Rocker setup, 7500 RPM SBF

General engine tech -- Drag Racing to Circle Track

Moderator: Team

xr4x4ti
Member
Member
Posts: 65
Joined: Wed Jan 23, 2013 1:20 pm
Location: Minnesota

Rocker setup, 7500 RPM SBF

Post by xr4x4ti » Tue Oct 09, 2018 4:35 pm

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
Pro
Pro
Posts: 225
Joined: Sat Mar 03, 2007 1:01 pm
Location: massachusetts

Re: Rocker setup, 7500 RPM SBF

Post by hondo383 » Wed Oct 10, 2018 6:44 am

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
Guru
Guru
Posts: 2031
Joined: Mon Aug 27, 2007 9:59 pm
Location: Louisville, KY

Re: Rocker setup, 7500 RPM SBF

Post by blykins » Wed Oct 10, 2018 6:55 am

What are spring pressures?
Lykins Motorsports
brent@lykinsmotorsports.com
www.lykinsmotorsports.com

xr4x4ti
Member
Member
Posts: 65
Joined: Wed Jan 23, 2013 1:20 pm
Location: Minnesota

Re: Rocker setup, 7500 RPM SBF

Post by xr4x4ti » Wed Oct 10, 2018 10:05 am

blykins wrote:
Wed Oct 10, 2018 6:55 am
What are spring pressures?
Installed load is 155 lbs @ 1.780
Lift is .545 with 1.6 rockers

swampbuggy
Expert
Expert
Posts: 796
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: Rocker setup, 7500 RPM SBF

Post by swampbuggy » Wed Oct 10, 2018 10:41 am

Mr. Blykins wants to know your open pressure also.

xr4x4ti
Member
Member
Posts: 65
Joined: Wed Jan 23, 2013 1:20 pm
Location: Minnesota

Re: Rocker setup, 7500 RPM SBF

Post by xr4x4ti » Wed Oct 10, 2018 11:10 am

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

Casper393W
Pro
Pro
Posts: 401
Joined: Wed Jul 06, 2016 7:18 am

Re: Rocker setup, 7500 RPM SBF

Post by Casper393W » Wed Oct 10, 2018 4:42 pm

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
Member
Member
Posts: 65
Joined: Wed Jan 23, 2013 1:20 pm
Location: Minnesota

Re: Rocker setup, 7500 RPM SBF

Post by xr4x4ti » Thu Oct 11, 2018 11:32 am

Casper393W wrote:
Wed Oct 10, 2018 4:42 pm
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 :D

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 :o

I going to start looking for a shaft rocker system.

englertracing
Guru
Guru
Posts: 1117
Joined: Thu Sep 29, 2011 8:55 am

Re: Rocker setup, 7500 RPM SBF

Post by englertracing » Thu Oct 11, 2018 4:21 pm

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" :evil:

cjperformance
Guru
Guru
Posts: 3117
Joined: Tue Aug 19, 2008 7:20 am
Location: South Australia

Re: Rocker setup, 7500 RPM SBF

Post by cjperformance » Thu Oct 11, 2018 11:18 pm

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?
Craig.

gruntguru
Member
Member
Posts: 157
Joined: Fri Apr 10, 2015 7:56 pm

Re: Rocker setup, 7500 RPM SBF

Post by gruntguru » Fri Oct 12, 2018 3:04 am

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
Guru
Guru
Posts: 3117
Joined: Tue Aug 19, 2008 7:20 am
Location: South Australia

Re: Rocker setup, 7500 RPM SBF

Post by cjperformance » Fri Oct 12, 2018 5:50 am

gruntguru wrote:
Fri Oct 12, 2018 3:04 am
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?
Craig.

cab0154
Pro
Pro
Posts: 212
Joined: Sat Nov 12, 2011 10:09 am
Location: North Texas

Re: Rocker setup, 7500 RPM SBF

Post by cab0154 » Fri Oct 12, 2018 8:06 am

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.
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.

xr4x4ti
Member
Member
Posts: 65
Joined: Wed Jan 23, 2013 1:20 pm
Location: Minnesota

Re: Rocker setup, 7500 RPM SBF

Post by xr4x4ti » Fri Oct 12, 2018 10:38 am

cab0154 wrote:
Fri Oct 12, 2018 8:06 am
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
Pro
Pro
Posts: 212
Joined: Sat Nov 12, 2011 10:09 am
Location: North Texas

Re: Rocker setup, 7500 RPM SBF

Post by cab0154 » Fri Oct 12, 2018 10:44 am

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.
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.

Post Reply