The NYC TR chronicles, vol. 1: NYC / Carb problems

[newmexTR3]

Hey guys,

I hadn't given you a full update yet on the 3, but here it is: The car was finally delivered from Albuquerque to Brooklyn 2 weeks ago. I ended up using Four Corners Transport Services (www.fourcornerstransportservices.com) and even though it took longer than expected for the car to get picked up, they kept me updated and were very courteous. I would definitely recommend them. The car was on an uncovered transporter and the whole move cost about $1150.

Within a couple of days of arriving, I showed the car in the annual 5th Avenue Street fair here in Brooklyn. I was parked alongside a nice group of American classics from the Brooklyn Antique Automobile Association. I joined the group on the spot and met a wonderful guy by the name of Lenny who is the president of the club and has over 70 cars stored in various parts of the borough. As an added bonus, car owners who showed off their beasts in the fair got 10 bucks- which paid for some ribs and beer! I now have some solid leads on affordable garages in the area as well as a nice network of car freaks to tap. So far life with a classic car in the big city has been great. The looks I get when driving through Brooklyn are really priceless.


Now to present my issues to the collective wisdom here:
Just over a month ago I was in New Mexico and had no real issues with the car- it started up fine even when cold (although it would take a few minutes of warming up before it would run smoothly)Since it's been here, I've had major problems with it starting hard, then idling roughly with major backfiring going on through the carburettors. The car rarely ever backfired through the carbs while in NM. Once the car warms up a bit, the problem goes away.

I have a relatively new distributor (less than 5k miles) and the ignition system seems to be operating properly (although I do not have the vacuum advance hooked up, but never have). I have cleaned the plugs and will be replacing the wires this weekend, so i suspect very much that this is a carb problem, specifically the front one.

The obvious environmental factor that has changed is the altitude- In NM I was at bone dry 5500+ feet. Here I'm at sea level with some humidity. I've gone by the book and adjusted the fuel/air mixture with the air cleaners off, but the mix didn't seem to be that much off. However, my plugs are still showing an overly rich mixture.

Other issues possibly effecting this are that the front carb's piston is stinking towards the bottom of its travel at times. I've cleaned it up as much as possible and it functions better, but I think it still sticks intermittently for a second before going all the way down.

Could this be a timing issue? My dad suggested I play with the distributor a bit and see if that makes it any better. What do you think? Any ideas from you guys would be appreciated.


Cheers,
Gavin

 

[Brosky]

Don, Randall??

Where are our resident TR3 experts when we need them?

Hang in there Gavin, they'll be around soon.

 

[TR3driver]

Other issues possibly effecting this are that the front carb's piston is stinking towards the bottom of its travel at times.

<span style="font-weight: bold">We don need no stinking pistons !</span>

Seriously, the slightest sign of sticking can cause serious mixture problems, so I would address that first. Remove the dome & piston from the carb (3 screws) and make sure the piston doesn't drag on the sides of the dome, even enough to make noise. Also examine inside the dome for any shiny spots, indication that the dome has been dented. The domes and pistons are theoretically matched sets, so if it drags for no apparent reason, you might try swapping pistons with the rear carb; perhaps some DPO (dumb previous owner) has inadvertantly swapped them.

Clean the mating surfaces then install the dome (with piston & spring) back onto the carb. Rotate the dome slightly in place, to be sure it's seated before putting the screws back in. Now check again that the piston moves with no signs of dragging. If it drags now, the jet is not properly centered (or the needle is bent).

Another thing I'd try is adjusting the valves. A too-tight valve can cause the symptoms you describe.

Also check that the chokes are reasonably synchronized. Pull the knob out and turn to lock (or stick a clothespin on the shank), then check that the jets are pulled down equally. Having only one carb choked can also cause hard starting and backfiring.

 

[newmexTR3]

Re: The NYC TR chronicles, vol. 1: NYC / Carb prob

Hey Randall,

Thanks for the tips. On Friday I did completely remove the dome & piston and cleaned it out with carb cleaning fluid (there was a lot of carbon build up from the backfiring I assume). There were no obvious wear marks. Plus, I've had the car for 15 years so I'm pretty sure that the pistons match the domes.

With no oil in it, the piston moved completely freely with very little play along the rod. I was careful to not torque the 3 screws too tightly when I reinstalled. Once I put oil back in however, the intermittent sticking (I would say 2 out 7 tries) in the last 1/3 of the travel still happens.

Buffing the inside of the dome with steel wool is a no-no, right? That could just cause an air leak, right?

Cheers,
Gavin

 

[TR3driver]

Re: The NYC TR chronicles, vol. 1: NYC / Carb prob

Buffing the inside of the dome with steel wool is a no-no, right?

Right. Besides, since you've proven that the piston doesn't rub on the dome, there is no point to increasing the clearance there. Has to be the needle rubbing on the jet, meaning you need to re-center the jet (or the needle is bent).

 

[newmexTR3]

Re: The NYC TR chronicles, vol. 1: NYC / Carb prob

That makes sense. How do you go about straightening the needle? Rolling it on a flat surface to see if there is an obvious warp?

ps- what kind of oil should go in the pot?

 

[TR3driver]

Re: The NYC TR chronicles, vol. 1: NYC / Carb prob

That makes sense. How do you go about straightening the needle?

I wouldn't, rather just replace it. <div class="ubbcode-block"><div class="ubbcode-header">Quote:]Rolling it on a flat surface to see if there is an obvious warp?[/QUOTE]That would tell you if it's bent.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]ps- what kind of oil should go in the pot? [/QUOTE]Lots of debate on that topic over the years. The heavier the oil, the richer the mixture goes when you first open the throttle (it basically acts like an accelerator pump on conventional carbs). The optimum amount for your engine probably depends on things like climate, general state of tune, etc.

But after some experiments, I settled on straight 20 weight motor oil as being best for my TR3A.