Valve springs 101

I've been reading a lot about valve springs, what is good, what is bad when it comes to setting up a head to work with a particular camshaft. The most interesting part to me is how close to coil bind you need to shoot for.

I was going to just run the springs that came on the new heads (TFS 325's) and call it good. They are PAC springs, installed height of 2.00" and they coil bind at 1.050". Awesome, or so I thought.

After doing some searching and reading, it seems having a spring too far from coil bind can be a really bad thing. Surging, overheating, valve bounce and spring breakage are some of the things that apparently can happen. The ball park number I kept seeing is 0.070-0.080" from coil bind. That means, I'd need a camshaft with A LOT more lift than the 0.697" lift solid roller cam I am currently using.

The Isky 9965 Tool Room springs I used for a short time on the other engine seem to be the ticket. They install at 1.95" and coil bind at 1.170". Before lash, they are still 0.083" from coil bind. I will probably shim them 0.030" or so to get them in the ball park.

Does it sound like I am on the right track or am I over thinking stuff?  The PAC springs would be over 0.25" from coil bind, which does not sound like a good thing to me.  I drive this thing on the street and on Drag Week style events and it runs for hours at a time on the highway.  Although I have never had any problems with springs, I have seen guys kill buckets of valve springs on DW and can't help but think this is probably a big part of the cause.

Is your PAC spring a 1224?

They appear to be similar. Although I have not found a direct part number cross reference.

http://www.trickflow.com/partdetail.asp?part=TFS-16414-16&autoview=sku

They are 1224......same thing the TFS A460 heads have. Good spring.

So is running it 0.25"+ from coil bind a bad thing? Or is it something I don't even need to worry about?

I just put my new springs on with a different array of locks and retainers to get within .060 & .065 intake and exhaust.seat psi ended up some higher than it was but it'll run.

BigBlockRanger wrote:So is running it 0.25"+ from coil bind a bad thing?  Or is it something I don't even need to worry about?

It's not the preferred way but, it'd depend on how smooth the lobes are, rpm, etc.

Keep the springs and put a bigger lobe in it

The thought has crossed my mind more than once!

Thanks Randy. I love learning about all this stuff and sometimes it's tough to know if a principle that applies to a 9000 rpm race motor really makes any difference in a garden variety street/strip engine.

That being said, I think I will go ahead and swap to the Isky's. They just seem like a better match for what I am doing and I had good luck with the last set of Isky springs I used with this cam. 9365's I think.

Now if Probe will just finish up my pistons, maybe I can get with putting this thing together!

The 1224 is more spring than should be on a street driven car.

I'm glad you got the V/S figured out they are very important for all applications but I would like to through something at you, I know you drive it alot and do drag week my thought is when you are finished with your build and it tests out ok, then when you drive from track to track I would change the rocker ratio to 1.5 or 1.6 to ease up on the valve train parts, then when you get to the track just change the rockers, this just seems like it would help out alot anyway good luck with your build

I don't know if anyone has tried that. Seems like a lot of work! lol

Like I said, I have never had any spring issues with my stuff, maybe by pure luck, but I do know there have been others that really has serious issues with breaking springs on the drives.

BigBlockRanger wrote:I don't know if anyone has tried that.  Seems like a lot of work! lol  

Like I said, I have never had any spring issues with my stuff, maybe by pure luck, but I do know there have been others that really has serious issues with breaking springs on the drives.

I'd say that avoiding some sort of silly cam with overly quick "drag race" lobes would be the best thing to do if you're going to do the Drag Week thing.