vincentnova

hi
im chasing some performances issues
engine is an ls truck 5.3 , street truck on pump gas , nothing fancy
this evening i wanted to check the temp at the exhaust manifold near the heads , with a laser gun
on the surface of the exhaust manifold near the port
engine has the original cast iron exhaust manifold manifold
with the engine idling at temp
-Looking at the front of the engine.
On the Left from the front,310F ,180F , 200F , 194F
On the right from the front, 336F , 330F , 260F , 230F

look like there is a big gap in temperature on the left side no ?

what do you guys think ?

vincentnova

any one ?

MySons68C20

Explain your performance issues please.

vincentnova

engine has an hard time to go over 4000rpm , max rpm so far about 4300 and max speed about 90mph
going from 3000 to 4000 rpm , in 4th gear 1:1 , it takes almost 7 seconds , it is very slow .
i end up wondering if i was getting enough combustion/heat at each cylinders , this is why i i did a temperature test .

i checked and cleaned each injectors
swap new spark plugs .040 gap ( made no difference )
rev limiter set at 6800 rpm
at wot timing is set a 23
at wot AFR is 12.5
at wot fuel pressure steady at 58
compression test ea cylinder show 145-150psi
manual transmission ,
fuel : regular pump gas 87
dual flowmaster exhaust ( no catalytic )
engine runs at 198 F
map at wot fluctuate 98.1 to 100.1

Full Power

Can you hear a miss at idle ?
How many hours/ miles on the camshaft and (stock?) Lifters ?
Have you tried moving injectors around? ( Swap positions, see if the COLD cylinders follow a particular injector )

vincentnova

no miss as at all , the engine idle really good , i can not complain about that
its cruise very well as well...if i was not looking for speed...i think i will be happy loool

How many hours/ miles on the camshaft and (stock?) Lifters ?
well this is a junk yard engine , swapped....i would say 150 to 200k .
yes everything is stock

yes i swapped injectors with differents injectors and didnt see a big difference
i also swapped the coil pack just to see
the cylinders 4 , 6 , 8 remain always cooler that the rest.
even after a drive

Jake Wade

Fuel pressure?

Metalchipper

Cats plugged? If you have them.
check the low temperature side first.

vincentnova

at wot fuel pressure steady at 58

vincentnova

i have dual flowmaster exhaust ( no catalytic )

Che70velle

iTrader: (6)

Are the cast iron manifolds coated by chance? I’ve had header coatings throw me some extreme differences in thermal readings with my gun. The coating thickness MUST be exactly uniform or the temp differential is all over the place.

Jake Wade

Not throwing any codes? Air intake restriction?

LilJayV10

iTrader: (39)

Full list of mods and a log would be helpful.

Maybe it's the combination. Maybe your expectations are too high.

There's no way for any of us to know without more information.

All we know is it's a truck with a 5.3

vincentnova

i have the original cast iron manifolds . no cooated

vincentnova

factory 100% stock 5.3
with a manual transmission
i use a microsquirt and tuner studio

i dont see anyway of attaching a data log here..

Woodylyf767

Pull plugs and have you a lookey

vincentnova

i installed spark plugs like a week ago
i looked at them this morning , they look a bite white

Che70velle

iTrader: (6)

Post pics of the plugs. Sounds like it’s lean.

vincentnova

here a picture , they all look the same on both side.
spark plugs are new , less than 2 weeks nows

Che70velle

iTrader: (6)

That is with AFR readings at 12.5 WOT? I 100% always check my tuning….irregardless of what my wideband says…with plugs. I this was mine, I’d try 12.0 at WOT and see how it responds, then check plugs to verify. Plugs don’t lie.