Hi Guys,

I am working on a 421 SBC EFI project. At this pont, just a planning phase.

The goals are a Torque peak around 4800 RPM and a Horse-Power peak around 6000 RPM. I think this would make a great street motor!

Been running many Dynomation simulations to figure out the Cam requirements.

Here is the build idea. A 93 Octane pump-gas motor.

Bore=4.155.
Stroke=3.875
CR=10.75:1.
TPIS Miniram : 1206 Ports & Internal Porting to support a 421.
TPIS 58mm Throttle Body.
AFR220 Eliminator Heads.
DART SHP Block.
Hydraulic Roller Cam.

I have not yet decided on the Cam Lobes (XFI, XE, etc.). Presently run XFI on the street. But I only put 2000 miles on the car per year. The new Comp QXI Lobes look interesting. They are a litttle easier on the valvetrain when compared to the XFI equivalent.

Since I have data for the XFI Lobes, the early simulations were run based on XFI.

So far, I am looking at the following options.

XFI : 236/242 @ 0.050, LSA=113.

XFI : 236/236 @ 0.050, LSA=112.

The Centerline Angles are interesting.

ICL : Intake Centerline Angle.
ECL : Exhaust Centerline Angle.

XFI : 236/242 @ 0.050, LSA=113 : Approach.
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The best Torque (543) and Horsepower (549) were obtained with a 106 ATDC ICL and 120 BTDC ECL.

In the past, the ICL range that I have seen is between 104 and 114 degrees and the ECL range is 118 to 110?

Here are the valve events: seat timing.
IVO = 39.0 BTDC
IVC = 74.2 ABDC
EVO = 88.7 BTDC
EVC = 32.8 ATDC

With 1.6:1 Roller Rockers, the lift (I/E) is 0.581/0.578.

The expected Dynamic Compression Ratio is 7.95:1.

If I changed the ICL to 109 (more conventional) degrees, the performance is as follows.

Torque Peak = 537 @ 4800.
HorsePower = 550 @ 6000.


Valve Events:
ICL = 109
ECL = 117
IVO = 36.0 BTDC
IVC = 77.2 ABDC
EVO = 85.7 BTDC
EVC = 35.8 ATDC

The expected Dynamic Compression Ratio is 7.7:1.

With the conventional ICL, I lost Torque due to the later IVC.

Opinions?

XFI : 236/236 @ 0.050, LSA=112 : Approach.
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Torque = 543 @ 4800.
HorsePower Peak = 543 @ 6000.

Valve Events:
ICL = 106
ECL = 118
IVO = 39.0 BTDC
IVC = 74.2 ABDC
EVO = 84.0 BTDC
EVC = 32.8 ATDC

The expected Dynamic Compression Ratio is 7.95:1.

Comments on this option?

Thanks guys.

Best Regards,

Bruce

 

I also have a 400 stroker with AFR235s and a mini ram with a mono blade T-body.
My cam is a solid roller with right under .700 lift and 260ish dur @.050 on a 110 (I think) It slobbers on itself until about 3-3500rpm but still makes more power than a stock motor by far.
It drives just fine for me. I drove it 6hrs one way with stock tune and 24lb injs just to break it in.
It also went 150mph (with stock tune on my wedding day) with only 2hrs of run time on the fresh motor. It did it effortlessly.

 

Nice build. You may want to bump up the compression as you still have a little wiggle room on the dynamic compression. If you havnt bought any parts yet pm me Im putting together that combo now and cam steer you in the right direction to somone who has done more 421 combos than anyone I can recollect. The Xfi lobes may be a bit taxing on any spring but the extreme energy with the .050 duration 236/242 roller is a good pick as well. If your going to use 220 afrs get the comp ported versions. Good luck