HS4 Jet issue

[Pete Lewis]

if you buy the silly priced wax stat conversion i can assure you half of it wont fit the linkage will jam and you will be worse off than when you started all this  

Pete

[cliff.b]

7 minutes ago, Pete Lewis said:

if you buy the silly priced wax stat conversion i can assure you half of it wont fit the linkage will jam and you will be worse off than when you started all this  

Pete

Is there a better solution, other than replacement Waxstat jets?

[Josef]

2 hours ago, cliff.b said:

Unless mine was made in 77 and hung around for a while before being registered.

You can get an idea of manufacture date of your car (and engine) by comparing the commission number with other examples. An original engine is usually close ish in number to the commission number, within a few thousand or so.

[cliff.b]

13 minutes ago, Josef said:

You can get an idea of manufacture date of your car (and engine) by comparing the commission number with other examples. An original engine is usually close ish in number to the commission number, within a few thousand or so.

Just checked and my commission number is well in the middle of other 78 cars so that would be right. The engine number has a prefix of DM and a suffix of ESS which I believe means it was a factory exchange unit. 

[Josef]

37 minutes ago, cliff.b said:

Just checked and my commission number is well in the middle of other 78 cars so that would be right. The engine number has a prefix of DM and a suffix of ESS which I believe means it was a factory exchange unit. 

Interesting. DM was an export only Dolly 1500 block originally! https://www.teglerizer.com/triumphstuff/spit_and_gt6_specs.htm I guess it was shipped back as an exchange or something.

[cliff.b]

17 minutes ago, Josef said:

Interesting. DM was an export only Dolly 1500 block originally! https://www.teglerizer.com/triumphstuff/spit_and_gt6_specs.htm I guess it was shipped back as an exchange or something.

I got the factory spare information from a table at thriumphspitfire.com

Also saw it somewhere else that I can't remember.

Maybe they were spare blocks 🤔

 

Edited September 23, 2023 by cliff.b
Add text

[cliff.b]

19 minutes ago, Josef said:

Interesting. DM was an export only Dolly 1500 block originally! https://www.teglerizer.com/triumphstuff/spit_and_gt6_specs.htm I guess it was shipped back as an exchange or something.

Ah, it actually says it in the link you posted

[Pete Lewis]

2 hours ago, cliff.b said:

Is there a better solution, other than replacement Waxstat jets?

not really   a 2p mod to waxstats is fine   but if its bent  then its where from here ???

the rods/levers in the kit sold by the many as a replacement are pretty hopeless

 

 

[cliff.b]

27 minutes ago, Pete Lewis said:

not really   a 2p mod to waxstats is fine   but if its bent  then its where from here ???

the rods/levers in the kit sold by the many as a replacement are pretty hopeless

 

 

It's not bent, it's just that the jet pipe came loose. Maybe I have fixed it and it will be fine.

If I do need to replace it though a new Waxstat jet would be easier and presumably certain to work ok. Are all the problems with them just because they are old or did they always cause issues?

[Pete Lewis]

any wax plug goes out of spec after some years  thermostats are the same 

they are easy to change  so a  wax stat with the 2p mod will remain reliable , ie there is nothing left to fail

only if the needle has worn the jet orifice.

pete

[cliff.b]

1 hour ago, Pete Lewis said:

any wax plug goes out of spec after some years  thermostats are the same 

they are easy to change  so a  wax stat with the 2p mod will remain reliable , ie there is nothing left to fail

only if the needle has worn the jet orifice.

pete

Yes, I suppose so. As a matter of interest, what would be the symptoms of a worn jet orifice? I'm assuming not maintaining correct mixture through the rev range but would it make it too weak or too rich at higher revs?

[Pete Lewis]

a worn jet would be richer  as the hole bore becomes larger , adjusting does compensate a bit the start of all needles is the same diameter 

so winding the jet upwards when the bore is worn makes up for the problem in way generally to be quite workable but not utopia .

biased needles wear the jet as they rub the side of the jet bore hole 

if you have a depth gauge use it to measure the height of the jet in the carb throat get both the same and adjust from there for best running idle 

if you have lifting pins    just touchy feely contact with the air piston and lift a couple of mm  

if it faulters a few rpm its lean    if it raises the idle a few rpm its rich   if nowt happens its about right 

you are looking/listening for a hint of change nothing radical 

never do this with the cleaners off  thats just a waste of time 

 

Pete

 

[cliff.b]

18 minutes ago, Pete Lewis said:

a worn jet would be richer  as the hole bore becomes larger , adjusting does compensate a bit the start of all needles is the same diameter 

so winding the jet upwards when the bore is worn makes up for the problem in way generally to be quite workable but not utopia .

biased needles wear the jet as they rub the side of the jet bore hole 

if you have a depth gauge use it to measure the height of the jet in the carb throat get both the same and adjust from there for best running idle 

if you have lifting pins    just touchy feely contact with the air piston and lift a couple of mm  

if it faulters a few rpm its lean    if it raises the idle a few rpm its rich   if nowt happens its about right 

you are looking/listening for a hint of change nothing radical 

never do this with the cleaners off  thats just a waste of time 

 

Pete

 

I can set the mixture ok at tickover but find if I then stop at a layby during a journey and check the plugs they usually look light greyish or even white if I have been driving fast. Other people have said similar here.

I usually then richen a little thinking it is better to be rich at low speed than weak at high speed. 

Was wondering if this is indeed normal or if perhaps could be due to worn jets or something. It's not a problem, but I assumed the mixture should stay roughly right throughout the rev range once set.

[Steve P]

1 hour ago, cliff.b said:

Was wondering if this is indeed normal or if perhaps could be due to worn jets or something. It's not a problem, but I assumed the mixture should stay roughly right throughout the rev range once set.

That depends if you have the optimum needles and springs and then setup properly.

Steve

[cliff.b]

44 minutes ago, Steve P said:

That depends if you have the optimum needles and springs and then setup properly.

Steve

Yes, which ties in with the other things discussed. Probably need to look at the carbs in detail at some point and see what is actually in them. 

[Pete Lewis]

the 1500 is designed to run on the leaner side of whatever, hence they use a 88c thermostat etc  as the car is in the beginning's of the  emission control era.

i would expect on a fast cruise the colour  will be lighter .

think you need to stop checking and do more driving  Ha !

finding just what needle and spring is fitted will be a good call .

Pete

 

[cliff.b]

31 minutes ago, Pete Lewis said:

the 1500 is designed to run on the leaner side of whatever, hence they use a 88c thermostat etc  as the car is in the beginning's of the  emission control era.

i would expect on a fast cruise the colour  will be lighter .

think you need to stop checking and do more driving  Ha !

finding just what needle and spring is fitted will be a good call .

Pete

 

Yes, now I know what to look for I will check it all out at some point 👍

[johny]

yes in my experience the car lets you know when youve adjusted the carbs too lean as it bogs down. I know that in theory you can do damage to an engine running too weak but think thats only likely to happen with air leaks and if purely jet setting youre going to know about it...

[cliff.b]

12 minutes ago, johny said:

yes in my experience the car lets you know when youve adjusted the carbs too lean as it bogs down. I know that in theory you can do damage to an engine running too weak but think thats only likely to happen with air leaks and if purely jet setting youre going to know about it...

That's exactly what I was experiencing I suppose when the original fault I described was occurring. And as the jet tube on the rear carb had worked loose and risen, it made that carb run very weak. Before I found the cause I put my Colourtune on no4 and could see the actual spark and just a very slight flame which confused me at the time but made sense in the end.

[johny]

I wonder if getting the absolute weakest mixture that will still allow the engine to run satisfactorily even makes much difference to fuel economy because perhaps theres a drop in power which you have to make up for by opening the throttle more anyway... 

[cliff.b]

1 hour ago, johny said:

I wonder if getting the absolute weakest mixture that will still allow the engine to run satisfactorily even makes much difference to fuel economy because perhaps theres a drop in power which you have to make up for by opening the throttle more anyway... 

If it does make a difference I suspect it is only when "cruising" at moderate speed. Prior to my recent problems I unusually used almost an entire tank in a day driving mostly in the 55 to 65mph range with as little throttle as possible and covered 225 miles on the tank. Worked out about 35mpg which is better than usual and I think not too bad for a non overdrive car. Will be interesting to see if that improves now I have spent some time setting the car up, although I rarely get to go through an entire tank without some (ok, more than some) "enthusiastic driving" lol