Did some valve spring calculating

gnxtc2 · Nov 28, 2013

I did some valve spring calculating before I do my swap.

I have Comp 910 sitting in the box.
Specs-
92lb @ 1.850
300lb @ 1.350
coil bind - 1.280 (1.330 max lift with .050 safety margin)

Factory specs for valve springs:
71-79lb @ 1.833
225-249 @ 1.352
Gives us a total lift of .481

The stock cam lobe lift is .253 on both Intake and Exhaust

So to get rocker arm ratio - .481/.253 = 1.90 rocker ratio (If I did it right)

So we can agree that max lift in the 7.3 is .481?

After countless hours of search on PSA and PSN, most are installing the 910springs in 1.750 - 1.780 range.
1.750 - .481 = 1.269 (past coil bind)
1.780 - .481 = 1.299 (not coil bind but not within .050 for coil bind)

By my calculations, the Comp 910 are at coil bind unless installed at factory spec or at 1.811.
99lb @ 1.833
107lb @ 1.811

Someone please correct me if I calculated this stuff wrong.

Thanks

Billy T.
[email protected]

kanuck15 · Nov 28, 2013

This all baffles me, but I want to learn about this stuff. I just did 910s on my 7.3 and am paranoid about install height since I didnt have a fancy tool. I had to measure it out the hard way

TyCorr · Nov 28, 2013

Let me ask, not necessarily to the previous two posters, but is.there a difference in the trucks performance after the springs and p.rods are done? Does it run smoother, quieter, or better?

Sorry for a dikc queztion but Ive always wondered.

kanuck15 · Nov 28, 2013

no idea, mines on an engine stand. This is just something I figured I aught to do while its out of the truck

Petro · Nov 28, 2013

Just installed 910s in my truck, I haven't noticed any difference but I didn't figure I would either.

powerstrokenstang · Nov 28, 2013

Factory rocker ratio is 1.6 not 1.9.

gnxtc2 · Nov 28, 2013

powerstrokenstang said:
Factory rocker ratio is 1.6 not 1.9.

Where did you find this info? I've been looking for hours on the web.

If the rockers are 1.6 x .253 = .404 max lift

Then 1.750 - .404 = 1.346 (well within the acceptable range)

I took the factory published specs and calculated from there.

Thanks

Billy T.
[email protected]

powerstrokenstang · Nov 28, 2013

Was told by someone forget who. Matt or carson prob.

m j · Nov 28, 2013

measure valve lift
I cant see them having .480 but my google mojo has failed to find the spec

TyCorr · Nov 28, 2013

powerstrokenstang said:
Factory rocker ratio is 1.6 not 1.9.

Should properly setup aftermarket valve springs change anything noticeable by the user?

@petro-thanks for sharing.

littleredstroker · Nov 29, 2013

I went 1.750 on mine...

Smoked a bit
Turbo lit
That was it

powerstrokenstang · Nov 29, 2013

TyCorr said:
Should properly setup aftermarket valve springs change anything noticeable by the user?

@petro-thanks for sharing.

You would think but ive never actually felt anything on mine just knew there was no more piston contact lol.

littleredstroker · Nov 29, 2013

TyCorr said:
Should properly setup aftermarket valve springs change anything noticeable by the user?

@petro-thanks for sharing.

I would say no. It's a hard part. You don't notice any performance with billet rods. Push rods, coated pistons, billet shafts.. its just the peace of mind.

Smoked a bit
Turbo lit
That was it

97f350stroker · Nov 29, 2013

I also installed mine at 1.75. No notice in performance or smoother running just the piece of mind that I'm not floating a valve and smacking pistons.

kyle43335 · Nov 29, 2013

valve spring keep the valves shut when they are suppose to be period.

After you increase boost, and drive pressure that overcomes the seat pressure (factory psi rating of stock springs) of the original springs.

that increased pressure can push the valves open, or at the very least not allow them to close quick enough causing valve float, and or piston contact with the valves.

TyCorr · Nov 29, 2013

Got ya. I didnt know if valves got sloppy enough that you could tell a difference in some way.

I knew it was to make sure you didnt suck.a.valve open. And to stop the pistons from headbutting the piston.

Thanks for a clean answer from about four or five of you! Much appreciated.

JD3020 · Nov 29, 2013

I think mine are at 1.74 or 1.745? All i remember is that there was almost no wear so i was putting a .060 shim right on the factory specs, or something like that. Hell its prolly been 9 or 10 months since i did it all.

MossBack · Nov 29, 2013

I did mine as a peace of mind. I still haven't had the opportunity to run it up to 5,00 rpm either. I have had a few 3900 shifts that seemed scary... I need to build a transmission before i go for 5k shifts...