• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR6 1971 TR6 won't idle.

Share this page

It depends on how "sporty" a cam he put in. Most of the sporty street cams should still idle OK. As you go to a cam with more duration and overlap, it will lope and if you go further it will be difficult to get it to idle at low rpm. I would expect that you would have to go to a full race cam before that alone would give the problems you have.

You should be able to remove the tops without pulling the carbs off the car. The tops are held on by four screws. You probably don't have take the damper piston out (the black knob on top unscrews and it lifts out) but it seems to me that it is easier to put back together if you do.

Bryan
 
Thanks for the quick response Bryan. I will try to give it a try tonight after I get the kids in bed and a couple other chores out of the way. Probably be another late night for me...
 
BJones said:
I do recall the PO did tell me he put a sportier cam in it, but I guess I don't really know what that means or what it effects.
Click to expand...
Among other things, it frequently means the valve lash should be set larger than the factory value. Having the lash too tight can definitely cause problems at idle.

If you can, ask the PO what the lash should be, or check for it to be written down somewhere. If not, try opening it up to .020" and see what happens.

The Bap-Geon "3/4 Race" cam I had in a TR3A many years ago had a mild lope at 1000 rpm but was reasonably smooth at 1200. Had somewhat less power below 3000 rpm than the stock cam, but around 3500 it "woke up" and pulled like a banshee out past 5000. Used to beat 289 Mustangs at the "Friday night drags" until I broke a tooth out of the diff & retired /bcforum/images/%%GRAEMLIN_URL%%/smile.gif Sure wish I'd saved the specs, that was a lovely cam !

ISTR it took .018" intake and .024" exhaust, but I may be wrong about that.
 
Yes, you can remove the carb tops without removing the carburetors.

Reasons why I want you to start there.

Diaphragm tear is a common pattern failure as the rubber gets older. When you remove the air filter housing, look into the throats of the carburetors and lift up each one separately(engine off) and feel the resistance. We're looking for comparable resistance on each one. Should have a slight lift, 1/16 to 1/8 inch free then resistance felt as you lift the piston up against the oil.

If not find the fault and fix it. Often the oil in the dampers will leak past the o-rings and you can get new o-rings from Moss, they also sell the fuel mixture tool. Allen wrench with a pinned holder to hold the piston in place so you can turn the needle separately. One reason why the diaphragms get torn is that people will not have the right tool(inserted) and turn the allen, tearing the diaphragm.

Also, when you have the filter housing off, check the linkage. Have someone inside pedal press and make sure the throttle levers are being moved approximately the same amount. Might need bushings, linkage, etc.(You know you already need a choke cable.).

When you take the screws off, I recommend doing one carburetor at a time, as you can refer to the other one. Make sure that before you undo them that both the carb tops are facing the same direction. Possible a "Carlos" had them apart and didn't refit them properly.

The screws on the top are not regular phillips. They are a crosspoint called Pozidrive. But a good SnapOn/Matco/Mac 12inch or longer shank phillips #1size(if I remember right) should work fine. If you have any concerns on tight screw not coming off and you are afraid of stripping the screw head then head for Sears, or whatever and pickup an impact screwdriver set for around 20. Use the large philips in it, a ball peen hammer and one sharp whack on each screw will loosen the threads up.

After you get the diaphragm/linkage problem taken care of then we can move on to possible fastidle diaphram leakage.

But, one step at a time. Unless you are famailiar with the Zenith Strombers.
 
But be careful once you get the carb top off; you can easily drop something small down the throat and it will end up in one of the cylinders; of course you're not allowed to ask how I know this!
 
If unfamiliar with removing the carb tops, I don't think whacking them with an impact screwdriver is a good idea. Just get a really tight fitting phillips - or ideally Pozidrive bit - and make sure it fits perfectly. Then leaning down firmly into the screw, slowly begin applying and increasing counterclockwise pressure. Don't rush, keep the downward pressure on - they will unscrew easily if you have the correct fit. BTW - you can buy the right Pozidrive for less than the cost of the impact driver.
 
Here, I'm gonna disagree with you. If there's any concern with using a screwdriver impact, It's easy enough to try it on a couple of other screws that aren't in pot metal to get a feel for them.

I mentioned ball peen, not 5 lb. sledge. Most of these screws that are put in ZF's develop a film of corrosion on the threads over a period of time,as they are dissimilar metal, if the installer did not put some antiseize on them.

The carb body that the screw threads into is rather thick.

I've seen too many pozidrive screw heads stripped because the remover didn't get the INITIAl turn free. Once the screw starts turning, then use a screwdriver. But I myself(over 35 years in the auto trade) have had to whack a couple of ZF screws several times, just to "break" them loose.

And I recommended only one hit with the ballpeen.
 
I haven't been able to work on this issue as life tends to get in the way, but I did print out the Carb section of the Buckeye Triumph's archived web site. Hopefully Ron and anyone else will be willing to walk me through this process. I will definitely feel much more comfortable knowing I am doing what is instructed cross-referencing the other guide. My main concern is to accidentally unscrew the wrong thing while intending to follow instructions.

I will start by removing the air filter housing and check the resistance. Then I will remove the tops one at a time to check for tears in the diaphragms. I will let you know what I find.

Thanks,

Brent
 
Ok, I removed the air filter housing and checked the resistance. I noticed I had around a 1/8" - 1/4" of slack before I felt the resistance against the oil. I then removed the tops to each carb and checked the diaphragm's. I was not able to see any tears or pinholes. They looked brand new. I am not sure where to head from here, please let me know any suggestions you may have.

Thanks!
 
BryanC said:
Once you can get some sort of idle, you can work from there - changing the timing, adjusting the mixture, etc. Changing the timing or mixture will alter the idle speed and you'll have to go back and change the carbs' idle speed screws again.

If the vac. unit hits, then you probably have the distributor indexed over a spot or two. That's not a big deal and the only problem with doing that is that the vac. unit hits. There was a long discussion about how to change this in an earlier thread:

https://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/showflat/Number/216494/page/0/fpart/5

Bryan
Click to expand...

I think this is what I will work on tonight. I have not heard back on the next step when it comes to the carbs. They were extremely clean and new looking when I took the tops off last night. The PO told me he had a Jaguar mechanic rebuild them a few months before I bought it and I have only put around 500 miles on it in the last year. When attempting to adjust the timing before I didn't play with the idle any. Maybe I can set it to 4 after and then adjust the idle screws and see if it will idle around 850. Right now it will idle at 1100 to 1400 and kind of bounce up and down.

Any input would be greatly appreciated!

Thanks!
 
My GT6 I just got is doing the same thing. I remedied the vacuum leaks, tightened the exhaust and intake manifolds and tried adjusting the idle on the carbs with the manual but it still has a lumpy idle I got mine to where its bouncing round 1000rpm. If you figure yours out please post the solution up here!

Zack
 
A high idle speed is often caused by the pollution control crap the FEDs mandated to be put on our starting in 1968.
My 6 would not idle down, and here is the solution to what was my problem.
The plastic oblong cover on the right side of the carb is the temperature compensator. Remove the two screws holding the cover. Inside, you will find a nyloc nut. Run that down to the carb body. Put the cover back on.
Next, behind the temp. comp. is the bypass valve. It looks like it has a high headed nut protruding from it. There are several screw heads visible. Some are holding a diaphragm in place, the others(I think the slotted heads) are holding the unit to the body. Remove the bypass valve. Inside you will find a gasket. Carefully remove the gasket so not to damage it. Get some black gasket paper at an auto parts store. Trace the outside of the gasket onto the paper and cut it out. Use the solid piece of gasket paper when reinstalling the bypass valve. Repeat this on the other carb.
You can then set your idle.
 
I know it has been a little while since I have added to this, but I have been playing around with it and I have found out a little more information. I set the timing statically to 12 BTDC per the instructions in the link in my post above. It seems to be running a little worse. The idle is less consistant. So I think I need a little more work in that area.

I was able to dig up the PO's phone number and took a chance on him providing me some additional info. I was able to find out that the Camshaft he installed was the GP2 from goodparts.com. I will try and email the site tonight and see if they have any tuning information. Maybe they will be able to provide me the info I am lacking. The PO said he had set up everything to work with the upgraded Cam, but I dont know what all that means.

Now the questions. Besides the valves what else would need adjusted when adding an upgraded Cam? I have been told upgrading the Cam will throw off the idle and now I will idle closer to 1000 RPM and it will be a bit lumpy. Will this upgraded Cam also change the timing values from stock? How hard is it to check/set the valve clearance? Is this something I can do myself amd would any special tools be required? Any input anyone has would be greatly accepted. Especially if anyone has experience with this GP2 Cam.

Thanks!
 
Richard at GoodParts will have all the info about any other changes needed with the cam. Lumpy idle generally also means the idle mixture is off even when the carbs are properly adjusted, so ask him his recommendation for setting mixture.

Setting the valves isn't hard at all, just a few things to learn. No special tools beyond a feeler gauge, wrench and screwdriver. In a nutshell, you take off the rocker cover, then turn the engine so each valve in turn is fully closed, and stick the feeler gauge in between the rocker & the valve stem. It should slide in with some resistance, but not too much, even when you get it aligned just right. If the resistance isn't right, you loosen the locknut, turn the slotted screw until it is right, then hold the screw still while you retighten the locknut. Then check again.

Easy way to learn, IMO, is to double-check your work with gauges that are .002" larger and smaller than the target clearance. .002" smaller should be so loose it rattles, while .002" larger should be almost impossible to get in.

You can actually buy gauges that have a step built into them, but I've never bothered with them.
 
Uh, curiousity aroused now that you mentioned cam installation.


Have you done a cranking rhythm test? A compression test?

Reason I ask is, possiblity that a lifter/lobe may be damaged.

Battery fully charged, disable the ignition, Just pull the coil primary supply wire, make sure it isn't touching anything and crank it over for about 8-10 seconds. You are listening for an even cranking rhythm, if it goes up and down in speed, then one(or more) of the cylinders is weak.

Compression, battery fully charged, all plugs removed, ignition disabled(I pull the cap and primary supply wire) warm engine(run it for 10-15 minutes before testing) install compression gauge, with throttle fully open crank each cylinder 5-6 seconds, at least 4 compression strokes each cylinder. Compare compression make sure you are within 15-20 lbs of each other.
 
Back
Top