T Robinson Posted January 5, 2009 Report Share Posted January 5, 2009 Hi, I have a pair of 1 3/4 HS6 SUs that I wish to fit on a 3. They have been rebuilt and are in fine fettle. The carburettor bodies carry an angled port that I assume should be piped to a PSV valve or to a vented valve cover. Should I blank off these ports? or should they be piped to the valve cover? Or will this just let un-metered air into the carbs? Thanks, Tony Quote Link to post Share on other sites
vivdownunder Posted January 6, 2009 Report Share Posted January 6, 2009 Hi Tony, The HS6's used on TR4A's just had a small diameter port on the top of the front carby body, for a distributor vacuum hose. I'd blank off any other ports for starters, and see how they run. You'll probably need TW needles, but they better suited the 2138cc engine, so if you have a 1998cc engine and can't get the mixture right, you may need to go a shade leaner with the C1W needle. However, the pair you have with ports may be balanced to receive some air from the engine, in which case you might need to obtain an alloy rocker cover with a tapping to run hoses to the carby ports. An inline mesh flame trap is needed in the main hose before it branches to each carby, and these tend to gunk up, and are best cleaned by immersion in a container of petrol once per year. Cheers, Viv. Quote Link to post Share on other sites
rudi Posted January 6, 2009 Report Share Posted January 6, 2009 I think the HS carbs need to be fitted on a TR4A inlet header. S stands for short. Original the TR3 has H carbs. But this needs to be confirmed. Quote Link to post Share on other sites
Andrew Smith Posted January 6, 2009 Report Share Posted January 6, 2009 I think the HS carbs need to be fitted on a TR4A inlet header. S stands for short. Original the TR3 has H carbs. But this needs to be confirmed. Rudi is correct, the TR3/3A was originally fitted with H6 (1 1/2") and the HS6 fitted to the TR4A were 1 3/4". To fit HS6s you will need the 4A inlet manifold 307455 (HS6s and this manifold are considered the best set-up), blank off the breather outlet for the PCV value and fit slimmer air filters to clear the inner wing, see photo: Cheers Andrew Quote Link to post Share on other sites
Rhodri Posted January 6, 2009 Report Share Posted January 6, 2009 (edited) H6 carbs are 1 and 3/4", as are HS6s. H4s are 1 and 1/2". As Rudi says the S series are shorter and will need the longer manifold. Edited January 6, 2009 by Rhodri Quote Link to post Share on other sites
Andrew Smith Posted January 6, 2009 Report Share Posted January 6, 2009 H6 carbs are 1 and 3/4", as are HS6s. H4s are 1 and 1/2". As Rudi says the S series are shorter and will need the longer manifold. So they are Rhodri, I must have had a brain fade! Cheers Andrew Quote Link to post Share on other sites
vivdownunder Posted January 7, 2009 Report Share Posted January 7, 2009 Hi again Tony, Looking at Andrew's photo of a pair of later HS6 SU's on a 3A reminds me that the throttle linkage for these is quite different from the original H6 carbs. The H6's were operated from a spindle lever at the front of the front carby, but with the HS6's you've got a fuel bowl in the way. So you'll have a bit of work to do sorting out a modified linkage. It's not essential to have a curved branch TR4A manifold, as the HS6's will fit on the original inlet manifold, but as Andrew says, the curved inlet manifold was (the last) and best for the 4 pot TR engine. However, the TR4A curved manifold has the smaller 1.5" diameter branches to match with the TR4A head inlet ports, whereas the original TR3A inlet manifold has larger diameter ports which match the TR3A head. As far as I know a mismatched TR4A inlet manifold on a TR3A head wouldn't matter too much on a road engine, but for mine I'd be looking for a TR4A head so it all matches up correctly. Incidently, the ports were reduced in diameter to speed up gas velocity into the engine for a small HP increase. Regards, Viv. PS Andrew, with Linda draped all over your car, who'd give a fat rat's about the size of the carbies. Quote Link to post Share on other sites
Nick Webster Posted January 7, 2009 Report Share Posted January 7, 2009 Fitting HS6 carbs to the TR3 inlet manifold will give you a bit of room to fit ram pipes to the carb inlet. This helps offset the slow gas speeds inherent with large ports. Fitting rams to H6 involved modifying the inner wing. Unless you are immune to digesting grit, a nice air box and remote mounted air filter would probably be a good idea for road use. Nick Quote Link to post Share on other sites
Andrew Smith Posted January 7, 2009 Report Share Posted January 7, 2009 PS Andrew, with Linda draped all over your car, who'd give a fat rat's about the size of the carbies. Hi Viv No 'carbies' on that car, it's a 6 - Linda was a girl who loved her injectors!! Cheers Andrew Quote Link to post Share on other sites
T Robinson Posted January 7, 2009 Author Report Share Posted January 7, 2009 Thanks Guys, I will blank off the ports and go from there. I have the later TR4 manifold that I am currently opening up to match the ports to the head. The set up on the 3A looks very good - just what I am looking to do. Are they K&N filters. Thanks to all, much appreciated, Tony Quote Link to post Share on other sites
Andrew Smith Posted January 15, 2009 Report Share Posted January 15, 2009 The set up on the 3A looks very good - just what I am looking to do. Are they K&N filters. Tony Yes, they are - the tapered type, see: KN56-9327 Cheers Andrew Quote Link to post Share on other sites
Dave Larnder Posted January 23, 2009 Report Share Posted January 23, 2009 Thanks Guys, I will blank off the ports and go from there. I have the later TR4 manifold that I am currently opening up to match the ports to the head. The set up on the 3A looks very good - just what I am looking to do. Are they K&N filters. Thanks to all, much appreciated, Tony Hi Tony I have HS6's on a TR4 manifold on my TR3A. I got a kit from Moss for the linkage problem - dead easy! I saw another such set up at the IWE last year and the owner had connected those 2 extra ports together with a copper pipe and rubber pipe ends like the fuel supply lines. Remember though you must put a tee piece in the fuel line so that both carbs are supplied equally if your float chamber tops are like mine and dont have a through pipe on no.1. I also have "offset" K&N filters (offset up and down, not left and right) pancake type, they miss the wheelarch by miles. Dave Quote Link to post Share on other sites
Badfrog Posted January 23, 2009 Report Share Posted January 23, 2009 Thanks Guys,I will blank off the ports and go from there. I have the later TR4 manifold that I am currently opening up to match the ports to the head. The set up on the 3A looks very good - just what I am looking to do. Are they K&N filters. Thanks to all, much appreciated, Tony Hi Tony, The other guys gave you the full insight so just go ahead. My tuppence from a hard-line SU-maniac: SM needles with a 2138 cc, TW needles with a 1991 cc. Do a bit of radiusing on the pistons, use 8103 dampers and POSITIVELY NO KN bull**** filters. Keep the wire mesh originals, well cleaned and slightly oiled. They look the part and they do play it. Il you go for stacks, try all kinds : short, medium and long. Linda would go for the long ones but she's partial on intake. Remember you're doing it only for the fun because without a better cam and dizzy, it won't change the car a bit. Cheers, Quote Link to post Share on other sites
T Robinson Posted January 23, 2009 Author Report Share Posted January 23, 2009 Hi Tony, The other guys gave you the full insight so just go ahead. My tuppence from a hard-line SU-maniac: SM needles with a 2138 cc, TW needles with a 1991 cc. Do a bit of radiusing on the pistons, use 8103 dampers and POSITIVELY NO KN bull**** filters. Keep the wire mesh originals, well cleaned and slightly oiled. They look the part and they do play it. Il you go for stacks, try all kinds : short, medium and long. Linda would go for the long ones but she's partial on intake. Remember you're doing it only for the fun because without a better cam and dizzy, it won't change the car a bit. Cheers, Quote Link to post Share on other sites
T Robinson Posted January 23, 2009 Author Report Share Posted January 23, 2009 Hi Guys, I will connect the redundant ports. good idea! My engine has a fast road cam and a modified dizzy with no vac advance, Thanks, Tony Quote Link to post Share on other sites
Badfrog Posted January 23, 2009 Report Share Posted January 23, 2009 Hi Guys,I will connect the redundant ports. good idea! My engine has a fast road cam and a modified dizzy with no vac advance, Thanks, Tony Then you're set. Connecting ports appears logical but it may perturbate the mix flow. Just try both ways. Quote Link to post Share on other sites
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