LS4 Performance - Figured out why our engines suck!

We only have a 3.78" bore! Very shitty.....
Valves are very shrouded and with our large stroke these aren't really good rev motors either. Plus, high RPM's won't really fill theses dinky cylinders very well, do to smaller valve size's. Yes.. there are 5.3's out there that scream.

Borexstroke
283 Chevy 3.88"x300"
305 Chevy 3.736"x3.4803"
302 Ford 4"x3.00"
327 Chevy 4"x3.25"
326 Pontiac 3.875"x3.75"

Anything under a 4" bore is garbage. Ford's 302 and Chevy's 327 really rock for small cubed motors. We could debate these engines flaws too, I know!

then do it

then do it

Doing it will mean that I'm about to force feed this Mutha fuker. I just need a little more $$$

Seriously... thinking about this engine has left me with wanting more. We have excellent heads, and I wanna use them dammit. Sick of 5.0's LS1's and other V8's with simmilar mods wooping my ass!

Remember how much horsepower the older engines made? It was pretty rare to find an engine of our size (325ci) making as much HP as ours from the factory, and if they did , they were fairly radical and had poor idle and manners and got 10 mpg. Our engines do pretty good for 3.78" bore. The heads flow pretty well and computers help them run efficiently. Doesn't take very much to make 1 horsepower per cubic inch, which used to considered fantastic years ago

Remember how much horsepower the older engines made? It was pretty rare to find an engine of our size (325ci) making as much HP as ours from the factory, and if they did , they were fairly radical and had poor idle and manners and got 10 mpg. Our engines do pretty good for 3.78" bore. The heads flow pretty well and computers help them run efficiently. Doesn't take very much to make 1 horsepower per cubic inch, which used to considered fantastic years ago

Think about the amount even the worst LS heads flow compared to the best SBC factory heads. And we have the best cathedral port heads GM made.

I'm with you, our engines are FAR from terrible.

Yep... I made a come back comment about these cars and engines not to long ago stating the same. Put these heads, cam and intake on a 4" bore motor that's the same size, and feel what happens! The stroke is good for torque, but for raw power, a little more bore with a little less stroke would be better IMO.
I not trying to compare old engines to new, I'm just trying to compare the bore sizes of similar engines. It would be cool if GM really did make the 5.3 a 327. Guess we're more of a 326 Pontiac.

Yep... I made a come back comment about these cars and engines not to long ago stating the same. Put these heads, cam and intake on a 4" bore motor that's the same size, and feel what happens! The stroke is good for torque, but for raw power, a little more bore with a little less stroke would be better IMO.
I not trying to compare old engines to new, I'm just trying to compare the bore sizes of similar engines. It would be cool if GM really did make the 5.3 a 327. Guess we're more of a 326 Pontiac.

Yep. Surface area means a lot when making power. Especially when going F/I or Nitrous. That's why the 6.0L responds so well. Same stroke, bigger bore.

There really are only three viable options...

Turbo...

Bolt ons...

Engine swap...


If you want to have a lot of power n/a you need a bigger engine....

Buy an LS1/2/6 block, modify the crank, and swap the accessories over.....




Either enjoy her as a DD, make her breath harder, or put a bigger bore engine in it. I think an LS1/2/6 would work well.

you are right the small bore is the down side to the 5.3 but with an LS6 intake, headers, big cam and maybe some head work you can make 450hp, that's not too shabby.

another way to look at it is to compare your engine to the LT1 or L98 or even the old 5.0's, it's clearly a winner.

There are some pretty stout 5.3s, as you mentioned. My 2007 Tahoe ran strong, especially for a 4400 lb truck. While you make a valid point that our bore size isn't the optimum for power, I think that the main reason our LS4s aren't very strong is because the intake and exhaust are compromised in the name of FWD packaging.

For the record, the LS1/LS6 is only a 3.90 bore, only .12 larger than the 5.3. Few people would say that THEY suck!

I think that, with a proper intake and exhaust, these motors will make similar street power to 5.7 LS1s. Sure, the LS1 will always be able to make more maximum power due to it's inherent size and bore-stroke combos, but on the street, a properly modded LS4 should not be too far behind.

I'll be curious to see what you think after you do your LS6 intake.

you are right the small bore is the down side to the 5.3 but with an LS6 intake, headers, big cam and maybe some head work you can make 450hp, that's not too shabby.

another way to look at it is to compare your engine to the LT1 or L98 or even the old 5.0's, it's clearly a winner.

i like my LT1, got some nice torque :D

i like my LT1, got some nice torque :D

LT1s feel stronger because all of the torque is down low. When I drove my first LS1 (a 2000 Z28) car, I thought it felt weak, even compared to a bolt-on L98 Trans Am I once had. Then I nailed it on the freeway on the way home from the dealer, and was shocked. It pulled HARD all the way to 5500 RPMS...A place where the LT1 is out of breath.

The lesson for me is, linnear torque across the whole powerband doesn't feel as strong as peaky torque at low RPMs, assuming the same max torque. It definitely affects SOTP feel.

LT1s feel stronger because all of the torque is down low. When I drove my first LS1 (a 2000 Z28) car, I thought it felt weak, even compared to a bolt-on L98 Trans Am I once had. Then I nailed it on the freeway on the way home from the dealer, and was shocked. It pulled HARD all the way to 5500 RPMS...A place where the LT1 is out of breath.

The lesson for me is, linnear torque across the whole powerband doesn't feel as strong as peaky torque at low RPMs, assuming the same max torque. It definitely affects SOTP feel.

I have to agree with this. The LT1 feels really strong from low rolls and stops but much like our cars, racing with the car in any gear besides first is pretty much useless.

I love the LS1 feeling. The first LS1 I drove was a C5 vette and I was amazed that through every single gear, the car pulled evenly and smoothly.

When I drive the monte, it is the exact opposite of the LS1...its like a FWD LT1 that doesn't sound as good. All the power of the LS4 comes on like a sledge in first gear, but 2nd and 3rd combined with a poor flowing intake and a poorly designed exhaust for a V8 makes for a lazy powerband. I can tell that this engine makes some power, but the FWD transaxle set up is not conducive to great performance.

LT1s feel stronger because all of the torque is down low. When I drove my first LS1 (a 2000 Z28) car, I thought it felt weak, even compared to a bolt-on L98 Trans Am I once had. Then I nailed it on the freeway on the way home from the dealer, and was shocked. It pulled HARD all the way to 5500 RPMS...A place where the LT1 is out of breath.

The lesson for me is, linnear torque across the whole powerband doesn't feel as strong as peaky torque at low RPMs, assuming the same max torque. It definitely affects SOTP feel.

agreed, my freind has a LS1 that i do all his modding (all the work that is) it has full bolt-ons and yeah it pulls hard, highway monster!!

LT1's are torque monsters! My cousin had a 95 T/A with the LT1 and it was a real tire smoker! It wasn't all that impressive on the freeway but on the street it was a different story.
LT1's have a 4.00" bore and is a true 350/5.7L. as most of us know. Those engines were extremely choked up from the factory with small heads and cam.
I can't wait to get my intake on, I need to hurry up and get back home from duty, Im still stuck in Cali. with no car to drive.

Think about the amount even the worst LS heads flow compared to the best SBC factory heads. And we have the best cathedral port heads GM made.

I'm with you, our engines are FAR from terrible.

Quoted for truth.

The GM Gen III/IV heads rival 80's NASCAR heads in terms of flow. The LS-series heads have a 15-degree valve-angle, way more vertical than the original small-block and LT1 motors. This allows for a shallow combustion chamber and lets the air/fuel burn more efficiently and completely. There are many more reasons that make a 5.3 desirable, but i'm sure you get the picture.

In the end, there's a lot more to the equation than just bore and stroke.

Quoted for truth.

The GM Gen III/IV heads rival 80's NASCAR heads in terms of flow. The LS-series heads have a 15-degree valve-angle, way more vertical than the original small-block and LT1 motors. This allows for a shallow combustion chamber and lets the air/fuel burn more efficiently and completely. There are many more reasons that make a 5.3 desirable, but i'm sure you get the picture.

In the end, there's a lot more to the equation than just bore and stroke.

Yep. It'd be nice if we had a short stroke and large bore. But with an LS6 intake/headers there's no reason to complain about the LS4 at all. Only the platform lol

The engine is the best part of the car IMO... its the transmission and the computer that sucks.

The engine is the best part. everything else sucks. The exhaust is too quiet for it to be a v8. The horsepower sucks, the trannys suck, and its FWD

With a proper tune and catback exhaust, this engine is plenty stout. I've had chevy 305HO, Ford 5.0 302, Chevy 350 L98, Pontiac 350 LT1, and 3.8l supercharged GTPs, and this LS4 is probably one of the most responsive engines of them all (maybe the 302 Ford was meaner). This is not a bad setup at all, considering it's a 300+ horsepower V8 in a FWD car that keeps up with many of the other RWD V8s out there. I'm not dissapointed at all :cool:

:lol: @ this thread.

:lol: @ this thread.

You should know nothing productive happens in the LS4 section. I think this is the 4th mod visit to our section in recorded history.

After doing heads, cam, intake, headers, exhaust, CAI, LS6 CNC oil pump, C5-R chain, and Harland sharp roller rockers. I still want more :( I would drop 2,000 on a re-sleeve job in a heartbeat!

I think this motor is good for 115mph in the 1/4 as it sits now. With tires, I am certian I can hit 12.2's I just need a 1.8 60ft.
400whp?

I've given up trying to make hug numbers with this combination. Everyone who does needs major $ for minimal gain.

Im doing DT headers , Exhaust (Full3"- Dual 2.5") , LS6 Intake , Mild Cam , (Mayyyyybe some spray just for shits and giggles) , with a tep trans , with 3.69's. And calling it good. I love my ca , but i have come to terms with its inability to make big numbers. But lets be honest here guys , a mid to low 12"s Daily driver is nothing to sneeze at...

115 trap speed seems pretty good to me. yeah your not going to get the 120ish that the ls fbody are getting but there is a little weight difference, a few ci, plus less drive train loss.

i was trapping 118 in my lt1 with similar mods but a big ass cam... i'd be pissed if a gp was right their with me lol

Car feels pretty good to me. Definitely a lot better then stock.
I am just sad because I feel like this car is tapped out now. A bigger Cam will be useless since I pass through the 1/4 at 5400 rpm. Bigger heads will kill port velocity, and intake options are very limited.
Weight reduction ruins the look and purpose of this car.. Nitrious is like steroids.


Hopefully, tuning will add more some more power. Bigger tb,and maf? Minimal... Gains

I would drop 2,000 on a re-sleeve job in a heartbeat!

Before you did that I would look into a LS2 block & pistons with LS4 internals with a trans adapter. Hell Summit has a 6.0 .030 over for around $900. It's around 80lbs more?

The trans adapter will make it wider and make you need more custom parts...

Id try looking into other cams. It doesnt neccessarily have to be "bigger" but there may be a cam better suited for your new setup. I really don't see why you can't make 400 whp with a head/cam 5.3.

I dont know man i seriously think the tb and maf are seriius choke points on a 5.3 small bore aside i bet u break 400 with a ls2tb fully adapted on that ls6 intake manifold and the maf good for f/i but imo ls6 or any other 85 mm would work way better

I have thought about the adapter plate. I am not certian it will work for sure though. Would be an expensive test lol..

I don't want anyone to think for a second that I am unhappy with my car. I love the power and the look on peoples face when I pop the hood. I just want more!!

When I got done with my head swap, I took my G/F for a ride and tapped the car into 2nd at WOT and dam near side swipped the car next to me. Lesson learned LOL. She thinks I am obsessed and need theropy.

My best dragstrip battle to date is a 4.6 supercharged Mustang GT 07? He has an auto with gears, headers, exhaust drag radials, and gutted back half. He runs 12.45's all day long at 112.5-113. Guess he dyno's 450whp plus.
Seems like a lot of cars are over rated since this car puts down around 380 untuned. Last week he was trapping 115mph. He did some more weight reduction and added 100 octane.

Lots of Hondas running some pretty good times now days with crazy trap speeds. I would sure hate to race one of those guys on the freeway, since they would already be hooked up. I watched a couple of guys run mid 13's at 130mph!

Guess my next set of mods will be the TPiS 90mm snout, with a 88mm truck tb/MAF combined with a mild shot of water injection. Thinking I should have used a thinner head gasket for more compression. I am at 10.6 right now. 10.9-11.0 would be ideal:)

:lol: @ this thread.

:wrongforu

I have thought about the adapter plate. I am not certian it will work for sure though. Would be an expensive test lol..

I don't want anyone to think for a second that I am unhappy with my car. I love the power and the look on peoples face when I pop the hood. I just want more!!

When I got done with my head swap, I took my G/F for a ride and tapped the car into 2nd at WOT and dam near side swipped the car next to me. Lesson learned LOL. She thinks I am obsessed and need theropy.

My best dragstrip battle to date is a 4.6 supercharged Mustang GT 07? He has an auto with gears, headers, exhaust drag radials, and gutted back half. He runs 12.45's all day long at 112.5-113. Guess he dyno's 450whp plus.
Seems like a lot of cars are over rated since this car puts down around 380 untuned. Last week he was trapping 115mph. He did some more weight reduction and added 100 octane.

Lots of Hondas running some pretty good times now days with crazy trap speeds. I would sure hate to race one of those guys on the freeway, since they would already be hooked up. I watched a couple of guys run mid 13's at 130mph!

Those honda guys have that monster vtec/DOHC combo combined with light weight....jealous a little but hell fuck em i could throw a civic in my trunk and drive home lol

Guess my next set of mods will be the TPiS 90mm snout, with a 88mm truck tb/MAF combined with a mild shot of water injection. Thinking I should have used a thinner head gasket for more compression. I am at 10.6 right now. 10.9-11.0 would be ideal:)

:wrongforu

THIS^^^^ exactly my plan i remember reading about out TB's being diffrent voltages but it should be easy with hp tuners to recalibrate those settings and get the car to "learn" a GTO or truck TB....once i get time to figure this shit out after i pass this FAA test ill start digging into that starting with the 85mm maf kind of thinking about a SD tune to be honest.

building my Pontiac 400 to clean house on a lsx, if you like that ls feeling you gotta get behind a built pontiac, nothing quite like it.

I remember reading about out TB's being diffrent voltages but it should be easy with hp tuners to recalibrate those settings and get the car to "learn" a GTO or truck TB....once i get time to figure this shit out after i pass this FAA test ill start digging into that starting with the 85mm maf kind of thinking about a SD tune to be honest.

Yes sir, the newer truck style TB's or any LS2 style will work with pigtail adapters and tuning. The required (larger) intake tubing should add some good power. The CAI/Stock coupler bend has got to be a restriction.
I won't know tell next season.

Plans for the winter:

TPiS 90mm inlet
LS2 TB
LS2 MAF
Matched tubing
Custom rear coil overs w/adj shocks
26x11.5 MT ET streets
ZZP front lower control arms
Water meth
Tuning

i remember reading about out TB's being diffrent voltages
I posted this up before.
Hooked up the TB and logged with Hptuners

ETC Position----------TB90-25% 50% 76% 100% / LS4 TB-25% 50% 76% 100%
ETC TPS 1--------TB90-3.43V 2.45V 1.53V 0.59V / LS4 TB-3.51V 2.57V 1.55V 0.59V
ETC TPS 2--------TB90-1.55V 2.53V 3.45V 4.41V / LS4 TB-1.45V 2.37V 3.41V 4.37V
Throttle Position (SAE)-TB90-31% 51% 69% 88% / LS4 TB-30% 49% 69% 88%

Looks good I need to order a 6 pin connector now.
That was a newer truck tb.

I posted this up before.

That was a newer truck tb.

Thanks Brain:drive: