Ya know, Stu, if you want to run dual SU's then run dual SU's. Seems like that's what you want to do. You've already got the manifold, right?
Can't you buy them brand new from Moss? So pay the man and get 'er going!
Or rebuilt Hitachis would work too. You mentioned those repeatedly.
No, Scott, I'm actually talking myself into the Mikunis... same manifold, same linkage (mostly), less money than new SUs and a more modern design. But I guess you're tired of hearing me piss and moan about what to do, so you'll not hear about the dilemma until it's resolved.
Just wanted to throw out my recommendation for National Carbs. They're local to me and do a great job either stock or custom.
My vote is still for a roots blower and Holley double pumper.
But im a neanderthal.
Stu Lasswell said:No, Scott, I'm actually talking myself into the Mikunis... same manifold, same linkage (mostly), less money than new SUs and a more modern design. But I guess you're tired of hearing me piss and moan about what to do, so you'll not hear about the dilemma until it's resolved.
I tuned a set of those on a friend's 240z. The thing pulled like a tractor when we were done. I see nothing wrong with that plan.
Edit: My brain is scrabbled lately - The Z I helped tune had the original Hitachi carbs. I have no experience with Mikunis. Generally my carb experience is shaky at best - mostly trying to get SU's on a Spitfire to run right at altitude (they refused).
Post a link or pic for the Mikunis - I'm curious what you're looking at!
In reply to TVR Scott :
I can't figure out how to post a link with my chromebook, but the company is Vintage Performance Developments (VPD). The Mikunis are a single throat design similar to SUs or the Z-S carbs but with accelerator pumps and no oil-damped dash-pots! Ask any Harley rider and they should know about the Mikuni HSR carbs. You mentioned Mikunis and Datsuns. Mikunis were the hot set-up for Z-cars in the day but those were basically Mikuni-built Weber DCOEs... at least that's what they look like to me.
Found it here.
And a pic of a dual setup on a TR6 from their website:
Very cool. I don't think you could go wrong with that set-up.
I think it's cool in it's simplicity. Three of them would look cooler. Then again, with the triple Weber manifold I could do SIX Mikunis, one for each cylinder! That would look very cool... but a pain to set up, not to mention stupid expensive!
Hmmm.....
Individual carbs....
Soooo sexy......
Still way too complicated for me. I have a hard enough time with a simple holly!
FWIW, the Stombergs on a 6 are not the difficulty or even hindrance to making power (no other dual carb system is going to make more power).
The issue is the manifold and how dual carbs feed each of the cylinders via the branches in the dual manifold. A triple manifold is only marginally better.
The manifold and how it feeds the cylinders is a big reason why triple DCOE's and the stock PI setup made more power.
I've driven a TR6 with nothing more than a hotter cam, a tubular exhaust, and Richard Good's triple ZS intake. It was quite a lot more fun than a stock TR6 and reved much better, especially over 4000 RPM. My problem with this setup is difficulty in tuning, and I suspect that will be an issue with the engine you are using. That's why I'd go with SUs or Mikunis. But I do like the idea of a triple carb setup.
I understand that the Zenith-Strombergs, SUs, etc. all breath enough for a 2.5 liter engine. Trying to get 10-20% more flow would probably not gain any actual bump in horsepower, and could even result in a bog or flat spot in low end or mid-range acceleration. I think that the gain most people feel from the triple carb set-ups, be it RG's Z-S or Webers is due to the direct intake flow. I can't get past the 1) the complication or 2) the expense of triple anything right now, but I think that the Mikuni carbs represent the best compromise in performance for the price, and there is always the option of adding a GP manifold and a 3rd carb in the future. Three carbs always look cooler than two... I do think that the accelerator pumps (Mikuni, Weber) do result in more immediate throttle response than the dashpot/vacuum chamber system.
OK guys, this installment isn't actually about the TVR, but I know most of my "followers" are British car gearheads...
So, I just fell into a great acquisition this past weekend. A guy asked the Triumph club to come clean out his huge store of excess TR2, TR3 parts on the condition that ALL of it needed to go away. I walked away with a nice block, crank, 2 heads, radiator, half-dozen assorted carbs, and boxes of yet to be investigated small parts. Truly a score, as all FREE! When I casually mentioned that a limited-slip diff would be nice, he said "Oh, that completely rebuilt axle has a positraction in it". I grabbed it immediately, but didn't check it out until I got it home. Sure enough, it's an LSD axle, and even the brakes on it are all gone through with all new parts throughout. Now here's where you Triumph racers can help me out... just what have I got here? A Quaiffe clutch-type would be great (least intrusive in operation) but I suspect it's a gear-type "detroit locker" unit... but I don't know what either type looks like. I read some scary things about the lockers... abrupt engagement, loud noises, even that they're "dangerous" on the street. I do know that when I'm autocrossing the TR3 I find myself wishing I could just get the power to the ground in the corners/sweepers, So what is it and do I really want to install it?
I don't know the solid axle TR stuff well enough to guess, but I've never seen one like that (does look a little like a Quaife for a Stag).
Interested to hear from someone who does know.
I wish I could identify it. Nope....But I will say I have driven a TR4 on the street with a Detroit Locker. As well as about 20k miles street and track with my own A-H 100-4 similarly equipped. You need to learn how to drive it, but the overall effect is much quicker off the corners. What you cannot do is enter on the power, it will push badly, and you really have only one opportunity to accelerate out, so timing is everything. If you are clumsy/heavy footed it will make abrupt oversteer. I am not as sure I would like it in a TR3 due to the narrow track
You can identify a locker by turning the axles. It is possible with the pinion locked to the case you should be able to make either hub turn freely with no more leverage than a wheel diameter. A clutch type will require from 40 to 100 lb/ft of torque to move depending on set-up, and will not spin free at all.
Thanks, guys. I have determined that the axles wont turn in opposite directions like an open diff, but haven't been able to set it up to see how much leverage it will take to turn a hub. I will probably have to change my driving style, as in autocross I'm usually hard on the throttle or brakes!
I'll be interested to see where you go with this. Good find!
Turner X19 made me look up the specs. I didn't know the Healeys were that wide. Internet says that the 3000 has a rear track of 50". TR3 is a mere 45" across, so yep, that's quite a deficit. TR4s were 3" wider (48"), but my TR3 has cut that difference in half as I'm running 3/4 inches of spacers on each side to clear a tube shock conversion (long story, don't ask).
More LSD notes. Clutch type units that have been stored dry, or long term will usually require far more torque to break loose than they were set up for. I built quite a few for small racecars years back. A unit set to slip at 35lbs would take 100lbs/ft to break loose the first time after a few weeks sitting dry. Since these were ENV style "pumpkins" they were never stored in lubricant. A Spicer like yours should always be stored wet.
Well, I may not be using that LSD axle in my TR3, at least not in its current state of tune. I now believe that it's basically a Detroit Locker, which would be OK, if not for the fact that it seems to be a 4.55 ratio! With my low profile tires and low red-line motor I can't see this being workable in a street car, even with the 5-speed. Maybe when I build the next motor for it I will be able to fully make use of that stump-puller ratio!
However, I HAVE gotten something done with the TVR, that being what this thread was supposed to be about before I hijacked it. I had some issues with the throw-out bearing, first with getting the yoke reinforced, then with the bearing sleeve. I got Moss's finest brass sleeve, pressed on the new bearing, and then couldn't get it to slide in... seems the pressed-on bearing deformed the sleeve. I had to use a cylinder hone to open it back up to its original diameter. Then I really just needed someone to provide more hands and muscle to assist in bolting the gearbox to the engine. Once that was accomplished, we went ahead and dropped it into the chassis. Now the components are taking up far less space in my garage!
I had to test fit my shiny new header and the intake manifold. It looks like there should be no fitment issues. Also the driveline angles appear to match up very well, but I'll be verifying that before I tighten it all down.
That looks amazing! Very exciting stuff!
Great to see this coming back together, always a great feeling to get the engine back in the chassis! TVR did a really good job of building a proper chassis and suspension for the TR6 running gear, this will be better than new when you are done.
Looking very good! I probably missed it, what's the engine combo? Going to try and do a break in before the rest of the car comes together or wait until closer to completion?
Sorry for the delayed response, ViperT4. I had Sam Halkias build me the motor. It's .030 over, 9.5:1 compression, roller rockers with 1.65:1 ratio. Installed cam bearings, and GoodParts GP3 cam. GoodParts Super Damper, external oil feed line, spin-on filter, lightened flywheel, GoodParts tuned 6-3-1 ceramic coated header, recurved distributor...that's all the specs I can think of right now. Horsepower should be at least 140, optimistically maybe 160+. I currently plan on using a pair of Mikuni HSR carbs. Sam Halkias did the preliminary start-up/break in at his shop. It may be a while before I actually do my own start up!
No worries, you mean you can't reply to a build thread for a forgotten model during the workday?
Sounds like a serious combo. Are you tracking the car? I went with the GP2 cam myself and am also .030" over and going to 9.5:1 compression and will have a FiIdanza flywheel but elected not to do the headers, cam bearings and roller rockers. My distributor is being posted to Rob at British Vacuum Unit as I type. With my stock Strombergs I'd hope to be around the 130 mark, I'd say you'll be another 20 beyond that. Sam didn't get yours on an engine dyno for you when he was doing the break in? Are you going to machine adapters for the MIkunis to the factory manifold?
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