Valve springs

[1931 flamingo]

Looks like "we" could use a new valve spring "cottage" business...............
Paul in CT

 

[BRENT in 10-uh-C]

Lack of seat pressure adversely affects heat transfer from exhaust valves. Valve float, resulting in burned seats, is a function of both seat pressure and spring harmonics. Nobody ever talks about it here because likely less than 2% of A owners ever rev past 3000, or 1,500 camshaft rpm.

Modern cars sometimes use a second, counter wound inner spring of a different rate and thus different harmonic profile to run interference, cancelling the harmonic peaks that will float the valves. Perhaps a second inner spring of reverse wind could be found and added. That would accomplish two things- increased seat pressure and reduced harmonics.

Abandoning the rather narrow "A" spring completely is another possibility. There are other spring retainers available in a multitude of diameters. Perhaps a little valve spring catalog shopping is in order.

FWIW, I'm not running stock springs in my 160B with a stipe RR340 cam and big valves. I picked up a set of NORS springs in a box marked KONG at Hershey several years ago. They are visibly thicker and a lot stiffer. I never measured their rate.

I suppose those springs you have were originally sold by Kong Jackson back when he was alive??

One thing I would like some clarification on is you said that lack of seat pressure adversely affects heat transfer. Providing the duration was the same for both scenarios, are you suggesting that a valve with 65 lbs of seat pressure would cool "better" (quicker? more efficiently?? evenly???) over a valve that only had 35 lbs of seat pressure?

Personally I am NOT a fan of excessive spring pressure in today's Model A/B engines. I feel additional pressure was a plus back when using two piece guides, however one-piece guides and modern stainless valves with multi-angle seats have changed many 'needs' IMO. Remember that gravity & RPM also play a factor in not needing that much pressure in an A/B. I would be interested to hear how much Jim Brierly uses on his flathead Bonneville engines.

.

 

[Joe K]

Amazing thing this Internet. There is a whole bunch of information about Charles "Kong" Jackson over at HAMB.

Never knew.

Those springs might have been aimed at a 40 Ford Flattie?

Joe K

 

[Vic in E-TN]

With a 3 bearing/bushing cam, too much valve spring pressure will cause the the cam to flex or if the cam bores are too large the cam will float. Some years ago I saw this in an engine prior to a rebuild. I saw over 10 thou movement in the cam when rotating it by hand. This led me to look for some blocks with 5 cam bearings. I found two and have them stashed away. The next rebuild I had the cam bores bored out and had bronze bushings installed. About 15 years ago there were a few articles in the SOSS magazine about valve spring pressures. I believe that H&H out in California wrote some things about this also. High spring pressures are necessary for high rpm's.

Thanks to James for bringing this up.

Vic

 

[MikeK]

. . . One thing I would like some clarification on is you said that lack of seat pressure adversely affects heat transfer. Providing the duration was the same for both scenarios, are you suggesting that a valve with 65 lbs of seat pressure would cool "better" (quicker? more efficiently?? evenly???) over a valve that only had 35 lbs of seat pressure?. . .

Brent, I'm no fan of excessive pressure either, but there is a link between heat transfer and pressure between metal surfaces. There is no such thing as two absolutely perfect metal surfaces. Heat transfers faster through contact than a gap, even if that gap is on the atomic level. Pressure causes some temporary deformation, increasing the surface of the actual contact on that level. 35lbs is not nearly enough to compress two less than perfect metal surfaces into compliant contact. The valve may be sealed to air, but the contact is never absolute. A bit of a side note here- a valve lapped with 220 grit compound will have an Ra surface of ~20 to 30 micro-inches. It will be air tight. That same seat, after burnishing itself in at 100 miles will be near 4 Ra and have greatly increased contact heat transfer.

35 lbs has indeed proven sufficient in an low performance stock A, but most of today's A's are pushed to higher average running speeds. Add to that cams with more duration, thus less cooling seat time.

So how much is necessary, and how much is too much? I'll cheat here and look back at references for a multitude of later engines. After WWII stock flat tappet engines with similar sized valves usually ran in the 75-100 lb seat pressure range. Why? They had heavier valve trains and also easily peaked 1000 rpm higher than an A. Yet none of those needed ZDDP oil. High perf factory V8 street stuff (needing ZDDP) ran 120-150 lb seat pressure. Racing valves start at 150 and go up.

I don't think (my opinion only) 60-70lbs is too much seat pressure for an A that someone wants to wind to 5000+ rpm without valve float and without burning exhaust seats. It is still nowhere near the valve train load that necessitated ZDDP. I've also heard people say the cam gear load will go way up. Not exactly true either, as energy required to compress the spring on a cam acceleration ramp is recovered on the back side during closure- unless you float the valves. Then the load goes up, you hammer the profile off the cam, and the shock waves eat the cam gear teeth.

Brent, the valve seat pressure on your 4.6 Aviator is about 78 lbs.

 

[just plain bill]

This information is from Jim Brieley,


VALVE SPRINGS
Stock installed spring length is approx. 2½ inches. Spring pressure at that length is approximately 32 lbs. Following is a chart giving spring pressures at different lengths. (Model A springs). A Metal cam gear is recommended on all performance grinds and is a good idea even with a stock cam. An aluminum gear works well and are not noisy as some claim.

LENGTH PRESSURE
2 3/8" 40 # (Recommended for stock B or C cam)
2 1/4" 52 # Note: A spacer made from 3/4" water pipe
2 1/8" 62 # works nicely and will stay in place if
2" 73 # cut off squarely, such as done in a lathe.
1 7/8" 83 #

Coil bind occurs at approx. 1 1/2" (with A springs). 60 lbs. pressure, on the seat, is recommended for most "street" cams/engines. 90 lbs. is recommended for racing, a different type of spring is needed for racing engines in order to achieve this pressure.



BRIERLEY CAMS
page 2

 

[Joe K]

Can't Bill Stipe make a cam where the segments between the individual cams is not turned down to stock? This won't help bearing loading on a three bearing cam, but it will keep the cam from "whipping" and increase rigidity?

Just thinking out loud.

Joe K

 

[James Rogers]

I don't know what is going on with these springs but I had all 8 of the custom springs measured at 2 different shops on 2 different Rimac machines and all were at 90# seat pressure with the spring compressed to 2.375. We measured 2 full sets of replacement springs one set from Snyders and one set from AER and all 16 measured 50# at 2.375 compressed seat pressure. I installed one valve in the block and measured the spring compression from the block to the rotator and 2.375 was right on.

I also found after finishing the bottom end work, the pistons have some funny witness marks which mimic the combustion chamber design on them. I don't know if the pistons are hitting the head or if this is caused by detonation. The head is a polished Winfield and has no counterbore. I have run many heads and sold many that had very little to no counterbore and never seen this. I will try to post some pics later for evaluation.

 

[Mikeinnj]

You can print this out....

View attachment img015.pdf

 

[James Rogers]

OK, here are the pictures of the pistons and head. The first picture shows #3 and the damage to the piston. It is worse than the other 3 but all have some. The #3 piston (picture 1) is deep enough to feel with your finger. I measured the composite gasket and it's compressed thickness after removal is over .050 and lass than .057. If you look at the head you can see this damage mimics the combustion chamber. 3 and 4 look oily 1 and 2 are dry sooty. One thing I noticed is the pistons protrude more on the inboard or valve side which is where the damage is.
Pictured also is the head and the combustion chambers. Anyone know which Winfield this is? I have never seen pistons damaged like this but I have never run or worked on a motor with a head like this. I think the pistons may be the problem with the damage and the noise the owner thought was in the valve train. We have decided to install a Stipe IB330 cam with .003 over bearings and line hone the block to fit it and do a valve job with new springs to eliminate the valves.

 

[Bill Stipe]

Can't Bill Stipe make a cam where the segments between the individual cams is not turned down to stock? This won't help bearing loading on a three bearing cam, but it will keep the cam from "whipping" and increase rigidity?

Just thinking out loud.

Joe K

Joe I do have a stock pile of 5 bearing oversize blanks for performance cams, and you are correct even if you do not support the extra 2 bearings it does make the cam a little stiffer.

 

[40 Deluxe]

Try assembling the head with clay or wadded up aliminum foil strips to determine actual piston to head clearance.

 

[James Rogers]

I have some solder that I am going to use to measure that but I don't understand the pistons being higher on the valve side. I haven't measured the head surface to pan rail yet to figure out if the block is cut out of square or if the pistons are modified.

 

[MikeK]

James, I don't know if this will help with your ID question, but the aluminum copies of the Winfield (originals were iron) are advertised as 6.4:1 with 131cc, 6.7:1 with 124cc, and 8.5:1 with 86cc chambers.

Pistons appear to show something once called "incomplete detonation scuffing" caused by squish height being reduced to near, but not at the point of contact. The hypersonic velocity is so great the internal friction of the moving air ignites the charge, but the extreme close metal surfaces spontaneously extinguish the flame by heat absorption. The result is localized fine metal erosion on the piston, without the typical detonation hammer pocks, and incomplete combustion deposits on the much cooler water filled head. Sounds like a dull clicking at high speed rather than a knock. Experienced this in my SBC days pushing things to the limit. I could be completely wrong.

 

[Joe K]

Sounds like a dull clicking at high speed rather than a knock. Experienced this in my SBC days pushing things to the limit. I could be completely wrong.

Hmm. Reminder of the CFR Variable Compression Engine used to study Octane determination found in my college engineering heat lab.

"DON'T run the engine for very long at high compression ratio" the professor said.

Gosh, it's been a long time...

Joe K

 

[James Rogers]

James, I don't know if this will help with your ID question, but the aluminum copies of the Winfield (originals were iron) are advertised as 6.4:1 with 131cc, 6.7:1 with 124cc, and 8.5:1 with 86cc chambers.

Pistons appear to show something once called "incomplete detonation scuffing" caused by squish height being reduced to near, but not at the point of contact. The hypersonic velocity is so great the internal friction of the moving air ignites the charge, but the extreme close metal surfaces spontaneously extinguish the flame by heat absorption. The result is localized fine metal erosion on the piston, without the typical detonation hammer pocks, and incomplete combustion deposits on the much cooler water filled head. Sounds like a dull clicking at high speed rather than a knock. Experienced this in my SBC days pushing things to the limit. I could be completely wrong.

I agree with all this because of the look of the piston and the witness mark. The #3 piston protrudes more than the rest and has the most damage. What is the best course of action to remedy this? Cut the pistons square? Deck the block square? There must be something causing the pistons to not be square in the block. I have never had any that were like this so I don't know if it is normal or what. I would have thought, if one side would be higher, it would be the driver side so as to allow a smoother transition of fuel/air mix. I understand there must be some turbulence but this would be like the fuel hitting a wall with the inboard side being .015 to .025 higher.
Any help is appreciated.

 

[PC/SR]

Check that the bores are true perpendicular. Had a similiar problem, front of pistons higher, the machinist that corrected it said the prior guy's table was not true.

 

[MikeK]

I don't know what kind of equipment and measuring tools you have, but if it were mine I'd first want to determine if the bores are perpendicular to the pan rail and at the correct 0.125 centerline offset.

I've seen blocks where, on large boring machines, the base offset of the bores was moved from the original offset to zero, and the deck center was located off the old, original holes. The result of the 0.125 shift with a 4.000" bore and 11.500 deck height works out to a total tilt of 0.032 across the piston face, in the same direction your pistons are tilted. A base offset change of a different amount will, of course, produce a different total tilt.

I've also seen blocks from production line rebuilders where a piece of pan rail gasket wasn't completely removed and the block then fed to a blanchard with the rail base tilted. Result: tilted new deck.

I'm interested in what you find. I'm also curious as to how the pistons were lowered from the stock 0.03125 protrusion. Either pistons with a lower deck height, or rods with shorter than 7.500 centers.

If I had a block like that I'd get a rope and grab my tackle box and rod.

 

[d.j. moordigian]

James,

1. Why is the "bypass hole " plugged in the block? I do it in my race Chevy's, but
why here. Does it have a thermostat? My race stuff have "blanking sleeves", no
thermostats.

2. Yep...3 & 4 are sure "wet"! When you get the pistons out, I'd look at the rings,
are they lined up?

3. I think Mike hit it on the head @ 8.5 with 86cc in the head, plus the 1/8"
bore! I'm sure the head was calculated with a 3 7/8" hole...not 4".

4. I think the "quench" is OK. If the rings are lined up....I'd be looking at the
timing/distributor which will cause this problem. Find some one with a Dist. machine
too check the lobe spacing. What kind of Dist.? Every engine I build...I run the Dist.

5. I'd also like too see photos of the rod bearings...especially the rod side.

Dudley

 

[just plain bill]

I have one of those heads on my engine with .040 clearance over top of piston ATDC and haven't seen this condition. The head is a repop and is called a "Crows Foot". I do know that my bores are perpendicular to the crank centerline because of an earlier problem caused by crank centerline error when main bearing babbit was bored off line and had to be corrected.
As to "normal" piston Above deck protrusion on my engine I just chucked the pistons in the lathe and faced off the desired amount. I'm using J and E pistons.
The chambers in my early repop head measure 123 cc's.