Hey 6t Falcon - tried the 30-degree valves?

[Anonymous]

Hi, Dennis;
Just curious - I know about your back-cutting experience on intake valves and such, but, have you tried any of the 30-degree valves, like Milodon sells? The make a 1.88" (I don't know the stem size yet), which looks like it will fit in the 200 (D78) heads, leaving just a shrouding issue to fight.

MarkP

 

[Hot 6t Falcon]

Hi Mark,

Nope, not yet.

I like the idea, but I haven't done enough research on the 30 degree angle yet. Do you have any magazine articles that discuss this idea?

I guess that I'm not interested in building an all-out racing engine. It has to make power and be reliable as a street engne.

I am just starting to work on a head. I was planning on SI stainless valves (1.8 intake: 1.50 exhaust; already backcut). Two Pinto Holley/Weber carbs. I'm going to use PC valve seals instead of the stock umbrellas - I have trouble with too much oil leakage past the valve stems.

I was thinking of a "normal" three angle valve job, but this 30 degree may be OK too.

Thanks

 

[goinbroke2]

They really pick up flow on the bench and hp in the engine, if your serious into hp. I wouldn't use them on the street for a # of reasons. The reason you go to this angle is a last resort at getting flow. When you have a limited lift because of class limits (stock/SS) or max lift with a particular valve (stem length/others) then you do what you gotta. If your running .800 lift, 300# on the seat springs, max valve diametre, then last resort is 30 deg seat. Problem is, even with 45 deg you pound out the seats or pop the head off the valve after a certain number of passes. 30 deg just shortens the life and # of passes before replacement.
Bottom line, yes in an all out engine it is worth the hp in spite of the increased maintenance, in anything less, it's a waste of time. Instead of going 30 deg, leave it at 45 and go 12-14% bigger in valve dia.

 

[Anonymous]

Hi, Dennis;

This is the first I've heard of increased maintenance. I can't think what that would be, because bike engines have used 30-35 degree intakes and exhausts since the 1980s.

I had to put the PC seals on mine, too - the oil consumption was outrageous with the unbrella types after my rebuild, which was the main reason for re-pulling the head. The intakes on #3 & #4 were so crudded up that the engine had GREAT difficulty starting when hot: they were only opening about .110" around the crud, which was over .400" thick, and shaped like the intake tract!

When I did the first rebuild, I had the guides knurled - bad choice, I guess. This time I had them 'bored & bronzed' with inserts, cut deeper bowls so the springs could be shimmed up a bit, smoothed out the bowls and the combustion chambers, then milled and used the steel head gasket. Much better performance and MPG now. The oil consumption was immediately better, not great.

As it turned out, the distributor cap I had installed after the rebuild was "clocked late" for the last 3 cylinders in the firing order by 2 distributor (4 crank) degrees. It was mis-manufactured. This caused the rings on #3, #4 and #5 to not seat at all. Now they're beginning to show signs of seating and the engine feels smoother and stronger every day. The oil consumption is dropping noticeably every week, too, so I think I'm on the right track.

The only thing I can think of (about the higher maintenance issue) involves the use of hi-pressure valve springs for hi-RPM work. But, at the normal pressures of the stock springs and the typical 4000 RPM range of the log-headed engines, I can't see why high-force springs would even be needed. I only shimmed mine because they have over 200,000 miles on 'em and the seat pressure was borderline low (and I'm too cheap to buy new ones right now ). Since the primary boost in intake flow would be most evident in the 1000-2100 RPM range with these valves, it seems to me to be the ideal setup for daily street use.

 

[Anonymous]

Problem is, even with 45 deg you pound out the seats or pop the head off the valve after a certain number of passes.

MarkP, the increased maintenance goinbroke2 is referring to is the need to install new seats or replace the valves after this (above) happens on a race engine.

 

[Anonymous]

Well, I guess I don't think in terms of the all-out racing thing.
My use is mostly grocery-earning or grocery-fetching...

I know the 30 degree valves have less mass (thinner faces) than the 45 degree versions. Maybe that's what pounds out in the racer's top ends, but, still, bikes frequent the 10,000+RPM range with these valves and still reach 50k miles without problems.

Could it be valve material differences? Hmm... Most Rice bikes use stellite exhausts, a few use stainless, but most use ordinary intake types.

I guess I'll have to go find out some more about the valves...

 

[Lazy JW]

I suspect that the heavier valves used in Ford sixes compared to most 10.000 rpm bike engines would have some significance in this matter. However, rpm is even more significant, as Kinectic energy increases with the square of velocity. It is easy to see that 30 deg. valves wouldn't last as long in a race car engine, but I have to wonder how they would work in a 2500 rpm 300-6 truck engine? Instead of lasting 300,000 miles they would "only" last 200,000? I'm not going to tear down my truck just to find out though, just speculating. But then, how many motorcycles actually run 10,000 rpm for 100,000 miles?
Joe

 

[Anonymous]

Good points, JW;

The bikes at 10k RPM usually last around 10k-15k miles under hard riding conditions. However, the things that give out first are the rings at this kind of constant engine speed. The lubrication slips off the rings (usually the top 1 or 2 rings) and they wear. The valvles usually do fine, even under hard conditions.

The more I think about these things, the more I'm inclined to go find another head and do some mods. After I pass the 25-year emission-test mark with the Fairmont, I can do some mods, so long as it doesn't generate too high a hydrocarbon count (the tailpipe sniffer boys here are going 'automatic' on the street corners in a few years). I'd like to do a head with 9.25:1 CR, 30-degree intake valves, .020" quench height and the H/W 2-stage carb (to save some MPG).

I've learned from the stock exhaust header that it has vacuum moments right at the exit into the tailpipe, because this is where the AIR system delivers the fresh air (for the catalytic). It delivers it with nothing more than a check valve, and the amount of suction at the pipe is surprising! This tells me that the stock exhaust header is at least better than the ones in the dual-inline fours (351 and 360), which have to have a pump to get the air into the headers!

 

[goinbroke2]

Lazy JW said it best about the kinetic energy increasing at the square of velocity. In my less eloquent terms, I would of said that bikes use tiny light valves(4 per cyl in a lot of cases requiring even smaller valves) and at 10,000 rpm have about the weight of a 2" valve at 4500 or so.(guessing, not proven)
That said, in your specific application(low rpm,street use) you might be able to benefit from the increased low lift and not have the adverse effects of high spring pressures.
High spring pressure is for stronger cams=higher rpm/power.
30 angles are for more flow=higher rpm/power.
Results from higher rpm/power=fatigue and failure.

Stock springs/rpm/power levels and increased low lift flow for more low rpm torque from 30 deg angles.......... I think your onto something I had not considered.
Mark P, ALL I DO is think in terms of all out racing!

 

[Anonymous]

Now you're gonna make me go weigh my bike valves. :roll:

I gotta find some math for all this...the engineer in me is keeping me awake nights.

 

[xctasy]

Buy an A gradePyrex 250 ml measuring cylinder, and drop your valves in. Archimedes said the item, imersed in a fluid, recieves an uptrust equal to the weight of water displaced. So if your measuring cylinder is set at 100 mls, and then reads 250 mls after the valve is poped in, it weighes the same as the amount of water displaced. That would make it close to 150 grams at 20 degrees centigrade.

1 gram of water is approximately 1 ml of volume at that temp.

The idea of backcutting or reprofiling sounds great. The value of dropping the mass of the valve will be very slight at high rpms. Having a valve that flows well yet doesn't loose its head at rpm is what your after.

 

[addo]

You better edit that one, XE. Displacement like this, merely gives equivalent mass in water. Multiply that by the density of the valve material.

 

[xctasy]

Oh yeah Adam .

The weight in air is they key. A simple set of flour scales or shop scales would be the idea.


What I nattered on about will give the mass (amount of territory the object covers). If its lead or wood, the displacement will be the same if its fully immersed. Ships use draft to measure weight, but thats a different set-up where the ship is displacing water with air and metal, not just metal on its own.


Gosh I make simple things complicated.

Glad your awake. I'm gald I've got parking space for two of my sneekers....

 

[Anonymous]

"Archimedes said the item, imersed in a fluid, recieves an uptrust equal to the weight of water displaced"
Only true if the object floats.
Are your valves made of wood?
Then it doesn't work.
Still useful, though: 1 cc of water weighs exactly 1.00000 gm (isn't the metric system wonderful - water is the standard). Multiply the weight of displaced water by the specific gravity of the item measured; steel is about 7.3 SG, so 150 cc of water displaced makes the valve weight 1185 grams.

 

[Lazy JW]

I had my John Deere manual out looking up specs for the thread about the Model G that got broken in half, so I took a peek at the valve specs. Guess what? They used 30 degrees on the intakes and 45 on the exhaust. Also no overlap between intake and exhaust valve timing.
Joe

 

[addo]

They used 30 degrees on the intakes and 45 on the exhaust. Also no overlap between intake and exhaust valve timing...

No wonder it broke.

 

[StrangeRanger]

"Archimedes said the item, imersed in a fluid, recieves an uptrust equal to the weight of water displaced"
Only true if the object floats.
Are your valves made of wood?
Then it doesn't work.
Still useful, though: 1 cc of water weighs exactly 1.00000 gm (isn't the metric system wonderful - water is the standard). Multiply the weight of displaced water by the specific gravity of the item measured; steel is about 7.3 SG, so 150 cc of water displaced makes the valve weight 1185 grams.

But if the object does not float it displaces its own volume. If you know the density, you've solved the problem or, you can weigh it to find the density. Archimedes originally came up his principle when asked by a monarch to verify whether a goldsmith had cheated him. The goldsmith was to have made a crown out of a bar of gold. The finished crown weighed exactly the same as the bar, but the king suspected it had been adulterated with alloying elements. While sitting in his bath, Archimides came up with the solution. If the crown were in fact pure gold, the crown and the bar would displace the same volume; if the gold had been alloyed, the equal weights would have unequal displacements.

I do not recall whether or not the goldsmith was proven a crook. See what you can learn in "The History of Western Science and Technology"

 

[Lazy JW]

They used 30 degrees on the intakes and 45 on the exhaust. Also no overlap between intake and exhaust valve timing...

No wonder it broke.

Sorry Addo, the specs I quoted are for a stock engine. I suspect the one that broke had a bit more overlap etc. (800 cubic inches )
Joe

 

[Anonymous]

"But if the object does not float it displaces its own volume"

Yes, exactly as I described in my post, including how the calculation is performed, and the resulting weight from the (sample) volume given.

 

[MustangSix]

I've bookmarked your tech papers. Very nicely put together and quite informative. Thanks!