gnx7

iTrader: (28)

Take a laser temp gun and shoot it at all the primary header tubes to make sure they are firing. Between the 4L80e, 9", and that medium sized cam for that intake that wants to REV.... I don't always trust dyno numbers. The track with 1/8 mph and 1/4 mph will tell you how it's running based upon weight.

My 11:1 LS7 with 243/256 .650" lift cam, stock LS7 heads/intake, 1 7/8" long tubes, and M6 transmission only made 522rwhp/472rwtq on a Dynojet... but it went 110mph 1/8 and 138mph in the 1/4. (2900lbs with driver approx)

WE TODD DID

iTrader: (2)

This is why I don't like chassis dynos. If you have an issue, sometimes it can be challenging to pinpoint where the issue actually is. With an engine dyno, you're only dealing with the engine.

cyrus buhari

So I checked the plugs which were all good and hit the runners on the intake and no big temperature differences. I shot an email over to Mamo motorsports and they seem to think it's the intake manifold thats holding it back. I purchased a ported Fast 102 intake manifold which should be here in 10 days. I will post an updated dyno sheet. Hopefully, that lets this engine breathe.

JoshHefnerX

You temp checked the intake or the exhaust.. The Intake isn't going to show anything.

cyrus buhari

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I checked the intake manifold and the exhaust at the very end of the header

speedfreak440

iTrader: (9)

By end of the header you mean the primaries coming right off the head correct?

Kawboom

I would expect the change in intake would pick up 30 torques just about everywhere on the power curve.

01CamaroSSTx

iTrader: (3)

Do M311 heads outflow say the TSP PRC LS7 265CC or LME Brodix BR7 cylinder heads? Probably not

Does the Holley Sniper Low profile intake out perform a FAST LSXr LS7 style intake? Nope

Does a 240/256 .629 I/E on a 113+4 make more power than a 243/251 .660 I .633E on a 115+5? Questionable.

Does a 4L80E rob your of more power than TR6060 or T56 magnum? Yes it does

That's comparing an LSX 427/LS7 top end with a manual and S60 to your LS 427/LS3 top end with 4L80E and Ford 9"

Darth_V8r

iTrader: (4)

Also, compare to "Aint Skeered" 427 build.

Ported GM casting LS3 heads, 246/262 solid roller cam (roughly 240/256 in hydraulic numbers), 4L80, 9" rear, 4.xx gearing (can't remember exactly) made ~570 to the tires, ran 10.3 on a 3800 lb car. Multiple intakes, same result. I agree with everything you listed, but I still feel the motor is way off somewhere more fundamental.

jmilz28

iTrader: (13)

You'll need to temp gun the header primaries, as they come off the head. Are you getting any misfire codes? Stalled 4L80 and 9" is a HP sink as far as chassis dynos go - figure WELL over 20% drivetrain loss. Also, comparing 1 dyno to another is a fool's errand without a **** ton of comparable data. Run it at the track, your time/weight/DA math will tell you if you're making the HP you should. It will also be a good sanity check for that dyno...which may just be stingy. You probably have multiple "issues" going on.

cyrus buhari

Added the build sheets from Thompson motorsports

01CamaroSSTx

iTrader: (3)

It's a mute point but I only see invoices.

Have you ran any of the tests mentioned to confirm whether or not you have dead or weak cylinders?

jmilz28

iTrader: (13)

This. ^^^^^^

Razor

Which converter?

Jimbo1367

if it says “low profile” in its name, then YES. It’s killing torque

cyrus buhari

Swapped out the low profile intake for mano motorsport ported 102 intake. No retune done yet but it did pick up power across the board. The red line was my hp with old intake they didn't have a tq number for some reason.

01CamaroSSTx

iTrader: (3)

And for a 427 it's still down on power.

Jimbo1367

Do a compression test on all cylinders. Temp gun the headers primaries next to the header flange. It’s down power.

Mavn

iTrader: (3)

My 416 made identical numbers to your 427 when i had a coil go bad. 480 wheel. Replaced the coil on the dyno and bam. 610 wheel first hit lol

Johnnystock

iTrader: (6)

Well, it depends what kind of dyno it is. Dyno to dyno are honestly useless without having other date on each dyno to compare. As an example, my friend's solid roller Mamo top end LS7 made 585rwhp, big cam and all the upgrade from Mamo. It could seem 'weak' to some people, but 1 week after, a C6Z with heads and stage 3 cam(dont know specs), intake manifold maybe stock, it made 525rwhp, which people will say it reallyyy weak. But this dyno is robbing around 26-27% of the power. My friend's LS7 made barely 400rwhp on this dyno, so he gained 185rwhp(+26%), which is astonishing.