I only managed to put down right at 400 HP to the wheels during a dyno tune. This was a LS1 to LS3 motor swap into a 1999 4th Gen F-Body.

• Freshly rebuilt LS3
• BTR Stage 2 Cam & supporting valvetrain (Specs: 225/238 .612"/.585" 113+3)
• Yank 3600 Stall
• Built 4L60E
• Stock LS3 Heads
• Stock LS3 Injectors
• Speed Engineering Headers, Hi Flo Cats, Speed Engineering True Duals

Choke Points:

• Stock F-Body Fuel Pump
• Stock F-Body MAF
• 76mm FTP LID

The shop felt my stock fuel pump (aprox 4 years old as is not the original factory pump but a replacement) was good enough to handle 500 whp so they recommended against installing my Racetronix unit. The shop was also unable to use the 100mm MAF I provided them because they needed a conversion harness and of course without the MAF, my 98 MM lid was also not installed.

During the tune we monitored fuel pressure, it remained between 61 and 62 PSI. The injector duty cycle was 'okay' per the tuner. He stated that it was running too lean at the top end and he was afraid of pushing it further.

It drives decent but my 6th Gen still feels faster and that kind of disappoints me given how much I invested in the swap. I was certain a cammed LS3 would put me close to the 500 WHP range

 

Unplug the maf, straight pipe the bigger lid to the throttle, and run in SD. Surprised the shop did not try that simple thing.

What was map reading at wot? Also what is your exhaust setup? Most of the cam only ls3 in the 500 range run much better exhausts than the f cars.

 

My tuner didnt think it had much more left. He didn't give me specifics other than it was running lean toward the top end.

Exhaust setup are Speed Engineering Headers, Hi Flo Cats, Speed Engineering True Duals.

 

Time for a new tuner....sometimes these guys just arent into it. It becomes just a job for them. You need an enthusiastic tuner! IMHO

 

The tuner is a vendor here. I don't exactly have cash to throw away at tuners just because they aren't into it.

 

What specific questions should I ask my tuner to get to the bottom of what is going on when I go back? Some say the stock F-Body pump will handle up to 500whp, others say it will not.. but given fuel pressure was there and the duty cycle was good it seems like even on the stock pump I should beable to make more power.

 

You won't see 500rwhp without a bigger cam and heads if you're running an A4 transmission. Just ain't happnin. 400 is low for your combo though. 440ish if probably where you should be equipped as you are.

 

LS3 stock compression, 225 intake duration cam, I'd guess about 430whp to 440whp in a stalled auto.

The stock MAF & 76mm Lid are definitely hurting.

Seen many fresh stock fuel pumps do 450whp to 475whp. Lean up top? What was the injector duty cycle?

I'd want to try with the 100mm MAF & 98mm lid and a new tuner. Or SD no MAF and 98mm lid and a new tuner.

 

Noted... what do you think is holding me back?

 

You need more camshaft.

 

Is mine so weak as to put me down by 50 - 100 rwhp of the average cammed LS3?

 

With the proper bolt-ons and a dead-on tune, you'll end up somewhere short of 450hp to the wheels.

My guess is mid-430's....maybe low-440's on a cool day.

KW

 

Got it. Do you think my fuel pump is holding me back or is it more my MAF and LID?

 

The cam has plenty duration to get 480-500whp but you’re missing the rest of the combo for it.

 

Makes sense, what else do I need?

 

You should be in the 430's for HP to the wheels.

A stock LS1 fuel pump and 76mm LID are a problem.

Also....didn't see you mention anything about header tube size/length or exhaust tube diameter. I would recommend the largest diameter long-tube headers made for your car, and 3" cat-back exhaust......if possible.

Ported heads and a ported/rod-modded intake should be good for at least another 40 HP.....particularly if the compression ratio is increased to about 11.1 to 11.3:1

My heads/cam LS3 in my impala puts down mid-490's to the wheels through a 4L60E trans....but I have a 2 1/2" exhaust that holds me back a bit.

KW

 

Header size is 1-7/8" and 3" pipe per bank on the true duals.

I'm going to tackle the fuel pump soon, I intend on replacing it and the LID/MAF at the same time as to avoid multiple trips for a tune

 

If you can get info from tuner or logs -- what is your map reading at wot? If it matches ambient, then I would go to the fuel pump. If it is not matching ambient - example 90 kpa vs 100 kpa ambient, the problem is in the inlet tract. You can get this info for free to prevent unnecessary work.

Your cam is plenty to make power. The ls3 heads are plenty to make power without porting. 400 rwhp is cam only Ls1 territory. My bet is the motor Aint breathing because it is breathing through a straw.

 

If it was leaning out you need more fuel pump. go speed density with your bigger lid.

 

What about that stall converter?
These can eat up the power too.
We can't tell how efficient/inefficient it is.