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Seems low on power at higher RPM's?

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allzway Avatar
allzway James P
Paris, TX, USA   USA
So this car is still being brought back to life after a 25+ year storage.

Most recently I had to have the head rebuilt due to a bad fuel and junk build up around the valves causing them to stick. Before the head build, the engine initally ran fine, but over time the junk seemed to make the valve sticking worse to a point of bending valves.

Fast forward.. I have it all back together and it is running. It is very hard to start in cold temps, but on warmer days it starts up fine. It doesn't have the vaccum hose connected at the backend of the distributor, does that have any control over it?


Next issue, is that it seems to be down on power from before, especially at higher RPM's and seems sluggish getting up to highway speeds. It doesn't backfire or cutout, just seems really slow to get up to speed and seems slower than it did before the head rebuild.

Attached is a picture of the distributor, does rotating the end of the distributor effect the timing of the engine? I had just moved it around while it was super cold and was curious if I need to find the correct spot for it?


James

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Attachments:
distributor2.JPG    45.6 KB
distributor2.JPG

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sampattr250 Avatar
sampattr250 Sam P
Harwinton, CT, USA   USA
James,

You said that you had bad fuel. Was the fuel system cleaned and or replaced when the work was done on head and valves?

If fuel system is still dodgy you could be starving for fuel at higher rpms.

Has you carb been rebuilt what about the distribuitor plugs wires cap rotor etc?

Secondly. Yes you probably need to reset your timing. I recommend you get a light if you don't have one and follow the many posts about setting timing. There is a direct correlation between proper timing and performance.



Sam

1968 TR250
1972 MK IV Spitfire

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allzway Avatar
allzway James P
Paris, TX, USA   USA
In reply to # 1602255 by sampattr250 James,

You said that you had bad fuel. Was the fuel system cleaned and or replaced when the work was done on head and valves? Yes.. completely gone through from end to end.

If fuel system is still dodgy you could be starving for fuel at higher rpms. It does almost feel like a fuel starvation.

Has you carb been rebuilt what about the distribuitor plugs wires cap rotor etc? Yes.. replace wires and cap also. The carbs were rebuilt before I ever got the car running.

Secondly. Yes you probably need to reset your timing. I recommend you get a light if you don't have one and follow the many posts about setting timing. There is a direct correlation between proper timing and performance.

I have a light and just quickly looked the other day and I can see the timing mark and it is just slightly off of the mark, but I haven't read up on how precise the marks have to align.



Thanks,

James



Edited 1 time(s). Last edit at 2019-03-15 11:51 AM by allzway.

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
Try slowly and a little at a time rotating the distributor clockwise when the engine is idling. See if the engine speed increases as you do.
Be sure to loosen the horizontal bolt on the clamp around the distributor so you can rotate the distributor...not the vertical bolt that hold the clamp onto the engine.
This picture shows the pinch bolt that needs to be loosened to obtain maximum rotation.
The tach cable should prevent you from going too far in the clockwise (advance) direction.
Let us know how the engine responds.



ZS carb repairs
kencorsaw@aol.com



Edited 2 time(s). Last edit at 2019-03-15 12:19 PM by poolboy.


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Distributor pinch bolt .jpg

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Krom Avatar
Krom Paul K
San Rafael, CA, USA   USA
James- I didn’t see mentioned your model year, but it appears that you have an early distributor. Ensure the vacuum lines are attached to the proper spots as incorrectly located or loosely fitted vacuum lines will add to your symptoms. As you have had the head off the car, you likely removed the carbs and disconnected the plumbing. Check for vacuum leaks all through the intake area and reset to detailed diagrams. PK

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dsixnero Avatar
dsixnero Dan Colanero
Westville, NJ, USA   USA
James, make sure the vacuum lines are plugged at the carbs, set the static-timing at 10 btdc, page 520-Bently manual. Make sure your chokes are working for cold start.

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tirebiter Avatar
tirebiter Jeff Garber
Dighton, MA, USA   USA
Did moving the distributor or ignition timing make any difference in power or cold starting ability ? It could help pinpoint the issue if it did.

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frostr6 Avatar
frostr6 Bill Connell
St. Paul, MN, USA   USA
Since the distributor has both advance and retard modules, this must be an early model. If it’s a ‘69, make sure either all of the vacuum lines and the valve under the front carb are working properly, or that they’re disconnected and closed off.

I have a ‘69, and the vacuum lines around that lower idle vacuum valve like to fall off when bumped, making for a vacuum leak and running issues.

And, as other have noted, if it’s been sitting a while make sure the fuel system is clean and supplying enough fuel. Maybe change the fuel filter and check the screen at the top of the fuel pump and make sure it’s clean.

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LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
If you haven’t done this lately oil the dizzy plate and weights. Pull the cap and rotor and put a few drops of light oil in the center where the screw head is. This will flow down and oil the weights and plate to make sure they can be moved easily by centrifugal force of to provide the proper mechanical advance.

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tirebiter Avatar
tirebiter Jeff Garber
Dighton, MA, USA   USA
By the way Ken,

That picture you provided in post #10 is a great training aid referencing the slot on the distributor hold-down plate. The range of static timing variation provided by the slot is sufficient to compensate for octane differences and engine wear-and-tear isn't it ?

The slot which is next to the "octane pointer" is a certain length according to what the engineers decided on, I believe. Maybe I'm wrong but I don't think it's just a randomnly sized slot size. If I remember correctly it allows more than enough variation. I think TR-6s are the only cars that utilized the slot.

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allzway Avatar
allzway James P
Paris, TX, USA   USA
This is a 1970 car, but I guess someone removed and plugged all vacuum lines. The distributor is plugged on the end.

I played with the timing a little moving the distributor around and looking at the timing mark. I did seem to get some better, but it still seems like it just runs out of fuel. At speed, pulling the choke a little seems to help some also.

It is just so slow to get up to highway speeds. Doesn't seem an issue under 40mph and keep the rpm's higher.

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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
The '69, '70, and '71's are the snappiest of the USA TR6's. They have the highest CR's (if one want's to claim 8.5:1 is high) and a larger exhaust valve. Not knowing what you expect, performance wise, makes it hard to gauge the problem. Time to go at this in a methodical manner. Make sure the vacuum lines are plugged at the carb. Don't just move the dizzy around, Set it @ 10° BTDC, Take the cap off and twist the rotor back and forth. It should be free. If not dig deeper into the dizzy to free the advance weights. Take the carb tops of and carefully check for splits in the diaphragms. What color are the plugs and the tailpipe? - Pete

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tirebiter Avatar
tirebiter Jeff Garber
Dighton, MA, USA   USA
The cylinder head was off but there was no mention of adjusting the valves. In case you didn't know, they should have been adjusted before even trying to start the engine.

Fiddling with the timing apparently doesn't seem to fix the problem at all except you feel it runs a little better now. Do you know if the timing ended up advanced from where it was initially ? Or did the timing end up being retarded from where it was initially ? Or did it make no substantial difference in either direction ?

Pulling the choke out should cause the engine to stumble at any and all RPMs if the engine is fully warmed up ... but you probably knew that already.

Going with the diagnostic aid;

"pulling the choke a little seems to help some also" tells me one of two things,

1) the ignition timing is WAY too far advanced. Peter made a very quick and simple suggestion you could try but unfortunately it doesn't involve "playing" with the timing

or

2) the air-fuel mixture is WAY too lean. Have you considered there might be a massive vacuum leak somewhere in the intake system ?

another question to ponder ...

Is it ? ... zero to sixty miles per hour takes over 20 seconds?

or

is it ? ... zero to sixty miles per hour happens in under 15 seconds?

that you are meaning when you say "It is just so slow to get up to highway speeds" ?



I am so sorry that I have to ask so many difficult questions in order for my brain to comprehend what could be going on with your engine.

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NHinNC Avatar
NHinNC Larry C
Greensboro, NC, USA   USA
You stated that the vacuum lines are off. put them back on.



1976 TR6 Mimosa Yellow - not original
Purchased July 2015

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allzway Avatar
allzway James P
Paris, TX, USA   USA
All good questions and I appreciate you trying to help.

I haven't found any obvious vacuum leaks. I even sprayed starter fluid around the different connections to see if it was pulling in air. Timing changes were just minor movement of the distributor both directions. Where it settled eventually was very close to where it started, but I don't know if that was advanced or retarded from the beginning.

Zero to 60 in 20 seconds or more. I am not that familiar with these cars, but it ran better before the valves got all gunked up and I head to have the head rebuilt. I have put about 40 miles on it since the rebuild, so need to recheck the valves.

I'll try to explain what caused the head to be worked on.

This car was stored for 25+ years and I brought it back to life. Poolboy rebuilt the carbs. The fuel tank was dry, but fuel lines were completely clogged. I replaced the rubber parts and cleaned out the hard lines and I replaced the fuel pump. The car ran pretty good initially, but the more I ran the engine, the more the valves appeared to be gunked up with sludge around the valve stems, to a point that they were sticking and sticking badly and it eventually bent a couple of pushrods.

I think as fuel was added and sat in the tank, it loosened up the old dried fuel in the bottom of the tank and that may have been my sludge build up around the valves. So I guess it is possible I could have carb problems again. I did drain and pull the tank, cleaned it and re-coated it for rust protection. It had mild surface rust.


I am still running two fuel filters, one at the back and one below the fuel pump.. so I also thought perhaps they were restricting fuel delivery. I did also replace plugs, wires, and cap.


James



In reply to # 1603383 by tirebiter The cylinder head was off but there was no mention of adjusting the valves. In case you didn't know, they should have been adjusted before even trying to start the engine.

Fiddling with the timing apparently doesn't seem to fix the problem at all except you feel it runs a little better now. Do you know if the timing ended up advanced from where it was initially ? Or did the timing end up being retarded from where it was initially ? Or did it make no substantial difference in either direction ?

Pulling the choke out should cause the engine to stumble at any and all RPMs if the engine is fully warmed up ... but you probably knew that already.

Going with the diagnostic aid;

"pulling the choke a little seems to help some also" tells me one of two things,

1) the ignition timing is WAY too far advanced. Peter made a very quick and simple suggestion you could try but unfortunately it doesn't involve "playing" with the timing

or

2) the air-fuel mixture is WAY too lean. Have you considered there might be a massive vacuum leak somewhere in the intake system ?

another question to ponder ...

Is it ? ... zero to sixty miles per hour takes over 20 seconds?

or

is it ? ... zero to sixty miles per hour happens in under 15 seconds?

that you are meaning when you say "It is just so slow to get up to highway speeds" ?



I am so sorry that I have to ask so many difficult questions in order for my brain to comprehend what could be going on with your engine.

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