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weber intake manifold dimensions????

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trfourtune

Jedi Knight
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hi,
can anyone give me the dimensions for a tr4/4a intake manifold (twm or cannon) for weber dcoe or dellorto dhla carbs? i need the face to face dimension and if there is a vertical offset or slope/angle of the carb relative to the head. my research leads me to believe that they only come in 45mm but i am going to use 40's so i plan to make manifolds that are 40mm. /ubbthreads/images/graemlins/tongue.gif
rob
 
Hi Rob,
Not sure if you prefer to make them, but Pierce Manifolds carries DCOE 40 manifolds for what they call "High Port Heads" Pierce
 
hi,
when i talked to them previously they said they are the same as the 45mm with a 45mm inside diameter.
rob
 
Hi Rob,

I've not got either of those brands of manifolds. Mine is a Warneford (which I chose because it's a one-piece manifold).

However, I can tell you there is a slight amount of tilt to most (all?) Weber manifolds I have seen. The outer end of the carb, at the filter, is the highest point. Per the Weber manuals I've got, it's not supposed to be any more than 5 degrees max off of vertical, which is exactly what it measured on my car.

I think I know what you are trying to achieve, a constant sized intake path, matched from carb to valve. However, I'm not sure that would necessarily be a good thing.

My car always ran quite well with 40 DCOE on the larger diameter manifold runners, also sized to accomodate up to 45 DCOE. Also consider that TRs were originally most often fitted with 42 DCOE, when that size Weber was commonly available (but, interestingly, could never be fitted with as large venturis as 40 DCOE can be).

I think the larger diameter manifold matches well with the head ports (and Tony Lindsey Dean at Kingston is enlarging those even more, too, with good success increasing torque). Running smaller dia. carbs on the larger dia. manifold will increase gas speed into the head, which is a good thing for a street car engine that's working in the lower and mid-rpms.

Think of the venturi effect. The greatest "restriction" of the entire intake, from the carb's mouth to the back of the valve, is at the Weber's main venturi (aka, choke), which will likely be 32, 33 or 34mm in your car. Everything after that point is a little larger, which should best draw fuel/air into the cylinder.

The "step" between the carb and manifold may cause the fuel/air mixture flow to tumble a little (as likely does the "step" in Tony's design, between manifold and head port), sort of like a waterfall, which can also be beneficial.

I'm sure it would be a problem if the "step" was the other direction, smaller diameter restrictions that would cause a stumbling point for the flow. So any mismatches the other way would be of more concern to me.

So, personally, what I would do is just go ahead and mount the 40 DCOE on any good quality, available manifolds and see how that works on a dyno, first. After that, a baseline would be established for future tweaking and tuning, perhaps including experimenting with the manifold's inside diameter, but also perhaps not.

Let us know what you do.

/ubbthreads/images/graemlins/cheers.gif
 
i thought tony's design was the exact opposite to that.that the manifold was smaller than the port at the mating face, then the port became smaller as it approached the valve (venturi shape).my guess was that the step had an effect on the "reflected" wave that comes back out of the port towards the air filter, creating a second wave that bounces back to the valve at a faster frequency than the wave that bounces from the valve to the inlet face at the filter or inlet to carbs. help me out here. have you talked to tony? /ubbthreads/images/graemlins/confused.gif

also, you get a HIGHER velocity with SMALLER diameter but the friction can goe up if too small.
"uncle jack" says you want a SLIGHTLY converging shape from the carb to the valve.
with a 45mm intake manifold you get two steps.carb to manifold, then manifold to port (unless you increase the port size).i am trying to keep the port size down.it's already too big (based on others comments).unless your racing.
rob
 
[ QUOTE ]
i thought tony's design was the exact opposite to that.that the manifold was smaller than the port at the mating face, then the port became smaller as it approached the valve (venturi shape).

[/ QUOTE ]

Yes, that's right. Maybe my description wasn't clear. Tony enlarges the entry of the port quite a bit, then tapers it down gradually as it approaches the valve. The intake manifold is left smaller, and there is a step created between the two. It's sort of the opposite of "port matching". He's deliberately mis-matching them.

Further inside the head, he tapers the port smaller but I'm not sure if he goes as far as welding up the port right behind the valve (see below).

So, I think we are saying the same thing. Tony's idea is to increase torque and let HP take care of itself. His is a somewhat radical approach to porting and a bit surprising how well it seems to work on both the 4- and 6-cyl. TR motors.

[ QUOTE ]
my guess was that the step had an effect on the "reflected" wave that comes back out of the port towards the air filter, creating a second wave that bounces back to the valve at a faster frequency than the wave that bounces from the valve to the inlet face at the filter or inlet to carbs. help me out here. have you talked to tony?

[/ QUOTE ]

No, I've not yet talked with Tony, I don't dare until I save up my pennies to have him build up an aluminum head for my TR4! /ubbthreads/images/graemlins/wink.gif(Can't afford the shipping on a cast iron head, to and from England! /ubbthreads/images/graemlins/eek.gif)

However, your point about the reflected wave might be good one. I don't know for certain, but imagine there might be some effect on each - inflow and that reflected wave - alternating as the valve opens and closes. The slight steps at both the carb-to-manifold and manifold-to-head junctions might act to some small degree to counter that reflection, as you say. (But, after all, we're only talking about the difference between 45 and 40mm - a 2.5mm "step" - at the carb-to-manifold juncture.)

But I would think the main thing those small steps would do is cause a a bit of nice, even turbulence in the gas flow that can have the effect of keeping the fuel/air mixture "stirred". I would think that would be a good thing and is basically the same thing that Tony is doing with his porting technique at the manifold-to-head juncture.

[ QUOTE ]

also, you get a HIGHER velocity with SMALLER diameter but the friction can goe up if too small.
"uncle jack" says you want a SLIGHTLY converging shape from the carb to the valve. with a 45mm intake manifold you get two steps.carb to manifold, then manifold to port (unless you increase the port size).i am trying to keep the port size down.it's already too big (based on others comments).rob

[/ QUOTE ]

I agree. A gradual tapering of the entire intake from the carb to the valve is the ideal. I'm just saying a couple small steps along the way might also be beneficial, and do no harm, especially in a street car.

[ QUOTE ]
(unless you increase the port size)

[/ QUOTE ]

I'm not sure I understand this point. If you mean increasing the port size at the manifold, that will increase the size fo the step between the two. That's exactly what Tony is doing.

If you mean increasing the size of the port all the way to the valve, no, I agree it needs to be gradually tapered smaller as it approaches the back of the valve.

In fact, that's one area where a lot of improvement can be done to the TR 4-cyl. head. The chamber just behind the intake valve is oversize and can be welded up quite a bit, with a new shape port created as it approaches the valve. A gentler curve and smaller diameter (about valve-size) is ideal, IMHO. The stock head has what amounts to almost a wall at 90 degrees to the valve, that sort of acts like a dead end for the gas flow. (Kastner's second book has an illustration of this sort of port modification).

I would think that improving that area of the port - right behind the intake valve - would be far more beneficial than fooling around with the intrenal diameter of the manifold might be.

That's just my opinion and certainly not something I've had a chance to test and prove on a dyno or in any other way. /ubbthreads/images/graemlins/cool.gif

The main thing I'm saying is just that it would be far simpler to buy and install one of the commonly available manifolds and save making a custom one. Try that, see how it works, and then make changes later if you wish, once you have something for comparison. If you go straight to a custom-made manifold, you'll never know if you have actually improved the engine, or not.

/ubbthreads/images/graemlins/cheers.gif
 
Hi again Rob,

One other thing regarding Weber manifolds... I've got a slight clearance issue between the deep K&N filter on the front carb and the hood of my car. The leading corner of the filter is very close to the sheet metal now and engine torque and vibration will almost certainly cause it to rub. I've toyed with the idea of milling the face of the manifold slightly, to reduce the 5 degree inclination of carb to maybe 2.5 or 3 degrees. In this case, that would give the clearance needed I think. According to Weber installation info, anything between 0 degrees (perfectly level) and 5 degrees is fine with these carbs.

I still haven't decided if this is I'm going to handle this on my car, but it's just something I wanted to mention to watch out for with whatever manifold you end up using. Generally, filter-to-fender clearance and overhead linkage-to-hood are not a problem on TR4. The latter fits within the hood's "power bulge" area.

(p.s. I use the 3.5" deep K&N filters because I have 40mm air horns on my Weber DCOEs.)

/ubbthreads/images/graemlins/cheers.gif
 
alan,
i plan to build an air box as big as possible with a large, flat filter near the rad (probably in the rad cowl in the side)and a second one at the back of the box so i don't create pressure. this way i get fresh air and flow through. if i added fender vents the back filter would be in front of the vent (this is a low pressure area). use a rubber seal between the carbs and the box so the venturi's are inside the box and sealed.ps-i'm using dellorto 40's. better atomization supposidly.
rob
 
alan,
so how long is that manifold? 4"? just curious.and yes it would be easier to just buy a twm manifold from pierce and get a benchmark, build a custom after and if the custom worked better i'm sure i would have no problem selling the twm on e-bay.
rob
 
[ QUOTE ]
alan,
so how long is that manifold? 4"? just curious.

[/ QUOTE ]

Hi Rob,

I'll get those dimensions for you asap. (The garage is getting painted and the car is all covered up right now.)

/ubbthreads/images/graemlins/cheers.gif
 
[ QUOTE ]
so how long is that manifold? 4"?

[/ QUOTE ]

Hi Rob,

You're close!

I finally got a chance to uncover the car and get the measurements you needed. The manifold is 4-1/8" from face to face. As I mentioned before, the carb mounting flange is angled about 5 degrees from vertical to give the carbs a slight upward tilt. So this dimension was taken at the top of the flange, the bottom of the flange would measure something more like 4-1/4".

It's also got a very gentle rising "S" curve that positions the center of the carb outlets 1/2" above the center of the ports in the head. Not sure that's critical, but it does move the carbs a little farther away from the exhaust headers.

Again, this is a Warneford manifold, which is a one piece design. (Part of the casting extends from one carb mount to the other. It's simply a solid cross brace joining the front and rear manifolds together, not a balance tube.)

Note: if the manifold were straight, no slight "S" curve, I probably wouldn't have an interference problem with the forward air filter. The 3.5" deep K&N just barely touches the corner of the power bulge on the inside of the hood. Of couse, you can work around any issue like that with the air box you plan to build.

A related thought... Webers don't like to have air forced into them. The best arrangement for the carbs is "still air" at the mouth of the carb, letting the engine draw in what it needs through the carbs. Otherwise, the mixture can be upset. So, personally, I'd not route an intake to the radiator shroud or in any other way ram air into the air box. Nor would I make it a flow-through design, with front inlet and rear outlet.

/ubbthreads/images/graemlins/cheers.gif
 
thanks again Alan.
points well taken.
rob
 
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