Sixslow

I recently built an LQ4 6.0 in a 2002 Silverado. My 0-60 time is 2 seconds slower and the quarter mile is 4 seconds slower. I don't understand how I can completely rebuild an engine and beef it up and it run slower. I think I made the mistake of installing a stock stall. The website said that cam didn't require one but I think I'm going to get a 2800 or 3000 stall. And yes the truck has been tuned. By a reputable tuner at that. He also did my previous tune. This weekend a valve stuck the day after I got it tuned and the piston came up and bent it. Also broke the pushrod. I took the heads back to the machine shop and they said all the intake valves weren't given the right clearance. Could that be my performance problem??? Truck idled and ran great. Even got good gas mileage. The performance just wasn't good.
214/222 cam .585 lift 155 LSA
7.375 pushrods
Dual valve springs
Stainless steel valves
Heads milled .020
28lb injectors
Bored .030 over flat top pistons
Tuned
Longtube headers
Stock stall (probably part of my problem)
P.S. cam company said the pushrods shouldn't be too long even with the heads milled.
Any advice would be great!

stockA4

With that mild of a cam you don't really need a looser converter. I'd get the engine sorted first before I did anything else

Sixslow

Okay that's what I originally thought. But alot of people said just because it didn't require one doesn't mean it wouldn't like to have one. But do you think the sticking valves hindered my performance that bad? They didn't give them enough clearance. I don't get how you can build something up and it be slower than stock. It's running 10 second 0-60. Was running 8.0 with a 300k mile engine with only injectors and a tune

stockA4

Any cam will benefit from a looser converter, even a stock one. Still, my car went .5 tenths faster with a mild cam still running the stock converter. Something is still wrong with the engine or the tuning. I wouldn't touch the trans until you've got it running as good or better than before. Have you had it on a dyno?

Sixslow

No I haven't. I probably will have it dyno tuned next time. I mean it runs normal and doesn't miss or sputter or anything. Gas mileage is better than its ever been. Only clue I have is the valves not sealing properly. They told me the intake valves all had to be redone. Still haven't got the heads back yet though. I'm just trying to find possibilities. Cam is timed correctly and injectors are also big enough from what I've been told. And they're at 70% duty he said

stockA4

Get it back together and let us know how it runs. Good luck!

ss454327

iTrader: (10)

Who built the motor? What heads and who worked them?

A.R. Shale Targa

iTrader: (2)

what Pistons ???

KCS

iTrader: (20)

Post your time slips, before an after. Include MPH.

My stock Trans Am ran almost a full second slower with nitrous. Gained a lot of MPH though...

thunderstruck507

iTrader: (18)

also if you aren't factoring in DA then that could be the main problem

My car has varied as much as .5 from fall to summer

Sixslow

I built it. The machine shop assembled the heads. Valves , Springs, and all. They're 317 heads. They said all the intake valves were real tight and sticking.

Sixslow

.030 over flat tops. I'm unsure of the brand. Stock stroke and crank though

A.R. Shale Targa

iTrader: (2)

Some cheapie brand X Pistons move the wrist pin which pulls the piston down creating huge quench numbers on an Undecked block. Lower than desired compression ratio and perhaps a cruddy timing chain (retarded cam) with a stock converter can all lead to weak acceleration in a heavy vehicle

Sixslow

So you don't think the sticking valves have anything to do with it?

A.R. Shale Targa

iTrader: (2)

Wouldn't they be bent/broken cuz if they stick, a non relief flat top will smack them

Sixslow

One of them got smacked last weekend and bent. But when I took the heads back to the machine shop they said all the intake valves were tight and not given enough clearance. But I had been driving it and letting it run for a little while and never had a problem of them touching until last weekend. That's how I know they were sticking in the first place. So would them sticking and not seating properly cause me to lose that much performance?

madmike9396

iTrader: (29)

How are you calculating your 0-60 times

Sixslow

EDGE CTS monitor

A.R. Shale Targa

iTrader: (2)

Rare that it would be an intake valve. That usually points to an oiling/seal issue. Most times the exhaust valve will gal/stick cuz it operates so much hotter and expands more

Sixslow

See that was the thing. They gave a little more clearance for the exhaust for that specific reason but didn't touch the intake valves. And the intake valve on cylinder one was the one that stuck and got bent. And they also admitted to all the intake valves not being given enough clearance. So that's my only lead on my performance problem because I can't find any abnormalities wrong with the motor. Cam is timed properly too. I can't find anything as to why this motor is slower than it was before the rebuild. Could it also be a possible this engine is still pretty fresh and not loosened up yet?