Valve springs

James Rogers

James Rogers

Well-known member
For the first time, I have occasion to need the compression height and spring pressure for the valve springs in an A engine. I have always used new springs and never had a problem but I have a performance engine in that needs to have the springs checked.Les Andrews book states the springs are checked at 2 3/8" and the springs should be at 60#. I have checked every spring in the shop and none are over 37# at that height, what's up? This is new, old, and originals. We used a bathroom scale on a bridgeport and a rimac spring checker and both were consistent. Are the springs that bad or is Les wrong? I have always heard that 60# was correct but never checked it till now.

Any help appreciated.
 
The stuff I have says 50-55# at 2.25" and then at 2" should be 70#+. New springs are within those numbers. Old ones are a little weak.
 
None that I have found are even close. I get 36# at 2.375" and 45# at 2". This is on a Rimac spring checker, old or new.
 
James,
As a side note, wondering, with occasional sticking valves, wonder if a 1/8" spring spacer could be squeeked in above the spring with the head on? Some old springs are really soft. A friend increased his top speed from 51 MPH to 65 MPH by merely replacing his stock springs with NEW stock springs to eliminate valve float. Bill W.
 
Just checked a couple of not very used ones on the Rimic tester, came out at 47 at 2.375, at 2.250 the pressure was 57#. Overall free length was 2.970--3.00 They were bought from Macs. Mac's specs in their online catalog says springs are "[FONT=&quot]comp. length 2-1/14" (57-64 lbs.); tension (closed) 34 to 38 lbs."[/FONT] I assume "comp. length" means compression length when the valve is open, and the "(closed)" means pressure when the valves are closed. Their spec sheet does not give a valve closed spring length. Jim Brierley wrote an article on spring pressures in the FAST magazine awhile back. Where did the new ones you have come from?
 
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I use a rather simple tool that has a Plumb Tool Company tag. Use a torque wrench to measure the load. I've compared it to the expensive ones and it is quite close and a lot cheaper. A friend was using it as a door stop and gave it to me.
 
James,

I know we should have figured this out 6-8 months ago when we discussed it.
I don't have any springs here at work now,...I'll bring some from home tomorrow.
 
The new springs I use are from Snyders. I have some from AER that I haven't measured. I will measure them and post it here.
 
OK, I measured 4 of the 8 springs in an AER valve kit and all measure 33.5# exactly. This could be some of the problems with people complaining that their cars don't run as fast as they have heard they should. I don't know where Les got the figures he put in the book.
 
As an add on to post#5, the Mac's springs are 38# at 2.5". James-Sent you a PM.
 
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I took a set out of this engine that are extremely stiff but considerably shorter than the stock replacement springs. These even had spacers on top that are 1/4" thick but at 2.375" they only show 10# pressure. I discussed the problem with my crank grinder who runs a performance shop and he thinks the low spring pressure closed is what is causing the noise in the lifter area. Opinions?
 
Opinions?
Click to expand...

This credible. Not only for power but also for reason of reversal of motion.

The problem would come during the interval between exhaust valve closed and intake valve opened. Weak springs would cause the exhaust valve to not follow the cam fast enough and actually lift tappets from the cam. Force equals mass times acceleration. With low spring force, acceleration happens less if mass is the same. This in turn causes delay of closure of the exhaust valve. Delay of closure creates TWO paths for gas to enter the cylinder (the intake valve is still connected to the cam, of course, and on time.) This recirculation of exhaust and more importantly starving the cylinder of fresh charge will cause the lack of power.

And noise as the exhaust valves/tappets rejoin contact with the cam.

Joe K
 
James,
Does it have the Model A retainers or the 2 piece locks with a retainer?

If it has the 2 piece style...were the locks hard too get off? With low valve
spring pressure they dig into the valve stem groove harder.

The noise....ya, the valve is bouncing on the seats! What does the seats
look like?
 
It has the modern 2 piece retainers and valves. The retainers were hard to get off but not because they were imbedded but for lack of room to compress the spring. It is a lousy way to spring the valves. The seats are burnt especially on the exhaust. I didn't pay attention to the intakes but will inspect them tomorrow. I know I will have to do a valve job to get them to work correctly. They sure need one anyway after this abuse.
 
The seats are burnt especially on the exhaust.
Click to expand...

Run rich attempting to get power? Lotta fuel not enough oxygen?

Car probably stunk of unburned gasoline.

Otherwise on the FSB report I'm seeing a confirmation of Les Andrews number.

Joe K
 
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 have 6 valve springs from a WELL USED and unmolested mid-28 engine. The wire
diameter is .138", with a free length of 2.940",...close too Mr. 1930 coupe's.

45# @ 2.375"
68# @ 2.075".......300" inches of lift

I think that's about 5-10# short for a good running STOCK Model A. But without
knowing the " install height "....also the difference(if any) between the 2 retainer/
lock systems..+ the difference in the spring seats(the block), stock type guide
and the "straight" style guide, were in the dark.

As a note, I like valve spring pressure! If you don't have enough valve spring pressure
the valve system isn't following the shape of the cam....your not getting the performance that the cam has too offer.

btw....what is the exhaust seat width?
 
I've just checked these 2 used springs from my motor I tore down on a rimac tester. Left one is 50 at 2.250 & right is 43 at same measurement. 2 different length springs. Left has a bigger diam coil. Left uncompressed height is 2.826 & right is 3.450. These were out of the same motor.
 
Forgot to attach pic
 

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