Throttle body rebuild and butterfly adjustment

[Jonny TR6]

My throttle bodies are all cleaned up, as are the spindles and butterflies. Carbon, oil, dirt - everything has gone and I now have a nice clean setup.

I’m going to run a bleed screw at both ends of the throttle bodies and will be feeding in fresh air, courtesy of the Bauly Cars catch can.

Given the ability to control the air flow at idle a lot more efficiently than the original setup, I was thinking of setting the butterflies with zero clearance at full closed position.

It’s a relatively new area of experimentation for me, so welcome all thoughts and ideas.

Edited December 16, 2023 by Jonny TR6

[TR NIALL]

41 minutes ago, Jonny TR6 said:

My throttle bodies are all cleaned up, as are the spindles and butterflies. Carbon, oil, dirt - everything has gone and I now have a nice clean setup.

I’m going to run a bleed screw at both ends of the throttle bodies and will be feeding in fresh air, courtesy of the Bauly Cars catch can.

Given the ability to control the air flow at idle a lot more efficiently than the original setup, I was thinking of setting the butterflies with zero clearance at full closed position.

It’s a relatively new area of experimentation for me, so welcome all thoughts and ideas.

I don’t think you’ll achieve a fully closed position on the Throttle Body.

[Mike C]

Won't fully closing the butterflies destroy the throttle body?

[Z320]

4 hours ago, Jonny TR6 said:

My throttle bodies are all cleaned up, as are the spindles and butterflies. Carbon, oil, dirt - everything has gone and I now have a nice clean setup.

I’m going to run a bleed screw at both ends of the throttle bodies and will be feeding in fresh air, courtesy of the Bauly Cars catch can.

Given the ability to control the air flow at idle a lot more efficiently than the original setup, I was thinking of setting the butterflies with zero clearance at full closed position.

It’s a relatively new area of experimentation for me, so welcome all thoughts and ideas.

Just one thought: with the trottle fully closed you get no fuel / air mix and the engine dies.

Could you please explain exactly what you want do do and what your hope is, please?

Ciao, Marco

[Mk2 Chopper]

12 hours ago, Jonny TR6 said:

My throttle bodies are all cleaned up, as are the spindles and butterflies. Carbon, oil, dirt - everything has gone and I now have a nice clean setup.

I’m going to run a bleed screw at both ends of the throttle bodies and will be feeding in fresh air, courtesy of the Bauly Cars catch can.

Given the ability to control the air flow at idle a lot more efficiently than the original setup, I was thinking of setting the butterflies with zero clearance at full closed position.

It’s a relatively new area of experimentation for me, so welcome all thoughts and ideas.

You need to achieve as near as you can fully closed without the throttle plates/ butterflies digging into the throttle body itself. That is the idea of having the bleed valve. You may find now they are cleaned up it's not as easy to fully reduce air flow around the throttle plates. 

Look forward to seeing how the two bleed valves works. 

Gareth

[Mk2 Chopper]

8 hours ago, Z320 said:

Just one thought: with the trottle fully closed you get no fuel / air mix and the engine dies.

Could you please explain exactly what you want do do and what your hope is, please?

Ciao, Marco

On petrol injection, you have a air bypass valve, so when the throttle plates/ butterflies are fully shut you get idle air from this valve. 

Gareth

[JochemsTR]

if you can get the butterflies to completely close, this is most favourable. The air required for idle will come via the Idle Set Screw located at Cylinder 1.

The WHB specifies a MAX Gap of 0.05mm. Since the butterflies do not perfectly fit inside the TB especially when cleaned up, there already is an uncontrollable amount of air passing by the butterflies. This amount is enough to drive most mechanics crazy since they cannot get the idle set or run smooth. Running few hundred miles will cause the butterflies to get "dirty" again, since the oil fumes from the valve cover are fed into the airplenum which in turn clogg up the butterflies. Clean butterflies are NOT desireable on a PI.

[Z320]

Ok,

I thought is is a carb car.

Jochem, thank you very much for your explanation!

Isn’t this a reason even to have more doubt about the sense for the fitting of a catch tank?

Ciao, Marco 

Edited December 17, 2023 by Z320

[Ransomes256]

There is a special fully hardening paste to paint around the edge of the butterflies which once hard you break the seal by opening them.  This is commonly used on modern throttle bodies on EFI set ups to get as near to zero air flow as possible.  

 

[Jonny TR6]

3 minutes ago, Ransomes256 said:

There is a special fully hardening paste to paint around the edge of the butterflies which once hard you break the seal by opening them.  This is commonly used on modern throttle bodies on EFI set ups to get as near to zero air flow as possible.  

 

 

3 minutes ago, Ransomes256 said:

There is a special fully hardening paste to paint around the edge of the butterflies which once hard you break the seal by opening them.  This is commonly used on modern throttle bodies on EFI set ups to get as near to zero air flow as possible.  

 

So my thinking that zero air flow, or as close as possible is correct ? The inefficiency and poor idling in the original set up was caused by a single bleed screw and relying on the gunk produced by the rocker, to seal up the miniscule gap between butterfly and throttle body bore ?

I think I’m on the right track then in having 2 sets of idle screws to help balance out the air flow at idle and using something like the paste or a spray I read about on an Aston thread gives that “perfect” seal ?

 

[Ransomes256]

Try looking at this u tube video.

https://www.youtube.com/watch?v=rrb6HJRi5iQ

I will also try to find details of a suitable product.

Neil

 

[Jonny TR6]

Thanks Neil - funnily enough I’d watched that earlier. Very helpful video and illustrates how the sealant provides a very close to 100% seal.

Been trying to find some DG213 but it doesn’t seem to be available in small quants, so anything else you can find that does the job will be appreciated.

I’ll keep looking as well.

[PodOne]

Try D-321R Molykote. It's what I've used on my rebuilt PI bodies and other projects in the past. It creates a good seal and is used by a lot of car/bike manufactures.

https://www.ebay.co.uk/itm/115999799178?epid=18061607938&hash=item1b0220778a:g:f4gAAOSw6B9kWnUX&amdata=enc%3AAQAIAAAA4ItOOqjz9HjkH%2FAcyKTB0gQkj0emCNuZ9W6h1KIRsFeFjhH7tBUTMb8TkNuoYbi9zB1%2FUTrtUjH8BEVKNRw6lHWrrKgHEg0LY%2FKITu4RM9Szt3IRnBqgeiQpUIPyhkwDzlUh9JKARdzAPqOc24lRe7ckb54XlNG%2FBMbTjSVZ7lbFKExc3p9D9dLMXE%2FiFjbai9qAjdi1GR%2F0yoaz1feRfnZ9IajoEVRfMTuXbm7hmXyBg4Ft5lgG5GRcc6gAaDk1DNAsYXl6fhYIqKcmcabwdc02IA8epyRxu7aXlhzFnVjm|tkp%3ABFBMypqx-Y5j

Andy

[Ransomes256]

1 hour ago, Jonny TR6 said:

Thanks Neil - funnily enough I’d watched that earlier. Very helpful video and illustrates how the sealant provides a very close to 100% seal.

Been trying to find some DG213 but it doesn’t seem to be available in small quants, so anything else you can find that does the job will be appreciated.

I’ll keep looking as well.

OK here is another video which gives some home made solutions.  I still have not found what is available commercially.

https://www.jalopyjournal.com/forum/threads/sealing-tripower-end-throttle-bodies-with-common-materials.1029907/

Neil

 

[michaeldavis39]

Used Molycote on my rebuilt early throttle bodies- could not get a low idle on engine until I treat it to this super stuff- left it to fully harden for a couple of weeks before I cracked the throttles open- it's soft but does its job spot on

Edited December 17, 2023 by michaeldavis39

[super6al]

Hi there

Ive been doing a similar job on my TB's. Mine is a CR car so different design to CP manifold. However I would think the butterfly to body fit will be similar. My spindles were worn so I fully disassembled the spindles & butterfly disc. I found there is a very small amount of adjustment possible between the disc & the throttle body. After spindle repair I did a dry fit without the butterfly fixing screws  & found I had no gap at the bottom of the butterfly plate to body but a 2 thou gap at the top. By manipulating the  disc in the spindle it was possible to even out the gap (the spec on CR setup says it should not be possible to pass a 2 thou feeler between disc & body).  Some clearance is necessary & don't allow the butterfly disc to seat hard into the body otherwise it will stick. 

I've heard of people using Molykote 321R & there's also a product from Tomei Japan that is developed for coating throttle bodies. I haven't used any of these so can't comment on effectiveness.

Alan

[Jonny TR6]

Thanks Andy and Michael - having done a bit of research it looks like this is the stuff to use, so ordered a can.

Its quite a satisfying job putting the butterflies back in. You basically get them in place and pop the screws in lightly, then snap the spindle a few times and the butterflies find their natural seating position. Important to get them the right way round of course and there’s a small groove on each butterfly which should face you and be level.

Once seated, you can snug the screws up. I’m not using Loctite as the screws were a bugger to get out, so tightened them sufficiently that they should stay in place.

Putting the barrels up to a bright light should show any areas where the butterfly doesn’t seal. Pleased to say that mine all look very good, the only light bleed was at the spindle to body area and only in 2 out of the 12 junctions. It was very minor, but the Molykote will sort that out.

Now confident that my throttle bodies are in optimum condition and there’s no going to be no issues with air bleeding through the butterflies.

Next step is the bleed screw on the other end (cylinder 6). There’s a copper core plug which can be popped out and that leaves you with the same situation as the front and ideal to pop an additional bleed screw in. The plenum will need drilling and a suitable connector installed, so watch this space.

[Jonny TR6]

2 minutes ago, super6al said:

Hi there

Ive been doing a similar job on my TB's. Mine is a CR car so different design to CP manifold. However I would think the butterfly to body fit will be similar. My spindles were worn so I fully disassembled the spindles & butterfly disc. I found there is a very small amount of adjustment possible between the disc & the throttle body. After spindle repair I did a dry fit without the butterfly fixing screws  & found I had no gap at the bottom of the butterfly plate to body but a 2 thou gap at the top. By manipulating the  disc in the spindle it was possible to even out the gap (the spec on CR setup says it should not be possible to pass a 2 thou feeler between disc & body).  Some clearance is necessary & don't allow the butterfly disc to seat hard into the body otherwise it will stick. 

I've heard of people using Molykote 321R & there's also a product from Tomei Japan that is developed for coating throttle bodies. I haven't used any of these so can't comment on effectiveness.

Alan

Hi Alan - happy to pop my tin of Molykote in the post when I’ve finished with it if you want to use it. I can’t imagine too many situations where I’ll need it again and happy to help out a forum member.

They’re 400ml tins, so doubt I’d use more than 50ml and it can then be passed on to others who are doing the same.

[Andy Moltu]

Slightly loosen the 2 screws that hold the butterflies onto the spindle

Open the throttle and allow them to snap shut a few times and then tighten. 

This will effectively centre the butterflies and minimise the air leaks. Balance the throttles so they are fully shut when off the throttle pedal. Also they should open synchronously. Adjust the air bleed t set tick over.

An alternative is so use a balancer by setting a fast idle by adjusting the throttle cable, (with the air bleed valve closed) and measuring the airflow through each set of butterflies and adjusting until the flow is the same. Once achieved, slacken the throttle cable to allow the butterflies to close and open up the air bleed valve to set tick over.

Some early PIs didn’t have an air bleed valve (although many TR5s went back to have them retro-fitted by the dealers.) If you have of these then the aim is to balance the butterflies to be slightly open to achieve tick over. Historically this was done by opening up enough to just allow a fag paper to be able to pass without being caught by the butterflies.

 

[Jonny TR6]

Thanks Andy - will follow that procedure once all back together.

[Ransomes256]

4 hours ago, Jonny TR6 said:

Thanks Neil - funnily enough I’d watched that earlier. Very helpful video and illustrates how the sealant provides a very close to 100% seal.

Been trying to find some DG213 but it doesn’t seem to be available in small quants, so anything else you can find that does the job will be appreciated.

I’ll keep looking as well.

Finally found it !!!

https://www.ebay.co.uk/itm/224584354729

Neil

[Jonny TR6]

Thanks Neil - ordered the Molykote, but it’ll be a useful alternative for the future generations.

Will be interesting to see the state of play of butterflies and plugs after 200 or so miles.

[BlueTR3A-5EKT]

Are there seals on each end of the throttle butterfly spindles?    
If not I suspect the air will howl in through the spindle to throttle body bearing gap.  It certainly does on worn out SU carb spindle/bodies.

That will stuff the tickover nicely with the none seating throttle butterflies.  

[Jonny TR6]

3 hours ago, BlueTR3A-5EKT said:

Are there seals on each end of the throttle butterfly spindles?    
If not I suspect the air will howl in through the spindle to throttle body bearing gap.  It certainly does on worn out SU carb spindle/bodies.

That will stuff the tickover nicely with the none seating throttle butterflies.  

You’re right Peter - there’s no spindle seal, however the original design relied on oily gunk from the rocker to seal the spindle to body gap to an extent. That’s if they ever really thought about it back in the 60’s.

What the Molykote and similar products will do is reduce any gap to an absolute minimum - assuming a completely straight spindle of course.

FI was in its infancy when these cars were designed as you will know better than most and it’s British engineering to a budget, rather than German (Porsche, Mercedes) or Italian (Lancia, Ferrari, over engineering).

[PodOne]

If you have a mind to while they are off the car you could consider having sealed bearings fitted to the throttle shafts to reduce further any air getting past. Not something I've had done at present but I suspect going forward will make the whole system more responsive and possibly easier to balance, adjust and prevent wear to the shafts.. Probably what was needed back in the day before the accountants had their say, but then they weren't expecting the cars to still cherished!

Andy.