What is the heaviest spring I can run here?

[FieroNelson]

This thread is a direct offshoot of this thread: http://realfierotech.com/phpBB/viewtopic.php?t=5782

Here's the specs on my engine build:
'94 3.4L Camaro PR Block
Stock Crank, & Rods
.030 over Forged pistons, stock compression
Crane H272 camshaft
Dual Throttle Body Intake Manifold
t3/t4 57 trim Turbo @ approx. 10psi
1.6R aluminum extruded Full Roller Rocker Arms
Titanium Valves, Titanium Spring Retainers
Falconer Racing P&P Cylinder Heads
Headers

I looked up factory specs for the 2.8L in my '86 Fiero and my spring installed height should be 1.570" at 88# per spring. I have been told that I shouldn't go any more than 120# @ installed height for fear of either breaking something, or just losing horsepower.

The springs that I got with my racing heads measured at 170# @ 1.570" and 150# @ 1.70". Here is the video:

http://videos.streetfire.net/video/1504a0bc-7abd-4602-ab2e-98c1018b67a5.htm

I am using a hydraulic flat tappet camshaft, and would like to know what you think about using these "godzilla" springs. Here is an argument FOR using these springs:

I dont' know. You plan to run higher rpm, you plan to run a bigger cam, and you plan to make 300+ hp. You are going to need that extra spring rate to help get that valve closed with that much hp especially if you plan to boost it.

The stock gen 3 valvesprings are fine under normal hp ratings. But with nothing more then boost, they start to float and they have to upgrade to ls1 or ls6 springs With boost I have seen dynos where the springs start to float as early as 4500 rpm on a stock gen 3 motor

They need more pressure to help the lifter to follow the lobe with more hp then stock, and to make sure that valve is opening and closing when it should.

I think with proper cam break in they should be ok. But thats my opinion.

Please help me decide what to do with these springs. If I don't use them I'm going to sell them.
Falconer Racing springs on the left, and stock springs on the right:

[SappySE107]

You sure its not 1.7" install height? I don't know the iron heads and im not sure if the specs are on our site right now. Id be more worried about the spring too be too strong for a hydraulic setup. Iron heads will take more spring than you will need to run. I have been told to try and keep the spring pressure below 350 at peak lift for gen 3 motor by the machine shop. Aluminum heads aren't as strong as iron being one reason, and roller hydraulic lifter being the other reason.

Get a solid roller setup like curtis was using.

Why are you using a dual throttle body setup with a single turbo?

[Superdave]

i'm using comp cams P/N 26915 with a much bigger cam than the 272. here are the specs...

Seat Load: 105@ 1.800
Open Load: 293 @ 1.200
Coil Bind: 1.140
Rate(lbs./in.): 313


this is in a gen4 engine though...

[treeZ24]

i would be looking for a beehive design spring personally.

[ezrollin]

If you are using the crane 272 cam,you should be using the springs they recommend,the stock springs are no way strong enough if you expect to get full benefit of the cam. I find it amusing that some people think they know more than the eng. who design the cam .Too much pressure causes premature cam wear,too little doesn't let the cam reach it's full rpm.

[SappySE107]

I am glad you are amused. Im not amused that you think the engineers designed the cam and the springs and there is nothing you should do to adjust for boost or higher RPM than the cam was designed for (because of boost).

I would use a beehive spring as well if you can find one with the specs that work for you. The 26915 spring coil binds too soon so you would have to cut the seats down and increase your install height, if it is 1.57".

[ezrollin]

Now that I've re read the the post I see that I didn't really get the jist of it,I shouldn't be watching the news and typing replies at the same time,my humble apology. I do have a question,what's up with the ls springs as applies to the iron head 660, I keep seeing them mention.

[geoffinbc]

That Falconor racing spring is way too big. I can tell just by looking at it. The Crane 272 cam is not that agressive and the lift is not very high. Running the Comp beehive spring is your best bet. It will control the valve and keep harmonics down. Use the comp retainer (for non LS series engines) and it will also increase the installed height. Using a hydraulic lifter is still fine and it will work well for your application.