ORIGINAL: 5spd GT

There is a 23% difference between the ls1's 346 CI, and the mustang's 4.6L, 281 CI engine.

Ls1's average in the +/- 300 rwhp range (depending on a few factors), compared to the 3V 4.6L that puts down 265-270 rwhp.

58.6 rwhp per liter for the 4.6L.
52.6 rwhp per liter for the 5.7L.

So does anyone want some more information on the 346 Ls1 engine? Comparing it to the 347 is a better comparison of course, but I consistently see a little better HP per cube on the ls1, compared to the 347.

Here is some information that I got off-hand...

I am a big fan of ls1 engines and the potential they have. Some get by with 500rwhp out of their 346 N/A combinations.

The ls1 platform is great, because GM kept exploring it past the Ford pushrod days in the early 90's.

The ls1 346 (not 350) has a 3.62" stroke and a 3.90" bore, which aims more of a square design than a 347 stroker of 3.4" stroke and a 4.030" bore.

The ls1 features a 200cc runner volume head, with 2.00" valves on the intake and 1.55" on the exhaust.

Those head ports are also a taller design, which also allows for a better fuel injector placement sprays the fuel on top of the intake valve, while a 302 design sprays it near the end of the lower intake runner ports.

Also the ls1 heads have 15* valves, compared to 20* valves of a standard 302 design. A shallower valve angle (15*) becomes less "shrouded" by the cylinder wall with that angle approach. It also puts the intake valve closer to the piston center, which in turn allows for a larger intake valve, i.e., 2.00" on the intake side.

The ls1 heads also come with 8mm valvestems and lighter valvetrain, as opposed to a 302's standard size of 8.73mm valvestems. The ls6 heads are even better, down to sodium filled exhaust valves

Airflow Chart for stock LS1 Heads:

Lift Value (in.) - Intake Flow - Exhaust Flow

Inches - CFM - CFM

0.100 - 067 - 052
0.200 - 122 - 097
0.300 - 178 - 133
0.400 - 215 - 156
0.500 - 219 - 170
0.550 - 223 - 176
0.600 - 227 - 180

As you can see, the stock aluminum ls1 heads flow quite close to an AFR 165cc head from the mustang world, just losing a little bit in the exhaust portion (AFR > LS1).

The ls1 block is a 4 bolt aluminum block with a 9.24" deck height as opposed to the 302's deck height of 8.20." The ls1 engines come internally balanced from the factory.

The pistons coupled with the 67cc chamber is already getting the ls1 to around 10:1 compression, because after all more stroke, coupled with a taller deck height helps compression ability.

Back up top, you have a plastic composite intake (much like the 4.6L) with a 15" runner, and 536 cubic centimeters of volume, which all makes up the cross section. The intake flows in the 265-270 CFM range.

The cam specs are smaller in "our circle," as stated. But, they are billet steel and a larger base circle cam (larger lobe area) from the factory, which is great for stability at high rpms with some 1.70" roller rockers sitting on top of the heads.

1998 - 2000 LS1

202*/210* Int/Exh @ 0.050" Duration, 0.496" / 0.496" Lift, with a wide Lobe Seperation Angle of 116*. That gives it a broad torque curve.

2001-2002 LS1

197*/207* Int/Exh @ 0.050" Duration, 0.467" / 0.479" Lift with that same LSA of 116*.

With larger flowing heads, you do not need a "larger" camshaft.

Large Heads = Small Cam
Small Heads = Large Cam

These are generality's but remain quite true in most circles of designing a combination.

This just helps us see what "we" are up against.

It is not to hard to see why a nice longtube swap, coupled with a camshaft swap, can put these ls1 platforms well over 400rwhp.

There is not much room for stroking the engines to much, without getting another block with longer cylinder skirts, or sleeving the existing block for a little more room to play with.

The ls1 pushrod is a beast for OEM, but the modular engine line has it's pros as well.

An overhead engine, like the 4.6L engines, allows lighter valvetrain weight and mass which is great for increasing hp/tq per Liter of engine size.

A 4.6L pushrod would make less horsepower per liter than a 4.6L OHC (Single or Dual). Also, Ford knew that going overhead cam was the best way to be on the heels of cutting edge. Putting the cam "on top" allows them to use, 4 valves per cylinder like in the DOHC engines that came in the '96-04 Cobras. Greater rpm potential and stability. The only expense that I see with going this route is increased size needed. Although the engine weights are similar between the 5.0L pushrod and 4.6L SOHC/DOHC.

The 4.6L intake weighs 11 lbs from the one I weighed, while 5.0L intakes weigh in the 40-low 50 pound range. A single head is 43 pounds WITH a camshaft and full valvetrain, because they are aluminum.

They all got potential to make great power per cube.

If you are going to compare the 5.0L to the 4.6L, it is like comparing a 331 cube, to a 302. That is a 5.4L to a 5.0 (4.9L).

I wish I had more time...

ORIGINAL: stanggang1892

also show me a 4.6 that will have 350 rwhp with full exhaust... my TA is over 420rwhp with full exhaust, cam and intake manifold... the Ls1 is a far superior motor to the 4.6 or 5.0... end of story

ORIGINAL: bikeboy587

well of course stroking our engines is a usual must...no replacement for displacement. 347vs346 just makes is a more fair playing field. i'm gonna be using my gas to take out some stock el es juans this summer and hopefully some full exhaust ones too

ORIGINAL: ncplaya88

well what about the 351 in a fox compared against an ls1. I know a stock fox 351 swap still could not beat a stock ls1. What more would it take to overcome the ls1????????????

ORIGINAL: bobbyward

yeah you never hear the 305chevy boys braggin about whipping a 302 mustang do you ? lets always compare apple
to apple, a ls1 to a 302 just isn't a fair comparsion anyway you look at it unless you own a gm .................