Single Sidedraft

67 1/2 1600 · Post by **67 1/2 1600** » Sat Dec 17, 2005 8:41 pm

Saw this on craigslist and was curious if that manifold could have been out of a forklift? Would a single sidedraft solex/weber boost up a little juice on the 1600?

Post by **dbrick** » Sat Dec 17, 2005 11:19 pm

It would sure simplify the tuning. As long as it flows enough air and is jetted right, it might be better in daily driving than a pair that's too big.
My MG kitcar had a Ford 2.3 liter with a single Weber 32/36 downdraft and was very nice to drive, that carb is progressive, runs on 1 barrel and the second kicks in.

Can you email this person and get some info on the manifold, just for reference?

Post by **spl310** » Sat Dec 17, 2005 11:25 pm

I am willing to bet that the owner says that it was on the car when he got it or some such answer. The manifold design looks like a Lynx unit. I wonder if it is from a British car and modified to fit a Roadster. It could be an L series manifold modified to fit as well as I believe that the port spacing is really close...

Post by **dbrick** » Sun Dec 18, 2005 12:54 am

I noticed that, alot of the L series and some of the MG stuff looks real close. I'm still tempted to try the dual downdrafts I have, but they would probably not be very good, except WOT.

67 1/2 1600 · Post by **67 1/2 1600** » Sun Dec 18, 2005 2:44 am

I emailed the guy he said nothing about what I asked and said it runs good when its warm. So im assuming it was on it like Sid mentioned.

datsunfreak · Post by **datsunfreak** » Sun Dec 18, 2005 7:13 pm

dbrick wrote:I noticed that, alot of the L series and some of the MG stuff looks real close...

I've used a U20 intake on an L-series before. The "balance tube" is just a bit different in length, had to cut and paste a bit. I assume on a Weber-style intake, you could just take out the balance tube altogether, or replace it with some rubber hose.

glennhuff · Post by **glennhuff** » Sun Dec 18, 2005 8:45 pm

I'm building a manifold for the R16 and a weber 32/36. I'll post pictures when I get it all tacked together. Hopefully it will fit under the hood.

ambradley · Post by **ambradley** » Sun Dec 18, 2005 8:55 pm

I was about to mention this car. Like solexes you shouldn't use the choke on a DCOE so that'd explain why it runs well when warmed up. About it being for an L series, those engines have a notable slant (20 degrees IIRC) and a sidedraft manifold wouldn't rest flat unless it was modified both for port and slant. I suppose it could be done.

Pierce Manifolds still has a cast dual DCOE/Solex/etc. manifold for the R16 - I believe Mike Young has this on his stroker. The issue brought up before with a single Solex/DCOE/etc. is the issue of the manifold having different sized runners to the shared cylinders so one cylinder will always run leaner than the other (1&2, 3&4). This doesn't occur on the dual SUs because the manifold puts each carb equal distance between the shared cylinders so the runners are the same, or at least nearly so.

For those more in the know, an offbeat technical question. I'd read that the dual SU arrangement on the Z's L6 was less than optimal due to runner length and firing order, and that three SUs on a custom manifold would be superior. Anyone have a three SU Z?

Post by **spl310** » Sun Dec 18, 2005 9:22 pm

Adam,

If I am not mistaken, that is a cross over manifold similar to the ones that Lynx made and sold. The thought process was that the runner lengths were closer to the same, and the design was such that it evened out the pulses.

ambradley · Post by **ambradley** » Sun Dec 18, 2005 9:39 pm

Sid,

I agree, it looks like a crossover manifold (i.e. rear barrel feeds front two cylinders, front barrel feeds rear two cylinders) and I suppose that is a closer length percentage-wise, but then you're making the path to the cylinder more complicated, more turns, longer length. Doesn't that hurt performance?

This is where the MGB's have an advantage. The siamesed intake ports mean identical runner length to the head, then it just either goes slightly left or slightly right once inside the head.

Import_sounds-of-mid-GA · Sun Dec 18, 2005 9:51 pm

not to get off topic.... but do spacers work on 2000's?? I know on v8s they do b/c air/gas is cooler and all that good stuff!

datsunfreak · Post by **datsunfreak** » Sun Dec 18, 2005 10:23 pm

Import_sounds-of-mid-GA wrote:not to get off topic.... but do spacers work on 2000's??

If they didn't, Nissan wouldn't have installed them from the factory.

And alot of V8s benefit from it because you are lifting the carb, increasing plenum size, etc. And they don't work on every V8, see this month's PHR for carb spacer tests on various V8s.

And the SUs won't get the exact same effect as the V8 because it's a side-draft, not down draft. I think Nissan mainly used them as heat insulation. That would at least explain why they are phenolic resin. And if they just wanted longer runners, they could have designed them in the intake casting...