TR4 Roller Rockers...what I have learned...

[Tabcon]

...The hard way.

Unfortunately, I tend to be a bit complusive when it comes to buying new and "improved" parts for my TR4 as evidenced by the last topic I posted, "1.65 roller rocker dilemma".

For what it's worth, I did learn a lesson here. Of course it was an expensive lesson, but I felt as though I should pass on what I discovered just in case anyone else may be considering the same route.

It doesn't work. Forget about it and don't waste your money.
If I'm wrong and there is a simple solution, please don't tell me, it is too late and where the heck were you in my last topic...lol.

For the 1.65 ratio rocker arms to work, the distance between the centerline of the rocker shaft opening on the arm and the adjustment screw at rear must be decreased. No way around it. What this ends up doing is pulling your push rods closer to the rocker shaft, in turn, placing them on an angle and in my case, actually rubbing the wall of the push rod tube. If your head is off and you have the tubes enlarged, I suppose it may work a little better, but your push rods will still be at an angle. So for what it's worth, in my case about 700 bucks, take my advice and forget about it.

The problem, as I see it is caused by the location of the stud the rocker pedestal slides over. The stud is too close to the rocker shaft and the only way to offset this is to push the the pedestal closer to the puh rod tube, which in turn places the stud inside of the rocker shaft opening on the rocker arm. I suppose that something could most likely be engineered to make this work, but trust me, there is no simple solution. At least none I could find.

 

[Michael Oritt]

"I suppose that something could most likely be engineered to make this work"
----------------------------
Tab--

That is what the people who are selling application-specific kits are supposed to do before they sell them! If the rockers were sold to by someone who claimed they should simply be a bolt-on fit you should get your $$ back.

On a side note I saw a CNN article shot at Acme Oyster Bar the other day and they only had a few sacks of oysters left in their cooler. What a sin! I ate my first raw oyster at Acme when I was a freshman at Tulane in 1960--my sympathies go out to you fine folks in N.O.

 

[Hap Waldrop]

I forgotten most of what we talked about, in the other thread, so forgive me if asked this before, you do have pedestal that reflect the ratio of your new rockers arms, if not it was always destined to fail, and we also find out that shimming the pedestal up corrects alot of the geomentry woes, but first you have to have pedestal with the shaft pivot hole that relfects the rocker arm ratio. You can sometime get by with small changes in ratio with stock pedestal, but it not the ideal way to do it, like the MGB going for 1.42 to 1.5 or the Midgets going form 1.25 to 1.3, but if the ratio change is bigger, like a MGB goign from from 1.42 to 1.625, or the Midget going form 1.26 to 1.5, with these set up new pedestal reflecting that ratio have to be part of the equation. We got a few people on Ebay and elsewhere selling HS rocker arms, that are not engine builders, and their knowledge is not much, so they are trying to sell you stuff they have never done, not good. I on more than one occasion sent Ebay sellers messages telling them you can't sell 1.5 ratio racker arms to MG A series engine owners without 1.5 ratio pedestals, there's no excuse for their ignorance, people buying this stuff are taking them at their word, and they do not what they are talking about. I would dare to say that half the HS rocker arms sold on Ebay end up on the buyer's shelf in the garage, not his engine.

 

[Michael Oritt]

"you can't sell 1.5 ratio racker arms to MG A series engine owners without 1.5 ratio pedestals, there's no excuse for their ignorance, people buying this stuff are taking them at their word, and they do not what they are talking about. I would dare to say that half the HS rocker arms sold on Ebay end up on the buyer's shelf in the garage, not his engine."
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Hap is absolutely right here--don't ask me how I know.

 

[Tabcon]

Thanks Hap, your advice is always appreciated.

I bought the rocker arms from Richard Good @ Goodparts based on a recommendation. The rocker arms are very well made and I'm sorry I cannot use them. Unlike the complete assemblies he sells for the TR6, you can only buy the individual 1.65 arms for the TR4. After much experimentaion, I contacted him several times, but his only solution was to either use smaller diameter push rods or enlarge the tubes. I really don't see either as a viable solution as the geometry will still be displaced.

I ordered a set of new 1.5 arms from Cambridge Motorsports in the UK. These arms are made by Titan. Since I'm not running a standard cam and using the roller rockers, I have done the calculations required to determine how much to shim the pedestals. The pedestals need to be raised about .193" to get the proper geometry with the Titan arms. I am also going to use the stock aluminum pedestals. I polished them and they are almost like like little works of art. Tbey should hold up fine. I bought 12 feet of some chromealoy steel tubing from McMaster to make new push rods from. I should have enough for 8 push rods by the time you consider how much I will probably waste in getting to the right size.

If anything, the engine should respond favoribly to it's new rocker arms and correct geometry. Maybe not as much uumph as the 1.65 would have provided, but I doubt the difference will be noticable.

 

[Hap Waldrop]

Tab, your Titans should come with pedestals that reflect the ratio for the rocker arm, I can't really speak about Triumph Titan roller rocker arm set ups, but for the MG A and B Series engine they are unique to themselves, meaning they have their own unique shaft and shaft size, not reflecting stock shaft size, also their adjustment hardware is unique to them as well. The key is to have a pedestal that relfect the ratio of the rocker arm, otherwise it's not going to work. I think when you get those Titans you'll se they are sold in assemblies, with everyhting you need, not just roller rocker arms. About the only thing I ever had to add to Titan assembly is solid space in ue of the springs, and shim for under the pedestal shims to get more lift and help with geomentry.

Just for curosity, what is the stock rocker arm ratio, same as a Spitfire about 1.47 to 1 (if I'm not mistaken).

You can make the other ones work if you have pedestals made, but using the stock pedestal ans you have discovered will not work, it was way too much of a ratio change to use stock pedestals.

Here's the deal with the pedestals, as ratio increases the pivot hole in the pedestal has to move closer to the pushrod to keep the geomentry in check, I even seen guys use HS rocker arms and modify their stock pedestal with a bushing and off set bore hole to accomplish this.

 

[Hap Waldrop]

Here's a good example of the work involved with roller rocker arm set up and how to make them better. I have a buddy who I've helped him with this project, but he's putting it all together, it's stupidly trick MG A series 1380 street engine ( a big bore 1275 engine if you will) with H beam aftermarket connecting rods and a Moldex billet crank (you have to know this guy to know why he would put a billet crank in street motor ). Anyway he has the Mini Mania/Titan 1.5 roller rocker arms for the A series 1275 engine engine, this set of Titans comes as assembly, rocker arms with adjusting hardware, shaft, pedestals, the whole assembly. When he did his first trial fitting, he noticed the angle of the rocker arm on the valve tip was running uphill towards the valve, he measured his valve lift and noticed had .050" less than he thought he should have, he knew this because he had taken camshaft lift x rocker arm ratio - valve lash to see in a perfect world what his lift should be and he was .050" less than that. Now here's the deal, rocker arm move in a arc motion, not stright up and down, so they will lose ratio thru that arc, the more lift cam you use the further downward the rocker has to travel and the more ratio you'll lose. In the case of the Titan 1.5, as with many other roller rcker arms set up, you can shim the the pedestals up to get some of this lost valve lift back. I suggested that he use .125" waser and use them under the pedestal as trial shim with everything torqued down and see if he got improvement in valve lift, he did, he gained .025" back in valve lift, now he can play with that some more and see if he could get more back, if you perfect the pedestal height you can get probably 90% of your projected valve lift, of course valve cover clearence in some engines might be your limiting factor as well as coil bind on your valvele spring, or evne stud length, of course all these things have to be accounted for and sometimes compromises have to be made to get it all to work.

Here's some pictures of the Titan roller rocker arms bolted on with no shims, you can see the angle of the rocker arm at TDC, also notice where the adjustment hardware is. Now look at the second photos with the washer shims in place, and look at the angle and the adjustment hardware and pushrod, much better and .025" more vlave lift, now he will need to make some .125" pedestal shims, this will ne his limit without reinventing the wheel, because he has the end of the head studs thread, anymore shim thickness an he would have to have longer head studs, and those are not readily available, so this will probably as far it goes, but thats .025" more lift, and better geomnetry and that for sure is a nice gain.

 

[MadMarx]

I still run my TR4 with 170 HP with stock rockers and valves and they seem to be reliable. No need for a roller rocker. I also use stock cast valve guids.

Sometimes the stock items are really well done. Even with 15mm valve lift.

Cheers
Chris

 

[Hap Waldrop]

I still run my TR4 with 170 HP with stock rockers and valves and they seem to be reliable. No need for a roller rocker. I also use stock cast valve guids.

Sometimes the stock items are really well done. Even with 15mm valve lift.

Cheers
Chris

Yeah but who knows with more ratio and the valve geomentry optimized you might make 180 hp :wink: We're always trying to make better mousetraps. You should do roller rocker arms in my opinion, for only one reason, more ratio which equates to more valve lift. Adding to that most stock rocker arms are all over the place as for ratio, alot can been done with optimizing the pushord length as well, which you can check with a adjustable test pushrod, which is actually a pretty affordable tool. With the 1275 and the MGB race motors thats exactly what we are doing, more ratio, on the race engine we're lifting them somewhere around .530", thats real valve too, not theorectical valve lift, even with the most radical race cams the only way we can get there is with more rocker ratio.

 

[MadMarx]

I think as the cam was designed for the stock items a different ratio would disturb the result. And I have no valve travel left. More lift would destroy everything.

 

[Hap Waldrop]

I think as the cam was designed for the stock items a different ratio would disturb the result. And I have no valve travel left. More lift would destroy everything.

Maybe so, but that where valve reliefs in the pistons come into play. Just for curiosity what is your cam or lobe lift? For example we run a cam on the 1275, Comptune HL12, it has .366" lobe lift and there only two grinders in the world that offer lobe lifts that high for that engine, and one is for all actual purposes, retired, for example the highest lift APT offers is .340" for the 1275. Our limit on the 1275 is vle spring coil bind, and higher than we are going now and the spring would have to be re-thought.

 

[MadMarx]

the lobe lift of my cam is 0.39"

 

[Hap Waldrop]

the lobe lift of my cam is 0.39"

Wow, thats alot of lobe lift, probably .040" more than I ever seen advertised on any Triumph race cam, BFE shows a cam at .348", I guesing that is near the limit of a good reground core, so maybe a new billet could get that much lobe lift. Most cam grinder show their full race cams at somewhere around .325".

Just for grin sometime put a dial indicator on top of one of your retainer, and check the valve lift, you'll probably be shocked at how much you are giving up.

 

[MadMarx]

The roller rockers do have lots of advantages about the stock parts but if you run under FIA rules you have to use a lot stock parts. Roller rockers aren't allowed for <65year cars.

I just wanted to point out that stock items do work properly.

Cheers
Chris

 

[Tabcon]

Hap-

I had several conversations with Michael at Cambridge Motorsports in England about the Titan set up. As it turns out, Michael designed the set up several years ago and had Titan manufacture 100 units. He said that it took forever to sell them, but the finally did and now they are sold out. For some reason Titan has not removed the Triumph assembly they show on their website. Assemblies for MG's are still being made.

I designed a set up that would work, but it's a lot of effort and expense for only a slight gain in HP, especially considering the fact that I'm using a moderate camshaft and nothing like Chris is using.

I'm still going with the Titan roller arms but in the stock 1.55 ratio.

 

[billspohn]

I used to run some fairly high lift cams in my TR engines (though not as high as Chris - don't think I've ever SEEN anything as radical as that) and agree that the stock rockers are just dandy.

All this rocker talk sure makes me happy to have a proper MGA that doesn't use rockers!

 

[MadMarx]

you mean your twin cam?

 

[billspohn]

you mean your twin cam?

Yup. But of course they come with their own idiosyncracies and challenges....

 

[Monkeywrench]

Roller rockers do work, but it does take some machine work to do it. There are gains to be had, but it's coming from the increase in motion ratio, not less friction. Sorry, I can't be more of a help. On a street car / mid pack racer it shouldn't matter as there are gains to be had elsewhere.