PDA

View Full Version : Newbie Missing or Broken Timing Chain Tensioner?



PlaidMan
03-18-2006, 12:33 AM
Hi everyone. This is my first post . I'm a Triumph Fan since the early 80's, own a TR3A & TR4 which need to be restored. I've also owned a Spitfire 1500 that I enjoyed immensely but I'm really looking forward to restoring the 3A. I've waited 20+ years to start, the frame is stripped and ready for paint now, yes I'm excited. Just lately I had the opportunity to help with the restoration of a 3A which has motivated me to start my restoration. At the moment I'm helping a friend who has a 66 TR4A. It had a leaking needle&seat on the front ZS carb, fixed , put in new ignition,points,condenser,rotor,cap & wires, adjusted valves and carbs. The engine runs great on acceleration and has a decent idle but when you raise engine speed slowly to between1400-2000, it really jumps around alot but smooths out at higher rpms. Also, when driving in 4th gear at speeds of 40 mph or less, the car lurches back and forth mildly instead of just pulling consistenly,sort of mirroring the fast idle jumping around I mentioned earlier. I know that the engine was rebuilt once and was wondering if maybe the timing chain tensioner missing or broken could cause these symptoms?

Dave Russell
03-18-2006, 01:45 AM
[ QUOTE ]

Hi everyone. This is my first post . I'm a Triumph Fan since the early 80's, own a TR3A & TR4 which need to be restored. I've also owned a Spitfire 1500 that I enjoyed immensely but I'm really looking forward to restoring the 3A. I've waited 20+ years to start, the frame is stripped and ready for paint now, yes I'm excited. Just lately I had the opportunity to help with the restoration of a 3A which has motivated me to start my restoration. At the moment I'm helping a friend who has a 66 TR4A. It had a leaking needle&seat on the front ZS carb, fixed , put in new ignition,points,condenser,rotor,cap & wires, adjusted valves and carbs. The engine runs great on acceleration and has a decent idle but when you raise engine speed slowly to between1400-2000, it really jumps around alot but smooths out at higher rpms. Also, when driving in 4th gear at speeds of 40 mph or less, the car lurches back and forth mildly instead of just pulling consistenly,sort of mirroring the fast idle jumping around I mentioned earlier. I know that the engine was rebuilt once and was wondering if maybe the timing chain tensioner missing or broken could cause these symptoms?

[/ QUOTE ]
It's not likely to be a cam timing problem. If it was, it would be more noticeable at other rpms & loads. More likely, a small carb or ignition problem.
D

TypeRboy
03-18-2006, 01:53 AM
I would put the old condenser back in and see if that cures the problem, and maybe the points as well, but I doubt the points are the problem. A bad condenser can cause just that problem.. Did the car have the same problem before you replaced all the ignition stuff? If not then you know where abouts the problem lies!

PlaidMan
03-18-2006, 11:42 PM
Thanks guys for the quick response. Today I had a chance to put on a new condenser as you suggested but the engine reacted exactly the same as before. Let me give more history of the vehicle: Originally brought to me running rich and upon initial test drive noticed heavy vibration at 40mph+. Fixed the carb problem, rear transmission mount was bad, a new one eliminated 90% of the vibration problem. However, as you accelerate through each gear you can feel a distinct roughness from the engine especially at highway speeds. Today I reset the idle mixture using the colortune system and noticed on #1 cylinder the blue glow was not consistent , there would be a spark but not ignition of the fuel every once in a while. This coincided with an exhaust stumble sound and also showed on the tach as a momentary drop in rpm's. All the other cylinders were igniting consistently. Could this be a intermittent stuck valve? The engine still jumps around at about 1400 rpm but seems to smooth out only because of higher rpm's, maybe contributing to the roughness I noticed. Under hard acceleration, the car performs well but raising rpm's slowly I noticed the misfiring is still there. The car when brought to me had Pertronix Ign. on it but it was bad so I have no idea how it ran before except very roughly. The #1 cylinders compression was also about 5-8lbs lower than the highest reading taken on a cold engine. Not sure if I did it right but that is also one of the cylinders that had the carb with the stuck needle and seat, dumping gas into the intake which I thought might have affected that cylinder. I had the pleasure today of driving a TR3A and the engine felt much smoother than this TR4A and idled with an even sounding exhaust note , slightly different than the 4A. I would really apreciate any advice on how to proceed with diagnostics. Thanks again.

martx-5
03-19-2006, 07:21 AM
This sounds like a problem with the secondary part of the ignition system...plugs, wires, cap, rotor. Most misfire and "carburetor" problems are ignition related. I would start with a new set of plugs and wires. /ubbthreads/images/graemlins/driving.gif

thegoodbeamer
03-19-2006, 07:38 AM
I would check the distributor bushings.I had a similar problem on a Mopar 440 way back when.Machine did not show on a bench test.Fortunatly there was a super guy that test drove the car if the customer was not happy.In 2 blocks he said the bushings.They pulled the dizzy apart.replaced the bushings and problem solved.

PlaidMan
03-27-2006, 12:43 AM
Hey, you were all right about it being ignition related. This weekend I replaced the Dist. with a good used one and it now fires consistently, However it still misses on #1 cyl. I used the colortune system to view the idle mixture setting on #1 cyl., but was unable to tell when it was adjusted properly. Had to put the colortune on #2 to adjust the idle mixture. #3&4 were adjusted normally. On #1 , the blue glow appeared sporadically coinciding with the engine miss. Could this be valves or rings ?

03-27-2006, 06:16 AM
PlaidMan, are you resting your thumb on the spacebar while you are thinking about your post?
Trying figure out why such a large gap in your post before the wording begins.

Thought maybe there was a photo we weren't picking up.

Bill

WhatsThatNoise
03-27-2006, 07:27 AM
What do your plugs look like.........

I'm a firm believer in plug reading.

hondo402000
03-27-2006, 02:42 PM
could be a vacuum leak

PlaidMan
03-27-2006, 11:32 PM
Don't know what happened, I might have pressed enter instead of shift. I will check the plugs and also see if there is a vacuum leak on #1 cylinder. I did change manifold gaskets already, might look closer at the intake manifold . What's a good way to check if the valves are seating properly? Thanks for the replies.

WhatsThatNoise
03-28-2006, 06:38 AM
[ QUOTE ]
What's a good way to check if the valves are seating properly? Thanks for the replies.

[/ QUOTE ]
I have heard of 2 ways....(to check for sticking valves)

1) Use a timing light on different plug wires to strobe the top of the some reference point on the valve in question.

2) Put yer finger on top of the rocker, while it is running, and check for a difference in "feel"

BTW.....See if there is any agreement amongst the experts here before you try either........