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I've spent the past couple of weeks making a start on my maiden TR 6 project...a 1974 CP PI

Having replaced the exhaust manifold gaskets, water pump, thermostat and new radiator, I have reinstalled the inlet manifolds and air intake plenum etc. Prior to undertaking these jobs, the car started first time every time, but after reinstalling it took a fair few attempts to get the engine to fire up. Once it did eventually start, without the need of the cold-start lever, the engine is running far too high 2-2500 revs and it is smoking from below the manifolds.

I'm concerned that maybe I haven't achieved a decent seal on the gasket between the manifold and the exhaust pipes - which may account for the smoke, but that wouldn't explain the high revving? I have also noticed that a small amount of fuel is leaking from the top of at least one of the injectors where it joins the fuel pipe from the metering unit. I have disconnected the injectors cleaned and checked the threads and re-joined the fuel lines, but still getting a dribble of petrol.

Any suggestions as to what I may have done wrong?

 

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1 hour ago, Dan Middleton said:

I've spent the past couple of weeks making a start on my maiden TR 6 project...a 1974 CP PI

Having replaced the exhaust manifold gaskets, water pump, thermostat and new radiator, I have reinstalled the inlet manifolds and air intake plenum etc. Prior to undertaking these jobs, the car started first time every time, but after reinstalling it took a fair few attempts to get the engine to fire up. Once it did eventually start, without the need of the cold-start lever, the engine is running far too high 2-2500 revs and it is smoking from below the manifolds.

I'm concerned that maybe I haven't achieved a decent seal on the gasket between the manifold and the exhaust pipes - which may account for the smoke, but that wouldn't explain the high revving? I have also noticed that a small amount of fuel is leaking from the top of at least one of the injectors where it joins the fuel pipe from the metering unit. I have disconnected the injectors cleaned and checked the threads and re-joined the fuel lines, but still getting a dribble of petrol.

Any suggestions as to what I may have done wrong?

 

You dry fitted the gasket  

Edited by ntc
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45 minutes ago, Dan Middleton said:

It's a metal gasket and I used a small bead of silicon sealant on both sides to try and ensure a good seal.

It will be a composite one and silicone is no good 

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Your air leak causing high revs  is in the inlet somewhere. Could be the inlet manifold gasket.

I always lubricate exhaust gaskets with copper coat before fitting.

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If you have a vacuum gauge plug it into the brake booster connection and see what vacuum you have at idle. I have to have something like 10 inches of mercury for my PI system to work properly. Much less and you have a leak somewhere.

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1 hour ago, Mike C said:

If you have a vacuum gauge plug it into the brake booster connection and see what vacuum you have at idle. I have to have something like 10 inches of mercury for my PI system to work properly. Much less and you have a leak somewhere.

I don't have a vacuum gauge unfortunately. I'll re-check the gasket and see if that makes any difference, but since it was a blown gasket that lead me to this point, I think an air leak is more likely.

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Certainly worth closing them up to almost shut, on a CR you should be able to push a thin feeler gauge through, forget the exact size but it'll be a quick Google away to find out. CP version you fully close them, not sure which you have because you said 1974 CP, but CR was from 1973 on. 

Anyways for sure an air leak past the butterfly's will cause it to rev a little more at idle, so setting them up correctly and in balance will help no end. 

Gareth

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6 minutes ago, Mk2 Chopper said:

Certainly worth closing them up to almost shut, on a CR you should be able to push a thin feeler gauge through, forget the exact size but it'll be a quick Google away to find out. CP version you fully close them, not sure which you have because you said 1974 CP, but CR was from 1973 on. 

Anyways for sure an air leak past the butterfly's will cause it to rev a little more at idle, so setting them up correctly and in balance will help no end. 

Gareth

Yes, I meant CR! Thanks for the info...I will Google it.

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Hi Dan

A 2 thou feeler gauge is what is recommended.

In addition to manifold sealing & balancing, check the throttle bodies are in line horizontally with a straight edge, check for wear in the butterfly spindles & linkages, make sure the rubber balance tubes are secure & ensure the throttle return spring is man enough to return the butterflies to the closed position.

These are all problematic areas for both balancing & air leaks with the CR cars. I had endless hours of fun with mine.

Good luck.

Alan

 

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On 5/5/2022 at 3:43 PM, Mk2 Chopper said:

Certainly worth closing them up to almost shut, on a CR you should be able to push a thin feeler gauge through, forget the exact size but it'll be a quick Google away to find out. CP version you fully close them, not sure which you have because you said 1974 CP, but CR was from 1973 on. 

Anyways for sure an air leak past the butterfly's will cause it to rev a little more at idle, so setting them up correctly and in balance will help no end. 

Gareth

To do it accurately you need an air flow gauge and this can be used to balance all 3 manifolds to get the same reading. You will then find that the pick up will be instant and the air valve has much better control over the tick over.

Bruce.

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3 hours ago, astontr6 said:

To do it accurately you need an air flow gauge and this can be used to balance all 3 manifolds to get the same reading. You will then find that the pick up will be instant and the air valve has much better control over the tick over.

Bruce.

Like one of these Air flow meter

Stuart.

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8 hours ago, astontr6 said:

 

Yes +1, 

Bruce.

Thanks for the recommendation. I've re-checked the connectors and the butterflies as suggested. On 1 & 2 there was a gap of a couple of mm which I have now adjusted to 0.002 mm as suggested. This has made a slight difference bringing the idle down to around 1500 rpm, but i can't get it any lower and while it is idling, every 3-5 seconds the revs increase to 2000 rpm and then drop back to 1500...it is as if I am blipping the throttle pedal even though I'm not touching anything.

A flow meter might be the next step.

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Could also be the o rings on the outside of the injectors, air can be drawn in past the injectors. Old rings sometimes don't seal well.

Do you have an bleed valve on the front inlet manifold, this should control the idle speed.

Have you checked the butterfly shafts for wear, this is another possible air leak area.

The bushes on the throttle shaft underneath the throttle bodies,  138490.

John

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Hi John

The 138490 bush isn't used on the CR throttle body set up, only on CP cars. The accelerator pedal shaft does us the same bush.

Alan

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Hi Dan

Close the butterflies completely & screw in the bleed valve. If you still can't get the idle below 1500rpm then you probably have an air leak elsewhere. If not from the manifold then it could be from the throttle body spindles (wear) or as John suggests the injector O ring seals. Also check the MU vacuum pipe & the servo pipes are ok.

Alan 

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18 hours ago, Dan Middleton said:

Thanks for the recommendation. I've re-checked the connectors and the butterflies as suggested. On 1 & 2 there was a gap of a couple of mm which I have now adjusted to 0.002 mm as suggested. This has made a slight difference bringing the idle down to around 1500 rpm, but i can't get it any lower and while it is idling, every 3-5 seconds the revs increase to 2000 rpm and then drop back to 1500...it is as if I am blipping the throttle pedal even though I'm not touching anything.

A flow meter might be the next step.

Have you checked that the throttle cable is not jamming and the choke cam is off the counter shaft adjuster? The dim of .002mm is under .001" are you sure that you have the dims right?

Bruce.

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Bruce is correct it should be 2 Thou but if its still at 1500 rpm at >2 thou theres a leak elsewhere (assuming the throttle cable & choke cam are working correctly). My suggestion earlier to adjust the butterflies closed & wind in the bleed valve should cause the engine to stall/almost stall if there are no other leaks.

Alan

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7 hours ago, super6al said:

Bruce is correct it should be 2 Thou but if its still at 1500 rpm at >2 thou theres a leak elsewhere (assuming the throttle cable & choke cam are working correctly). My suggestion earlier to adjust the butterflies closed & wind in the bleed valve should cause the engine to stall/almost stall if there are no other leaks.

Alan

I think an air leak elsewhere is the most likely although I will check the throttle cable. The choke cam is OK, but the bleed valve is closed and engine is still running too fast. I am planning to remove the throttle bodies tomorrow and give them all a thorough check for wear on all the moving parts etc.

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Note: that over cleaning the throttle bodies in and around the butterflies can alter the airflow and increase revs. 

Gareth

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