Flat Tappets or cam wouldn't last 5 minutes with a roller, the ramp profile is much steeper on a roller cam, plus I am using 140 pound springs at the seat Roger
the ramp profile is much steeper on a roller cam Let me guess: you read that somewhere? It's true only for some roller cams (those with equal or higher curve area, etc.), and only partially true even for those. The initial take-up after lash for a roller is milder than for a flat tappet, and becomes faster as it progresses. How much milder is a function of the thrust vector and roller radius.
I understand what you are saying, and most of what I know is from reading and doing. My comment on steeper profiles is from reviewing roller cams verses tappet cams. I appears that after the take up ramp, the roller opens up the valve much quicker per cam degree. I always willing to learn more. Still don't think a tappet would survive 140# springs and that steep a climb
From what I've read & understand most engines with an .842" diameter lifter have on average of .003"-.0035" rise per degree of camshaft rotation. The average "Roller" cam has an average of .008" per degree of camshaft rotation. Now getting to our "Nails". Buick knew they had a breathing problem & to over come that they wanted to get the valve open as quickly as possible, keep it open as long as possible & close it quickly. Then again you can't get TOO aggressive or else the valve springs would have had to be much stronger , especially on the seat, than they were which was 50-60pds. seat pressure. Also, in stock form most "Nails" could make 6K RPM's stock & this was with no more than 200lbs. open pressure. I believe this started with the 401 in '59 & continued until the end of production in '66 on all the 401's & 425's. The ramp rise on those was .007" per degree of camshaft rotation. This is one reason back in the day a performance upgrade was to put solids on the stock hydraulic cam & there was almost always a performance increase. This is where my "Rockers" shine because they increase the ramp rise even faster because of the added ratio. Most all engines you couldn't do that to because they didn't have the fast ramp rise of the "Nails" & if you tried the engine most times lost power big time. Ask any of the older guys here that messed with the "Nails" back in the day & they'll tell you the same thing. Just my dimes worth. Tom T.
And just to add to that. We have run as much as 150lbs. on the seat. Right now we are approaching 400 lbs. open & this is with a flat tappet solid cam.
I profiled both a stock 66 401 cam and a relatively mild Poston NH400 cam. On the Exhaust lobe: Stock cam lobe has approx 0.0031" rise per crankshaft degree. At the valve, it's 0.0049"/crank degree with stock rockers, 0.0055"/crank degree with Toms rr. The Poston cam has a slightly faster rate of 0.0051"/crank degree and 0.0059"/crank degree with Toms rollers. Pushrod length was on the long side. A longer (EDITED) pushrod would give more rocker ratio when used with Toms rockers. More accurate results would be obtained with a Cam Doctor. Pretty sure Carmen Faso has one. Bet he could tell us how the other cams compare. If only Carmen had a computer!ou:
Walt, you have that backwards & I've noticed that on a few other threads also. the LONGER the pushrod the MORE ratio. The shorter is less ratio. Tom T.
The nailhead does not need/can't to run high rpm's(and make power). For the average nailhead owner it is not feasible for them to make the heads flow enough to allow higher revs. $2,000 for ported heads that flow less than a sub 300 cubic inch motor would have for flow, 200-220cfm. That is what limits the rpm and thus the power of the nailhead. Build the motor for the rpm range that it runs best in. 3,000-5,200rpm. Choose tire height and gearing that will have the motor run through the traps at 5000rpm, after you have some DYNO pulls done to see where the power starts to drop off. Given the flow and the size, 401-430+ a nailhead's power will drop off like a lead ball of a table Comp cams has lobes that the nailhead can run called XFI, quick opening lobes. If the Buick opens .008" as stated per degree and the fast ramp of the Comp lobes you will get near the same quick opening of the roller and use the difference in cash for head work. Perhaps Gessler would work out a group buy deal. There must be other head porters that may ofer there services for a group purchase. It seems the omly way the nailhead is going to get the attention it deserves is by numbers. Some nailheads running low 13's would get some attention. Maybe with slicks and some prepped tracks would yield high 12's? That may get the attention of some manufacturers. What made the Buicks the least bit competetive was their torque, low rpm torque. Keep te motor in the power range and see what happens. A roller will not overcome poor flowing heads. Give them the attention along with a good cam and you'll get results Tony.
the LONGER the pushrod the MORE ratio Lest some be confused by this statement, let me elaborate. The critical factor isn't the length of the pushrod (which, like Lincoln's legs, are "as long as needed to reach the floor", or tappet in this case). The critical factor is that a short pushrod requires the adjuster to be extended farther to obtain the correct lash, which has the effect of adding a percentage of the extra thread length to the rocker arm's pushrod lever length (which is measured from the shaft center to the adjuster radius, not to the end of the rocker), which reduces the ratio. The highest possible rocker ratio will be obtained by using a pushrod of the exact length that the adjuster is bottomed out in the rocker, but of course lash must then be adjusted by shimming the stands, re-facing the stem ends, etc. by a few thousandths. Why would someone ever use less than the maximum lift? 1. Not enough valve to piston clearance. 2. Better low speed manners (slight drop in the overlap triangle window area). 3. Reduced spring load at both ends: the valve spring itself isn't compressed as much, and the spring load multiplier which determines the pressure on the tappet is reduced by both factors.
Sorry Tony I have to disagree. It mostly depends on what your looking for & the amount of $$$$ you are willing to spend. Yes, you are correct when you mention the flow capabilities. As fully ported at 260+ for the intakes & 190+ for exhaust can really only support 320 or so cubes. Gee, why doesn't someone build a GOOD "322" with the newer heads!!!! But, & this is a big BUT, they will run the numbers irrespective of the flow capabilities. The proof in point is the '66 Skylark GS that I'm involved with & my friend Bob Quigg. His GS weighs in at about 3200pds. with him in it & loaded ready to go. With no traction mind you he ran an 11.08ET@122MPH!!!!! When you compare the weight & the MPH the car should have run a 10.8ET. We are working on that now. Now this was really nothing special as far as an engine goes. 401+.030", about 12-1, longer rods, forged pistons, the "PROPER" head work & paying attention to the details. No matter how small or seemingly insignificant they are ALL important,etc. On the engine dyno it peaked, just like ALL 364/401/425 "Nails", at 5800RPM's & fell off the end of the earth at 5900. Now with "MY ROCKERS" it kept the HP up to 7100RPM's & the HP didn't fall 30HP. It was still making HP!!!!! at this RPM. All this tells you us "I WANT MORE AIR!!!!!! With more air I can & will run the numbers even though I can't breath that well. Making HP is all about passing AIR!!!! As far as I'm concerned you can NEVER over port a set of "Nail" heads if done PROPERLY. The valves NEED to open a fair amount to be able to pass the air needed. With the stock rockers it's difficult to get .500" lift AT THE VALVE!!!!! Forget camshaft lobe lift X the rocker ratio. You need to measure it AT THE VALVE!!!!! & you will see exactly what I'm talking about. My '64 Riv. at 4400+ pds. has run a best of 13.902ET@98MPH with over 180K on the engine. Tony's '64 Riv. with more than 120K has run a best of 14.445ET. This is with an all stock, never takin' apart engine. Head work does NOT seem to kill or hurt the low end torque our "Nails" are so famous for. I could type for days with one finger & not get the point across. Ask those who have been there & done that. Just my Nickels worth. Tom T.
Don't be sorry unless I say I have nothing more to learn, then be really sorry as that would neam I was dead or should be. 1. Whose ported nailhead heads flow 260/190 and please copy the sheet showing the flow per cfm. 1b. #As fully ported at 260+ for the intakes & 190+ for exhaust can really only support 320 or so cubes.# Again, my point. Support what? Same as a small block chevy? Remember "Run what 'ya brung". having a nail beat a car it shouldn't beat is ...well...priceless! 2. I don't see a 425 flowing what you say is poor yet the car can run nearly into the tens and with a little better traction will. 3. How much HP did the motor make on the dyno and was that an engine dyno or chassis? I believe you havbe reached the tarket which seems to nbe unreachable, 400HP and 500TQ if the goal is engine dyno, actually chassis dyno would have passed those targets. To move 3200# to an 11.08 @ 122 wouild require near 440whp. Quite amazing as is that 11.08 4. I thought I WAS speaking about head work! 7100rpm and still making peak power would require a LOT of air and what is there magical with the longer pushrods that allow this much extra air? So it peaked at 5900rpm and stayed flat to 7100rpm after that? I'd like to see a copy of that run also That is my point. A roller rocker cam will not get the air into the chambers without a LOT of headwork an actually get the air into the chambers. Given the same amount of cash the headwork and a modern cam will make more power than a roller that has little cash left for ANY HEAD WORK BY FAR. Maybe somebody smart could calculate how much fuel is required to make 400whp and change that figure into cfm of fuel and from fuel into air. Then run injectors at the end of the runners with a megasquirt system or something from www.sds.com to control the fuel if that would open the manifold appreciablly without ther fuel passing through and raise the air CFM with the "extra" space? Worth it for extra air alone? Please explain how the roller rockers and whatever you have for the valvetrain allows so much air into the motor as at the rpm levels mentioned that would require a lot of air! Tony.
Fixed it. sorry 'bout that! But my degree wheel is only calibrated in Crankshaft degrees!:bla: In camshaft degrees, I measured 0.0062" lobe lift/ cam degree on my exhaust lobe. Intake lobe is a hair steeper. At the valve it's 0.0098" valve lift per cam degree with stock rockers, and 0.0118" valve lift per cam degree with Toms rr.:TU:
If the rockers have a slight diference in length from the pivot point to the roller in this case the one with the longer length would open the valve the greater distance, another way to increase the rate of lift. Each rocker would also need to have the exact ratio, sometimes tough to measure, so a manufacturer's ratio has to be accepted as is, and truthful/acurate. During overlap the rate of lift is increased. I imagine each cam would have to be set at a pre-determined point after BDC, say the popular .050" of lift before starting the test for acurate info but it does seem that Tom's rockers are indeed quicker reacting and, hence opening a cam quicker. STILL the flow of the intake and the heads must be there to make the modification to roller rockers the best choice. The 260cfm stated for the intake flow of a nailhead is something I have never heard of. Even Gessler's stage 4's are not advertised to flow that much and the guy who can get the nail's heads to flow that number and sell the work at a reasonable cost will be the way to go until an aftermarket head with the nailheads external specs so that the nailhead's unique look is not diminished. Heads that use the stock fitting manifolds but flow closer to 300cfm would be the trhing to make the nailhjead become the motor it would have become if Buick had not changed the design back in the day when the different divisions of GM were also competing against each other as well as other makes like Mopars and Fords. I'll still stay with my original statement that the aqverage nail enthusiast stay within the rpm range that the nail will make a lot of torque easily and not try to make power revving to a range where the power actually has already dropped off. "Run what 'ya brung" & build it for the rpm range it is best capable of making the torque to jump out and have enough ground between your competition and yourself and keep it before the 1320 comes along Best to all!
The craziest flow numbers I've see for a 'Nail are 247/188. I don't remember what thread they were in, but the heads were ported by Ed Mosler and had 1.94" intake valves. Tom, can I send you my heads? 260/190 would be fricken' awesome :eek2: !
the heads by ed mosler never were what they said, they were like more gesslers stage 3 about 218/132. dont now what toms heads flow but the times he is running are very good for a nailhead.
you can never get them flow numbers out of a iron head you will hit the water jackets.with after market heads and big valves it would no longer be a nailhead. when i run in the 12s with small valves,2 speed tranny,323 gears and idles almost stock it blows chevy ,ford and mopar guys minds.and i am an old mopar guy.
he might get you 226/138 he puts in bigger intake valves, he really doesnt even want to do them because every head is different and easy to go into the water jackets.its says on the web site the stage 3 heads are the best bang for the buck
After lots of talks with Tom T. about heads and flow, I took a few pointers and went with a 1.90 valve and used a scrap head and played with some short turn shapes and got 237 at .600 lift on the intake. I know there is more in there. Now as I opened things up a little at a time I was watching my velocity go up over 400 fps. It wasnt anything hard to get just a lot of work experimenting. If I can get that then if Tom says he is getting those # I belive it.
