Best Velocity Stack Size for Weber's?

[Tabcon]

I have been told not to use the velocity stacks that came with the Weber's I bought for my TR4, they're pretty tall and I imagine the reason for not using them is a fitting problem once you add and air filter.

Aside from that, does anyone have a recommendation for the size of stack I should use? I've also heard to avoid the bolt on units and to use only the type that insert into the throat of the carb. There are so many sizes available that I really have no idea which size to use. My main concern at this point is that the air filters clear the body. I will most likely use the sock type filter such as ITG, or maybe even the mesh type if it allows for a better fit with a longer stack if the longer stack is what provides the best overall performance.

As I've said, this car will be used only as an occasional track day car and not will not be a 10/10th's racer. Maybe a 7 or 8/10th's fast road car.

Thanks

 

[Monkeywrench]

Tab,

Use the shorties like on this car https://britishracecar.com/CraigChima-Ginetta-G4.htm

Ideally, they would have a full radius, but if they don't (like the ones pictured), then it's not a problem. You might notice a few cfm gain on a flowbench with the full radius, but on the dyno and track you would never notice it if your carbs are tuned right.

Stay away from the screen stacks. Go with a foam ITG set up or K&N's. Be careful though, over oiling them will give you worst performance than a crappy, clogged paper air filter (you see Spec Miata racers do this all the time).

Hope this helps..

 

[Tabcon]

Thanks, just the info I was looking for. When you say full radius, are you talking about stacks that look like these:

The one above is 45mm tall and has the insert that slides into the throat. It looks about the same size as the ones shown on the site you listed. Not sure about the blue color, but with the filter socks installed you won't see them anyway.

I assume this ITG will fit, it not they do make the sock type also.

 

[Monkeywrench]

Yep.

 

[Grantura_MKI]

You have to run some sort of stack in order to keep the ventori..sp in place. If not, you will bore outthe carb. I do not like sponge filters, as a back fire will cause a fire if you do not keep cranking the starter motor, or do not see the fire.
Cheers,
D.

 

[Tabcon]

A fire would cerainly not be on my top ten list of things that could happen.

What's the fireproof alternative? A steel screen?

 

[Grantura_MKI]

What happends with foam filters is that when the carbs spit, the petrol is stored in the foam. One spark, and a fire. Many a Ferrari, and other vehicles have burned from this. I did see this happen on my show field and yelled at the owner to keep cranking the starter motor and the fire went out. Fire shold be on the top of your list.
I would fit deep K&N filters to the carbs.
Just my 2p. Been there done that. Fit a fire system to be sure.
Cheers,
D.

 

[Tabcon]

Wow, really, really great advice. I sincerely appreciate it.

I still remember, and remember it well, the day I installed the rebuilt, modified, pristine engine in my '72 911-S. Everything was going perfectly. I should have had a helper, but as usual I was doing it myself. I had checked and rechecked everything about 10 times before I finally decided to crank it. It fired right up, and I mean literally FIRED right up. One of the injectors was not quite tight enough and hit a spark plug or some form of spark and the whole engine bay ignited. Fortunately I had a fire extinguisher which put the fire out, but left a terrible mess. That stuff is caustic.

It took a little more effort to get it back to pristine, but fortunately nothing was damaged too badly, just a few melted wires and mucho, mucho clean up, re-clean up and a little paint work.

I found a pretty decent deal on some velocity stacks for about $32 each, most I found were around $50 each.

I'm not sure I know what you mean by "deep" K&N Filters. Do you have a part number or pic? Something like this?

Piper Cross

 

[Tabcon]

I found these K&N which are 1.75" deep. The velocity stacks are just a hair over 1". That would give me about 3/4" clearance between the top of the stack and the top of the filter. I would think this would be enough clearance and with these, I only need 2 instead of 4 filters.

The next size up is 3.5" deep. If these will fit between the carbs and the wheel well, these may be a better choice.

Here's a good shot of the clearance and it looks like the deeper filters may fit.

Those Pipercross socks are 4" tall.

 

[Grantura_MKI]

Nice looking Porker! Your second picture is what I mean by deep. They do make shorter stacks made out of spun alli. Dave Bean sells them. A bit $$ though. I run a shallow filter on my B with stacks inside. Not able to post pic's, sorry. I would order one filter to see if it fits just to be sure, unless you are positive of you measurments. Best of luck!
Cheers,
D.

 

[Michael Oritt]

Wow, I never thought about foam filter material absorbing gas fumes. I have K&N's on my Elva and a cold air box on my 100 but my wife's street Healey has foam filters. I think they will have to go!

Thanks for the tip!

 

[Monkeywrench]

We've used foam air filters for years in dirtbikes and never had one go up in flames. Not saying it can't happen, but I haven't seen it.

 

[DrEntropy]

Under an enclosed bonnet it can happen kinda quick. The foam is a fuel depot. Grantura explained the mitigation procedure: "Keep cranking it!"

Many a "POP" from a cold start has resulted in FLAMES.

Not certain but: now that we're seeing more volatility in fuels (ethanol) it may be an even nastier circumstance. Eschew the foam filters.

You're likely better off just running the stacks with screen-door mesh over the holes to keep th' BIG pieces out.

 

[Monkeywrench]

I'm from a post carburetor (on cars) generation, so that's new to me.

The screens KILL flow. An enclosed airbox with some sort of prefilter would be ideal.

 

[dougie]

I have since added stainless steel screens over my 3.5" ram pipes and didn't see any drop in hp or torque on my last dyno run. I think it would have to be a pretty fine mesh screen or there's poor air flow to the carbs to begin with.

Dougie

 

[Tabcon]

That's not my porker, its a picture I stole from Racestorations. Mine will be much nicer...lol, sorry Darryl.

I spoke with Richard Good of Good Parts today and he is going to look into fabricating an airbox like he makes for the TR6. I would think all he would have to do is shorten it a bit. I do like the idea of a forced air flow at speed.

 

[billspohn]

Always a good idea to use filters if you have anything but a race car. Filtron foam socks are fine, but I would change the elements once a year. And they can be a problem if the engine backfires through the carbs and you previously gas soaked the filters!

MGB engine in a TVR