exhaust systems
Re: exhaust systems
Hi Chris,
Intererested in that exhaust, what does the manifold look like and is it similar to the Mini 1275 one in the picture below?
Thanks Ed
Intererested in that exhaust, what does the manifold look like and is it similar to the Mini 1275 one in the picture below?
Thanks Ed
- Attachments
-
- 1275 Inlet and exhaust.JPG (176.84 KiB) Viewed 580 times
Re: exhaust systems
Not far off, though mine had an inlet manifold allowing more options. I have a separate water-heated inlet so I cut the Marina's(?) inlet off to eradicate the hot-spot (as recommended by Vizard). I'm possibly regretting that move as I now need choke for much longer, and even after short stops like trips to the supermarket.
Chris T.
Chris T.
- Attachments
-
- Little n Large.jpg (190.28 KiB) Viewed 579 times
-
- Manifold.jpg (132.88 KiB) Viewed 579 times
400,000+ A30 miles in 40 years
Austins <=> sustAin
Austins <=> sustAin
Re: exhaust systems
Thanks Chris, the bottom one in your first picture is the same casting number ie 12G 787. What is the exhaust diameter and assume it is bigger than standard A35. Is it the same as the other casting? I'm running a 12G295 head on a 1098 but with completely standard 11/4 SU set up. I do get more performance but think I would benefit from a 11/2 in SU and slightly larger diameter exhaust. I've already sourced the carb which was from a 1.3 marina so float chamber is on the correct side. Many thanks Ed
Re: exhaust systems
Hi Ed, the bigger 12G 3538 manifold has an internal diameter of about 36mm at the exhaust flange. My new 1.5" exhaust pipe provides about 35mm internal. The 12G 787 manifold & earlier exhaust I'd been using were standard A35 width.
I only changed to a 1.5" SU (with DZ needle) last autumn and was surprised by the astonishing performance improvement and even more surprised by an unexpected MPG improvement. I do a few motorway journeys and soon felt that the standard exhaust was probably too restrictive, hence the experimentation with a wider bore.
My current problem is that my 1.5" SU does not have a vac advance facility (it's the front carb off a twin set-up). I naively believed some advice on another forum that the vac pipe on the inlet manifold can be used. Don't try this! Ha-ha! The dizzy just runs permanently at max advance. I'm going to have to somehow drill the SU and insert a vac pipe.
BTW the 1.5 SU was a complete pig to drive initially and impossible to drive smoothly, either stalling on take-off or leaving melted rubber on the tarmac. Horrid and dangerous. I've improved this significantly by ensuring that all the accelerator rod joints are completely free to twist & turn however they like. I understand that cable operation is the answer, but I'm not interested in that route yet.
Chris T (With apologies to Alan for hijacking his Maniflow thread)
I'd been running a 1.25" SU on the 1275cc motor since about 2003. I wasn't interested in performance; avoiding downtime & promoting economy & reliability were key, so I retained the previous 948cc motor's ancillaries (with a few richer needle swaps in the early days). I only changed to a 1.5" SU (with DZ needle) last autumn and was surprised by the astonishing performance improvement and even more surprised by an unexpected MPG improvement. I do a few motorway journeys and soon felt that the standard exhaust was probably too restrictive, hence the experimentation with a wider bore.
My current problem is that my 1.5" SU does not have a vac advance facility (it's the front carb off a twin set-up). I naively believed some advice on another forum that the vac pipe on the inlet manifold can be used. Don't try this! Ha-ha! The dizzy just runs permanently at max advance. I'm going to have to somehow drill the SU and insert a vac pipe.
BTW the 1.5 SU was a complete pig to drive initially and impossible to drive smoothly, either stalling on take-off or leaving melted rubber on the tarmac. Horrid and dangerous. I've improved this significantly by ensuring that all the accelerator rod joints are completely free to twist & turn however they like. I understand that cable operation is the answer, but I'm not interested in that route yet.
Chris T (With apologies to Alan for hijacking his Maniflow thread)
400,000+ A30 miles in 40 years
Austins <=> sustAin
Austins <=> sustAin
Re: exhaust systems
Chris, I might have an 1 1/2, need to check the stores.
Re: exhaust systems
Thanks Chris, that's really helpful, think I may try the HS4 on the smaller bore manifold and my current exhaust first. Carb needs a rebuild first so its a bit down the line but good to know the options. do you happen to know if the HS4 fits the HIF38 flange just in case I do want to go down the bigger bore route? Are the two diagonal holes correct? All Best Ed
Re: exhaust systems
Not sure this is right. Assuming you mean the thin (apx 3mm) pipe that runs from top of dizzy to inlet manifold, then it should not be a big issue. This device adjusts advance curve (timing) slightly at part throttle, for fuel economy and smoothness. Not having it wont make your dizzy run at max advance, it is not that significant.My current problem is that my 1.5" SU does not have a vac advance facility (it's the front carb off a twin set-up). I naively believed some advice on another forum that the vac pipe on the inlet manifold can be used. Don't try this! Ha-ha! The dizzy just runs permanently at max advance. I'm going to have to somehow drill the SU and insert a vac
All it does is uses the vacuum from in let manifold to expand a diaphram in dizzy to increase or retard timing very slightley at part throttle opening
In fact Cooper S and some MG midgets were fitted with 23D dizzys that dont have a vacuum adv/ret at all - assume they saw it as pointless ( excuse the pun)
- Attachments
-
- Cooper S and Midget Dizzy - without vac advance retard
- A2592700-9593-4028-9909-D9EAF14B5072.jpeg (15.22 KiB) Viewed 537 times
Last edited by exminiman on Sun Feb 18, 2018 9:10 pm, edited 1 time in total.
- gazza82
- Site Admin
- Posts: 5585
- Joined: Sun Nov 24, 2013 3:39 pm
- Committee Role: WebEditor
- Location: Buckinghamshire
- x 2
- x 17
- Contact:
Re: exhaust systems
I'd be more inclined to look at the springs in the weights that handle the mechanical advance.
"If you're driving on the edge ... you're leaving too much room!"
Club WebEditor.
Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
Club WebEditor.
Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
Re: exhaust systems
gazza82 wrote:I'd be more inclined to look at the springs in the weights that handle the mechanical advance.
Re: exhaust systems
Think you've got Chris wrong here, my take on his post was that he had tried linking the advance pipe to dizzy to another vacuum offtake on the inlet manifold and it was giving him too much vacuum. Maybe issue with springs as well of course! Anyone have an answer to the SU carb flange and whether HS4 fits diagonally on the HIF 38 flange holes? ie can square flange be used for both types? Thanks Ed
Re: exhaust systems
Just a quick note on Chris T’s big bore exhaust, the club spares scheme will soon be selling standard bore, stainless steel exhaust systems made on this exact jig
Matt Wood BSc (Hons)
Spares Co-Ordinator No.2
Tweed Grey 1959 4 Door A35 NSJ 831 (Nellie)
Membership No. A1865
Spares Co-Ordinator No.2
Tweed Grey 1959 4 Door A35 NSJ 831 (Nellie)
Membership No. A1865
- gazza82
- Site Admin
- Posts: 5585
- Joined: Sun Nov 24, 2013 3:39 pm
- Committee Role: WebEditor
- Location: Buckinghamshire
- x 2
- x 17
- Contact:
Re: exhaust systems
I'm pretty sure that they won't.Edosan wrote:Anyone have an answer to the SU carb flange and whether HS4 fits diagonally on the HIF 38 flange holes? ie can square flange be used for both types?
"If you're driving on the edge ... you're leaving too much room!"
Club WebEditor.
Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
Club WebEditor.
Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
- David Swain
- Posts: 3707
- Joined: Wed Jan 18, 2012 7:08 pm
- Location: Suffolk
Re: exhaust systems
That sounds good Matt, I may one day need a few of those.
Surprised the club isn't selling the big bore versions aswell, seeing as how many members have updated their Austins....
Surprised the club isn't selling the big bore versions aswell, seeing as how many members have updated their Austins....
David Swain. Member No. A1743
Contact for 'The Suffolk Group'.
Contact Email suffolk@austina30a35ownersclub.co.uk
A30 van 55 'R.G. Swain', A35 4 Door 59 'Little Gem', A35 2 Door 59 'The Rev' '+1'
Contact for 'The Suffolk Group'.
Contact Email suffolk@austina30a35ownersclub.co.uk
A30 van 55 'R.G. Swain', A35 4 Door 59 'Little Gem', A35 2 Door 59 'The Rev' '+1'
Re: exhaust systems
Agree with David here, I may be in the market for one in the future. Would suggest they could be offered on a made to order basis, guess it depends on how much extra work it is to set up manufacturing for different sizes. Also been checking on some Miniforums about the flange question and they seem to indicate that the HS4 will fit on the square flange. Be good to get a definitive here. Think I will initially go with the HS4 flange and normal bore to see what it is like after I've rebuilt my HS4 and then try to move upto the larger one as Chris has done. It will be great to get an exhaust that actually fits properly at the same time. My 3 piece SS Bull Motif one doesn't although it works well enough.