Eggplant Jeff

OK My 175K mile 305 was (Shocking!) floating valves above 4000. Stock valve springs.

So I called up Summit and got some "stock size" summit brand springs... Except that they call for an installed height of 1.700 and from what I found on the board here the stock height is probably 1.718. Oddly enough (maybe my stock ones were just smooshed) the new ones sitting free were taller than the stock ones.

Now, being a doofus and not looking this up ahead of time, I just went ahead and installed the springs. And they work great!

Engine revs smoothly right up to 5200 shift point. Still no power thanks to the peanut though.

So anyway I am now thinking of getting a cam... Enter valve springs again. I spoke to people at Summit and Comp Cams, and a basic fact was that I better get the installed height right! So my question is, how close does it have to be?

Do I need to pull all the springs again (PITA) and install shims? Obviously if I am going to that much trouble I will MEASURE the installed height not just shim them all .018.

Or is this close enough? I'll probably put a fairly decent cam in (I've got a 2500 rpm converter and with a good cam I don't mind moving the shift point up to maybe 6000). But I'll aim for as close to the .490 lift limit on these springs as I can get.

Thanks for any insight you can offer!

mrr23

.018 won't make any difference whatsoever.

RB83L69

You could put some .015" shims in it if you want perfection.

IROCZZ3

I shimmed my Comp 987 springs to within +/- .010" of the recommended 1.750" installed height.

But you should be fine with what you have, I wouldn't bother going to the trouble of reshimming.

BadSS

To elaborate on what's been said (that you'll be OK),,, the Summit springs are 110# at 1.700" and rated at 360 lb/in. IF, repeat if, your installed height is 1.718",,, you're looking at .018 x 360, or 6.5# difference - giving you an installed pressure of 103.5#. That's WAY more than you need with your current set up and should be fine for a pretty sizeable upgrade. I'm thinking coil bind on those springs is at 1.160" so you should be OK with an up grade around the .480 lift range (@ 1.700") and you should be able to run a fairly aggressive cam profile with the 360 lb/in spring rate,,, especially with the 305 valves.

IROCZZ3, unless Comp changed their recommended, installed height on the 987s use to @ 1.800" ---- not saying you have to set them there. The increased pressure at 1.750" may be exactly what you need.

Eggplant Jeff

That makes me feel a lot better.

According to summit it is OK to run .490 lift with these springs. Coil bind is 1.160, so that leaves a .050 clearance... which is actually less than the .060 that most people say... but that's direct from the mouth of the Summit guy.

So since my installed height is greater, I should actually be less likely to get into coil bind, right? Does that mean I could actually run more than .490 lift? Say, .018 more :-)? Or is it unlikely that these springs could control that much lift since they have only 103.5# of closed pressure?

Vader

If you want "perfection", you'd get rid of the "L.A." (LameAss) cam, along with the retainers, locks, rotators, rockers, and studs. You'd probably also machine for 1.437" springs and install them at around 1.720".

You're splitting hairs. I've intentionally installed springs at well above their rated install height and on non-statndard length valve stems just to make life a little easier on a flat-tappet cam and lifters, while still enjoying a better spring rate than anything stock. Factory springs have only about 80-85# of closed seat pressure when NEW, and that fades quickly. If you're really concerned, you could shim, but unless you have aluminum heads (soft) there's really no reason.