HELP! Stumped! Need some help! 26lbs of boost and still slow!
#21
#22
8 Second Club
iTrader: (4)
Flat top 5.3? That’s really low cranking compression wise. For reference I had 190-200 with the isky triple 12 cam about 1 degree advanced. I had 140-150 when it was 8* retarded installed dot to dot. Who degree’d cam? Sure they did it correctly? I picked up 12 mph with no other changes after correcting the cam timing. I’d expect it to be a little lower with the 317 heads, but that seems excessive. ( I ran the 243s and LS9 gaskets) Not saying that’s your problem, but you might want to double check.
Boost leaks would be my next guess? Built a pressure testing rig?
Boost leaks would be my next guess? Built a pressure testing rig?
#23
Flat top 5.3? That’s really low cranking compression wise. For reference I had 190-200 with the isky triple 12 cam about 1 degree advanced. I had 140-150 when it was 8* retarded installed dot to dot. Who degree’d cam? Sure they did it correctly? I picked up 12 mph with no other changes after correcting the cam timing.
#28
for a low compression 5.3 that cam is huge. its basically the same thing as my stage 3.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
#30
for a low compression 5.3 that cam is huge. its basically the same thing as my stage 3.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
#31
TECH Fanatic
iTrader: (12)
for a low compression 5.3 that cam is huge. its basically the same thing as my stage 3.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
And just for reference... the stage 3 shelf cam is what is ran in JP Delisi's car Black Jesus.
So you have the same camshaft as whats in a 10:1 408ci stroker motor with LS3 heads and a Hi ram with a GT55 garrett hanging off it.
Id bet a fairly large sum of money that the car would go quicker and faster with a smaller camshaft.
#32
#35
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Flat top 5.3? That’s really low cranking compression wise. For reference I had 190-200 with the isky triple 12 cam about 1 degree advanced. I had 140-150 when it was 8* retarded installed dot to dot. Who degree’d cam? Sure they did it correctly? I picked up 12 mph with no other changes after correcting the cam timing. I’d expect it to be a little lower with the 317 heads, but that seems excessive. ( I ran the 243s and LS9 gaskets) Not saying that’s your problem, but you might want to double check.
Boost leaks would be my next guess? Built a pressure testing rig?
Boost leaks would be my next guess? Built a pressure testing rig?
#39
TECH Apprentice
when i used to do turbos i would make provisions to measure bosst before and after cooler, pressure before and after turbine and egt before turbine before attemptig a first pull.
#40
8 Second Club
iTrader: (4)
Sure the cams too big and not optimal for that setup. But you really think that’s the main cause of the car trapping 12-20mph slower than it should? Something seems way off with that combo, other than an overly large cam. Powers gotta be going somewhere. I’d find out what springs are on it and double check push rod length is correct. Are you running aftermarket lifters? Build a simple boost leak check rig. (lots of videos on you tube for this).
Think you could have something collapsed on the hotside? Flex coupling maybe? Rig up a quick back pressure gauge ($4 push to reset tire gauge works great) on the exh system and see where you’re at. Also turn the thing down. Try 15ish then bump a pound at a time watching gains. As soon as they level off, stop adding boost. When you stop seeing gains keep adding boost, things tend to break.
My Cam was cut fine, the key way in my crank was about 8* retarded. So when I installed my cam with the factory timing set it was 8* retarded from where it should have been. Seems a few newer gen4 engines have this issue, most do not. If the cam hit the card and was degree’d properly you should be fine there. If the “Professional engine builder” said they degree’d it and you have doubts, check it.
Think you could have something collapsed on the hotside? Flex coupling maybe? Rig up a quick back pressure gauge ($4 push to reset tire gauge works great) on the exh system and see where you’re at. Also turn the thing down. Try 15ish then bump a pound at a time watching gains. As soon as they level off, stop adding boost. When you stop seeing gains keep adding boost, things tend to break.
My Cam was cut fine, the key way in my crank was about 8* retarded. So when I installed my cam with the factory timing set it was 8* retarded from where it should have been. Seems a few newer gen4 engines have this issue, most do not. If the cam hit the card and was degree’d properly you should be fine there. If the “Professional engine builder” said they degree’d it and you have doubts, check it.