Maybe try another shop/dyno. Shouldn't guys tuning your car be able to tell you why the thing flattens off so soon? Puzzled should not be the acceptable answer.

Are you running an opti?

-Scott.

 

Here's what Jegs has as far as spec's on those springs.
Comp Cams #249-987-16

Dual Valve Springs
Outer inside diameter: 1.070"
Inner inside diameter: .697"
Seat load: 121lbs @1.800''
Open load: 343lbs @1.200''
Coil bind: 1.150''
Rate: 370lbs/in
With damper
16 per package

My spring kit is what I've heard called 'Big Block Beehive'. They are a single spring design and have 165lbs seat pressure, and 600lbs on the nose of the cam based on his designated install height.

 

Dave,

Nice info. Let's consider a 2.00" IN valve which has 3.14 square inches of area (well maybe not on the backside but close enough for representation). At 19psi of manifold pressure => 19*3.14 = 60lbs.

If 120lbs closed works for NA then you may need as much as 120+60=180 with that much boost.

600lbs over the nose? Are you sure?

Compared to the 987 you list below you have 36% more force at the seat and 75% more force open. Why do you need so much more on the nose. Obviously there is inertia of the valve to consider.

-Scott.

 

I asked Bret the same thing. It turns out he's referring to force the cam sees thru the 1.6 rocker ratio so it's actually 4xx lbs measuring the full open pressure, but multiplied thru the rocker ratio. it's over 600 lbs. Here's a cut and paste from my conversation with Bret about this topic..
Well.... you have to think about it the way I do.

400lbs open at the spring x rocker arm ratio of 1.6:1 = 600lbs at the lifter

Look at a LS7, 1.8:1 ratio and 400lbs open = 720lbs at the lifter

I've seen much worse than that.

Bret
----- Original Message -----
From: "Dave Wilson" <dave@gloproserv.com>
To: "'Bret Bauer'" <bret@bauer-racing.com>
Sent: Monday, November 19, 2007 2:47 PM
Subject: RE: Bret-Need a Turbo cam


> 600lbs on the nose on a Hyd roller? Wow.... I didn't know a hyd lifter
> could support that kind of pressure.
> Dave
>

 

Ahh, Ok. But we need to know force on valve here for Funky. Just so were apples to apples:

987
Closed:121
Open:343

Bret/Dave
Closed: 165
Open: 400 (400 at 1.6 is 640 BTW)

So I guess thats 36% more closed and 17% more open.

If I were Funky I would take as much data as I had and take it to the Advanced section.

 

Update: Just got home from the dyno. I messed with the tune a little bit and I was able to pick up 100 more hp. The bad news is its still running out of fuel and the fueling tables are maxed. I have reached the limits of the stock pcm it seems.
This is on 91 octane.

http://www.youtube.com/watch?v=BwJfOupomDs

 

That is a bad *** torque curve. Nice job. You are making 750hp at 5500 rpm if I'm reading it right. Long live the F1A!!!! What pulley combo are you using?

 

I'm running 3.40/7.65 I really need to figure out my fueling issue so I can see the full potential!

 

Are you running a methanol kit? That would probably give you the additional fuel you need. Are you sure you are not getting belt slip?

Steve

 

I have an AIS stage 2 kit running 100% meth. I don't think the belt is slipping, boost comes on linear and holds and there isn't any belt dust anywhere.

 

IMHO, your running out of fuel line now. Your PCM will fuel the daylights out of that thing assuming you have the volume to go along with it. The parallel dual pumps will get you there, but at that HP level (flywheel), trying to push that volume through a small line with a series rail setup isn't gonna work too well. Upping to an -8 AN line and paralleling the rails will give you tons of fuel, and i would guess at that point you'll be pulling all kinds of fuel back out of your PE tables. Just really quick though, you do have a good new fuel filter on it, right?

Ken R.

 

Have you tried to scale your injector flow rate by 10% and then also Scale your VE tables so you then have 10% more room on top to add fuel? With the 2Bar setup I've been using I've done this a couple of times (E85 needs LOTS of fuel) and it works pretty good.

 

Looks like my next purchase is going to have to be some bigger lines then. I put a new fuel filter on when I did the pumps earlier this summer.
I didn't change anything in the tune other than the PE table, I am very new to tuning.

 

Those are some sick numbers, finally putting down the kind of numbers I would expect from a F1a LT1 Big fuel systems require you to hold onto your wallet

 

my t-trimed 383 making only 600rwhp was having fuel and tunning issues until I put larger lines. I went from the tank with a gravity feed into an aeromotive pump to the front then into some custom rails into an aeromotive fpr and used the stock fuel line as a return. I also disabled the stock fuel pump but left it in the tank so my gauge would still work. Just because you have the fuel pressure doesn't mean you have the volume so safely operate at that kind of hp.