Originally Posted by That_Red_8.1
this hurt to read before coffee
this hurt to read before coffee
Idk what more i can say. It ran like a beast one time even with wrong injector data ripping 2nd gear burnout down to 2500rpm prooving that my setup isnt as bad as you keep saying. Now it pop in the intake and barely move at any rpm or tps from . please guys stop telling i need to buy 5.13 gear and 4000stall converter on a daily to get it move when it already move . i repeat
-65 psi fuel pressure under load too
-8x good 38lb injector
-8x good coil
-8x new ngk 8mm spark plug
-8x tr55gp plug
-2-3% leak on all cylinder
-180psi of compression on 8
-new intake gasket no vaccum leak
-new map, cam, crank, knock sensor
-good ground and 12v
-no resistance on any wire on the harness
I love mine. I would rather have a good converter than deeper gears in a state with 80-85 mph speed limits. Converter can be locked up in 2nd gear at light throttle at 20-25 mph. Converter stalls 3K in my Express van with a 4L85E, 3.73s and 30.5" tall tires. SBC 383 makes ~520 tq @ 3,700 rpm. With a 3K converter, touch the throttle and it gets up and moves for being 7,000 lbs. At light throttle around town it drives almost stock like.
Last edited by Fast4.7; 3 Days Ago at 02:20 AM.
My 2003 ECSB 5.3L truck needed a 4.30 gear, 3,600 rpm converter on 28" tall drag radials to run strong with the STOCK cam. With the stock converter and 3.42s it was a DOG and it had a 4L60E. It ran like 10.30s with the stock gears, stock converter, and stock rubber. 8.90s with gears, converter and radials. Both times were tuned with thorley tri-ys, 2.5" high flow cats and a 2.5 to single 3" Y-pipe exhaust using a Vibrant merge Y.
My 2006 Hemi Ram had P305/50R20s that were ~32" tall, 4.56s and a 3,400 rpm converter with a 212/212 @ 0.050 cam to get it rolling smartly. Truck was a DOG with the stock 5.7L, 3.55s and P275/60R20s. I put down 285 whp and 301 wtq with headers and a tune on that truck and it was still a dog. Ran like mid 9s in the 1/8 with the stock cam, converter and gears. Small torque cam, converter and gears knocked a full second off the 1/8 mile. Made like 350 whp and 370 wtq with the cam upgrade.
Being able to do a burn out with a gutless 4.8L proves nothing except you need better traction.
You have a BAD mismatch between engine displacement (short stroke & low compression 4.8L has ZERO torque even with the stock camshaft), camshaft timing events, torque converter stall speed, and gearing. True dual 3" exhaust is not helping anything either as it is killing even more low-speed torque due to lack of scavenging.
There are also atleast 3 different stock stall speeds for a 4L80E. The Big Block/Diesel is like 1,200 rpm. The small block gas unit is like 1,600 rpm. The 4.3L V6 is like 2,000. All numbers above are approximate values behind a stock 4.8Ls torque output.
I drove a new Uhaul Savana cargo van with a 4.8/4L80E/4.10s years ago. It could not get out of its own way empty and even slight grades had it kicking down to 2nd to hold 70 mph uphill on the interstate. Fully loaded on the way back home it could not even maintain 70 mph uphill and would slow down to 60 mph with a 75 mph run at the hills. Governed at 75 mph or I would have hit the hills even faster at WOT. That driveline was absolutely gutless.
Last edited by Fast4.7; 3 Days Ago at 02:18 AM.
Ok so reading what you wrote, it ran great before and it had a back fire in the intake and now runs terrible.
Is this correct to what you are writing down?
If yes, to me that is not tune related, but something mechanical.
I'm still curious about 65psi fuel pressure on a stock GM regulated setup. If the pump is overloading the regulator to higher pressure than it's supposed to have, that just looks like a problem waiting to happen. Is that not supposed to be a 58psi system?
its backfiring in the intake under load especially from a dig and absolute no power even at high rpm. No weird noise from the engine; good compression leak test, no ptv, no metal shaving, the cam is still aligned dot to dot. It seem to me to be a pcm problem related to the pcm.
You checked compression on every cylinder?
Majority of the time backfiring in the intake is either a lean pop or a ignition issue.
Overlap greatly exacerbates the issue especially with a converter that is too tight and fully loads the engine too early.
yep 180psi on every cylinder before the cam it was 190psi
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