6.0 S480 Combo low power and dropping off early. Help. Please.
07-05-2018, 09:57 PM
#41
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have had identical problem with iron block 403cube engine with BW 80mm single T6 1.32 rear. would come on boost about 5000rpm make great power climb to 5800 and them nose dive hard up to 7000rpm. would lose over 150rwhp between peak power and limiter in its nose dive.
turns out the shop that did the heads for the owner were miles short on appropriate valve seat pressure for the combo. once that was rectified with no other change power climbed all the way to 6800rpm with the most minute little roll over up to 7000rpm. with that fixed and a bit more wind combo went 1060rwhp on a mainline roller
I suspect you have valve float issues
turns out the shop that did the heads for the owner were miles short on appropriate valve seat pressure for the combo. once that was rectified with no other change power climbed all the way to 6800rpm with the most minute little roll over up to 7000rpm. with that fixed and a bit more wind combo went 1060rwhp on a mainline roller
I suspect you have valve float issues
07-05-2018, 10:21 PM
#42
Had similar problem. Changed pushrods, new plug wires, and new converter. Problem solved. Pushrods were too long, wires were suspect, and converter too lose. Don’t know which one was the main culprit or synergistic effect of all three.
07-06-2018, 05:38 AM
#43
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have had identical problem with iron block 403cube engine with BW 80mm single T6 1.32 rear. would come on boost about 5000rpm make great power climb to 5800 and them nose dive hard up to 7000rpm. would lose over 150rwhp between peak power and limiter in its nose dive.
turns out the shop that did the heads for the owner were miles short on appropriate valve seat pressure for the combo. once that was rectified with no other change power climbed all the way to 6800rpm with the most minute little roll over up to 7000rpm. with that fixed and a bit more wind combo went 1060rwhp on a mainline roller
I suspect you have valve float issues
turns out the shop that did the heads for the owner were miles short on appropriate valve seat pressure for the combo. once that was rectified with no other change power climbed all the way to 6800rpm with the most minute little roll over up to 7000rpm. with that fixed and a bit more wind combo went 1060rwhp on a mainline roller
I suspect you have valve float issues
Is there a way to check the seat pressure with the heads installed or is the only option taking them off and to a different machine shop? They are BTR .660 springs installed as is, per recommendation.
07-06-2018, 05:40 AM
#44
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My pushrods were too short, changed them out but have not run the car yet, plug wires changed over to a known good set also. Could be a converter problem I suppose, but hard to diagnose the car fails to carry good power at all.
07-12-2018, 03:45 PM
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Used a length checker, swapped in a set of 7.450's. Checked the seat pressure of the springs and all the ones i could get to took about 180 to unseat ( couldnt get the tool in for #5 and 7 due to the brake booster). Pulled the converter out and shipped it back to ptc today to have it checked out. Its possible it may be too tight (im not expert) Leaving the line at 10 psi with he 2 step set at 3200 there is no flash at all just a gradual increase in RPM, also the RPM dropped from 6500 to 4900 on the shift. Gonna throw a crank and cam sensor at it while im in there.
07-12-2018, 03:59 PM
#47
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Used a length checker, swapped in a set of 7.450's. Checked the seat pressure of the springs and all the ones i could get to took about 180 to unseat ( couldnt get the tool in for #5 and 7 due to the brake booster). Pulled the converter out and shipped it back to ptc today to have it checked out. Its possible it may be too tight (im not expert) Leaving the line at 10 psi with he 2 step set at 3200 there is no flash at all just a gradual increase in RPM, also the RPM dropped from 6500 to 4900 on the shift. Gonna throw a crank and cam sensor at it while im in there.
must have had minimal lifter pre load
07-12-2018, 08:17 PM
#50
Used a length checker, swapped in a set of 7.450's. Checked the seat pressure of the springs and all the ones i could get to took about 180 to unseat ( couldnt get the tool in for #5 and 7 due to the brake booster). Pulled the converter out and shipped it back to ptc today to have it checked out. Its possible it may be too tight (im not expert) Leaving the line at 10 psi with he 2 step set at 3200 there is no flash at all just a gradual increase in RPM, also the RPM dropped from 6500 to 4900 on the shift. Gonna throw a crank and cam sensor at it while im in there.
07-13-2018, 11:35 AM
#51
.05 change in pushrod length will do diddly IMO. 6500 to 4900 is massive. That’s likely a big issue. Converter is likely too tight for the power you are making. Do you know what stator was in the converter? What was the PN on the box? Make sure to ASK PTC what stator was in it and ask what stator they are replacing it with.
07-13-2018, 12:45 PM
#52
Warning...I'm not criticizing just questioning. If a converter "locks up" too early aka too tight, wouldn't it just be 1:1 up top and allow engine to RPM out as it should or are there other hydraulics that are happening to fight the engine and not transmit the power through to the trans?
07-13-2018, 01:09 PM
#53
I believe I have similar issues and haven’t ever sorted it out, so I sure don’t have all the answers. Just haven’t had the time to swap out different converters or gearing lately.
If it’s too loose the converter obviously never couples. So Engine RPM rises and the drive train tries to catchup never doing so.
I believe if it’s too tight the opposite happens. The driveline is trying to catch up to the engine and it never couples properly which causes the engine RPM to hang. Basically the converter tries to “lock” at an RPM/power level that is too low to accelerate/pull the driveline. This causes engine RPM to hang while the driveline accelerates to try and catch up. So RPM and power do not continue to rise as they should.
If it’s too loose the converter obviously never couples. So Engine RPM rises and the drive train tries to catchup never doing so.
I believe if it’s too tight the opposite happens. The driveline is trying to catch up to the engine and it never couples properly which causes the engine RPM to hang. Basically the converter tries to “lock” at an RPM/power level that is too low to accelerate/pull the driveline. This causes engine RPM to hang while the driveline accelerates to try and catch up. So RPM and power do not continue to rise as they should.
07-14-2018, 12:05 PM
#55
I know of a few with similar combos and the 15 should be fine. At 23lbs u shud make enough power for that converter Id think. I ran a 17 on my weak 5.3 and it worked really well. I run a 14 stator now and its on the tight side for my current power and gearing for sure. Im sure there is more to it like blade angle and what not, but thats my exp. Anyway. Good luck! Let us know how it goes...