Valve spring pressure

That’s a great street cam, but it only has .495 lift with 1.25 rockers. The standard springs probably would have been fine?

Is it running hot?

Stan

it seems to be running fine.  I have a CHT gauge and it never seems to get close to 200 degrees.  Most of  time is around 180, which makes me think its not working right.  My oil temp also stays pretty low.

I was thinking about taking that 1915 in corner of my garage and building it up a 2276 and putting that fk8 with 1.4 rockers as a backup motor.  I know you like that cam.

Cam and rockers are good to 6000-6500 so dual springs are right for your application, but those particular springs look like a little more than you need. 

Ed

I just don't want the additional spring pressure to wipe the cam.  I think it will be ok.

Refer to our long oil discussion for more on avoiding cam-flattening, lifter-cupping, and general ignominy. 

As said - the wrong oil will wipe your cam faster than a set of dual springs when only a single is needed.

Perhaps a set of HD single springs?  I have used them on set ups like this - never seen any related issues when tearing apart engines (usually due to drag race related failures like spun mains, tight flywheels and rods through cases.

Beehives.

110 lbs. seat pressure, 290 lbs. full lift pressure. Max .525 valve lift. Accurate valve control. On a beehive spring, the different size coils resonate at a different frequency for a harmonic canceling effect with no extra heat  (from the ad).  There's not much to not like.

This is new to the VW hobby, but not to HiPo world in general. A W120/Panchitos would be a perfect combination for these.

VW650 springs data

nstalled height of 1.540" gives you @ 160 lbs. of seat pressure, and @ .630'' lift you have an open load of 420 lbs. With the VW650 valve springs you can run up to .630 lift, 

Hey Stan

What would changing over to the FK8 Cam with 1.4 rockers do for performance on my setup compared to the w120 with 1.25 rr?

A very knowledgable headporter/engine builder (goes by the name of Kroc; he's a Vancouver boy and local!) once said on the Samba that for a street engine the intake valve should lift 35% of it's diameter. Since yours is at about 31% (40mm valve, 12 1/2 mm lift with W120/1.25's) and going to an FK8 with 1.4's will add 1 mm (about .040") lift, changing the cam and rockers may increase power a bit, but only you'll be able to decide whether it will make enough difference to warrant doing. It will be an interesting experiment- please report back what you find! What might make as much or more difference here is the ramp shapes and how long the valve is held open near maximum lift (for better cylinder fill), but no one (I know) has ever taken the time to plot that out for the various aftermarket VW cams. I have seen the lift/duration plotted out on a W125 with 1.1 versus 1.25 rockers and it does explain (in my wee pea-sized brain anyway) the increase in power that higher ratio rockers creates (if I can find it I'll post it at the bottom). I know, it's not the definitive yes or no answer you are looking for, but it's the best I got

Gene Berg claimed no damage ever came from too much spring pressure other than wasted hp (not sure if I totally agree with that- I think that as spring pressure goes up oil choice becomes much more important for lobe/lifter compatability) and lots of guys do run the 650 springs on the street successfully so I don't think your engine is in any immediate danger. That said, for a jump in and go anywhere driver (as opposed to a feared, fast high strung street machine) they are a little overkill, though, and some VW sized dual springs are more appropriate or (even better) the beehives Stan talked about are probably the best choice.

It sounds like you're describing oil temps- normal head temps when the engine is warmed up should be well above 200 to over 300 and even close to 400' F. (when you're really pushing it).

And here is the 1.1/1.25 rocker comparison on a W125 (a W120 will look similar, with the total lift being just a little lower). Look at the extended amount of time the valve is open at the higher lifts-

Bobby D posted:

Hey Stan

What would changing over to the FK8 Cam with 1.4 rockers do for performance on my setup compared to the w120 with 1.25 rr?

Generally, a bigger cam moves the powerband up the RPM register. The FK8 will start making power later, and for longer than the W120.

However, there's more to it than that. Everybody talks about compression ratio as if 8:1 is a little and 10:1 is a lot. The problem with that is that this is static compression ratio, which doesn't mean much. Dynamic compression is what is actually happening in a running engine, and takes into account valve overlap, etc. Generally, the more aggressive the cam, the more the dynamic compression ratio is lowered. Dynamic compression ratios are notoriously hard to calculate, so most guys just go by "folklore and common knowledge" (the SWAG method). SWAG-ing it, 8:1 (static) is a pretty decent compression ratio with a stock cam, 9:1 is nice with a W120, and an FK8 can sometimes tolerate up to 10:1 static compression ratio-- because the dynamic compression ratios of all three of these hypothetical engines is about the same.

So, if your static compression ratio is about right for the W120, it'll probably be a bit low for an FK8, as the dynamic C/R would be lower with the bigger cam. If you've got a big deck on the cylinders, you could always tighten it up to raise the C/R-- just don't go past .040 tightening it up.

Size also matters. Generally, the bigger the engine, the more cam it can tolerate. The reason for this has a lot of factors, but on it's most basic level a bigger engine makes more torque by the nature of it's size. This increase in torque means that a bigger engine with a bigger cam has enough torque (especially if it's running enough compression) to pull the engine through the normal slump it would have at lower RPMs due to the aggressiveness of the cam. Makes sense, no?

So, there are combinations that are sweet, and some that less so. A 2110 with a W120 and about 9:1 static compression, with a good set of 40x38 heads is a very, very sweet engine. Bolt on some 40 Dellortos and a 1-1/2" merged header with a good collector and things are happy, happy. Swapping out the cam for an FK8, without changing other stuff would help the engine very little, and would likely make it worse for most things. The engine would want bigger heads, bigger carbs, and a bigger exhaust. Power would come on later, but would make more in total. With the bigger support parts, you'd want more displacement, so you'd be best to swap the pistons for some 94s. At that point, you've kept the case and the crank-- the entire rest of the engine is new. That seems like a waste to me, but I've done this very thing several times.

Torque is power. Lord Acton said that power tends to corrupt, and absolute power corrupts absolutely.

Your move.

Yes, a W120 is a different cam than the FK8; normally the 120 would rev to about 6-6200 (or so depending on the rest of the combo) rpm with power whereas the FK8 will go to 6500 or slightly higher. It has a slightly lower powerband and can't stand quite as much compression, for reasons that Stan went into. Add 1.25 rockers to the W120, though, and that adds 5? 6? 7?degrees @ .050" valve lift (look at the chart above) and now they have almost the same effective duration, can run the same compression (or close), and will have similar powerband characteristics. Either cam/rocker combo in a 2 liter + engine with 40x35 heads (and the right carbs and exhaust)  would produce kick a** power and have great throttle response throughout the rpm range. Add some bigger valves and more intake port volume, though, and the FK8 (with 1.4's) lets the engine produce that much more power in the upper rpms', while the W120/1.25 combo, with 1mm less valve lift would start to show it's limitations.

Stan : Old German gentleman ( Grandfather ) once said: "  Torque creates power Horsepower,  is along for the ride "   ~

ALB posted:

... Add 1.25 rockers to the W120, though, and that adds 5? 6? 7?degrees @ .050" valve lift (look at the chart above) and now they have almost the same effective duration, can run the same compression (or close), and will have similar powerband characteristics. Either cam/rocker combo in a 2 liter + engine with 40x35 heads (and the right carbs and exhaust)  would produce kick a** power and have great throttle response throughout the rpm range. Add some bigger valves and more intake port volume, though, and the FK8 (with 1.4's) lets the engine produce that much more power in the upper rpms', while the W120/1.25 combo, with 1mm less valve lift would start to show it's limitations.

Al-- I didn't believe you, so I looked it up. You're right: the W120 with 1.25 rockers are very similar in duration to the FK8 with 1.4 rockers. It's lift that is the main difference.

Forget what I said, Bobby. Your engine would like an FK8, and you could use those springs then.