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Triumph TR6 - Roller Rockers
Let us know how the roller rockers work! Also what ration you are using and where you got em if you dont mind. Im really interested in the performance advantage of them. Anyone else who has them and can comment please do!
|Here Here !!|
After following a link on a previous post to http://www.goodparts.com I am also interested in their roller rocker setup. It looks good and appears reasonably priced compared to some I have seen. - Does anyone have experience with these particular ones??
The standard TR lift of .49" can be increased to .55" or .65" using different rockers. I think it probably best to go for more lift (is more better??) but I have read that the overlap of the cam, when combined with the speed and extent of the valve lift, plays a big part in the behaviour of the engine, particularly at low revs/idle. The reason being that overlap between an exhaust valve closing and an inlet valve opening, coupled with greater than standard gas flow (due to higher lift valves / cam), creates problems with the inlet pressure/mixture. The exhaust valve is still open as the inlet valve is letting the fuel/air mix in.
This gets better as the revs increase but as a road car,I see bottom end tractability and torque being more important than top end power.
My understanding of the complexities of combustion is fairly basic, but I would appreciate some input from anyone who have an opinion or experience with the TR6.
|Had a bit of a 'white out' in my last post - trying to think in feet and inches when we've been metric here for decades!!!!|
Lift ratio's are 1.49:1, 1.55:1 and 1.65:1 (not inches!!!)
|Changing the rocker ratio with new roller rockers will do as you say. Buy them after asking others if they had any unexpected wear problems. There are archives here on all kinds of wear - cams, roller rockers, bushings, rocker bars, pushrods etc.|
"Better" roller rockers will give you more lift which translates into a valve that will open more. Hence you assume you will get more air into (and out of) the combustion chamber. Not necessarily so. Think of the engine as an air engine where the fuel only causes the air to combust to expand to do the work of pushing the pistons down. It's air flow improvement you need. For more power, you need more air and more fuel per intake stroke and you need to get it all away from the cylinder after combustion as efficiently as possible with a smooth flowing and efficient exhaust system. This will permit the next intake charge to get into the cylinder more efficiently because all the exhaust charge got out efficiently.
If you don't "air flow" your intake manifold, the ports in the head plus the exhaust manifold (and/or put on exhaust headers that improve getting the burnt exhaust away better), you won't see all the improvement you were hoping for. Some will also put in valves that have a larger diameter to improve the air flow (ie - get more air in and out), but be careful that the larger diameters don't make the space so small between the edge of the intake valve to the edge of the exhaust valve - that the head cracks.
Have the air flow done professionally where they will provide you graphs of "before" and after". I met two Brits at Mid-Ohio in 1992 who had air-flowed many TR6 engines. The two Triumph Vitesses with the 2.5 litre TR6 engines at Mid-Ohio beat all the hottest TR6's there. When I visited then in Hounslow, England, they explained how it was all important. The graphs of the air flow at each stage of porting and polishing showed they knew what they were doing. And smooth porting of the head will streamline the air flow from the carbs to the intake valve, but a rough surface will cause a bit of turbulence and it's this turbulence which may cause the air/fuel mixture to become mixed better and give better combustion where you may get more power. They also showed me graphical outputs of their air flowed heads, with and without hotter cams. The hotter cams in a standard head gave a longer time that the valve was open, but air-flowing a head with a standard cam gave better and more air flow through it.
Richard Good has done some good engineering and testing before he put his parts on the open market. I saw him in his green TR6 at VTR in Red Wing, Minnesota in 2002 take "fastest of the day" in the autocross with his own triple Stromberg design.
Don Elliott, 1958 TR3A
I would not rely on roller rockers to give a tremendous power boost - let a new cam do that (I use the GP-2). The roller rockers will then snap the valves open quicker for better breathing. I use the 1.55:1 model. These have needle bearings, and I've noticed no unusual wear at all. Be sure and consider the maximum valve lift when you make the change - I'd get new springs if you opt for higher ratio's that get the lift around 0.39".
Although this has been a topic of much debate, use an external oil feed line to the head if you get RR's - the change in the relative amount of oil to the bearings is small and should be of no concern.
Also, you can't make a better choice than purchasing from Goodparts, IMHO. The quality of everything I've bought (and that's a bit) has been excellent, the prices good, and the tech help great when needed.
|Michael, Roger,Don ---I'm installing roller rockers made by Jim Swarthout in Tampa ,Florida. They are a 1.75 to one ratio and are made specifically for a stock camshaft equipped Tr6. They are very well made and come with excellent instructions and tech support from Mr S. His rockers use a phosphur bronze bushing and I'm installing a hardened rockershft and BPNW valve springs. (Seeing the old rockershaft gave me a new appreciation for the word "galling" -what a mess !) Jim S. also offers 1.50 (stock) and 1.60 ratio rockers (as does Richard Good and Ted Schumacher among other excellent tuners/suppliers) for those with interest in the hi-compression, alternative cam, multiple carb set-ups. These particular rockers fit my needs --as I'm about to supercharge the engine and will be relying on the stock (7.5 -7.75 to 1) compression ratio. The pistons are forged JE and rods will be stock , though carefully prepared--lightened,balanced and shot peened. My interest is to build a powerful , relatively low revving street car, no autocrossing, drag racing or road racing. I'm a retired motorcycle road racer who loves TR6's as a way to relax with the top down - as does my wife. However, I do think the 105HP 1975 USA version is a little too "relaxing". So, it seems that supercharging will offer a fun way to increase output to around 180HP (or more)|
but frankly I'm more interested in low to midrange RPM. I've long been a fan of long stroke British motorcycles, Triumphs and Nortons mostly (still ride a Norton Commando) and one thing I've learned in the last thirty five years is that hi revs and British long stroke engines don't go together "like a horse and carriage". I know that people can do it, but I guarantee they don't do it for long. I'm looking forward to one big SU HD8 carb to feed the car and leave others to properly synchronize
their multiple carb set-ups. The roller rockers (I hope) will help my specific application as the port shapes and overall flow characteristics of the cylinder head are not optimum in stock form - but with positive pressure from the supercharger ready and willing to push the mixture in, having the valves open farther may (?) help fill the cylinder and evacuate it more effectively without losing low RPM power. For me this a fun project, another way to skin the cat.I hesitated to even post this information as it seems that often readers of information assume the writer is advertising the products discussed and trying to convert everybody to their way of thinking --I'm not in this category at all. Jim's roller rockers are the only reasonably priced product on the market from my point of view --in the States he delivers a set for $216.00. I also feel a bit awkward because I haven't even started the car yet ,and frankly, I'm curious as hell to see if this works out. I'll keep you posted. All the best. David
For info on Jim's roller/rockers:
For an excellent look at supercharging a TR6 see Mitch Seff's site :
Sounds like you're going to have a nice set-up. when things get done. My only "problem" with Jim's RR's is that it's new to the market. Bushings instead of needle bearings, and at least one hint that oil drillings weren't made correctly. Why not spiral grooved bushes for better oil flow? And of course the high ratio will impose extra load on the cam and could overflex the the valve springs. My hat's off to you if you want to experiment - but let us know if you have a failure. I'm guessing that failure reports will increase as more kits get out there.
|Brent, I'm actually very impressed with the engineering, the oil galleries look fine to me. But, a new product is a new product and there may be problems. I work closely with a tool maker/machinist on the motorcycle race engines I build and he feels that a well machined bushing offers big advantages over a needle bearing "for this application"-- better total support for the rocker and good old fashioned simplicity. Frankly, I don't consider myself an expert on this topic, so the jury's definitely out for me - the proof will come in the performance. We'll see. I get the biggest kick out of the TR6 , it's fun on so many levels. It's also quite a kick for me to see so many people all over the world enjoying these cars in so many different ways. I'll definitely report any failures, and hopefully some success too !|
|Even us stock types enjoy reading about hot setups!|
|Thanks Don, Brent and David for your very informative and relevant comments - like most things though I'm going to have to 'bite the bullet' as everyone's setup differs. I guess it is difficult to quantify the actual effect of each variation without doing a lot of painstaking work and record keeping. |
I am generally quite happy with my 'baby' and the way she performs (not to mention the wife!!) but I ever since I got serious about the rebuild, something got buried in my brain that keeps saying "you must have roller rockers!!!!" it just keeps repeating itself - I don't know - maybe it's the hormones again.
If (when!) I go ahead with this, I'll get some measurements done on a dyno and report. My thoughts are to probably go with the 1.65:1 setup.
The rebuild was extensive (bare metal/nut and bolt - 9 years!) and I list the work done, in order of importance (as I see it anyway) for 'EC' and his mates who I hope will be drawn into the brotherhood of upgrades/improvements.(Is this where the voices start?? - We're only talking engine here)
OIL - 1. Spin on oil filter 2.External oil feed to valve train 3.Oil cooler 4. Competition pump 5. Baffled sump 6. tear-dropped galleries
BOTTOM END - 1.Balance 2.Polish, magnaflux & shot-peen. 3. H/T bolts
HEAD - 1.Early 'CP' series (larger inlet valves) 2. Polished ports, bullet nosed bronze guides, triple-cut seats 3.good double springs, alloy caps. 4.Solid rocker spacers, tuftrided rocker shaft, lightened and polished rockers. 5. matched and dowelled mainfolds 6.(Compression Ratio to suit fuel)
CAM - Fast road (TriumphTune 777) with drilled followers
SPARK - Pirhana Elecronic
LUCAS Mechanical fuel injection (CP manifolds) with Bosch pump.
The car is very driveable day to day but I must admit it is almost impossible not to give it heaps.
This thread was discussed between 10/10/2003 and 11/10/2003
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