What is the consensus on high performance cams out there for their 401/425's? Here is the engine it will go in: 425 bored .030 Forged Pistons 10.5:1 SP ST400 Automatic Air (yeah, I have horspower to spare!:bglasses: ) Eelco 2x4 intake Dual 625CFM Barry Grant Road Demon Jr's (non-progressive linkage) Tom's adjustable Roller tip rockers w/solid lifters Standard porting and polishing headwork and 11/32 stems TA (Riv only) Shorty headders (w/ old burnt out Purple Hornie glasspacks) 3:07 posi What can I get away with and I can still turn the power steering or stopping at a stoplight etc, without it stalling? I want the most performance and still maintain drivability. I have read what some of you have, but who can say theirs is "too much"? Please list yours and what you do or dont like about it.
Erik, this is one of the things I would like to converse more about with Gary. This is my personal opinion here. In a Riv. the ticking of solids doesn't keep up with the, quote/unquote, Personal, Luxury, Performance image of our Rivs. A good hydraulic cam, maybe with Schubech racing hydraulics, would be a better way to go. You gotta remember, torque is what gets us going & HP is what keeps us going. As you start climbing the HP ladder you start to lose some of that low RPM torque our "Nails" are soooo famous for. We have "HEAVY" cars & you would probably be very disappointed with the performance if the cam doesn't come in till 4K RPM's. It takes "LOTS" of torque to get our heavy cars to start moving, especially with 3.07 gears, but doesn't take alot of HP to keep us moving down the highway at 60-75MPH. Just me again, I would stay on the conservative side with cam selection. Let the "Rockers" do what they were designed to do. Just my thoughts, again.
The TA 413 is a great hot cam for the NH's and with the better rocker ratio will really make a difference. You can stay hydraulic with the TA 1406 lifter (which now shares the same body and valving as our 1405 lifter). The Schubech's need a lot of spring pressure which you won't be able to do with the NH. Matter of fact what is the plan for valve springs now that the heads have been switched to 11/32" stem valves? Often this is a fatal error that shops do and nothing "common" fits. TA also has plug-n-play high performance springs for the NH with higher lifts. If you want to go solid a good combination is to use a hydraulic grind like the 413 with solid lifters and minimal lash of .005", doing so will keep it quieter than "traditional" solids. This is possible because the ramp is not as aggressive on the hydraulic grind. You will have some gain from the "hybrid" solid method, but honestly, you won't be turning enough rpm to exceed the efficiency of the hydraulic lifters. Because of the better cylinder filling that comes from the overlap that a cam like the 413 has, you won't have a drastic loss of low end torque. Your peak and average torque numbers will be higher. Plus you will need a bigger cam to get rid of some of that compression to help with pump gas. I also suspect that you will need larger carburetors. When you get the combo together you can check vacuum at WOT, if manifold vacuum is more than a half inch (at WOT) you will need larger carbs, i'm assuming 750's. The carbs act more in parallel than in series, they just fill the plenum & runners faster than a single supply. check out our updated catalog for more info at www.taperformance.com
Sorry Dave I have to disagree with you on the Schubeck hydraulic racing lifters. They are a few grams lighter filled with oil than a stock "NailHead' lifter filled with oil. Something like 92 as opposed to 97 if memory serves me correctly. I have over 180K on my "Nail" since I rebuilt it in the early 70's, to completely stock specs. I installed the Schubeck racing lifters on my old 180K+ valve springs with no problems. You need to keep the overlap down around stock. On our racing engine we picked up more HP by using less overlap & a wider lobe separation.
If I may ask a stupid question.........why would a lifter need a lot of spring pressure? I would think that would only make it bleed down. o No:
Schubecks are a ceramic material and can break if they bounce off the lobe. This may only pertain to solids as the ramps are more aggressive. Schubeck increased they're spring pressure recomendations a year or so ago. A hydraulic cam'd NH will probably never see enough rpm for this to happen. But a solid profile may. Normal street pressures for a hydraulic .500 lift cam are around 280 to 320 lbs open, higher reving and combinations dedicated for race are running 325+. This does not cause the lifter to bleed down. Again, these are parameters that the NH usually won't see. But now that there are better rockers, we will start to see more aggressive combinations and they will include more duration, tighter centers and overlap. Try to pour gas from a gas can with the vent closed, open the vent and how much more does it flow??? How much quicker did it transfer? That is overlap! Blow into the vent, how much more does it flow now? That is supercharging!
How much more aggressive can a cam be over a stock "NailHead" cam. With a .842" diameter lifter a stock "Nail" has .007" rise per degree of camshaft rotation. Most "Roller" cams are .008" rise. So a stock "Nail" cam is pretty aggressive as it is. Surprising as it may be most stock "Nails" only have 50-60 PSI seat pressures & they can still do 6K RPM's. With a lighter lifter that can be higher, but we all know they fall off rapidly over 5-5.5K RPM's stock. Most people owning "Nails" will never see over 5.5K's ever. There are those that will & make power doing it. Not very many, but there are. On our "Nail" we were still making HP at 7100RPM's & because originally the engine wasn't designed to do that many RPM's we never did find the drop-off point as we didn't want to go any higher. I'm not here to start a shooting match with you Dave. Just stating from my experiences what I've been learning all along & sharing with others by doing. I've DONE engine dyno testing. I've DONE chassis dyno testing. Lots of this on my own dime. With T/A's support, (Mike) you have the means to outdo any of my personal efforts. I feel that there is sooooo much untapped potential in the ole "Nail" that hasn't been done yet. Just my thoughts & dreams.
I have read this thread and agree with both of your opinions and facts. The nail is my fav. Buick engine. I even thought of some clear rocker covers so the rocker arms could be seen at shows. ??????? Now, Just what do you guys know about the ''no zinc'' problem with engine oils.??
This is an assummption on my part, as I don't know what the lifter travel is, but cams that need 350+ or even 600+ valve spring pressure must have more aggressive lobes than a NH. Even the 455 engine sees problems with fast ramp designs beyond 5300 rpm. Many racers are increasing spring pressures beyond what is normal (on hydraulics) because they are getting better response that way. The oil issue is probably the most confusing situation that we have seen. We have NOT seen an increase in cam failures. We prepared for the worst and it isn't happening. We have always recommended light spring pressure at break-in, emphasized ZERO idle time before and during break-in, use of EOS, etc. We also have discourage the use of filling the lifter valley and crank scrapers on race set ups. The thing to remember is that cam lobes only get cooled and lubricated by splash oiling from the crank and secondarily by return oil from the valley. The whole reason for elevated rpm at break-in is to provide more splash off the crank. The only change that we have made is to recommend using Rotella 15w40 during break-in. I personally am thinking that the hard faced lifter that we have is a major factor on the success. But if you have a lifter that won't or stops rotating, that's what causes the failures. We know that Buick would break their cams in on a fixture before they were installed in the engine. We discussed doing something like that on a spare cylinder block (which would be very complicated to do), but because of the lack of problems, have not persued it. I have visited about a dozen cam manufaturer's web sites and not one agrees with another on the process. Many have their own lubricants to add. At least one says to NEVER use synthetics even after break-in. One recommends doing the break-in with the valve covers off and confirming that the pushrods are spinning and if not to spin them by hand to get them going.
