telling the tale, though, and is what you want to address. I'm assuming you're using the tube-type that sits on top of the carb and has a ball that floats inside it. These are great tools but you must realize they are the epitome of an analog meter in that what they measure flow only relative to themselves and because of this you must use only one for each set of carbs; if you set two meters on two carbs the readings would have nothing to do with each other. Use just one meter for both carbs because you're measuring fluid flow and you want to be able to compare the readings.

What I've always done is get the engine running with both needle valves open the same number of turns, then used that as a base. From there it's simply bouncing back and forth between the two carbs until you get the same reading. This "simple" step can take a lot of tweaking to get right, as in you may spend more than your lunch hour doing it, but once you get it right on the money your car will thank you profusely. It is well worth the time and effort to do right and if you just can't get it right them perhaps the jets are the wrong size, or something obscure like that, but if the engine has ever run well before and the carbs aren't filled with crud they should reward you for the frustration this seemingly simple task has dumped on you. I'll offer a place for you to start because your rear carb is going along for the ride while your front carb is doing most of the work and they obviously need to be synchronized. I'd bet the rear carb has somehow gotten its needle shut down and the front carb has been opened; it's a common occurrence that sometimes can take years to happen and evades most of our notice. Getting both carbs synched is where the vacuum meter becomes invaluable.

This thread was originally about a T&D meter and mine is a Car Quest #GPE 30419, although I don't necessarily feel you should make a great effort to match the numbers exactly because they're all made on the same foreign assembly line.

I tried to keep this reply simple but if you want me to go into greater detail on anything I'm happy to babble.

-Randy

Edited April 22, 2013 by randroid

[_shel_ny]

my old tach/dwell meter worked ok for tach, but gave unquestionably wrong dwell readings. I bought an older one on ebay that said it would work on 6v.  It does.   Your call, but I would buy one that is listed for 6v.

[TodFitch]

There is no voltage rating on my CarQuest tach/dwell meter that I can find anywhere. Seems to work just fine on my car. And Randoid mentions, hook red to positive and black to negative. Since many of the later 12v cars actually used a 6v ignition system, either with a "12v coil" with internal resistor or a separate ballast resistor, it make sense to me that a tach/dwell meter should work on both 12v and 6v cars.

 

But from your description and Randoid's explanation, I wouldn't be surprised if the problem is not in the electrical system.

[Plymouthy Adams]

it was also mentioned/recommended that if your dwell/tach was marked as 12 volt to use an external 12 volt battery to power whatever internal circuits as needed.

[_shel_ny]

it was also mentioned/recommended that if your dwell/tach was marked as 12 volt to use an external 12 volt battery to power whatever internal circuits as needed.

Really???? My tach/dwell meters have 2 wires. If they are not connected to the vehicle being tested, how are they going to work

[Don Coatney]

Is this thread about buying a dwell/tach meter? If so it belongs in the parts wanted forum.

 

If this thread is about carburetor syncronazation the how to answers have been given to the original poster in several other threads such as the two linked below.

 

http://mopar.pairserver.com/p15d24ph_forum/index.php?/topic/21392-george-asche/?hl=%2Bcarb+%2Bsync#entry206762

 

 

http://api.viglink.com/api/click?format=go&key=f0d80a80838754f59fa7fa48b7fd0bc8&loc=http%3A%2F%2Fmopar.pairserver.com%2Fp15d24ph_forum%2Findex.php%3F%2Ftopic%2F21392-george-asche%2F%3Fhl%3D%252Bcarb%2B%252Bsync%23entry206762&v=1&libid=1366643958233&out=http%3A%2F%2Fwww430.pair.com%2Fp15d24%2Fmopar_forum%2Fshowthread.php%3Ft%3D23427&ref=http%3A%2F%2Fmopar.pairserver.com%2Fp15d24ph_forum%2Findex.php%3F%2Ftopic%2F31047-my-offy-intake-reds-headers-transplant%2Fpage-8%23entry329677&title=George%20Asche%20-%20P15-D24%20Forum%20-%20P15-D24.com%20and%20Pilot-house.com&txt=http%3A%2F%2Fwww430.pair.c...ead.php%3Ft%3D23427&jsonp=vglnk_jsonp_13666440653124

 

 

I am very confused by the original question and the responses. Is the original question about use of a dwell/tachometer meter to sync twin carburetors? If so I dont get the connection. This dwell/tachometer meter will not work and is not required to sync carbs. A flow meter is required. And as has been mentioned many times carb syncing has nothing to do with the idle fuel mixture, nor the idle speed. Syncing carbs is all about the throttle linkage and nothing more. .

[Don Coatney]

Really???? My tach/dwell meters have 2 wires. If they are not connected to the vehicle being tested, how are they going to work

Tim must have been thinking timing light.

[Merle Coggins]

Don, I believe the connection comes in the fact that he wants to use the tach side of the meter to measure the engine RPM while adjusting his carbs. That was pretty aparent to me when I read his post.

 

By the way... my tach/dwell meter is clearly marked 12v, but it works just fine on my 6v truck.

 

Merle

[Plymouthy Adams]

Really???? My tach/dwell meters have 2 wires. If they are not connected to the vehicle being tested, how are they going to work

 

 

yes really...they make more than one model dwell/tach meter...the model I have (and others may fall into this category) being inductive..will have need for voltage inputs...and it was for this reason the statement was made tha tif you have meter that is 12 volt powered to use the aux battery...I use Sun equipment including a the large roll around multi-tester with o-scope  the one pictures is the quick to grab tester for out in the yard..

[_shel_ny]

SANY0125.JPG

 

 

yes really...they make more than one model dwell/tach meter...the model I have (and others may fall into this category) being inductive..will have need for voltage inputs...and it was for this reason the statement was made tha tif you have meter that is 12 volt powered to use the aux battery...I use Sun equipment including a the large roll around multi-tester with o-scope  the one pictures is the quick to grab tester for out in the yard..

OK, thanks for the clarification

[Plymouthy Adams]

^{Don  J. ask this question on chat the other night and I answered it as above at that time...I posted what I did as a reminded to that conversation...}

[Don Jordan]

Don Coatney: While many accept you as the resident forum curmudgeon I see no need for your acerbic reproofs. Yes, this thread is about carburetor synchronization - with an assist from a 6v tach. If this thread concerns you so much why don't you positively contribute; other wise why do you become involved? There are others on the forum that found the exchange of information interesting. Are you suggesting that if there is a legitimate question about a tool it shouldn't be asked in this forum?

I would like to thank Merle Coggins for putting things in perspective without being condescending or negative.

I am reluctant to post because of you.

[Don Coatney]

Don Coatney: While many accept you as the resident forum curmudgeon I see no need for your acerbic reproofs. Yes, this thread is about carburetor synchronization - with an assist from a 6v tach. If this thread concerns you so much why don't you positively contribute; other wise why do you become involved? There are others on the forum that found the exchange of information interesting. Are you suggesting that if there is a legitimate question about a tool it shouldn't be asked in this forum?

I would like to thank Merle Coggins for putting things in perspective without being condescending or negative.

I am reluctant to post because of you.

 

 

I have responded to this via PM

[Don Jordan]

Mr. Coatney sent me an e-mail suggesting I apologize for calling him names. He suggested I do this on the open forum. An interesting concept I have not been familiar with since the 8th grade. So let's see if we can cover some ground here.

First: I did not call Mr. Coatney a name. I merely made an assessment of his on line demeanor.

Let's begin at the beginning. I would like this to be for the record: Mr. Coatney you have made an effort to besmirch my legitimate question with pompous rhetoric and I would like to make clear my position. You said you didn't see the connection between adjusting the carbs and a tach meter. You intimated that I was trying to obtain the meter and suggested this was the wrong forum for that. Had you read the post carefully you would have seen my question was can a 12v meter work with a 6v system? You posted a reference (http://api.viglink.c..._13666440653124) which included a post (#15) by Dodgeb4ya. He included a page from a manual for twin carb adjustment. #3 - "Start the engine and set the idle speed to 400 rpm..." The same thread from Powerhouse mentioned "I then adjusted the mix screws... about 3/8 of a turn so it ran at 475 rpm." How did he know?

I must disagree with your premise that "the tach/dwell meter will not work and is not required to sync the carbs." If you want to dwell on semantics I will concede the tach is not "required" but it is still a useful tool when properly utilized. I will agree, however, it may have nothing to do with synchronizing - but tuning each individual carb first would be a prelude to successful synchronizing.

Finally: you are correct in that you have made many positive, helpful posts. It's the negative, snide, hurtful remarks that are the most remembered.

I must say that the idea of me apologizing to you for an honest opinion is ludicrous. I do so hope this will be the end of this.

[Don Coatney]

Tod;

As usual you are correct. Sorry for my lapse in judgement.

Edited April 24, 2013 by Don Coatney

[TodFitch]

Don & Don, Perhaps this off topic conversation would be best handled in PMs. . . .

[WatchingWolf]

Tell you what Don J. I have a tach/dwell meter here that I found on the shelf of a garage that was going to be burned down. Send me a message with your address and you can have it for whatever the cost of shipping is....the lens is foggy but a it of polishing should take care of that and apparently some guy named Jay owned it at some point as he scratched his name in the case. It's a Dixson model 1501.

[Plymouthy Adams]

Leno has been calling and calling about that dwell tach..I keep telling him I didn't have it...