000martin

Any input would be so appreciated! Having turbo issues or backpressure woes.

GenIII Sbe 5.3
Rings gapped .028 & .030
stock truck intake and 862s
Pac1218s
elgin 1840p 228/230
BR7EF gapped .022
80lb injectors
walboro 400
Innovate scg-1 wideband/controller
Gen1 cast vs 7875
80e w/ stock converter
3/4 ton ext cab silverado
pump93

2.25” crossover
3” downpipe to a five foot Straight tailpipe turned down under cab.
Log manifold


The first setup was a 6L with stock cam but had the same supporting mods as now. It would spool almost instant and was a blast to drive. Made 498 on 12 psi. Blew it up so I bought this 5.3 from a junkyard, had the block cleaned up and honed, new rings and bearings.

when the old engine came apart it sent metal through the exhaust housing, and dinged the wheel up a little. Nothing major (I thought). So I put it all back together as I had it. On the dyno it falls on its face over 5k rpms. It takes forever to spool it now and will barely turn the tire over. Soft timing until I get this methanol kit installed. Made low 400s on 10psi

I currently don’t know how to operate hp tuners so haven’t data logged anything. But could this be a bad backpressure issue or the wheel of the exhaust housing ? Hard to believe that this setup is having issues spooling this turbo and 3” downpipe especially seeing as how popular it is. This is my first turbo setup so any help or insight on how to verify would be welcome. I’m currently looking for a rebuild kit for this unit.

94heritage

For starters you say soft timing. What do you consider soft timing. You should have n/a timing in it out to about 4-5 psi. I run basically the same setup just an s475/83 instead of a 78/75 and have zero issue with spool. I have tuned several cars/trucks with with that cast 78/75 and never has it ever been slow spooling so it makes me think their is a tune issue or the damage to the turbine wheel is more significant than you thought. Also stock converter and that large of a cam is going to be a dog so that could be contributing to it as well.

000martin

yea, hindsight is 20/20, the stock cam 6L was much fun to drive. I found an exhaust leak on a band clamp last night on the crossover, gonna get that fixed and pull the turbo back off. When I do I’ll post some pics of the wheel. Fixing the exhaust leak should help some I’d hope

03sierraslt

iTrader: (22)

So your saying it isn’t tuned yet for the different engine.

000martin

[QUOTE=03sierraslt;5487773]So your saying it isn’t tuned yet for the different engine.

yes it has been tuned

03sierraslt

iTrader: (22)

Are you sure the cam is timed correct?

000martin

i believe so, dot to dot like my last 8 or so of these. I think it’s a combo of things, but this can on a stick converter ain’t helpin me

03sierraslt

iTrader: (22)

Stock converter isn’t making it flat up top, there is something going on.

000martin

Other than logging a pull and checking the data, is there something else I can do? I’m gonna do a leakdown just to confirm, add water meth and try a different turbo first. The more I think about it the more it makes sense that the wheel is damaged not allowing air across it the way it was designed. Slowing spool and top end power

03sierraslt

iTrader: (22)

Do you have any pics of the damage?