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TR2/3/3A carburator decisions for TR3A

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J

Jerry

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Group,
I want your advice. I will be rebuilding a TR3A engine with 87mm pistons. I have 3 choices for carburators:
1. Stock HS6
2. HD6
3. Webers DCOE 40s.

Question 1- Will the HD6s fit on the original intake manifold?

Question2- Is there anywhere to get just a manifold for the Webers?

Is there any advantage to any of these? While I am not restoring the car to strictly original, and I am not going to race the car, I would not mind seeing another 10-20 hp.

Jerry
1960 TR3A
 
Stock was H6, HS6 were for TR4A. If you are going to stick with the stock cam, I'd go for the HS6. Webers are hard to set up, and seem to be more for bragging rights or matching to a wild cam; than practical carbs for the street.
 
Webers run fine on the street, they can be hard to set up but it can be done, read up on them if thats the route you are going. And when they are right they run! Hoever if you are only putting a single DCOE on your car the jetting cost will be a lot less since you will only have to buy 2 of anything when you change things out, instead of 6 of each like on my TR6, I have a great assortment of things now. the Idle circuit is the hardest to get right

If you go the weber route send me a PM and I can share some knowledge with you

Most that have webers are very secretive about what they are running and I guess because we spent a lot of money on jetting

also get yourself an AF meter it will help a lot to dial them in

if you like the easy way go SU but not a lot of changing you can do to them, unlike a WEBER, you can jet for fuel economy, Low end torqure or High end power

Hondo
 
I think the DCOE setup would be a dual carb config. Always wanted webers, but never overcame the cost/my lack of experience hurdle.

I put HS6's on my 3A engine with a 4A long runner manifold - it fits just fine in the engine bay.
 
On my TR4A, I ran 40DCOE's on a mostly stock engine (4 into 1 header, re-curved distributor)for four seasons. While I had the best idle ever, I could either tune between too rich (poor gas mileage, black smoke out the exhaust) or too lean (always a stumble on throttle tip in). Never hit the just right. Finally had the 4A's original carburetors professionally rebuilt and have never looked back.
If you want to pursue going the Weber route, check out Pierce Manifolds (https://www.piercemanifolds.com/) - good company.
 
This is always a "fuzzy" topic.

The Webers alone are not gonna pump up the HP output much. They do have accelerator pumps, unlike the SU's, and give the seat-of-the-pants effect of <span style="font-style: italic">seemingly</span> more power. To gain HP, the whole engine whould need to be considered: cam, compression, CC'd head, ported intake & exhaust runners... Hondo went through the drill and dialed a set into compliance. It's a slog of a process, costly as well.

The SU's are VERY efficient devices, not to be dismissed. IMO it ultimately comes down to personal cost/benefit ratio. On a TR3 I'd stick with the SU's.
 
There is a set of HS6's in the classifieds
 
Is there really that much difference between the stock H6's on a TR3 and the HS6's. What is the physical differnce and the tuneability difference?
 
There's no perceptible difference between HS6 and the standard H6s on a TR3A and the the throttle linkage isn't so nice, so I went back to standard as well as exchanging a four branch manifold for the original type and fitting twin stainless steel silencers instead of one that hurt my ears and kept the wife out of the car.

I have the 87mm bore, a new distributor , I've carefully rebuilt the original carbs with original filters and I have overdrive and a 3.5 to 1 axle. The result is that it ticks over at 500 rpm, pulls like a tractor, is surprisingly fast and will cruise at anything you can stand.

I love the car, it's superb with the roof down and amazingly fast for a 53 year old, so I recommend doing the same. When I was younger I tuned everything including racing motorbikes, but now, if a car is for the road, I carefully, meticulously get it to run exactly as it left the factory and usually find its the best compromise.

The HS6 have their float chambers on the outside, so the pipe from the heater tap to the bulkhead must be re-routed and a new hole drilled in the bulkhead for it. Also air filters have to be thinner. All in all I wasn't comfortable with the mods for no noticeable benefit.

Just my thoughts

Ash
 
Well that's good to know.I'm running stock rebuilt H6's on my 3. It also has a rebuilt dist with Petronix, a mild street cam and an exhaust header. I'm running RH needles for a richer mixture as I was told I would need to because of the header. I'm using the 4A intake manifold as I was led to believe it would allow better "breathing" but I think I read somewhere recently that I would be better off with the stock intake? Know anything about this? The car is fast and fun to drive so no complaints there. :smile:
 
The TR4A inlet manifold is longer and a better design, but has to be used with HS6s, which are shorter. Otherwise the H6s are too close to the inner wing for air filters. There's no noticeable difference in power, or not as much as getting all the settings exactly right.

What inlet manifold you use dictates what exhaust manifold will fits, so beware.

I'd run standard needles unless a rolling road says otherwise, even though you've got a different cam and exhaust.


Best of luck!

Ash
 
Thanks for all the advice. Stock sounds the easist. Of course if I start dreaming again, maybe that fuel injection kit!!!!

Jerry
 
Just a thought but if the cam you're using is one of the common fast road ones, it may require the tappets to be set at 22 & 24 thou.

Ash
 
If you go the weber route, I found an article on the web thru searches, to cut down on the cost of buying a bunch of jets, mains, air correctors and idle jets, you can purchase micro drill bits from McMaster/carr, I dont have the article but you get .05 mm up to 2 mm drill bits in .05 increments and a pin vise. then when you are dialing in the webers, if its too lean you just drill out the appropiate jet up .05 in size, drive and if necessary keep drilling them out till you get it right. When you get them right, you can then order the right jets that have the correct number on them, it will save you a ton of money. the emlusion tubes cannot be drilled out but usually you can get those right with the information thats out there, I dont see any way to increase the chokes without machining them but usually information out there should be accurate and you not have to keep switching them out too. hope this helps in your decision making process

Hondo
 
Just for your information; when I rebuilt my TR3 engine I had it bored 40 over. I purchased a new set of Weber DCOE's from pierce manifolds and have not had to change one jet on the carbs. What I did find, was that I don't have to crank forever on cold mornings with the DCOE's, I'm using an electric fuel pump. As far as performance between the SU's and DCOE's, is like trying to compare apples to oranges. They're just not the same. If you go with SU's, I would have them professionally rebuilt; putting new gasket kits in old carbs usually is a waste of money. There's other parts that are usually wore out.
 
Terry you were fortunate that they were set up well for your car, On my TR6 theu ran really rich and washed the cylinders down and had the so called stumble off Idle, now that my engine was rebuild recently, bored to 2.7 Liters, mild street cam, shaved head ported and polished, 9.7 CR, I had to start from scratch since very few TR6 are this modified. Curious do you have an O2 meter and do you know what AF ratio you have at idle, acceleration and cruse speed?

Hondo
 
Hondo:

It's been quite awhile since I installed the DCOE's. If I remember correctly, I sealed off the vacuum advance line and used a vacuum gage and set the idle for the highest reading on each carb. Setting the needles the same number of turns to start with put the vacuum readings pretty close to begin with. I think I had to advance the timing which I did by watching the tach and going by how smooth I got the engine to run. I don't have timing marks on my 3, so a timing light isn't of much use. As far the jets, I didn't change anything. Once I had the idle setup, I didn't check anything at road speed. I ordered the carbs for a TR3A and just assumed it would be properly jetted and it turned out it was. What I can tell you is that I have it idleing at about 1000 rpm's. The acceleration is outstanding in all gears (laying rubber is no problem) my gas mileage is poor, (developed a heavy foot), of course, I'm going from two single barrels to a pair of two barrels. When I first installed them I didn't hook up the chokes, When the first cold weather came I had to change that. I'm running two down-draft webers on my 76 TR6. They work great. I'm pretty much sold on webers.
 
Terry
My DCOE run really good, just got to figure why no. 5 cylinder is not firing all the time

sorry dont mean to take over on the thread

So Jerry whats the decision?

Hondo
 
Hondo:
One final note. I'm sure you checked the plug and wire on the No. 5 cylinder, probably many times; you might want to take a close look at the distributor cap, even if you replaced it with a new one, I have found alot of the new parts are defective.
 
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