LT1-LT4 Modifications - LE3 dyno results, not happy. Thoughts?

I finally got around to getting my LE3 heads and LE ported intake on the car a few weeks ago, and had it dyno tuned yesterday. I had Ion from Madtuner do the tuning. I'm not really excited about the results, and wanted to see what you all thought.

For comparison, I'm also attaching my dyno from before the head and intake swap, when I was "cam only" and made 332/348. After the swap and tuning (nothing else changed but heads and intake), I made 362/329. Converter was unlocked both times car was dynoed, but the numbers just seem pretty low to me, I was expecting more then 30 rwhp after the head and intake swap.

Major mods are: 355, forged flat tops (-5cc), stock bottom end, LE3 heads, LE ported intake, COMP 280XFI cam (230/236, .576/570 113lsa), 52mm tb, Yank SS3600, FLT Stage IV 4L60E, Moser 9", Jet Hot long tubes/true duals with bullets.

The dyno operator said my torque converter is way too loose now and was flashing up to 4700 rpm, so we were not able to tune it for nitrous. I called Dave at Yank about getting the converter re-stalled, and he wants me to do a few things to check the stall speed before going forward. He said that stall speed on a dyno was not reliable info.

It looks like the cam only graph is uploaded as the .jpg and you seem to be treating the spike as real numbers.
The .pdf is the heads/cam setup.

Why did they stop the run so low in the rpm range? Big set of heads like that and a cam that large I would expect more rpm.
The graph is a hassle to look at with it zoomed to just a high HP range and the TQ and HP being on different scales. Being zoomed in like that makes the variations in power look a lot bigger than they are.

It looks like the cam only graph is uploaded as the .jpg and you seem to be treating the spike as real numbers.
The .pdf is the heads/cam setup.

Why did they stop the run so low in the rpm range? Big set of heads like that and a cam that large I would expect more rpm.
The graph is a hassle to look at with it zoomed to just a high HP range and the TQ and HP being on different scales. Being zoomed in like that makes the variations in power look a lot bigger than they are.

True, I didn't take into consideration the spike, though the hp numbers appear to be accuate as only the tq has spikes. Let's pretend the spikes aren't there in the torque curve, it would be around 320 lbft...I gained only ~10 ft lbs of torque with the head and intake swap? I'm not sure why he stopped the pulls at 6k, I told him to go to 6200.

I guess my question is this... I see the average LE2/LE3 car make around 400 rwhp, but are thos 6 speed cars with 10 bolts? I know my stalled auto/9" uses more power, but I was expecting a little more out of the combo.

Get it to the track first before you say your not happy.

My LE2 383 made 388/381 on the dyno. My converter wouldnt lock up and was flashing pretty high. After hitting the track it ran a best of 11.28 at 3700lbs. DA is in my sig. Pretty pathetic dyno numbers but the car gets down and moves for what it is.

Isnt that cam supposed to pull to 65-67? I think you need to figure out why its spiking and then make sure the guy running the dyno makes a full pull to make those heads work.

Get it to the track first before you say your not happy.

My LE2 383 made 388/381 on the dyno. My converter wouldnt lock up and was flashing pretty high. After hitting the track it ran a best of 11.28 at 3700lbs. DA is in my sig. Pretty pathetic dyno numbers but the car gets down and moves for what it is.

Very true

True, I didn't take into consideration the spike, though the hp numbers appear to be accuate as only the tq has spikes. Let's pretend the spikes aren't there in the torque curve, it would be around 320 lbft...I gained only ~10 ft lbs of torque with the head and intake swap? I'm not sure why he stopped the pulls at 6k, I told him to go to 6200.

I guess my question is this... I see the average LE2/LE3 car make around 400 rwhp, but are thos 6 speed cars with 10 bolts? I know my stalled auto/9" uses more power, but I was expecting a little more out of the combo.

To get the most out of that cam you'll probably want to be shifting around 7k with a good set of heads. I would expect peak power around 6500.

Isnt that cam supposed to pull to 65-67? I think you need to figure out why its spiking and then make sure the guy running the dyno makes a full pull to make those heads work.

Comp rates it to 6k, but it was clearly still making power at 6k. It was only spiking on the cam only pulls, though there was a dip on the pulls yesterday around 5800-5900, then it starts pulling again. I'm thinking opti.

Are you sure they are LE heads? Did you buy them used?

I'm pretty confident they are, I bought them from Clint, T/ALT1. Now that I think about it, I KNOW they are because I talked to Lloyd about those heads and intake and he remembers doing them for Clint.

I'm proud to see the AI guys helping out instead of bashing.

I would pull it to a higher RPM as stated, and TAKE IT TO THE TRACK!

Racing dynos gets you nowhere. None of the fast guys do it. Don't worry about what it makes, until you get it to the track and see what it traps, and ETs

As everyone has said, take it to the track. Big converter dyno numbers are always wonky.
I'm proud to see the AI guys helping out instead of bashing.

That hasn't happened in months.

Comp rates it to 6k, but it was clearly still making power at 6k. It was only spiking on the cam only pulls, though there was a dip on the pulls yesterday around 5800-5900, then it starts pulling again. I'm thinking opti.


Comp's numbers are wrong, they seem to be based on old dual plane gen 1 intakes, LT1 intake being very differnt plus LT1 heads being better shifts the rpm range upward substantially.

Hell the stock b-body cam is worth turning 5800rpm or so and it is 191/195 .418/.430 111

Far as jumping to the opti assumption like I said variations are not that big, it just looks like it because the graph is showing a narrow range on the HP graph.

Put in the stock 10 bolt and small TC and you will see a good dyno run.

I have seen many 383s get under 400hp and make what u did. It's fairly common. But none the less dyno is for tune only. So track that car and the real numbers will be surprising.

The Yank converters work pretty well, while I do agree many converters can show a lot of loss most of the guys doing careful analysis of Yank's performance find them to be highly efficient. Sure it will show some loss but it should not be the scapegoat here.

Run it, see what it does before you get caught up in the excuses guys are trying to give you.

FWIW, I dynoed my car after I ran an 11.4@118 with a 1.579 60 ft @ 3650 raceweight and it only made 355rwhp and 360rwtq. This was a 11.5 355lt1 with gtp lt4 stage 2 ported heads and intake, 236 242 112lsa cam with a th400, 9" rear with a nitrous converter.

Like the other guys said, don't be upset until you run it. I would have figured a 35-40rwhp gain at most from just a head and intake swap while leaving everything else the same. Now if you put in a much bigger cam you could expect 60-80rwhp depending on how radical you go with the cam.

Yup, One customer had a bottom of the page cam, Heads with huge runners and a 4500 stall, made in the neighborhood of 330 RWHP, Man I thought either he was going to cry or go postal, anyway at at the track he ran 10.90's...He was happy after that..

If you just wanna see a number you can lock the stall and spin higher.

Personally I wouldn't worry about it unless it doesn't perform at the track.

Racing dynos gets you nowhere. None of the fast guys do it. Don't worry about what it makes, until you get it to the track and see what it traps, and ETs

Sometimes it's all some of us have since there are no tracks anywhere near me. :( But I hope the OP has one nearby.

Does it feel like it has the power you expect? My butt-o-meter isn't accurate but after my build I knew that this thing had some pretty damn good power.

FWIW, I dynoed my car after I ran an 11.4@118 with a 1.579 60 ft @ 3650 raceweight and it only made 355rwhp and 360rwtq. This was a 11.5 355lt1 with gtp lt4 stage 2 ported heads and intake, 236 242 112lsa cam with a th400, 9" rear with a nitrous converter.

Like the other guys said, don't be upset until you run it. I would have figured a 35-40rwhp gain at most from just a head and intake swap while leaving everything else the same. Now if you put in a much bigger cam you could expect 60-80rwhp depending on how radical you go with the cam.

A TH400 soaks up a lot more than a 4l60E does on the dyno.

Don't sweat it, does the tune check out? If so get to the track and see what and how she runs......

Thanks guys, I guess I'm one of those guys who always has good advice but can't follow it himself lol. I've also always said the same about dyno numbers vs. track times, but then when it comes down to my own car, I got caught up in the "dick comparing contest".

I do have a track somewhat close and will try to get there soon. I'm also going to do the things Dave from Yank told me to do to try and verify the stall speed

Yep, I wouldn't worry too much about it. FWIW, my car dynoed low for what it is...track results will be soon to follow and I have a feeling, I won't be disappointed ;)

Good luck though!

My Ta made 360rwhp through an unlocked vigi 3200 & 12 bolt, with a six speed swap car made 415rwhp. Take it to the track.

That's actually a tight converter for that much cam, and very efficient. I wouldn't suspect it as being an issue.
That combo should peak around 6500. Hopefully the valvetrain is up to par for those heads and cam and you'll want to shift at 7000-7100 because that converter will pull it down to ~5200 in the next gear.
I agree with disregarding the numbers; I think a pessimistic dyno, your 9" rear, and not even revving to peak power all add up to make them irrelevant.
Just go run it :nod:

Like the guys above said, don't worry too much about the dyno numbers with an auto.
I saw a 30% difference (~300 vs 460) between locked and unlocked numbers with my first 383 build.
Use it as a tool to make sure things are working properly and leave it at that.

Good luck at the track; let usk now how it does.

It's ok I only made 358/350 :eek:

Tq falling off a cliff early, and all those bumps up top makes me think valve control issues. Clint ran a CC306 and may have some weeny springs on there. Just a thought?

He's running the converter unlocked, which makes a big difference. Add that to the early RPM cutoff and 9" and its not exactly a dyno queen :lol:.

It's ok I only made 358/350 :eek:

Tq falling off a cliff early, and all those bumps up top makes me think valve control issues. Clint ran a CC306 and may have some weeny springs on there. Just a thought?

I bought the heads without springs, and put the PAC 1215 beehives on. The dyno operator said he didn't think the dip was valve float since after the dip it started pulling again. He said if it was valve float it would have just nosedived and dropped off sharply. That's why I was thinking opti

I bought the heads without springs, and put the PAC 1215 beehives on. The dyno operator said he didn't think the dip was valve float since after the dip it started pulling again. He said if it was valve float it would have just nosedived and dropped off sharply. That's why I was thinking opti

Look at the scaling on the sheet. That "dip" is like 1 horsepower. A fly could have farted in the direction of the rollers to cause that. The torque "nose dive" is from like 327 to 315 as well.

Make sure they tuned it to all the way to 7k and then hit up the track. It looks like it runs fine, despite the spastic dyno sheet.

I bought the heads without springs, and put the PAC 1215 beehives on. The dyno operator said he didn't think the dip was valve float since after the dip it started pulling again. He said if it was valve float it would have just nosedived and dropped off sharply. That's why I was thinking opti

Those springs are definitely way to weak for that cam.

Those springs are definitely way to weak for that cam.

Ding ding ding

I bought the heads without springs, and put the PAC 1215 beehives on. The dyno operator said he didn't think the dip was valve float since after the dip it started pulling again. He said if it was valve float it would have just nosedived and dropped off sharply. That's why I was thinking opti
I had LE2's with a CC503 and 918 beehives and got valve float above 6200. And the 503 is a small cam than you are running.

racing dynos again!!!?!?!?!!? :bang:



guess im out of the equation my local dyno said my high compression stroked SR LT1 made 430rwhp.....8 more than my cam only LS2 GTO :(

:lol:

Those springs are definitely way to weak for that cam.


Ding ding ding

:werd:
I would suspect that insufficient springs might be limiting the motor the rev higher. I had similar springs on mine and power nose dived at 6K RPM. With better springs power held all the way to 6.5K RPM and I have a much smaller cam and heads. I dont really look at it as racing dynos etc. Its about seeing the curves, where they peak, troubleshooting and tuning. Thats about it.