1973 Opel GT
Good deal. It is a 2nd line either way. It can involve safety too so it needs to be done and understood. You make a good point on the function of the line and the material. (Of course Opel used hard plastic lines for fuel and EVAP venting! That always made me raise my eyebrows.)I see the above was from a vendor site, not the manufacturer; probably it's wrong. But I did post an request for clarification with the manufacturer.
Ya know.. I never thought of it that way. But I never have run valvetrains at the limit of floating and such. I've always ended up conservative on cam rate selection (either purposely in my later years, or just dumb luck in my early days LOL) to keep things under control.I believe the bottom end of the engine is rarely what needs to be protected with a rev limiter. It's the valve train I worry about.
I got feedback from HyperFuel:Good deal. It is a 2nd line either way. It can involve safety too so it needs to be done and understood. You make a good point on the function of the line and the material. (Of course Opel used hard plastic lines for fuel and EVAP venting! That always made me raise my eyebrows.)
Even the so called 'returnless' Edelbrock remote sump needs a 2nd line, so that is misleading marketing on the part of the manufacturer. For that product, the 2nd line is a vent AND a safety overflow too, in case the floats stick open, or stay open in a wreck with the car on its side or roof and the electric lift pump still running. Edelbrock describes it as 'mandatory' in their installation instructions... there is no free lunch!
Got it, and that is all good. Just my experience with the Isky Ultra Super Comp to well past 8k RPM was no problemo; that was for 4k+ rally stage miles; driven 'in anger'. No odd wear or damage in the old valve seats; the heads never got seat inserts to take the 'guff' of valve bouncing. This was with old Mantapart or C&R single valve springs and aluminum retainers.. what would nowadays be considered be old school 'hi-po' springs.I believe unless you've done testing to observe how your valve train is performing, it's hard to know what actually is a safe limit. You could be crossing into somewhat dangerous RPM limits at 6,000 without even knowing it. I know a guy who is fortunate enough to play around with a Ford SOHC on a custom made spintron. He did a bunch of testing to see which spring / valve / rocker setup worked the best and he ran the tests above 9,000 RPMs. The tests would be recorded using a strobe light to make it easy to see what is happening. His setup made it easy to observe valve bounce, which happens before valve spring surge and valve float. Valve bounce could be seen as the start of dangerous limits in my opinion. Even if your valve train doesn't fail when you're running the engine at 7,000 RPM, what is actually happening with the valve train? There could be a lot of valve bounce, which isn't good for longevity and this is different from valve float and also potentially more harmful.
Unless the crank and rods are junk, I expect the valve train to fail long before anything inside the block. I think a valve will drop, a spring will break, or a rocker will snap first and if I don't actually know when the valve train starts to get weak, I'm just hoping for the best at high RPM.
You're right about that. Cam profile is a critical part in all this. Usually the amount of jerk will be related to how much lift the cam makes, especially for a moderate duration but flat tappet vs roller plays a big part in this. I'm not a pro in understanding cam profiles and the equations that create them, but I have read a little on it. Complex math to say the least.the one thing I see on the few Opel and Isky profiles so far is that there is a 'softer'/slower closing ramp to help set the valves more gently in the seats. No high acceleration impulses at the beginning or end of the lobe profile to get the springs going.
Double roller rockers and adjustable lash "elephants foot" rockers were tested, I want to say always using the same cam. Cam profiles for the SOHC are more aggressive than what you would probably find in a CIH. I want to say the cams have more lift. Double rollers improved valve train performance but his tests were to find out when a valve train setup would start to run into trouble. All springs will eventually reach their limits and he intended to find out when for dozens of combinations. It was the sort of testing that left you with your jaw on the floor.I would bet that was the problem on your friend's Ford SOHC.. a strong acceleration pulse(s) in the lift cycle will get the springs vibrating.
I did say not junk, so that would require someone building an engine to know which parts would be junk if used.BTW, I mess with Mopar small blocks some, and the idea that the rotating assembly won't fail is not the case in all engines. And I have to wonder about the cast rods in these Opels.... I have never used them to know, however.
I like this idea but when I went to the site it said it could not be used for electronic ignition such as Petronix. Do I understand that correctly.no. they short to ground through center shaft.