Graham Baggaley Posted March 14, 2022 Report Share Posted March 14, 2022 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. Quote Link to post Share on other sites
Drewmotty Posted March 14, 2022 Report Share Posted March 14, 2022 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. Quote Link to post Share on other sites
james christie Posted March 14, 2022 Report Share Posted March 14, 2022 (edited) 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 March 14, 2022 by james christie Quote Link to post Share on other sites
Motorsport Mickey Posted March 14, 2022 Report Share Posted March 14, 2022 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 Quote Link to post Share on other sites
Hamish Posted March 14, 2022 Report Share Posted March 14, 2022 (edited) 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 ) 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 Edited March 14, 2022 by Hamish Quote Link to post Share on other sites
Quicksilver Posted March 14, 2022 Report Share Posted March 14, 2022 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.... Quote Link to post Share on other sites
TR4TUNE Posted March 14, 2022 Report Share Posted March 14, 2022 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. Quote Link to post Share on other sites
Graham Baggaley Posted March 15, 2022 Author Report Share Posted March 15, 2022 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. Quote Link to post Share on other sites
Ralph Whitaker Posted March 15, 2022 Report Share Posted March 15, 2022 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 Quote Link to post Share on other sites
Ian Vincent Posted March 15, 2022 Report Share Posted March 15, 2022 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 Quote Link to post Share on other sites
Drewmotty Posted March 15, 2022 Report Share Posted March 15, 2022 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. Quote Link to post Share on other sites
Lebro Posted March 15, 2022 Report Share Posted March 15, 2022 With HS6 carbs the 4A manifold would definately be a better bet. Bob Quote Link to post Share on other sites
Motorsport Mickey Posted March 15, 2022 Report Share Posted March 15, 2022 9 hours ago, Quicksilver said: this set up is on our TR4 .....yes it is a tight fit.... 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 Quote Link to post Share on other sites
Drewmotty Posted March 15, 2022 Report Share Posted March 15, 2022 Plenty of room with HS6s Quote Link to post Share on other sites
TR4TUNE Posted March 15, 2022 Report Share Posted March 15, 2022 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. Quote Link to post Share on other sites
Graham Baggaley Posted March 15, 2022 Author Report Share Posted March 15, 2022 Great reply from everyone. Good chat. Thanks everyone. I’ll keep my eyes out for a cheap 4 manifold and swap it in when I can. Graham Quote Link to post Share on other sites
Lebro Posted March 16, 2022 Report Share Posted March 16, 2022 It's the 4A one you want. Bob Quote Link to post Share on other sites
rcreweread Posted March 16, 2022 Report Share Posted March 16, 2022 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 Quote Link to post Share on other sites
Ian Vincent Posted March 17, 2022 Report Share Posted March 17, 2022 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 Quote Link to post Share on other sites
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