Bomb Shell venturis

[aumick10]

Thanks to all for the replies.
I confirmed most of my thoughts, and learnt some others.
Unless i can be bothered putting fuel injection on it, my thinking is a pair of 1 1/4", or 1 1/2" Linkerts, with the aftermarket bomb sights. This should give me a starting point to owrk with.

[T. Cotten]

Thanks to all for the replies.
I confirmed most of my thoughts, and learnt some others.
Unless i can be bothered putting fuel injection on it, my thinking is a pair of 1 1/4", or 1 1/2" Linkerts, with the aftermarket bomb sights. This should give me a starting point to owrk with.

Thanks Tom, i have 3 bolt manifolds so that is one constraint i have with carby selection...

If you have 3-bolt manifold flanges upon the cylinderheads, then doesn't that rule out 1½" models, Mick?

Even if you can fab some flanges, please consider the aftermarket "bombsight" offerings carefully, since they are apparently sold to fit every other 1½" model... so only perhaps the M53 series.

Please look again at the right side example of this pic I posted earlier. Note the differences with the OEM on the left.
I am not aware how many variations might be currently available, but with an o-ring, that one doesn't inspire me.

The drool pit was introduced with the bombsight, as best I can discern, and even though with a full-length venturi it is still exposed at the end, it really raises the question as to why the true bombsight left it entirely uncovered.

....Cotten

[aumick10]

Tom, you might be right about the 1 1/2" carbs, but these are not stock cylinders. I will have to dig them out and check the measurements.
I have three other motors to build first, so i don't need to decide yet what carbs i want to use.
Cheers

[T. Cotten]

Meanwhile, I just gotta ask, Mick,...

What kind of duty will this machine face?

Modern highway traffic, sidehack duty, competition, or just comfy tooling around?

....Cotten

[aumick10]

Just for fun, and because i can. I have a couple of STD JD's to ride around on if i want to go cruising.
I have a cutdown frame for it, 80" motor, probably an electric start 4 speed. Disc brakes, foot shift.

Been busy deburring, blasting and Parkerizing package truck check strap brackets. Finished for the moment.
Do some house maintenance then get into a motor rebuild.

[T. Cotten]

Just for fun, and because i can,.. probably an electric start 4 speed. Disc brakes, foot shift...

Its got fuel injection written all over it, Mick!

....Cotten

[aumick10]

That is also definetly on my wish list.
I had a Whitek injection on an Evo a while ago. I loved it and wish i hadn't sold it. I could change the fuel map and ignition map in real time. It had a very agressive cam where i had to take most of the fuel out of it at idle, then quadruple the fuel delivery over 1500-2000 revs. It would never react smoothly off idle with a carb.

I would like to put a lot of power into this motor but i think the std cases are going to be my limitation. On both my 4 valve evo's, there are no OEM HD parts,

[Jerry Wieland]

Where are you getting the canvas belting for the straps? I have not yet found a source for that thick belt.

Just for fun, and because i can. I have a couple of STD JD's to ride around on if i want to go cruising.
I have a cutdown frame for it, 80" motor, probably an electric start 4 speed. Disc brakes, foot shift.

Been busy deburring, blasting and Parkerizing package truck check strap brackets. Finished for the moment.
Do some house maintenance then get into a motor rebuild.

[aumick10]

Jerry, as i am sure you know, the strapping is not available in the correct thickness. I got close with army surplus products, but it was only short lengths.
I have three samples of the correct weave and material, but they are only between 0.100" and 0.125".
I am having the 1/8" strap doubled up and sewn together to see what it looks like.

The original straps were woven on a "Shuttle Loom". These are uncommon these days, a "Needle Loom" is the common machine. These looms produce slightly different weaves, usually just on the edges.
I think the thick strapping is a lost art,

[T. Cotten]

Back to topic, Folks..

Can anyone point out why bombsights were not a success?

Keeping an open mind for solutions...

.....Cotten

[RichO]

Like I said early on that the rings broke up the slug of air to mix it better with the fuel from the nozzle and was supposed to help increase velocity. It could be that simple. Maybe it helped, maybe it didn't. It doesn't have to be rocket science.

[aumick10]

The bombsight venturi has been used for many years on cars. I have only seen them on carbs with horizontal carbs, not the vertical shafts on the older bike carbs.
Is that some sort of clue?

[T. Cotten]

Lets not mix our apples and oranges, Folks,..

We can agree how a horizontal shaft avoids the bias that a vertical shaft offers one cylinder over the other when feeding an inlet pipe. But autos usually dump into a plenum, so shaft orientation matters little.
My Datsuns' secondary venturis were quite small compared to the rest of the throat of the carb, and primarily atomized fuel.

The Linkert secondary is a huge obstruction; Probably it increases the velocity over the nozzle at low speeds, but dramatically reduces the capacity at wide open.

Great for a tractor, I 'spose.

....Cotten

[Steve Swan]

I didn't know they were making Datsun's again... i had a 510, it was a screamer

[T. Cotten]

Most of my Datsuns, Steve,...

Were pickups. (*sigh*)

They had a window with a level line on the bowl, and I could see when the float swoll up!

I have some 2"OD x 1 1/2" clear acrylic tubing that begs for some polished acrylic venturis, and a Hoover.
This is also being discussed at http://forum.sscycle.com/viewtopic.php?f=21&t=12927

....Cotten