Valve Spring Pressure - BBC stocker

[gsa612]

The spring you have is to long.To have 250 on the seat your probably in at 2 in.,now subtract .400 lift your at 1.600.Coil bind is at 1.150,I can see the spring being unstable.The problem with the 325/396 is you only have.398 lift,so you have to find a short spring that would put you .50-.100 from CB.That would make it more stable.CC should have a spring that would work in those parameters.If you find one I would put it on the dyno and see if the rpm and HP go up.On your initial pulls your down quite a bit both ways.If it's still down after the change, give Bullet a call and see what they recommend for a cam.The good thing here is you didn't have the Shubeck's in it.. gsa612

[Rob Wright]

Originally Posted by Tom Broome

Pushrods are a spring also. The rate gets altered through diameter and wall thickness.

Correct. Same as the springs, sometimes more is actually worse. You can't know either way until you measure.

[Alan Roehrich]

Originally Posted by Chipper Chapman

Ferrea Competition valves (not the hollow ones as I was told they are illegal) and trend 3/8x.120 wall pushrods

Hollow stems are not illegal. According to Wesley Roberson,anyway, I've been running them ever since he told me they were legal about 8 years ago.


Your pushrods are a problem at the spring pressures you need. I suggest Trend 7/16" x 0.165" wall.


The intake is only going to hit between about 10-15 degrees BTDC and about 10-15 ATDC. After that, the piston is way out of the way.


I do not use clay to check. I check as run, complete the springs. Manley makes a tool to open the valve using the rocker arm. Check every 2 degrees between 25 degrees BTDC and 25 degrees ATDC. Your piston to valve clearance, as run, should be equal to or greater than your TOTAL piston to deck clearance. On the exhaust, you need 0.075", checked the same way.



I use the Comp 26115 spring, with the corresponding retainer and keeper.


My setup is good to over 8,000 RPM with the latest and fastest lobes Billy Godbold has designed for a big block at Comp. However, be aware that I'm using rectangle port cams, the lobes may be different. I have seen people run into trouble with the oval port stuff because it was designed for lower RPM. My stuff was all developed with the help of Billy and Tim Cole, who also did stuff for Wikle, Greene, and others. You need to talk to Billy, or at least talk to Dave McCarver and have him talk to Billy for you.

[Ed Carpenter]

Originally Posted by Chipper Chapman

Spoke to COMP today, they are claiming that the lobe is so aggressive I need to get a different spring that is going to allow me the same open pressure, but within .050” of coil bind. He claimed that the spring is most likely doing the hokey pokey since it’s about .400” from coil bind, and not designed to work there. I thought pressure was pressure, but is this something that could actually be going on and therefore causing such an issue?

Why didn’t they tell u that to behind with? To bad Tim Cole isn’t there anymore.

[Jim Hanig]

[QUOTE=Chipper Chapman;566240]My new motor 396/325hp stocker broke a valve first weekend out (had dyno time too), upon disassembly it was found that all 8 intake valves had been making light contact, of course it was one of them that broke.

My tightest ptv clearance upon assembly ( and checking again during autopsy) was .070" which should be plenty, which leads me to believe it must have been lofting the valves open due to lack of adequate spring pressure. Springs were setup to be 250# on the seat and 500# over the nose which all recommendations said should be enough. Obviously not however. Just wondering if any of you have suggestions of what we should set it up to this time. Cam is steel core, dlc coated trend lifters, pac 1325 springs and steel retainers. Fire away with any suggestions, and thank you
who told you needed 250 on the seat? I have ran several 396/454 oval port engines with no way near that much seat or open pressure. I wou call pac and get the correct spring.

[Darrin Christen]

[/QUOTE]I do not use clay to check. I check as run, complete the springs. Manley makes a tool to open the valve using the rocker arm. Check every 2 degrees between 25 degrees BTDC and 25 degrees ATDC. Your piston to valve clearance, as run, should be equal to or greater than your TOTAL piston to deck clearance. On the exhaust, you need 0.075", checked the same way.
Alan,
I know many people use this method for checking ptvc, but when you open the valve using the rocker arm to find the clearance you basically take all of the load off of the pushrod and lifter which doesn't account for any pushrod flex. Seems to defeat the purpose of checking the clearance in an as run situation. I do realize that the larger diameter and thicker wall pushrods would have minimal flex. Just a thought.

[Ed Wright]

There ya go!! ^^^^^^^
I did not know anybody used modeling clay these days.

[Alan Roehrich]

Alan,
I know many people use this method for checking ptvc, but when you open the valve using the rocker arm to find the clearance you basically take all of the load off of the pushrod and lifter which doesn't account for any pushrod flex. Seems to defeat the purpose of checking the clearance in an as run situation. I do realize that the larger diameter and thicker wall pushrods would have minimal flex. Just a thought.

Well, by ignoring the pushrod flex, you actually end up being conservative on your clearance. If the pushrod flex reduces lift,then you actually have more clearance.


Also, you zero the dial indicator BEFORE taking each measurement, so the measurement is taken from the point of the pushrod being loaded.

[Darrin Christen]

More the reason for stiff pushrods

[Adger Smith]

Keep the cam and get the right springs and pushrods.
Want to Place bets on the Peak's going higher?
The RPM peak should have told you it was unstable.
BTW check PSI for a spring, too.
I've had some good results with their springs lately.