Jim explained it as a difference in geometry and how the 1.6 ratio is too high which puts undue stress on the valvetrain. Also the roller tips aren't centered on the valve tip. He said it is worse if you have iron heads that have had a couple of valve jobs and the tips are too high.
Maybe he'll chime in and better explain it. I'll post my findings in a week or so after I get to run the Riv.
TA has the 1.55 ratio roller rockers --> http://www.taperformance.com/proddetail.asp?prod=TA_1312A Would those work better?
Was he talking in general terms or specific to your setup? Can you adjust for that by grinding the valve tips and re- checking your pushrod length?
I have run 2 413 cams with both being installed in at 109. They would both fly and pull hard past 5k. Never had them on a dyno to actually see the curve but the butt dyno said they still were pulling. Both these engines ran stock rockers. I have run TA rollers on a couple cams too. One being a slightly larger than the 413. The car died at 5k on a dyno early this year. I read about the rockers possibly being a problem and pulled them off to run originals. The car still died at 5k. Added a TA fuel pump and installed new pickup and tank along with a different carb only to see it die at 5k again. Pulled it down and checked the cam to only see it right where it was supposed to be installed at. Just couldn't figure it out.
Jeez, that's really strange. Thanks for the info, John. I know Yardley had his engine on a dyno and saw it flatten out too. As he has an electric fuel pump (was stock on a '69 Riv, but he's upgraded it), he must have used a mechanical pump or other sourse to supply fuel. Yards, what did you use on the dyno? I know you had fuel supply problems in the car that you straightened out, but the dyno was a different set-up and you still had the fall-off at 5k.
I just remembered this - Originally my motor was built by Jim with a 413 cam and he made several dyno pulls and strange things were happening. Out came that stick and in went the 290-08h, which was bigger than we wanted, and the problem was gone. Maybe when he chimes in he can add detail if it is revelant. This was 5 years ago ... ... Oh - Im not sorry he put in a bigger cam :TU:
Alan- Do you have power brakes? And if so, how many stops do you get before you have vacuum issues??? And are you running stock rockers?
TA 1.6 rollers. last build with a 413 cam, the brakes were actually worse than with the current 290-08h cam. I would get the occasional rock pedal and tought myself to think only one good shot at the brakes. Dont know if the current cam has anything to do with the way JW degreed it in, but while I have had the hard pedal its far from frequent and usually just after startup and I start the drive.
Actually, no that's not correct.. sorry for the misunderstanding Yards.. Let me explain.. I have been studying this "inability to rev" phenomenon in the BBB for a number of years now, since we first had an issue with a "fast ramp cam" over a decade ago. Back then, this aggressive ramp theory was touted by some as being a way to increase HP, with "area under the curve" and all that technical sounding stuff, in relation to camshaft design. This motor had one of those cams in it. That particular motor was built here, so everything was correct.. valve tip height, spring pressure, oil pressure ect.. but it would not rev past 5500.. My dyno operator had seen this many times, his term for it was "lifter crash", a condition in which the lifter gets pumped out of oil, by an aggressive lobe design, in an otherwise correctly set up engine. I called TA on it, and this was the very first time I had ever spoken to Mike T.. and mentioned the issue I was having with this motor. He had seen and worked with similar issues in the past, and was interested in doing some R&D on this with me. He sent me a 290-08H, the very first one I had ever worked with, and we put it in, with a new set of the same lifters that I had used on the first cam. Issue gone, would rev easily to 6000 rpm. After that, I had moved on to other things, but in appreciation to TA for helping me out on that one, I wrote a letter to them, outlining the issues. That letter was never really meant for public display, but not knowing this, TA put it on their website.. It caused an uproar.. and long story short, it spawned articles, and a huge dyno test by Scotty, to further prove the issue. And we did, completely debunking this whole fast ramp cam deal.. we proved that there was little to nothing to be gained by ramp speed, and noted that valvetrain stability could be compromised. In about 03, I picked up a board member's motor down in ST Louis.. A "Chevy" engine shop did it, and it was the typical mess.. main line all over the place, rod bearings burnt up, and the valves were sunk in the heads so the tip height was up around 2.175.. Fixed up the bottom end, installed his 413 cam, and his 1.65 rollers.. with the correct pushrods blah blah blah.. valve springs had to be shimmed for correct pressure (115 seat, 300 open) and we went to the dyno.. It wouldn't rev past 4800 to save it's life.. Pulled it off the dyno, and then corrected the tip heights by installing 409 valves, which have 3/8 stems, but are are shorter in over all length than the Buick valves, machined the intake valve to the correct diameter, and then set it up with the correct 7* retainers and locks, and set the spring pressure at exactly the same as the first setup. Back to the dyno.. Now it revs to 5400, still 400 rpm short of that motor's peak.. Tried running almost no preload, which had no effect at all. Still broke up at 5400. Shimmed the valve springs tighter.. then it got worst.. now it was down to 5200.. took the shims out, back to 5400.. The whole time, Ron (my dyno operator) is telling me we are experiencing hyd lifter failure again (we quit using the word "crash" as that gets some folks hair up).. After going down the road with all the valve float possibilities, with lifter pump up (no preload would have had an effect on that) or with valve float due to insufficient valve spring pressure (shimming the springs would have had an effect). I had to believe him. We were dealing with lifter failure.. simply put, the lifter cannot maintain it's function, due it's inability to stay pumped up. It's developing lash at rpm, thus positive control of the valvetrain is lost. In this motor, even with all other valvetrain specs at optimal, the cam, in conjuntion with the 1.65 roller rockers, made the lifters not happy.. these were even the Comp cams ones, which run very little preload. To test the theory, I bolted on a set of stamped steel rockers, and it then would rev to 6000 rpm with no trouble at all. All I did was reduce the rocker ratio from 1.65 to 1.55. Thus reducing the load on the lifter, at rpm. I "filed" this experience with a 413 cam in my head, for later... Sent the motor down the road, and it lived happily ever after.. I built numerous motors (about a dozen or so) after that, from 03 to 05, and stayed away from the roller rockers with hydraulic cams, and had no issues at all, with durability or the engine's ability to attain the rpm that it wanted to work at, which in most warmed up, cammed, ported head 455's, is right around 5800 rpm. I did not use a 413 cam in any of those engines. No real reason, other than I really like a bit smaller cam in a more street oriented build, and a larger one it a street/strip build. Used a lot of 288-94H cams, as well as the 290-08H. In 05.. Alan Wander sent me his motor, we upgraded to a set of new TA SE STG 1 alum heads, and being aware of the tip height issue, certainly all the specs were correct on the new heads.. Talked with Alan, and we decided to go with a 413 cam, as he had used one for years. That motor had roller rockers. 1.6 ratio. While it would attain the 5800 rpm it wanted, it didn't sound happy, and it's power was not where we wanted it to be. Had all the symptoms of the early stages of hydraulic lifter failure. Didn't go into lifter failure, but it was right there.. On disassembly, a really strange looking wear pattern was on the cam, looked like the lifters were dancing.. Swapped to a 290-08H, and it picked up a bunch of power, and was noticeably quieter on the dyno, at higher rpm. Since then I have encounter this a number of times, with several different cam grinds and builds, with hyd cams and roller rockers. The 413 and the 288-92H come to mind as cams that are more sensitive to this issue than others. In all cases, changing from the 1.6 or 1.65 roller rockers, to a set of stamped steel rockers, eliminated the issue, and allowed the engine to reach it's max rpm. Probably seen this a dozen times now. Either the heads have the tips too high, or the particular grind is too aggressive for the lifters we have available. So when you called me yesterday Yardley, that is the first thing that comes to mind.. try a set of stock rockers, and see what happens. Cam advance is not the issue. Now don't get me wrong.. You guys know there is no bigger supporter, and few bigger customer's of TA Performance than I am. But ever time the whole question of what alum heads to buy for a mild street build up, and the discussion turns to the cost of roller rockers, I stand on my chair here and yell "you don't need roller rockers for that buildup". And many times I have mentioned that they actually can cause issues, with some hydraulic cam grinds. Increasing the cam lift by .020 or so, via a rocker ratio, will do nothing for power. But the higher ratio can cause other issues with a hydraulic cam. TA's roller rockers are wonderful pieces of equipment that I love to work with, but I am careful to select particular cam grinds, and lower ratio versions of that rocker, with a hydraulic cam. Solid cams love the 1.65's, and there is no issue using them in that application. I will say that hyrdaulic cams, and their potential for noise, and their ability to rev are the number one issue that I have encountered in building the BBB. For Iron head motors, think low lifts, light valve spring pressure and long duration. That's what makes power, and produces a nice, quiet hydraulic valve train.
It's got everything to do with where it's in at. If it's not at 106*, with a well sealed up motor, there will be issues with the brakes. Count on it.
We're not worthy!!!! Thanks sooooo much Jim for your attention to detail in all this. Your piece right there should be an article in the BPG Build Sheet. I'm sure Adam Martin will be happy as well. I am picking up a set of stock rockers tonight and once I get my header back on I'll post the results.
Excellent info but is it the roller rockers or the higher ratio that causes the issue? Would the TA 1.55 roller rockers work with say the 413 cam? The rollers are nice because they are almost bulletproof.
Thanks as always for edjumikating us all :beers2: BTW Jim - the 11.993 from 3 years ago was finally backed up at Cecil a few weekends ago - ran a string of 11.9x's so now Moon cant say anymore that if a moth farted infront of me, I wouldn't have gone into the 11's uzzled: :laugh: Prolly had a bit more, but I was having problems hooking - that and I'm ashamed to say besides driving BigRed, I haven't done squat besides change oil this year. Was going to throw a timing lite on it and lower the tire pressure a bit but then blew out the header gasket and having to drive home 220 miles I decided to call it a day
The higher ratio. Based on my experience, all else being equal.. since I had a 1.65 not work, a 1.6 almost work, the logical conclusion would be that a 1.55 would be just fine. but I have never done it, so I can't say with certainty, and there are a number of other factors involved here. Particular master used to grind the cam, tip heights, brand of lifters, just to name a few.. JW
Wow I wish this was resolved 2 days ago, I just decided to get the 413, now I'm going to have to change again.ou: Jim, Clearly it would be best just either to swap the cam or the rockers out based on your experience, but hypothetically how do you think it would do if you ran solid lifters with the 413 and the 1.6 rollers?
Jim, You have tested this with Buick Iron heads & Ta Aluminum heads, did you test with Edlebrock heads at with a 413 or 288 92H with Chevy stil roller rockers?
I was wondering the exact same thing - I was going to ask you Jim if you substituted a set of solid lifters on a hydraulic 413 cam?
