there's lots of info on roller rockers thinking a few hp. now again a lot heaver more spring pressure needed than the aluminum stock rockers on a nailhead. almost have to go with roller rockers for strength and adjustability needed for lash or preload on lifters. plus like Tom T. says the stock ratio never gets to 1.6 ratio on full lift. also roller tips are easier on the valve guides. remember buick claimed 10 hp when they came out with light weight aluminum rocker arms.
Conventional small diameter lifters are limited as to how steep/fast of a cam open/close ramp they can work with. Too steep of a ramp and the edge of the lifter digs into the cam lobe, instead of using the face of the lifter. The old mushroom lifters and now the rollers allow us to use a fast ramp on a cam. One of the biggest advantages to fast ramps is they open/close the valves faster, getting it to max lift faster, hence more 'area under the curve'. They do this while keeping the valve seat-seat duration shorter (especially on the intake valve), which will increase cylinder pressure and boost performance. Tom's roller lifters, with the high 1.7-1.9 ratio, will also open/close the valves faster than the stock 1.6 ratio. Putting these rockers on a stock cam is like installing a fast-ramp cam design. Or, just use the stock rockers and buy a fast ramp cam. I imagine there are advantages/disadvantages to either method, I just don't know what they are! Too fast of a ramp can cause a noisy valvetrain and increased wear. Any method will require the correct valvesprings. As Joe said, roller lifters are heavy and need extra spring pressure to control them. It's likely not a big issue on a Nailhead at limited rpm vs a small-block screamer. Look up 'Isky Rev-kit' and you'll see their method of controlling roller lifters. Comp has different levels of cams ranging from the mild 'High Energy' up to the fast ramp 'XFI' series. Take a look. I'd like to see a Nailhead roller build. Especially if someone else is spending the $$ and having it dyno tested! Sure wish JW would get into the Nail market.
i myself would go with a solid lifter roller a little less lifter weight and will not bleed down and will be quieter than a hyd roller. if you look at ta-hyd roller for a nailhead there slower than a modern fast ramp flat tappet.
Walt, there was 2 big name nailhead builds posted on here, one was PEM with a flat solid lifter and can't remember the one using a hyd roller cam. they posted dyno graphs i think. but still not back to back testing that would prove anything.
In all fairness you can't really consider those an option unless you already have a set because they are not currently available and there's no firm indication as to when they will be. At least the TA rockers are readily available. I learned my lesson a long time ago about paying a deposit up front for parts or labor.
it seems to me that the biggest obstacle is finding a good reputable head Porter that is familiar with the nail heads. Years ago I paid a Nailhead expert to perform this task and unfortunately the heads that he sent back were deemed to be nearly worthless from a performance standpoint. turns out he was in poor health at the time and passed away not long after. I don't know of any commercial business that is doing porting of the nail heads.
To Joe's Point from A HR Article - Flat vs roller tappet: Which is better? "If you compare a hydraulic-roller camshaft to a flat-tappet hydraulic cam with similar duration at 0.050-inch numbers, the hydraulic-roller cam will always have a longer seat time. The roller lobe configuration allows for faster ramp acceleration, yet it also suffers from slow acceleration off the seat compared to a flat-tappet cam, which is the trade-off. As a result, the advertised duration numbers tend to be longer. A hydraulic-roller cam with the same duration at 0.050-inch lift as a flat-tappet hydraulic will not idle the same. More advertised duration increases the amount of valve overlap (both valves off their seats at the same time), which will cause a "rumpity-rump-rump!" idle. This is not always a major issue, but worth noting if you are considering swapping in a hydraulic-roller cam. If a smooth idle is important to you, the roller cam should be ordered with a greater lobe-separation angle (110 to 114 degrees) to reduce the overlap and smooth the idle."
if your going to keep things simple and stay stock and not go with 11/32 valves and beehive springs, any good head porter with a flow bench could do the job.
Mike Lewis at Pro Tech in Ca. has the experience as he's been doing them for years. Too bad Bob W. from Hazelwood, Mo. passed away going on a year now. He was doing his experimenting as a hobby & NOT a profession so he had the advantage of not having the over head associated with running a business. Bob got the BEST flow from a "Nail" than anyone ever. He worked mainly on the intake & got if I remember correctly 262CFM's. NO ONE HAS COME EVEN CLOSE. Ask Joe (gsgtx) about the work Bob had done for him. Joe has the most experience with Bob's head porting. He was just starting to work on the exhaust when he was stricken with his brain cancer. It's sad he was taken as he had advanced the possibilities. I'm working with Mike now as we speak & trying to get possession of the pieces of head my son & I cut up to send to Mike. We'll see how that turns out. Tom T.
Here's an example of how a stock cam with higher ratio rockers OR what a fast ramp/roller cam can accomplish over a stock cam with stock 1.6 rockers. For the sake of this argument, let's say the duration at 0.050" is the stock 209/209*. The roller rockers add about 5* of duration, but ignore that for now, it's fairly insignificant. Cam is a stock 1966 401 grind. A solid lifter was used, a dial indicator was set on the valve retainer to measure valve lift. Valve lash was at 0.002" to get rid of 'noise' on the cam base circle. Engine was rotated 2* for each data point and lift reading recorded. I had done this back in 2009. Lowest curve is the cam lobe only, next up is with stock rockers, highest is with TT roller rockers at high ratio (near 1.9). At a valve lift 0f 0.200", duration over stock increases about 15*. At 0.300" valve lift, about 20*/20* increase (Intake/Exhaust). At 0.400" valve lift, about 35*/47* increase in duration over stock! The point is, both profiles have nearly the same duration figures at 0.050". Vacuum for power brakes will be similar and drivability should not suffer with the rr. Similar improvement can be gotten from a fast ramp cam or a roller cam with the same duration specs. If you look at 'the area under the curve' for the stock rocker vs the roller rocker, it's obvious the curve with the rr has more area under it.... hence the concept of 'area under the curve'.... the valve is open higher and longer which should increase performance. It's difficult to compare cams without having all the data points like I did here. The duration and lift may be similar, but the 'shape' and 'area' of the curve can vary. Comp Cams does have a 'Lobe catalog' that gives duration at 0.050" and 0.200" lift so you can better determine ramp speed. https://www.compcams.com/lobe-catalog I don't have a lobe profile for a roller cam, therefor I can not determine the difference over stock. I would expect a roller cam with near stock duration specs to be a significant improvement over stock. Here's the cam profile I did of stock 1966 cam, with stock rockers, and with TT roller rockers:
Here's how the stock 401 cam compares to the Comp Cam offerings. It shows duration at 0.050" and 0.200" of lobe lift. I picked lobes that were closest to the stock duration of 209* and a lift nearest 0.450". Note how the 0.200" duration increases as you move up to the more aggressive cams. This also means the opening rate is faster.... one of the primary benefits of the roller lifter. The 'Hi Energy' cams are fairly close to a stock 401 grind. I've also added columns for a longer duration cam lobe in the 218-224* range. The last 3 lobes at the bottom are the Comp Roller cams.
going up 1 cam size is around 6*, so roller rockers ups the duration 5* that is a big difference. big help if want to keep the same cam, or something to consider when buying a new cam.
I hate to contradict a fellow Buick brother, but the above is simply not true. Installing roller lifters is a lot more expensive then sliding lifters, yet virtually all manufacturers of new cars have done so, just because the reduced friction improves power and fuel economy. If you want the most efficient engine, roller lifters are the way to go. In a low-RPM engine such as the Nailhead, the roller lifters have an even bigger advantage, a although the roller lifters are heavier, the RPM's are lower and the spring pressure does not need to be significantly higher.
Actually in the bold are just the side effects from changing to roller lifters and not the reason they went that way, manufacturers went roller for emissions reasons. The bean counters could care less about the reasons in the bold, the train drivers sold the idea to the bean counters that they could lower emissions by reformulating oil with WAY less ZDDP levels in it. The higher level ZDDP level oils eventually could plug up the catalytic converters and the bean counters didn't like the idea of warrantying plugged converters @ 30K miles because of the ZDDP that with an engine with the slightest oil consumption would cost more than using roller lifters in the first place. If the emission standards didn't get more strict over the years the bean counters would of NEVER agreed to factory engines to be equipped with more expensive roller lifters.
I know of a solid roller lifter Nail that shifts between 6200-6500. Close 165 over the nose 520 Special Pac springs. Installed height 1.750"
