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What is your favorite TR8 Carb and why?

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RossL Ross LoMonaco
New Jersey, USA   USA
I just bought a TR8 (still in transit) and it has the stock carbs. I have three Strombergs on my TR6 so I am not afraid of them. I am a little apprehensive about the choke set-up on the stock TR8. I always prefer a manual choke on a 5 speed car. I live in NJ I don't drive a lot in the winter but I do drive a bit whenever the roads are "salt free".

Has anyone ever converted the water chock to manual?

What 4 barrels are preferred? Edelbrock 500 or Holly 390?

I plan to drive the car a while before I change anything..................

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Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
If you check with some of the Triumph Breakers, Team Triumph, TSI, etc, you can get a set of ZS's off a 1975 or early 76 TR7 that have a manual choke and convert your TR8 ZS's. The geometry of the linkage will not allow you to just swap ZS's off a TR6 or TR7 to a TR8 but you can adapt the chokes between them.

Check with Ted at TSI, he advocates and had a set of SU HIF6's off a SD1 out of the UK that allows you to run the SU's on a TR8, they have a manual a choke also. . According to him it is about half the cost of a 4BBL conversion. Also According to Rimmers if you add K&N filters you can increase the needle and if you add headers you can increase the needle again on the SU's

Talk to Joe Curto I believe the jets on the ZS's can also be upgraded and if you are not going with headers and a cam this may be all you need.

In reply to # 1495643 by RossL I just bought a TR8 (still in transit) and it has the stock carbs. I have three Strombergs on my TR6 so I am not afraid of them. I am a little apprehensive about the choke set-up on the stock TR8. I always prefer a manual choke on a 5 speed car. I live in NJ I don't drive a lot in the winter but I do drive a bit whenever the roads are "salt free".

Has anyone ever converted the water chock to manual?

What 4 barrels are preferred? Edelbrock 500 or Holly 390?

I plan to drive the car a while before I change anything..................



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
On a four barrel manifold my favorite carb is a throttle body injection system. Easy to get dialed in just right.



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

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uspsmech Avatar
uspsmech Jim F
North Providence, rhode island, USA   USA
1978 Triumph TR8 "007"
Ok, I cheated. I dropped mine off to Woody at the Wedge Shop and let him put the Holley 600 with the Edelbrock manifold that he sells as a kit. 10,000 miles later it's still running great. Starts beautifully with the automatic choke and runs strong enough to get me in trouble! I also had the Pertronix distributor put in and have not regretted it



" Enjoy the Drive", Jim

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1495755 by uspsmech Ok, I cheated. I dropped mine off to Woody at the Wedge Shop and let him put the Holley 600 with the Edelbrock manifold that he sells as a kit. 10,000 miles later it's still running great. Starts beautifully with the automatic choke and runs strong enough to get me in trouble! I also had the Pertronix distributor put in and have not regretted it

Well that's amazing, I had nothing but trouble with The Wedge Shop's, ahem 'kit' on mine. The cheesy fuel pump leaked fuel from badly installed fuel lines from the get-go. They plumbed the crank case vent straight into the base of the supplied cheesy air filter and that is just easy and sloppy (use a proper PVC for crying out loud). They block off the hot water manifold by-pass from the waterpump through the intake manifold. This translate to up, down, up, down coolant temps instead of a steady reading. And last but not least, the 600 Holley is just too much carb for a stock or lightly modded 3.5. From the above mistake I went to an Edelbrock 500 and after remedying all the above sloppy work, and editional carb tuning got a fairly respectable package but the 500 was still too big =ing lazy. What I have now is a Holley 390 (Holley list# 8007). It's a correctly sized carb and is noticeably snappier all around than any of the others. I don't want to discourage you from using an American down draft 4bbl carb but do not think that simply bolting on a 'pre, set-up package' is really going fix all your whoa's. Unless you are willing to put up with hesitation, flat spots etc there is quite a bit of tuning involved to get it right. A correctly set up carb'ed engine should run as well as a modern FI, but you'll never get modern fuel economy.
Stromberg carbs are fantastic instruments. My car had terminal FI problems and carburation was the way to go for me. In hindsight I should have gone with Strombergs or SUs but opted to work with American downdrafts. That being said, I'm finally happy with the 390 on my somewhat modified engine.

Here is another option for you to consider, just brought to my attention by another forum member.

https://www.holley.com/products/fuel_systems/carburetors/quick_fuel/street/slayer_series/parts/SL-450-VS

Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
I forgot to add this possible change. Since you enjoy multiple carbs on your TR6 you should test your Carb balancing and tuning skill with 4 SU HIF6's on your TR8. Check out this link to the Rover SD1 forum where mobydick has a boxer manifold and 4 SU HIF6's for sale that fits a 3.5 rover engine.

http://www.roversd1club.net/forum/topic.asp?TOPIC_ID=15505




In reply to # 1495650 by Pat.L If you check with some of the Triumph Breakers, Team Triumph, TSI, etc, you can get a set of ZS's off a 1975 or early 76 TR7 that have a manual choke and convert your TR8 ZS's. The geometry of the linkage will not allow you to just swap ZS's off a TR6 or TR7 to a TR8 but you can adapt the chokes between them.

Check with Ted at TSI, he advocates and had a set of SU HIF6's off a SD1 out of the UK that allows you to run the SU's on a TR8, they have a manual a choke also. . According to him it is about half the cost of a 4BBL conversion. Also According to Rimmers if you add K&N filters you can increase the needle and if you add headers you can increase the needle again on the SU's

Talk to Joe Curto I believe the jets on the ZS's can also be upgraded and if you are not going with headers and a cam this may be all you need.

In reply to # 1495643 by RossL I just bought a TR8 (still in transit) and it has the stock carbs. I have three Strombergs on my TR6 so I am not afraid of them. I am a little apprehensive about the choke set-up on the stock TR8. I always prefer a manual choke on a 5 speed car. I live in NJ I don't drive a lot in the winter but I do drive a bit whenever the roads are "salt free".

Has anyone ever converted the water chock to manual?

What 4 barrels are preferred? Edelbrock 500 or Holly 390?

I plan to drive the car a while before I change anything..................



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

TeeR8 Avatar
TeeR8 Gold Member Henri Lefebvre
Calgary, Alberta, Canada   CAN
In reply to # 1495643 by RossL

What 4 barrels are preferred? Edelbrock 500 or Holly 390?

I plan to drive the car a while before I change anything..................

Ross,

My TR8 came with a Edelbrock 500 with manual choke. At the time I found that it would not run smoothly at low speeds and rpm, for example in slow traffic or driving in the neighborhood below 30mph. My mechanic tried to improve the running at slow speeds with some adjustments from the calibration kit and using the road dyno. He improved it a bit but not totally. I should mention that the cam does not seem stock but I have no idea which cam it is.

A few years ago the valves needed servicing resulting in a full rebuild of the heads, and at that time my mechanic recommended installing a Holley 390. In the end the TR8 makes more power on the dyno and is much smoother at low speeds. The Holley came with an electric choke which I dialed down very low on choke and throttle because I do not drive in very cold weather; the accelerator pump supplements the choke for starting, the same technique I used with the TR6 with triple Webers, never used the choke.

Either 4 bbl carb would improve power when dialed in properly and a TBI set-up would be great if money is no object.

By the way, my Edelbrock 500 is available for a good price, complete with the calibration kit.



Henri
1980 TR8, Platinum
1971 MGB GT, Midnight Blue

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, Oregon, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1495781 by POW
Well that's amazing, I had nothing but trouble with The Wedge Shop's, ahem 'kit' on mine. The cheesy fuel pump leaked fuel from badly installed fuel lines from the get-go. They plumbed the crank case vent straight into the base of the supplied cheesy air filter and that is just easy and sloppy (use a proper PVC for crying out loud). They block off the hot water manifold by-pass from the waterpump through the intake manifold. This translate to up, down, up, down coolant temps instead of a steady reading. And last but not least, the 600 Holley is just too much carb for a stock or lightly modded 3.5. From the above mistake I went to an Edelbrock 500 and after remedying all the above sloppy work, and editional carb tuning got a fairly respectable package but the 500 was still too big =ing lazy. What I have now is a Holley 390 (Holley list# 8007). It's a correctly sized carb and is noticeably snappier all around than any of the others. I don't want to discourage you from using an American down draft 4bbl carb but do not think that simply bolting on a 'pre, set-up package' is really going fix all your whoa's. Unless you are willing to put up with hesitation, flat spots etc there is quite a bit of tuning involved to get it right. A correctly set up carb'ed engine should run as well as a modern FI, but you'll never get modern fuel economy.
Stromberg carbs are fantastic instruments. My car had terminal FI problems and carburation was the way to go for me. In hindsight I should have gone with Strombergs or SUs but opted to work with American downdrafts. That being said, I'm finally happy with the 390 on my somewhat modified engine.

Peter:

You have stated what I have believed for quite some time: The Triumph engineers were not amateurs, they knew what they were doing when they set up the 3.5 with twin Zeniths. They flow about 440 CFM total, which is remarkably close to the Holly 390 and the slayer, which you praise as the correct size for the motor. Even the manifold on the stock 3.5 is a decent design for the street. In these areas you can of course improve on the factory equipment, but it is never compromise free and without some experimentation and optimization.

I have long held the position that one should not expect to gain oodles of power by simply bolting on SUs or Webers (both are good carbs, by the way) in the belief that Zeniths are "lousy". I advise people to rebuild their Zeniths rather than spend the money for SUs or other carbs. In particular I advise people to stay away from the Weber DGV carbs because of the horrible manifold compromises that must be made to adapt them to TR6s or TR7s.

If you do the math, at 100% volumetric efficiency - impossible to achieve on a naturally aspirated OHV street motor - 215 cubic inches requires a 373 CFM carburetor at 6,000 RPM. If you can achieve even 90% volumetric efficiency you have a very sweet setup. So a 600 CFM carb will be operating with less than optimum vacuum signal, even if you rejet it. So you get flat spots, hesitation at throttle tip in, etc.

Adding horsepower to a motor and yet keeping it pleasant to drive in stop and go traffic and on twisties is a balancing act. I have learned that the hard way. Some people love the rough idle and noise when building a stout street motor, but I find it fatiguing and so opt for more of a balance between smoothness and power.

OK, so where does that leave us? Careful planning and thought are required to get it right. I would hope that Woody would have the experience to get it right. But if you understand the history of his 600 CFM kit, you would know that he reluctantly switched to it because the Holly 390 was NLA. That Slayer carb looks like a new design, and perhaps Woody will revert to something like it for his kit in the future.

There is still room for more fully streetable power. Raised compression, porting, MILD cams, etc work well with a little care and proper carb jetting. Even headers are workable (at the expense of noise and occasional fitment and durability issues) for the street. I have added headers to engines before, and experienced all the usual problems with them. My car came equipped with them, but I removed them for emissions and fitment reasons. If you look at the stock exhaust manifolds they are very well designed, and will flow quite well, even if you do not get the advantages of scavenging from a moving column of gas. I went with the stock cast iron manifolds after deciding they were well designed - so the Leyland engineers were well informed and competent here as well.

Everyone who loves to tinker needs to remember that many of the power claims made by manufacturers are optimistic, to say the least.

Cheers,

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

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