Valve Seat Pressure

« **on:** June 06, 2013, 07:20:53 PM »

What is acceptable pressure loss from valves springs? This is the seat pressure that I just pulled from my heads...

How critical is this? Are they ok to run or mandatory to replace before I run them again? Should I be more worried about open valve pressure?

Basically, this is possibly a deal breaker for the Burley race if I gotta drop $275 for a set of springs, that wont get here for 8-10 days.....

Will I just suffer performance loss, or do I risk doing major damage running these springs in this condition?

« **Reply #1 on:** June 06, 2013, 07:37:20 PM »

Well , hears the deal if a valves spring wears out too much , you can float a valve, not will can! in the specs, there should be a good and no good wear limit. your going to have to find it.

« **Reply #2 on:** June 06, 2013, 07:55:06 PM »

# 3 and # 7 look way off to me! This is just an opinion! and my opinion i would not run them. Sorry Brad

« **Reply #3 on:** June 06, 2013, 08:27:50 PM »

ok....so I ran through them again.....

This time I made sure the roller of the tool was centered on the rocker....and the rocker was centered on the valve. I got a crazy low reading and looked and nothing was lined up.....redid it, and got a much better reading.

Also, previously, I was just getting the reading just as i pulled down and the valve lifted off the seat.....this time I pulled on it a few times "pumping up" the hydrolic gauge.....then took a reading as the valve started to rest on the seat.... just as the instructions told me to do - who needs instructions, right?

....and here is the results....much better

« **Reply #4 on:** June 06, 2013, 08:33:35 PM »

Call the cam grinder in the morning and see what they recommend, or ask
GN7 on PB. Either of those 2 options, mostly the later, will give you answers, not opinions.

Without knowing the cam, can't really
comment.

« **Reply #5 on:** June 06, 2013, 08:56:45 PM »

Yah much better , but ibhsbz is right opinions are just opinions and you need facts.

« **Reply #6 on:** June 06, 2013, 09:02:40 PM »

Normally 10% from each other is acceptable for performance engine but also check the the height as well?

?

« **Reply #7 on:** June 06, 2013, 11:56:13 PM »

Brad if the 888 needs springs without a doubt. Transwest ford will get you what you need to make it to burley.
Please call me if necessary

Chris!

« **Reply #8 on:** June 07, 2013, 12:29:04 AM »

I'm on board with that. I'll advance you next years 'no ad membership fee" if it'll help

« **Reply #9 on:** June 07, 2013, 07:51:58 AM »

Thanks Chris and Pat.....but I am going to run them. I'll change them out after the race - probably take them in and have them gone all the way through.

« **Reply #10 on:** June 08, 2013, 12:42:06 AM »

Quote from: Brad @ SCJB on June 06, 2013, 08:27:50 PM

ok....so I ran through them again.....

This time I made sure the roller of the tool was centered on the rocker....and the rocker was centered on the valve. I got a crazy low reading and looked and nothing was lined up.....redid it, and got a much better reading.

Also, previously, I was just getting the reading just as i pulled down and the valve lifted off the seat.....this time I pulled on it a few times "pumping up" the hydrolic gauge.....then took a reading as the valve started to rest on the seat.... just as the instructions told me to do - who needs instructions, right?

....and here is the results....much better

(Attachment Link)

If you need to make a race with your current springs, then shim the springs with lost pressure so that they supply seat and open pressures that are closer to the standard spring specifications and as the camshaft requires. For example:

On the springs that are down 5-15 pounds, you might want to add 0.015" shims to restore seat/open pressure, and
On the springs that are down 20-35 pounds, you might want to add 0.030" shims to restore seat/open pressure.
(Or maybe they will need 0.030" and 0.060" shims, respectively, to restore the spring pressures)

My point is: bring the weakened spring pressures back to what they should be for your cam/spring combo, especially for your multi-lap, hard-core, sustained rpm racing....rather than go out there with a few weak springs.

And yeah, order up the new valve springs to swap in for those that are nearing their end.

LO

Brad @ SCJB

Valve Seat Pressure

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