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From the top, I'll try to be as complete as possible here. Looking for insight on my combo. I had my initial tune done last week and I have some concerns, car is a 2002 C5Z. Racetronix 255 with harness and SD 60lb injectors (no fueling issues whatsoever) AFR holds flat entire pull.
1) where the power peaked.
2) how hard it dives off after peak.
430" 12.5:1 compression, .041" quench motor, 265cc PRC LS7 head,
243/259 .625"/.625" 113.5+4 (martin spec, can't get a hold of him), straub bronze bushings with OEM 1.8r, Morel 5294 lifters w/ ~.070" preload using 3/8" .080 wall pushrods. Heads are a fresh setup from Reid Sanders at Venom. Valves are Ti intakes @ 75g and solid exhausts @ 95g... PAC/TSP .660's. All set up between 1.755" and 1.765", including his valve job (~90.5% throat) and guide clearances, intakes were spot on and he had to loosen the exhausts a touch.
Spring Specs:
Install Height: 1.810"
Closed Spring Pressure: 160 lb. @ 1.810" Installed Height
Open Spring Pressure: 415 lb. @ .660" lift
Maximum Spring Lift: .660"
Coil Bind 1.015"
Intake is MSD LS7 (cleaned up, light port), NW 102, 4" MAF to Vararam.
Exhaust is Kook's 1 7/8" headers to 3" no cars X to OEM C5Z Ti mufflers. (Thinking 2.5" Ti mufflers choking the power out up top?)
... granted this dyno was only 20° timing, no octane yet, we're assuming once we get octane in it it'll take 25-27°. This graph is 0 knock with 91 gas at 20°.
I'm told my .070 preload is okay by several qualified individuals, yet Morel suggests .045-.050.
So 2 things I'm thinking...
Will run it next dyno session with .025" shorter pushrods (should get me right at their target .045-.050 lifter preload Morel recvomends... and I have purchased an LG BIG 3 exhaust to hopefully open the exhaust up.
So just some thoughts for comparison, after looking back at your Dyno Results and mine.
I went from 690 @ 7100-7300 on an engine Dyno to 592 RWHP @ 6800 on a Mustang
Dyno with 100 Unleaded, also, my exhaust has a catted X going down to 2 1/2" all the way back, I will
re-test with catless 3" X eventually still going to my existing 2 1/2" system. I was told and believe the
3" back would be worth no more then 10. I think with better gas/meth and 5+* timing you will pick up ~30 ish.
~560-570 on a Mustang, ~590-600 DynoJet would be good considering your Heads Intake
Port Size & Camshaft Lift. Just my thoughts.
Good Luck
So just some thoughts for comparison, after looking back at your Dyno Results and mine.
I went from 690 @ 7100-7300 on an engine Dyno to 592 RWHP @ 6800 on a Mustang
Dyno with 100 Unleaded, also, my exhaust has a catted X going down to 2 1/2" all the way back, I will
re-test with catless 3" X eventually still going to my existing 2 1/2" system. I was told and believe the
3" back would be worth no more then 10. I think with better gas/meth and 5+* timing you will pick up ~30 ish.
~560-570 on a Mustang, ~590-600 DynoJet would be good considering your Heads Intake
Port Size & Camshaft Lift. Just my thoughts.
Good Luck
Yes, my engine dyno showed a peak of 6800, so that would make sense I suppose. 30rw is what my tuner said ide gain with the timing it was going to take. I just assumed this dyno was 10-12% low from a dynojet.. he also said it being a 430 motor ide pick up at least 10rw and some tq going from the Ti's to a good 3" system. So your thoughts on why the power is diving? Do you think I'm good with the .070 preload or should I jump to a .025" shorter pushrod?
i can deal with the peak of 6300ish, but that dive is absurd. My valavetrain should be more than adequate and i feel like 16* exhaust split should get me to run clean to 7200 without a major dip from peak like it is here.
I am wondering if the timing / gas is the main issue here for it diving off here. 12.5 to 1 is a lot of compression for pump gas so I am wondering if you could get the 30 hp (say new high is 560 hp at 6300) more from the gas it may give you 40-50 hp in the higher rpms (but peak would not change from the 30 more hp of 560). For example instead of you being 480 hp at 7000 you are now like 525 hp so the drop is not so bad at the end. I do not know, any tuners in here chime in on how better / gas more timing will effect stuff at 6000-7000 rpm here. How were the flow figures here on the heads?
I am wondering if the timing / gas is the main issue here for it diving off here. 12.5 to 1 is a lot of compression for pump gas so I am wondering if you could get the 30 hp (say new high is 560 hp at 6300) more from the gas it may give you 40-50 hp in the higher rpms (but peak would not change from the 30 more hp of 560). For example instead of you being 480 hp at 7000 you are now like 525 hp so the drop is not so bad at the end. I do not know, any tuners in here chime in on how better / gas more timing will effect stuff at 6000-7000 rpm here. How were the flow figures here on the heads?
I hear you. I've also wondered the same, as I wasnt even going to post this until the tune was completed, but i had to throw it out there. Heads flow... not the greatest, I'm aware. These were also at a 88% throat before the valve job, I'm told they're now 90.5% throat with a better valve job then they came with.
PRC 265cc
LS7 Intake PRC LS7 Exhaust .200 169 118 .300 246 176 .400 304 208 .500348 221 .600380 230 .650383 235 .700388 240
When do you plan to go get the gas and retested? Yes the 2.5 inches may be holding you back up high a little only if it is over the axle back part if the neck down is by cats then could be more.
When do you plan to go get the gas and retested? Yes the 2.5 inches may be holding you back up high a little only if it is over the axle back part if the neck down is by cats then could be more.
it is just over the axle that is 2.5" but this is the inside of one of these mufflers...
Hi FRiCK, my observation is that your Spark Instant IS CORRECT at pear Torque, then too low when the RPM are increased.
Your 4.00" crank stroke with a 6.xx rod will have a low R/L good for Knock Resistance
I run 12:1 with long cranks often on Pump 91 (94 RON)
I WOULD ADD an EGT Gauge as this is a very good way to "see" the required Spark Advance.
Lance, BTW with the spark@20 your Mustang Rolling Road report is normal.
I know the exhaust is not hurting you, mine makes 630rwhp with the same exhaust. I did a back to back with a Kooks 3" axle back and picked up 0hp. Like Pantera says the engine is plain un-happy right now.
I know the exhaust is not hurting you, mine makes 630rwhp with the same exhaust. I did a back to back with a Kooks 3" axle back and picked up 0hp. Like Pantera says the engine is plain un-happy right now.
well, I picked up an LG big 3 exhaust. I used the Ti with my blower and made 646rw, NA is a little different I think.
so unhappy from lack of ignition timing. I'm assuming that's what Pantera meant by spark instant. I've talk with my builder and head guy. They both say its peaking g lpe from the low timing as well.
As rpm increases you need to give it more lead. I'm impressed it runs stable on 91 octane at 12.5:1.
Maybe I was informed wrong long ago, but I've always been under the impression that you need to retard the timing above peak torque because the "window/time" to burn fuel is less/shorter as RPM goes up. The timing demands of an IC engine should follow the torque curve pretty closely.
I've also seen a drop of 50 HP when going from 24 to 26 degrees on a healthy LS7 N/A combo on an engine dyno.
The combustion chamber design is going to dictate a lot of the burn rate and subsequent timing requirements. The small efficient chambers in most LS heads will require less timing. Also, as compression increases, timing requirements typically go down. The fuel type and octane will have an effect on the timing requirements as well.
Maybe I was informed wrong long ago, but I've always been under the impression that you need to retard the timing above peak torque because the "window/time" to burn fuel is less/shorter as RPM goes up. The timing demands of an IC engine should follow the torque curve pretty closely.
I've also seen a drop of 50 HP when going from 24 to 26 degrees on a healthy LS7 N/A combo on an engine dyno.
The combustion chamber design is going to dictate a lot of the burn rate and subsequent timing requirements. The small efficient chambers in most LS heads will require less timing. Also, as compression increases, timing requirements typically go down. The fuel type and octane will have an effect on the timing requirements as well.
I believe the correct way is to retard timing at MBT (peak efficiency/cylinder pressure) then as you come down from MBT you feed the timing back as RPM increases to redline. With 100% methanol injection I will have all the octane it will want I assume.
05-06-2018, 05:26 PM
ERL 430 w/ LS7 top end questions. HELP! 
