Flat line at 5.8k rpm
10-28-2018, 08:13 PM
#1
Heel & Toe
Thread Starter
Flat line at 5.8k rpm
I have a 5.3 iron block bored to a 5.7
243 heads milled .015
228/232 .600 and 111lsa cam
4l60 trans
3600 stall
ls3 coils
tr6 plugs
msd wires
push rods are 7.350
just got my car back from my tuner. Made 397hp 378 torque. Flat lined at 5500rpm and have no idea why. I still have plenty of fuel pump left. I was told It must be mechanical. I triple checked push rod length. My short block it brand new. Anyone have any ideas on why its flat lining at 5500 rpm
243 heads milled .015
228/232 .600 and 111lsa cam
4l60 trans
3600 stall
ls3 coils
tr6 plugs
msd wires
push rods are 7.350
just got my car back from my tuner. Made 397hp 378 torque. Flat lined at 5500rpm and have no idea why. I still have plenty of fuel pump left. I was told It must be mechanical. I triple checked push rod length. My short block it brand new. Anyone have any ideas on why its flat lining at 5500 rpm
10-29-2018, 06:44 AM
#4
Advanced
by your cam specs I'd say 5500 would be where it's done making power, or if the cam was installed advanced? was the cam timing checked when installed?
a duration of 228/232 isn't going to pull much past 5500 depending on the valve opening and closing events, and if it was installed advanced some, that will also take away from max RPM
a duration of 228/232 isn't going to pull much past 5500 depending on the valve opening and closing events, and if it was installed advanced some, that will also take away from max RPM
Last edited by monteholic; 10-29-2018 at 06:52 AM.
10-29-2018, 07:42 AM
#6
Heel & Toe
Thread Starter
10-29-2018, 12:40 PM
#7
Drifting
I have a 226/230 cam and it makes peak power around 6000-6500 and holds pretty well to 7k. I ran beehive springs for awhile as it was not a super aggressive cam...ran that for some time and then went back to the dyno--had valve float and saw similar results. I bought new springs and it's been fine ever since.
10-29-2018, 08:01 PM
#8
Le Mans Master
Member Since: Aug 2005
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St. Jude Donor '13-'14-'15
Even a STOCK C5 engine with a stock cam makes power up to 5800 RPM's --- In fact that is the shift point on a 4l60 ---
Your cam should easily make power beyond 6000 RPM's---- It is considered a cam on the high side of a mid cam
I would guess it should stop making any more HP about 6200 RPM
Something is amiss---- If you had floating valve springs your would hear a flutter at WOT----I assume you used the correct springs for your cam AND it was degreed properly---
What size are your injectors ? Stock or did you change them to something larger?
Just a guess sounds like you installed larger ones than stock and your tuner did not scale them properly in your tune
Do you also know from data logging what are your duty cycles at WOT ?
If you went to larger injectors than stock and they were no scaled right your engine will run pig rich and lay down on the top end-----These engines do not require lots of timing--- Normally timing would not be an issue unless the tuner askes for way too much that would cause detonation
Do you hear any pinging at WOT ? If your engine pings too much the ECM the will automatically drop into the "low Octane table" where the timing can be 1/2 of normal
More information will help diagnose----
Your cam should easily make power beyond 6000 RPM's---- It is considered a cam on the high side of a mid cam
I would guess it should stop making any more HP about 6200 RPM
Something is amiss---- If you had floating valve springs your would hear a flutter at WOT----I assume you used the correct springs for your cam AND it was degreed properly---
What size are your injectors ? Stock or did you change them to something larger?
Just a guess sounds like you installed larger ones than stock and your tuner did not scale them properly in your tune
Do you also know from data logging what are your duty cycles at WOT ?
If you went to larger injectors than stock and they were no scaled right your engine will run pig rich and lay down on the top end-----These engines do not require lots of timing--- Normally timing would not be an issue unless the tuner askes for way too much that would cause detonation
Do you hear any pinging at WOT ? If your engine pings too much the ECM the will automatically drop into the "low Octane table" where the timing can be 1/2 of normal
More information will help diagnose----