Rocker setup, 7500 RPM SBF

[xr4x4ti]

My car is going faster then I thought it would and now I am out of gear again.

Some background. I have a turbo 327 SBF in 3700lb (with driver) AWD car running a T56 transmission.

Transmission ratios are:
2.66
1.78
1.3
1.0
.74
.5

I am currently running 255 40R17 tires at about 20 psi and they result in pretty small effective diameter of a bit over 24in.

Up until this season I was running 4.1 gears front and back and I had to shift into 5th in the 1/4 mile and I was running 128-129mph trap speeds. I wanted to get rid of the need to shift into 5th so before the start of this season I switched to 3.73 gears. I figured that would give me enough head room, plus that is the only reasonable gear ratio common between my GM front and Ford rear differentials.

Well, on my first run out without even trying I run 10:81 @ 132mph. Now I am out of gear again! I have the rev limiter set to 7000 and I was bouncing off of it at the end.

So, getting to the point, I want to rev the engine to 7500. I am currently running
Jones 226/226 cam
3/8 crane gold roller rockers
ARP 3/8 rocker studs
BTR valve springs shimmed to his recommendation
The newer Ford Motorsport high rpm roller lifters
BTR titanium retainers on the stock AFR 8mm valve stems.

I don't want to change cam and lifters. I am concerned about the 3/8 rocker studs.

Should I at least go to 7/16 rockers? Shaft Rockers? Stud Girdle?

I am using Edelbrock Performer RPM2 intake which doesn't give you much valve cover clearance. I am not sure if I can fit a stud girdle.

If I get new rockers, are Scorpions any good?

Thanks,
Tim

[hondo383]

Agree 3/8 are sketchy at that rpm...invest in some t&d or jesel and dont look back lol you are not gonna start turning less rpm in the future

[blykins]

What are spring pressures?

[xr4x4ti]

What are spring pressures?

Installed load is 155 lbs @ 1.780
Lift is .545 with 1.6 rockers

[swampbuggy]

Mr. Blykins wants to know your open pressure also.

[xr4x4ti]

Installed load=155 lbs @ 1.78in
Max Load = 359 lbs @ .544in lift

[Casper393W]

I would go for a shaft rocker system..... While I do believe a good 7/16 stud rocker and girdle would work well, your limits on the valve cover issue might put a damper on that... I know that you are turbo but let me ask you this... With that cam and intake combo are you sure that it would make power up that high?

I would run a Jesel / T&D shaft rocker system with a good thick wall pushrod. ( At least .080") 5/16... 3/8's if you have room with your heads... Having proper rocker geometry is key to realiabilty and great power out put..

I have seen pretty big power increases from going a 3/8's regular Stud mounted roller rockers to a well setup shaft system and good pushrods...

Andy

[xr4x4ti]

I know that you are turbo but let me ask you this... With that cam and intake combo are you sure that it would make power up that high?

I would run a Jesel / T&D shaft rocker system with a good thick wall pushrod. ( At least .080") 5/16... 3/8's if you have room with your heads... Having proper rocker geometry is key to realiabilty and great power out put..

I have seen pretty big power increases from going a 3/8's regular Stud mounted roller rockers to a well setup shaft system and good pushrods...
Andy

I was wondering when somebody would point out my cam/intake VS the RPM I want to turn

Yes, this cam and intake is not going to make big power at that RPM, but I still think I am better off spinning the motor higher then shifting into 5th, which instantly drops the torque by a factor of .7 . Do other people agree with this?

If I could go to something like a 3.55 gear, then I would. I am running a Ford 8.8 diff in the back and a GM 7.2 IFS diff in the front and the next gear ratio that lines up is 3.08, which I think would ruin in the street driving fun factor.

I can also start playing with boost VS RPM and MPH. I should be able to keep the torque going at higher rpm by ramping up the boost, above say 6800. If the VE is dropping like a like a rock, I should be able to crank up the boost without worries of knock.

I am also still only running 15psi boost on 93 pump gas. Next years goal is to bump it to 20psi on 93 and I have all of the stuff needed to switch over to E85. On E85, HP will not be the limiting factor, destroying my drive train will be

I going to start looking for a shaft rocker system.

[englertracing]

shaft rockers

On the ford shouldn't there be all kinds of room for big push rods?
go as big as you can like 7/16" x 0.120" or even 1/2" x 0.120"

[cjperformance]

Yes more rpm if the bottom end will handle it, avoid 5th and the tq loss and shift time loss etc.
Definitely at least go 7/16" studs/rockers , and stiffer pushrods if possible.
Are your valves up to it? Are your springs up to the extra rpm with your cam profile?

[gruntguru]

If the shift to 5th puts the engine at a higher BHP, the engine torque will be MUCH HIGHER and the final drive and tyres will see higher torque (in the same proportion as the power). Rule of thumb - always have your engine as close to peak power as possible.

Not suggesting you should shift to 5th - the shift time may be a bigger loss - just saying.

[cjperformance]

If the shift to 5th puts the engine at a higher BHP, the engine torque will be MUCH HIGHER and the final drive and tyres will see higher torque (in the same proportion as the power). Rule of thumb - always have your engine as close to peak power as possible.

Not suggesting you should shift to 5th - the shift time may be a bigger loss - just saying.

So what is faster, forgetting a gear shift, just reaching peak hp at the stripe or reaching peak at say 1000' and running the last 320 above peak but still increasing rpm?

[cab0154]

I love my steel T&Ds, but I am running a solid roller on the street and 600lb springs. Nice thing about the shafts is that the lash is super easy to set and never changes, even if you remove the rockers and put them back. but, for a street engine with your spring pressures i think its a big expense. for your setup a 7/16 stud rocker will work fine. we have had good luck with the 7/16 studs with the comp ultra pro mags, even with over 700lbs of open pressure. if you do decide on shafts, due to aluminum having cycle time, i would spend the extra $ on steel shaft rockers. but with your spring pressure pretty much any 7/16 stud mount rocker will work.

[xr4x4ti]

we have had good luck with the 7/16 studs with the comp ultra pro mags, even with over 700lbs of open pressure.

I don't have crazy high spring pressure. How does the mass and/or moment of inertia of the steel rockers compare to the aluminum? Obviously stiffness is key, but if they are a lot heavier, won't that cause its own issues?

[cab0154]

we didnt test a bunch of different rockers on it, but it got shifted at 8k for years w/o any failure or parts replacement. i really doubt you would see any difference in performance one way or another in your application no matter what rocker was used.