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Jaguar Repair/TR4 Excessive Exhaust


First wanted to thank you for your advice awhile back with a pushrod situation I found myself in - your timely advice and recommendation to find the source of my problem, and not just to fix the problem, has made me much better at restoring antique cars. However, once again, I'm reaching out through a thick cloud of exhaust smoke for a helping hand & some advice to get my car back on the road.
Here's what I'm working with:
1963 Triumph TR4
1965 TR4A 2138cc
Pertronix LU-142A
Pertronix FlameThrower 3ohm
Alternator Conversion
Bosch Platinum Plus Plugs
Road Draft Tube install & Flame Trap Removal
..AND a God awful pair of ZS 175
The situation: Car has been running fine over the last couple months, constantly upgrading / replacing parts - had one minor disaster where lower coolant hose sprung a leak and I overheated, cracking my head. Head was replaced along with gasket...everything seemed to be fine. Lately, I can't take the car out of the driveway because once it warms up it spews out so much exhaust that I'm sure I'll get  pulled over for clouding up the road. Blatant rich mixture, scent of unburnt fuel - not burning oil or coolant. I'm pretty sure the problem doesn't have to do with the previous head replacement & is caused by malfunctioning / improperly tuned Carburetors. Here's what I've tried to do to fix the issue (but all has failed so far):
- Synchronized carbs
- Checked dashpot oil levels
- Recentered needles
- Applied Colortune and no matter how I turn the mixture screws, I just see orange in the window
I'm thinking about adjusting the float levels, but have never done this before - and I'm not sure if I'm barking up the wrong tree.
As always, I thank you for your time & much appreciated advice.

Hi Marc,

It is usually easy to diagnose smoke as the color is always a sure indication of the type of problem, then once you know the type of problem you can go after the detailed point of the problem.

First, when does it smoke? Only when first started? mostly on acceleration? On acceleration and at cruise?

Next, what color is it as viewed from behind? White? which is either coolant and or brake fluid. Blue? Which is oil only and if it is only on fresh start up and then gets less as it warms up. Which is valve guides / stems and or crank case pressure. If it is blue smoke on acceleration and cruise it is either / or rings and or crankcase pressure.

If it is black smoke it is excess fuel and nothing else. This can be the metering needles, Float levels, float chamber venting, Stuck pistons, Hydraulic lock in the top dampeners, torn diaphragms. Or choke problems.

I always look at the type or system first and once you ID the type or system then I go after a more detailed search.


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Howard M. Fitzcharles III


Jaguar from the XK 120 to XJ-6 ser. 3 1987


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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