PAC valve springs

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Jax

Jax

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I purchased a set of build cylinder heads from MRL performance 7 years a go. The head was built with PAC springs. We are inspecting the cylinders heads, and would like to replace the valve springs.
I am trying to contact Mike to find out valve springs used, however it seems difficult to reach.

Can you make some suggestions on the type of PAC valve springs I should purchase?

Following the specs from my cam:

upload_2021-10-11_15-35-58.png
 
Well, we need to know what kind of cam you’re using. Hydraulic or Solid, Flat or Roller? Measure the OD and I.D. and the free length of the springs and post back, and we can probably tell you. Better yet, what does the Rimac spring tester say about installed height (seat) and open pressure? Also, what cam manufacturer or grinder? The 1.5 vs 1.6 ratio valve lift is more like 1.5 vs 1.52 lift ratio.
 
Should be a bigger spread between the 1.5 and 1.6 rockers ratio's.
 
Jax said:
I purchased a set of build cylinder heads from MRL performance 7 years a go. The head was built with PAC springs. We are inspecting the cylinders heads, and would like to replace the valve springs.
I am trying to contact Mike to find out valve springs used, however it seems difficult to reach.

Can you make some suggestions on the type of PAC valve springs I should purchase?

Following the specs from my cam:

View attachment 1715804192
Click to expand...
Unless the motor has mega hours-miles on it I would not assume the springs need to be replaced just because they are seven years old.
1) figure out what PAC valve springs you have.
2) find the specs for those springs at your open and closed heights and the spring free height.
3) check the valve springs agains the specifications. That is not difficult to do but does require special gauges. Any good machine shop will be able to do that.
If the springs are still in spec, re use them. And, be careful on disassemble to note any shims under the valve springs, the shims could be different thicknesses.
 
Yes to the above. And if they’ve not had the snot revved out of them, it’s perfectly fine to reuse them. Just as long as they can be shimmed back to specified seat pressure and still have enough room to open. Generally, it’s safer to reuse dual springs than single springs. If a coil breaks on a dual spring, you’ll have valve float sooner and not be as likely to have a valve and piston collide. You won’t be so fortunate breaking a single spring.
 
Pretty sure that is a old hughes cam, iirc there 1129 was a really common spring, I believe the PAC number was a 1903, this is all off the hip, not dead sure on that!!!
 
As others have noted, the valve lift numbers for 1.5 & 1.6 rockers are wrong. Could be either or both that are wrong.
Correct valve lift needs to be determined in order to select the correct valve springs...
 
From what I understand, Mike has retired.
 
Did some looking last night, it is a hughes cam, I 563, E 569 at 1.5. I 600, E 606 at 1.6, the chart is messed up above. Springs are 1129 which are PAC 1903. It's a solid flat tappet.
 
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