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Redline Twin Sidedraught Manifold


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G'day guys,

so me and a mtae took the plunge and grabbed a set of dcf40 dellortoes to replace our aging 32/36. The probelms wever encountered have been numerous, mainly in the way of vacuum leak. the redline mainfold, whilst it does fit, it doesnt fit without fouling on our extractors, and we bent two manifold studs last time we placed the manbifold on the car and torqued it up. So, I have machined the intake manifold to fit on the head without fouling, and the mainifold itself has been machined to the extractor thickness yet I'm still getting the increasing revs after closing the throttle that indicate a lean run / vacuum leak.

 

What i really want to know is, to fit twin sidedraughts, what was required with regards too jetting and machining of the manifold? (machining mostly, our jetting shouldn't be too far off... we have the book)

 

TLDR. Have you run twin sidedraughts and if so, what did you have to modify on the manifold to make it work?

 

Cheers,

 

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You can expect to have to modify the manifolds, they just aren't made well enough. We overcame the flange height difference with half-washers tack-welded onto full washers. Another way is to insert pieces of soft wire behind the washers on the skinny side.

 

There's always grinding and filing to be done to make the inlet fit between the extractors too. The main thing is to have both manifods bolt up cleanly and smoothly, then fit the exhaust pipe and carbs afterwards. Taking the extractors off and putting them on with the exhaust pipe on just leads to leaks.

 

What are you using between carbs and inlet manifold?? Some of those Redline rubber O-rings are hopeless.

 

Nuts on the carb studs?? They should have Thackery washers under them to give them limited movement to soak up vibration and stop fuel from foaming, but most guys just bolt them up tight.

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Well, I expect to find they don't fit with the extractors around the studs, and I'm not usually disappointed. Once you get them to fit beside one another neatly you sort out the flange thickness. Then you tackle the alignment of the manifold holes with the ports on the head, so eventually the holes are the same size and line up. Then clean the casting marks out of the inside of the manifold and polish the walls up, and finally check the alignemnt of the Webers with the manifold.

 

Same with extractors, and it pays to shine a torch up to where the pipes join. I've seen them roll-cut and not cleaned up so the metal protrudes down into the airway. If the torch won'r show the joins, then you cut the cone in half to look inside.

 

This is not just Redline, the Lynx SU manifolds need the same tinkering. The Hurricane extractors for the 4K usually have welds that foul the washers of the stud nuts too. They need grinding back, either welds or washers.

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I Have a redline manifold on my ke55 was a shit of thing to fit, took to mine with a grinder, replaced all my studs and used washers, problem sorted took me a good 1-2 hours putting the manifold on and off marking it where it was fouling, grinding a little bit off at a time.

 

Make sure you use the one piece manifold gasket.

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yep so basically the same as any mix/match of aftermarket intake/exhaust parts on non-crossflow engine, modifications may be needed

 

and to OP all you can do is remove what you changed untill you find the non sealing face or parts and then make them fit properly

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Its possible that you have a manifold vacuum leak like you mentioned but it also could be the carbs are not synchronised which will cause the revs to hang high, one carby or even a single butterfly could be cracked open a fair bit more than the others ..

 

The revs will increase if it has a vacuum leak & its running very rich, if its not running rich the idle will be rough & could even stall if you have a vacuum leak, so do you think its running rich or is it just that the revs stay high ..

 

Listen around the carbies & manifold for a vacuum leak ..

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a single butterfly could be cracked open a fair bit more than the others ..

 

True, you should diconnect the two carbs so they are independent and see how it idles. If it still idles high then take the carbs off and look at the butterflies carefully.

 

I've had to undo the screws in the throttle plates to let the butterflies relax then do them up again. I think it comes from the shafts being over-stressed when people don't set up the throttle-stop on the cable/pedal, so the force of the foot acts directly on the poor little throttle shaft.

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If you find a single throttle plate out of whack compared to the others you can actually tweak / twist the throttle shaft to realign the throttle plate, but you need to do it carefully & in stages, on dellortto's for example they have flats on the washers on each end the throttle shaft at the outside edge of the carby body which you can put a spanner onto to tweak the shafts ..

Edited by lexsmaz
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