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The cast log manifold on my cf is a known power sapper.
I keep having thoughts that it needs a decent manifold. I know little about this though.
The hot 2.3 slant cars had 4 2 1 manifolds so i figure this is the best layout. If you can find an aftermarket manifold for them they are expensive and id guess probably wont fit, so i thought maybe i'd make one.
don't want to spend loads though and the only place ive found that sells exhaust parts so far are pretty expensive.
I guess id probably use mild steel as it would be welded with mild wire anyway.
Where is best to buy bends etc?
Ive considered buying a cheap used manifold or two and modifying them. Ive done it with 2 stroke motorcycle expansion chambers before. Stupid idea?
What sort of diameter should i use? Same as original, just rely on better flow design?
Its a van, so I'm not looking for every last bhp, is there things i should consider if torque is more important than not restricting the rev limit?
Car manifolds are 1+4 2+3. I was thinking of copying that.
So, diameter? Mild or stainless? Pair which cylinders? And am i daft to think about modifying something ment for another car?
I guess id like to get it made for £100 if poss, £150 maybe. Was sort of looking like £300 in parts though, hence looking at modifying something existing.
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stealthstylz
Club Retro Rides Member
Posts: 14,832
Club RR Member Number: 174
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Making a tubular manifoldstealthstylz
@stealthstylz
Club Retro Rides Member 174
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Search for whengparts and get them to laser cut you a manifold flange, then I've done as you suggest and bought a couple of cheap manifolds and chop them up for parts. Diameter wise meansure how big is needed on the exhaust ports, no point going a lot bigger than the ports if they're tiny.
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Search for whengparts and get them to laser cut you a manifold flange, then I've done as you suggest and bought a couple of cheap manifolds and chop them up for parts. Diameter wise meansure how big is needed on the exhaust ports, no point going a lot bigger than the ports if they're tiny. It doesnt need/cant use a full flange. It uses 4 individual 2 bolt flanges which are easy to find cheap. Ive been looking at crossflow manifolds and mx5, both look like they could probably be chopped about quite easily, but tbh most manifolds could be used as long as tube diameter is ok and its 4 2 1. I have found some diy kits for about £110 which may be easier than using an old used one, but they don't look super quality. |
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What are the pros and cons of 4-2-1 vs 4-1?
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Take a look at the Skid factory on You tube. They reguarly make manifolds. I believe Tig welding is the best for such a kind of job
Peter
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What are the pros and cons of 4-2-1 vs 4-1? 4-2-1 are better for torque and 4-1 are better for peak power BUT it all depends on matching the lengths of the primaries & secondaries to the characteristics of your engine. |
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Take a look at the Skid factory on You tube. They reguarly make manifolds. I believe Tig welding is the best for such a kind of job Peter I'm sure it is, but that aint going to happen 😂 I can weld sort of ok and have a rubbish welder. Fortunately a friend who owes me a favour is an amazing welder and has proper kit (but not tig) so ill probably try and rope him into it. Ultimately though you cant even see it in the engine bay so I'm not bothered what it looks like. I watched all the skid factory bedford vids, i really like their work and the way they do their shows. |
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What are the pros and cons of 4-2-1 vs 4-1? 4-2-1 are better for torque and 4-1 are better for peak power BUT it all depends on matching the lengths of the primaries & secondaries to the characteristics of your engine. Ok, so 4 2 1 it is then. The car ones are a little complicated as they had more engine bay restrictions. They have quite long primaries though, all equal length. Id try and keep something similar going but more simply routed. Most of the 4 2 1 ive looked at have long primaries, except the mx5, so if i modify something to fit maybe ill rule those out. |
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The most common car ones are these, still rare though, janspeed i think  This pic crops up too  |
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I guess id make something more like the second one but a bit less swept back i think if I'm remembering the available space correctly.
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This is another, but i think id rather have no connections. I don't like the last Y either. This is actually available but i think would still need chopping a fair bit.  |
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Take a look at the Skid factory on You tube. They reguarly make manifolds. I believe Tig welding is the best for such a kind of job Peter I'm sure it is, but that aint going to happen 😂 I can weld sort of ok and have a rubbish welder. Fortunately a friend who owes me a favour is an amazing welder and has proper kit (but not tig) so ill probably try and rope him into it. Ultimately though you cant even see it in the engine bay so I'm not bothered what it looks like. I watched all the skid factory bedford vids, i really like their work and the way they do their shows. I am not a welding specialist but using tig could have something to do with less stress in the manifold and therefore less prone to cracking |
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I'm sure it is, but that aint going to happen 😂 I can weld sort of ok and have a rubbish welder. Fortunately a friend who owes me a favour is an amazing welder and has proper kit (but not tig) so ill probably try and rope him into it. Ultimately though you cant even see it in the engine bay so I'm not bothered what it looks like. I watched all the skid factory bedford vids, i really like their work and the way they do their shows. I am not a welding specialist but using tig could have something to do with less stress in the manifold and therefore less prone to cracking It would be nice, if it was an option id rather it was tig welded. |
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Don't worry about it. Most of the mass market tubular ones are MIG welded anyway - it's much quicker and therefore much cheaper....
Nick
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Making a tubular manifoldPhil H
@philhoward
Club Retro Rides Member 133
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Would a nearside Rover V8 one (I’m thinking P38 Range Rover) be worth looking at as a starting point? Might not be ideal in terms if optimised lengths but got to be better than the stock one? Most are compromises between theoretical and practical anyway.  |
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Last Edit: Oct 9, 2019 3:08:13 GMT by Phil H
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The most common car ones are these, still rare though, janspeed i think This pic crops up too Manifold in first picture is what you want to aim for. Primary runners of equal length. Second manifold is a wate of time. You couldn’t make the runners more unequal in length if you tried 🤣🤣 |
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Would a nearside Rover V8 one (I’m thinking P38 Range Rover) be worth looking at as a starting point? Might not be ideal in terms if optimised lengths but got to be better than the stock one? Most are compromises between theoretical and practical anyway. I had noticed they may be close, worth looking at once ive got some measurements. |
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The most common car ones are these, still rare though, janspeed i think This pic crops up too Manifold in first picture is what you want to aim for. Primary runners of equal length. Second manifold is a wate of time. You couldn’t make the runners more unequal in length if you tried 🤣🤣 Indeed. Id try and get the primaries as equal as possible. There is a fair bit of space so shouldn't be too hard. The strange thing with the second one is it looks quite nicely made even if its not designed too well. |
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Last Edit: Oct 9, 2019 7:00:26 GMT by VW
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tristanh
Part of things
Routinely bewildered
Posts: 990 
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The most common car ones are these, still rare though, janspeed i think This pic crops up too Manifold in first picture is what you want to aim for. Primary runners of equal length. Second manifold is a wate of time. You couldn’t make the runners more unequal in length if you tried 🤣🤣 Admittedly so, but if the oe one is so awful, surely anything would be an improvement? |
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Whether you believe you can, or you cannot, you're probably right.
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Manifold in first picture is what you want to aim for. Primary runners of equal length. Second manifold is a wate of time. You couldn’t make the runners more unequal in length if you tried 🤣🤣 Admittedly so, but if the oe one is so awful, surely anything would be an improvement? If you are going to the trouble of making a new one, do it to the best of your abilities 😊 |
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