Looking to get new springs and valves for my 87 firebird has a 305 in it . Can anyone recommend a what’s a upgrade I can get without having to do anything else to the heads?

 

What's wrong with your existing valves that the guides and seats are fine but the valves aren't? Change the valves, you should probably be getting at least a valve job so they match the heads. If you pull the heads, you might as well pull the engine and have them switch the displacement numbers around for you.

 

Yep,

Even new valves need to be surfaced to ensure they are true, you could get lucky after lapping them in...maybe. Thing is since you have miles on the heads, the seats should be touched up as well, then have the heads surfaced. Guides might need replacing, or sleeved

You can port the heads, should be plenty of templates around to use.

Then consider that cost vs. aftermarket heads.

FWIW I had a low mileage set of L98's I bought years ago, spent a lot of time porting them and balancing the flow.

Heads sat unused until recently, I had new valves, springs, retainers, etc and a valve job, and resurfaced. Guides were good. Bill was a tad under $500, I knew that going into it, but wanted to see how the the work I did on them will perform.

 

Stock valves are CRAP. They're made of incredibly soft material, very weeeeeeenie in every way. (305 ones I'm talking about here)

But that's kinda … beyond the scope of the question at hand, at this point.

Problem is, if you have L03 heads (187 casting) the valves ARE NOT The Bottleneck. You can put 2.05" intakes and 1.6" exhausts in em, and not do ONE DAMN THING for the overall flow through the motor (which is another way of saying, POWER OUTPUT). NO IMPROVEMENT it possible from changing the valves, without changing AWHOLE HELLUVALOTTA other stuff too.

Now if your existing valves are farkled somehow, and just need to be changed out, that's a horse of a different color. But that's REEEEEEEEEEEEAAAALLLLLLLLLLY rare.

Springs are yet another different colored horse. Stock valve springs are GARBAGE. Were the day they rolled out of the engine plant. NO MATTER WHAT cam you want to put in, if that's the way you're going, they're inadequate. For that matter you can often improve engine output (user satisfaction) by just getting rid of that **it and putting something in there that actually enables the valves to follow the cam.

L03 heads aren't worth putting valves into. PERIOD. Doesn't matter if the valves are from a NASCAR build, and are free; the heads will defeat any possible advantage they could give.

A better way to start this conversation would be, what are you REALLY trying to do at the moment? What motor do you have NOW? What's inadequate about it, or, what are you trying to improve about it? Don't start at some point near the end of the train of thought that brought you here; go back to THE BEGINNING. What's wrong with what you have now? What other parts are already there? What parts are you looking to buy? Above all, WHAT IS THE PURPOSE OF ALL THIS? What do you intend to do with the car? Identify what's important to you. Drag race ON THE TRACK? Stop light to the next stop light? Impress the person of the other sex in your passenger seat? … Then, what might be more painful, but at the same time, more important to your own personal overall long-term satisfaction: WHAT ARE YOU WILLING TO GIVE UP TO GET THERE??? Gas mileage? Low speed grunt? High speed passing on the freeway? Be realistic. No matter what, ya gotta give up SOMETHING, to gain SOMETHING ELSE. Tell us what's important to you and what's not. Tell us what your purpose and reason is. Start at the start, instead of somewhere in the middle of all this.