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Pedal Smasher
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Discussion Starter #41
With the earlier Opel stuff, with the forged rods and crank, I don't think I would bother with a rev limiter....
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.
 

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Opel Rallier since 1977
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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.
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!
 

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Opel Rallier since 1977
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1,918 Posts
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.
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.
 

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Pedal Smasher
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Discussion Starter #44
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.
 

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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!
I got feedback from HyperFuel:
"The return line is a dedicated return line not a vent line. This is a surge style tank so your lift pump is constantly filling and return the tank so the EFI pump stays cool and submerged"

So you were absolutely correct in saying it is a return line, not a vent.

From what I can see, it looks like in the 1st gen product, it was a vent line, and they may have had trouble with fuel overheating, sometimes boiling and then getting pushed up into what was supposed to be a vent line. And that may have motivated a design change in the 2d gen product, as mentioned above, to keep things cool. Not entirely clear, but that's the way I read things from various posts. The naming may have led to some confusion in posts; similar product name, v1 vs. v2.
 

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Opel Rallier since 1977
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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.
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.

Now that I am starting to take some detailed cam profiles, 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. 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. It can be at the end or beginning of the cycle; that will cause valve bounce. (BTW, as I see it, valve bounce IS mostly the result of spring vibrations....)

So your words 'could be' are key: it depends on the cam and parts. I just profiled an Opel cam that to me looks like a disaster unless some very stiff springs are used, and in fact, may have caused a very early engine failure. The acceleration levels at the beginning and end are double what are found in the stock and Isky profiles and the rate of the acceleration increases are very high. (A factor called 'jerk', as the cam designers call it. Hey, I didn't name it! LOL)


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.
 

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Pedal Smasher
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Discussion Starter #48
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.
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.

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.
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.

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 did say not junk, so that would require someone building an engine to know which parts would be junk if used.
 

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Pedal Smasher
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2,156 Posts
Discussion Starter #49
I got my 6800 RPM rotor today and it seems to fit. Bosch part number 04024. Eventually a Pertronix Ignitor II will be put in this dizzy and maybe an adjustable vacuum advance canister.
428605
428606
 

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I would never even consider trying the original cast rods in a high RPM rally/race engine when there are still original forged ones available. But those are beginning to be 50 years old and often in need of a more or less costly rebuild so a set of forged aftermarket rods make more sense. But both of the original rods work just fine in milder street engines.
 

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I found a Bosch rotor p/n 98-9607 But in the description said that is won’t work with electronic ignition such as Petronix.
Oh well.
 

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Pedal Smasher
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Discussion Starter #53
I shared the part number for my rotor. I think it will work with Pertronix I and II.
 
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