[6pack] tr6 carb question

Mon Sep 14 15:21:49 MDT 2015

Hi Bill, 

I have more questions than answers, I'm afraid, and after 3 months you've probably asked yourself all of them but here goes: 

How do you know for certain that 3 cylinders are not firing? This points to a pretty weird scenario of 3 spark plugs, 3 spark plug leads or 3 terminals on the distributor cap all failing at once. Unlikely. Misfiring at temperature means that something is losing continuity when it gets hot. This will not happen due to the temperature compensators. Yes..the car may behave less then ideally if these things are out of whack, but I believe the cross-over on the intake manifold would ensure that the problem, if the compensators were causing one, would be apparent everywhere..not just on 3 cylinders. 

I'm definitely leaning toward an electrical problem. It's not the coil, the condenser or the points because their misbehaviors would not be cylinder-specific so I think you've got a spark distribution problem. 

Try swapping some leads between dizzy cap and plugs to see if the misfire migrates when it warms up. If it does…the lead(s) are the problem. I've had lead problems before so I'm leaning in this direction. 

Ditto with the plugs. Swap them around and see if the problem moves. If it does…plugs are the culprit(s). I'd be less surprised by 3 duds in a batch of 6 leads then I would be by 3 duds in a batch of 6 plugs because leads are more easily damaged. 

OH…a longshot: Have you had the air filter box off? If so, and if you mistakenly covered the hole on the carb throat face that doesn't get a bolt going through it, by putting the gasket on backwards, this will be your problem. If those holes are blocked, the car will run OK only up to about 2500 rpm. If you typically keep the revs at or below this level while you warm the car up, you could think the problem is temperature related. That said….I'm still thinking you've got a sparking problem, not an aspiration problem. 

Colin 
'74-1/2 
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Today's Topics: 

1. TR-6 Carb question (wcwellbaum at cox.net) 
2. Re: TR-6 Carb question (Mark J Bradakis) 

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Message: 1 
Date: Mon, 14 Sep 2015 02:18:22 +0000 (GMT) 
From: wcwellbaum at cox.net 
To: 6pack at autox.team.net, jpaynepbr at cox.net, Steve Kennedy 
<triumph971 at aol.com> 
Subject: [6pack] TR-6 Carb question 
Message-ID: <18cabb4.349f.14fc9a56096.Webtop.0 at cox.net> 
Content-Type: text/plain; charset=UTF-8; format=flowed; delsp=no 

My '75 TR-6 will run well until it warms up and will then drop down to 
the rear three cylinders with spitting and popping out the exhaust. 

Following is a list of what I've tried to correct my problem: 

New: 
Dizzy cap, rotor, points, ign. wires, coil, capacitor, plugs. 

Relatively new fuel pump, and a new fuel filter. Plenty of fuel being 
pumped into both carbs. 

Carbs: took them apart and cleaned all parts. Replaced the Grose jets 
and diaphragms. Took the bi-metal thingies apart and cleaned them out 
and reassembled. Set the float levels. Using 20 weight oil in the 
dashpots. 
Used compressed air to flush all fuel lines and can hear gurgling in the 
gas tank. Float bowels are squeaky clean. Carbs were rebuilt by 
Roadster Factory several years ago. All this work have resulted in NO 
correction of the problem. 

Put new fuel filter on today and it fired right up. Idled smoothly for 
about 5-8 minutes and dropped down to the rear 3 pots. Still have spark 
to the front cylinders. 

Don't have any overheating symptoms and don't smell any anti-freeze or 
the smell associated with overheating issues. I've been trying to 
correct the problem for about 3 months now and have run out of ideas on 
what it could be. 

Does NOT seem to be electrical in nature but DOES seem to be heat 
related. As is, runs fine till warm. Another Club mate suggested the 
bi-metal gizmos may have something to do with my problem. Any ideas? 

Clue: If I have spark to the three front cylinders and and I have 
gasoline being pumped into the front carb what would cause the three 
front cylinders to stop firing when warmed up. Need Help! 

Bill Wellbaum 
British Auto Club of Las Vegas 

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Message: 2 
Date: Sun, 13 Sep 2015 22:56:14 -0600 
From: Mark J Bradakis <mark at bradakis.com> 
To: wcwellbaum at cox.net, 6pack at autox.team.net, jpaynepbr at cox.net, Steve 
Kennedy <triumph971 at aol.com> 
Subject: Re: [6pack] TR-6 Carb question 
Message-ID: <55F6536E.6020503 at bradakis.com> 
Content-Type: text/plain; charset=UTF-8; format=flowed 

How do you know which cylinders are nit working? What have you done to check for vacuum leaks? 

mjb. 

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