Except you didn't take into account the step in the retainer and the added pressure it would yield. PAC Racing actually has some excellent videos on setup and choosing your valvesprings. Actually, if you deal directly with your cam grinder, they will typically give you some baseline info that your spring company of choice will use to fill in the blanks based on the weight of your valvetrain components (including the springs themselves). RPM, boost, nitrous, type of use (constant RPM Vs. Peak RPM) will all need to be taken into account. Buy once, cry once. Set it up correctly the first time or run the risk of parts failure and the hurt feelings that follows.
In the early 70’s, I was training / working in a one man shop who just spent 13 years at a speed/machine shop. I was taught to check the spring first against a 90 degree square to establish it was not bent or leaning. Keeping in order, but after passing, then using way less of a fancy digital pressure transducer, we had “Sioux” valve grinder and stones on seats. For spring pressure, we first checked “free” height to specs, but that’s where we did our load measurements differ. We placed the retainer on the spring to load test at installed height. It is almost impossible to get installed height on the head because the lack of room with any veneer calipers to measure up from the spring seat, to the bottom of the retainer. Preloading a naked spring to recreate installed load can be done if you measure the retainers thickness while off, then add the amount to properly lost test a closed valve. Am I wrong. We used shims after all if any was removed and the measured height from a bare spring seat to the top of the valve guide. We wrote it on paper as I am not sure if sharpies has been invented yet, like the 8-track tape was new. Valve guides where integral and had to be cut out & new ones installed at a machine shop, as we did not have that equipment. But the “Open” pressure in lbs. is not checked by most, unless at a speed shop with machining equipment. Our gauge had scales and a simple rule on the vertical rail and was adjustable. So spring, retainer, cam dial in with the ratio of rocker to be used was normal math, as you properly shown. At 0.500” lift at the valve, would change is the 1.5:1 rocker was changed to a popular 1.6:1 rocker. Beside valve to piston interference using a degree wheel, dial indicator with ball of (Dare I say play dough) was used. The other issue was the retainer may hit the stem seal. This too is rarely checked. A proper guide installed in a cutter, chucked in a drill was used. It was unheard of in most circles, we cut intake valve guides and purchase positive seals, while leaving an o-ring on the exhaust stem to allow lubricant inside. This was what we did 50 years ago, primarily on small block GM’s. Does this sound right? I became an ASE Master Tech about five years later in 1978. This experience benefitted me to pass the 8 test those few years later. Thanks for your video, subscribed.
Hello. Is it ok to mix springs for Cams? If the springs are all new and believed to manage the profile of the cam they will be working with ok, is it ok to mix springs? 8 of one brand and 8 of another brand, both specified for the same cam.
I thought the reason why use shims was to compensate these tolerance issues! I mean I'm a biker and I know the 10mm diameter shims comes in all thicknesses to get finer valve spring adjustment
They are compensating for valve spring height when assembled. I believe he said twelve thousandths of an inch difference in height, for that setup, was around 22lbs of pressure. Therefore shimming the spring seats or expanding them, helped equalize or balance the engine
Let me start by apologizing for my ignorance, can someone explain what in the world is going on w this head. Are the intake and exhaust ports on the same side? It also doesn't have press in seats, the valve seat is cut directly into the casting. The rockers are unlike anything I've ever seen. What block does this fit and what series is the head meant for?
It seem you have not heard of the BMC A Series engine, made from 1951 to 2000. Did you think it was for an American V8? Actually the A Series design owed a lot to an American engine that Austin had been making during the war under licence. The ports are all on the same side for reasons of manufacturing cost and compact design. Did you notice what was even more odd? The two centre exhaust ports only have one outlet, so the manifold is a three branch not 4. It really should not have worked as well as it did.
