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Hiya. 
has anyone bothered changing their manifold from a 3a to 4. ie short stubby trumpets to a longer more elegant and intentional flowed chamber. 
it seems that the gas flow on the 4 was far superior but in reality these aren’t race cars (well mine isn’t) so does anyone really see a huge benefit in changing?  I’ve pretty much made up my mind but seeing if their are any strong opinions out there?

thanks all

Graham. 

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TR  four pot engines are pretty well balanced in design terms so changing one or two components won’t make a noticeable difference. To reap any worthwhile benefits you will need to work the head, change the inlet, exhaust and cam. 
Having said that I’m all for marginal gains so go for it. Be aware that if using the long manifold with long H6 carbs there won’t be much room for an air filter. 

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Yes, I have a fitted a 4A manifold to my 3A with HS6 carburettors and 4 branch exhaust manifold. It is the latest mod I did and I’m still looking for new sensations.

So no, I have n’t seen a huge benefit. But I’m not the best judge….

james

Edited by james christie
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As said above, + 1.

If you just want to change it for aesthetics then go for it but do a dummy fit to see if air filters can be accommodated. The TR engine can be made to release good amounts...but benefits aren't visible...much, if you do dribs and drabs until you fit the last complimentary part or fettled item, then it will give you handfuls. The aggregation of small efficiencies in action.

Mick Richards 

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I had the later manifold ( it has a slightly cleaner air flow) and the original H6. Supposedly the longer inlet track is better for torque.

but you would struggle to fit air filters without modifying inner wing. I didn’t bother and had shallow radius stubstacks.(these were worth 8bhp over slightly longer trumpets with a gauge on)

I agree to the above, doing it peace meal you don’t see the benefits as it’s only a few bhp .

real power comes from a complete engine package ( ask me how I know :unsure:)

the best money I spent prior to new engine was a rolling road set up by a guy who really knows SU’s

http://jcprints.co.uk/MIKEANICS/

cr@p web site ace set up man.

Old set up for sale if anyones interested

9B7C36E4-C672-4E9C-BF3D-561FC56F1620.jpeg

Edited by Hamish
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5 hours ago, Drewmotty said:

TR  four pot engines are pretty well balanced in design terms so changing one or two components won’t make a noticeable difference. To reap any worthwhile benefits you will need to work the head, change the inlet, exhaust and cam. 
Having said that I’m all for marginal gains so go for it. Be aware that if using the long manifold with long H6 carbs there won’t be much room for an air filter. 

this set up is on our TR4 .....yes it is a tight fit....

carbs 1.JPG

carbs 2.JPG

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My set up with H6s and Kand N filters, fair bit of room and good bottom end torque.

Unfortunately for sale at present, too little use at 800 miles last year.

20220127_145234.jpg

20220127_145215.jpg

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14 hours ago, Drewmotty said:

TR  four pot engines are pretty well balanced in design terms so changing one or two components won’t make a noticeable difference. To reap any worthwhile benefits you will need to work the head, change the inlet, exhaust and cam. 
Having said that I’m all for marginal gains so go for it. Be aware that if using the long manifold with long H6 carbs there won’t be much room for an air filter. 

Ah. I should have mentioned that I’ve already gone for hs6 carbs and Phoenix 4 branch exhaust. 

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8 hours ago, TR4TUNE said:

My set up with H6s and Kand N filters, fair bit of room and good bottom end torque.

Unfortunately for sale at present, too little use at 800 miles last year.

Hi, like the heat shield, did you make this or was it a bought item, and if so where.

Ralph

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When I rebuilt my TR3a I didn’t bother with the original stubby manifold, I went straight for the TR4a version and  HS6 carbs. The stubby one just didn’t look right. I also fitted a Phoenix exhaust and I am very happy with the whole set up. 

Rgds Ian

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16 minutes ago, Graham Baggaley said:

Ah. I should have mentioned that I’ve already gone for hs6 carbs and Phoenix 4 branch exhaust

My TR3 with the same set up, standard cam and a bit of head work was producing 110hp at the flywheel.

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9 hours ago, Quicksilver said:

this set up is on our TR4 .....yes it is a tight fit....

carbs 1.JPG

carbs 2.JPG

You can gain a little space to give you a better clearance on that wing by machining or even hand filing the carb face of the manifold reducing it by about 3mm. If you do it carefully it isn't noticeable and in the past I've had no problems caused to the carb fuel level and their operation by doing so.

Mick Richards 

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Hi Ralph,

Heat shield already fitted by the engineer who rebuilt the car.

It is just a thin sheet of stainless , flat except for contoured (bent) ends, fairly simple to knock up I would have thought.

Usual mock up with a corn flakes packet and a bit of cutting ,filing and bending.

Thick carb gasket on the engine side and thinish paper one on the carb side.

Sorry for thread drift but it may help others who have, or think they have, fuel vaporisation problems.

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Bob - The later TR4 manifold fitted with Strombergs ie after the H6s, is to all intents and purposes the same as the later 4A one - the only differences between them is visually, externally in terms of a triangular bump cast onto the cross tube. You can see the difference in the attached photos of the different sets I do

Cheers Rich

IMG_0657 - Resized.JPG

IMG_3008.JPG - Resized.JPG

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Looking at the above photos, I now realise that my manifold is a TR4 one, (I persuaded the seller to remove the Strombergs) but one advantage is that you can tap into the triangular protrusion on the balance tube to add a vacuum take off.

Rgds Ian

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