So, I have a 99 LS1 swapped into my C10. Put it on a Dynojet dyno this morning at LS Fest West. Did several passes in third gear and got 250-270HP. Seems a little low. I'm trying to figure out where my problem is. I'm thinking I may have the cam degreed wrong (maybe the wheel slipped when I installed?). Going to pull timing cover off and verify it's not a tooth off somehow as soon as I have a chance.

Important info:

33" tall tires
4.11 gear ratio
Truck 12 bolt
4L80E with 2K stall (need higher)
99 LS1
Pac 1218 springs
Elgin 238/242 112LSA .595 cam
Truck intake & injectors
No MAF (Speed density OS)
1 3/4 shorty header with free flow dual 2.5 exhaust.
4" free flow intake (did a pull with no filter, no change)

I'm think even with the drivetrain loss from big tires and 4L80e I should be around 350-380. Peak power is around 4500. AFR during runs was 12.8-13.1. Changing timing from 24 degrees all the way to 34 had almost no obvious affect.

Truck runs great with no issues (have put about 5K miles on it since swap)

 

With it peaking at 4500, something really is off. I'd definitely start with the cam

 

 

Which truck intake?

Do you have a copy of the dyno sheet?

 

were other people getting low results on that dyno that day also?

 

Early style (03-06 I think), not the good one (07+)

No, Other LS1s were putting 375-400 down (what I'd expect on this).

I was thinking maybe a weak fuel pump would do this or maybe too small of injectors but wouldn't both of those make it go lean?

 

 

Yes, you'd see that in the AFR

 

That's a lot of cam for a truck on 33s...

 

That's what I'm thinking...+something else is up too, weird graph. OP did you ever check the cam degree?

 

 

Looks like I need more injector. I would think this much fuel would make more power.

 

 

You do need bigger injectors but that is not the problem since your AFR stayed good. Big tires are heavier and change your gear ratio plus a big truck that is why people are surprised at you cam size. That is a good size cam for a 3500 lb camaro. That cam should peak around 6500-7000 rpms so something isn't right.

 

I agree that the tires are heavier but not -100HP heavier. I didn't even lose 50HP with 39s on my other truck.

The 4.11s are a little tall for a 33" tire, but that is what the truck came with in the stock 12 bolt. I will be installing a 9" with 4.87 gears soon.

I have to weigh the truck since for the converter builder, and I will let you guys know what it weights but I don't think it will be over 3,800lb.

The cam wheel must have slipped advanced when I put the cam in or something... I can't think of anything else that would cause this without having other obvious symptoms.

 

 

Honestly, I would take my vehicle to a place that doesn't spit out bullshit dyno sheets. Horsepower compared to wheel speed is hilariously useless.

With that said, you currently have a camshaft that is trying to move upwards the powerband of an engine that is breathing through an intake designed for low rpm power. So, even if you have the camshaft degreed correctly, you're still stuck with a camshaft demanding more air than the intake can supply.

 

I agree, I just picked up a complete TBSS intake to install when I check the cam. However I've seen truck intakes flow to 6900RPM in other applications so I doubt that is the only issue.

I have several hours dyno time booked nearby but I'd rather things be right mechanically before I waste that. The dyno runs shown were free at LSFestWest.