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Thread: Overheating at greater than 2200 RPM

  1. #1

    Default Overheating at greater than 2200 RPM

    I'm having a cooling issue that's driving me batty. I'm running a circa 1988 Chevy 350, very mild cam (basically stock), Terminator EFI, stock heads, Novak aluminum rad with 3 Spal electric fans, GM large cap HEI, in my 88 Cherokee XJ.

    Everything was working fine earlier this year. Rock crawling at Rausche Creek, zero overheating, driving at normal speeds on the highway (90° ambient or so), no issue. I grenaded my Dana 35 over the summer, replaced that with a Ford 8.8, and since then, have had nothing but headaches with overheating. I'm sure one has nothing to do with the other, I only mention it because it was sitting around for a few weeks in a shop, not being driven. The day I get it back, it overheats on the drive home on a highway. Admittedly, it was hot out, maybe around 92 & humid. I would expect higher temps, but the temps just ran away from me, it did not level off. This is driving me crazy. At idle or in stop-and-go traffic, it sheds heat with no problem. But if I go over 2200 RPM or so, regardless of how fast I'm going, heat starts slowly climbing. At Rausche Creek two weeks ago, no issues with low idle crawling, but heading back on a long uphill access road, hit 230 before I had to pull over. Soon as I did, with the truck running, it was under 210° within 5 minutes. I've experimented on the highway and on access roads at different speeds, but at anything over 2200 RPM or so, regardless of how fast I'm going, the temps just keep crawling up, they never level off or stop. Even today, it's cloudy and 76° out, temps seemed to level off around 221, if I kept it at 55° (2300 RPM), but anything higher and the temps began climbing pretty quickly again.

    I've done just about everything I can possibly think of other than bring this to a specialist. Is there *anything* in the Terminator setup I can try? I'm running fairly rich, at 14.7 idle, 14.5 cruise, 13.7 WOT. I have a large cap, so no computer control on the distributor. My understanding is that the timing settings in the Terminator do nothing, since I'm running a mechanical distributor, correct? The truck idles fine, accelerates fine, etc. There are no coolant leaks in the system.

    In case anyone has any other general ideas other than checking the Terminator settings, this is what I've done so far to troubleshoot the issue:

    • Confirmed thermostat was working properly and right orientation. Tried a 160 degree thermostat, no difference. Tried no thermostat, no difference.
    • Lower radiator hose looked snarky, thought maybe it was collapsing. Replaced, no difference.
    • Checked timing, running 12° initial timing, 34° total timing. Timing was retarded, 26° total timing. No difference.
    • Flushed twice.
    • Bleed coolant system using vacuum kit designed to remove air pockets from coolant system (Mityvac). Burped system just for good measure.
    • Replaced water pump. Tried Advanced Auto and a high-flow from Edelbrock. Confirmed both were reverse rotation pumps. No difference.
    • Changed ICM. (I know, but I figured what the heck.)
    • Confirmed all fans are working. Confirmed they're drawing correct amperage (each has their own 60 amp relay). Set them to turn on at 180°F.
    • Changed tensioner and serpentine belt. (It was late and I ran out of ideas.)
    • Pulled winch, lights, and everything else from the front of the truck. Thought this may be impeding air flow. No difference.
    • Used a chemical kit to check for hydrocarbons in the coolant. Test negative.
    • Checked compression on each cylinder, all within spec.
    • Changed radiator cap. Used a brand new #12 & #16, no difference.
    • Filler cap is at highest point of the engine.
    Last edited by JMG; 09-03-2016 at 09:26 PM.
    Trail: 1988 XJ, ZZ6 350 Chevy, 700R4, 35" MTs, Warn 1200, 4.11 gears, Detroit lockers, Hooker headers, Terminator EFI
    Daily: 2018 Grand Cherokee Trackhawk

  2. #2
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    Quote Originally Posted by JMG View Post
    Is there *anything* in the Terminator setup I can try? I'm running fairly rich, at 14.7 idle, 14.5 cruise, 13.7 WOT.
    13.7 AFR is probably too lean at WOT. I'd connect a laptop and reprogram the Target A/F Ratio table (Fuel ICF). It might also be too lean toward the WOT area.

    The EFI (laptop) software, ECU firmware & touchscreen unit (if applicable) must all be version compatible (LINK).
    Your Terminator ECU is an HP ECU, when a USB cable is connected. Download the Holley V2/V3 EFI software to your laptop (LINK),
    open the software with USB cable (LINK) connected, click on "USB Link" to go "Online" with the ECU, and select "Get From ECU".

    I have a large cap, so no computer control on the distributor. My understanding is that the timing settings in the Terminator do nothing, since I'm running a mechanical distributor, correct?
    Correct. Since this isn't an ECU controlled timing application, simply ignore all timing related parameters.

    Checked timing, running 12° initial timing, 34° total timing. Timing was retarded, 26° total timing. No difference.
    Retarded ignition timing can cause overheating. Try 20° at idle, and 34° at WOT.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

  3. #3

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    Thanks Danny, a few follow-ups:
    Quote Originally Posted by Danny Cabral View Post
    13.7 AFR is probably too lean at WOT. I'd connect a laptop and reprogram the Target A/F Ratio table (Fuel ICF). It might also be too lean toward the WOT area.
    Do I need to use a laptop? Can I just use the 3.5" LCD Touchscreen to adjust idle, cruise & WOT AFR? What do you suggest? I know 15 is usually the upper range.

    Retarded ignition timing can cause overheating. Try 20° at idle, and 34° at WOT.
    I know, that's why I advanced it. I was originally at 2° idle, 28° WOT. Originally, I thought I had identified the problem, since I know retarded timing can cause overheating, especially under load and at highway speeds.

    Question though. 34-36° total timing is about appropriate for these engines. Since I'm only seeing overheating at higher RPM, why would setting the initial timing higher and keeping total timing the same address the issue? Are there any other settings in the Terminator I can check that may be impacting the overheating issue?

    I should also mention that I'm focused in on the Terminator for two reasons. (1) I've tried just about everything else I can possibly think of. (2) Having gone through all of this, I remember now that before I installed the Terminator (literally a month before), I drove the truck out from NY to Rausche Creek with a Holley monster carb on it (over a four hour drive in the summer), in high 80° weather, and it never broke 200°. I put the Terminator on over a year ago, but this is really the first year I've had a chance to drive it in real, New York summer weather. On the motor, I really changed nothing, other than what I've listed above.

    Is there anything else I may have changed by virtue of putting the Terminator on? When I had the carb on, the mixture was (improperly) way over rich. Maybe I need to be closer to 15 or over on the AFR at cruise? I'm at my wits end with this. Would switching to a small cap HEI and let the Terminator control the timing help anything?
    Last edited by JMG; 09-04-2016 at 10:25 AM.
    Trail: 1988 XJ, ZZ6 350 Chevy, 700R4, 35" MTs, Warn 1200, 4.11 gears, Detroit lockers, Hooker headers, Terminator EFI
    Daily: 2018 Grand Cherokee Trackhawk

  4. #4
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    Quote Originally Posted by JMG View Post
    Do I need to use a laptop? Can I just use the 3.5" LCD Touchscreen to adjust idle, cruise & WOT AFR?
    I would do so. The laptop EFI software allows you to view the full table and MAP kPa & RPM axes.

    What do you suggest? I know 15 is usually the upper range.
    Try 12.5 AFR at WOT.

    Since I'm only seeing overheating at higher RPM, why would setting the initial timing higher and keeping total timing the same address the issue?
    In post #1, you stated the overheating was happening at anything over 2200 RPM.

    Is there anything else I may have changed by virtue of putting the Terminator on?
    I would ensure all four injectors (annular discharge rings) are spraying fuel.

    Would switching to a small cap HEI and let the Terminator control the timing help anything?
    Yes, it's a lot easier to adjust ignition timing on a laptop computer (LINK).
    Also, without ECU timing control, I don't know what your timing is at the problem area.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

  5. #5

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    OK, I took this out again for a drive. Decided to play with the Target A/F Ratio values with the handheld before connecting a laptop.
    Lowering target for WOT to 12.5 as suggested increased the rate at which coolant temps increased. This is all somewhat subjective of course, since I'm trying to drive while monitoring temps and don't have a passenger to help :-)

    I pulled over, and tried increasing the Target A/F Ratios. I started with something I consider very high; 16.5 cruise AFR & 14.5 WOT AFR. This had a significant impact. Driving at 65/2800 RPM in 4th gear, the coolant temp actually topped out at 210. At 16.7 cruise AFR, 14.8 WOT AFR, running at the same speed/RPM, the tuck actually dropped to 209, and vacillated between 209 & 210. At those setting, even if I stepped on it, uphill on the highway at 75/~3200 RPM, coolant temps hit 214, and stopped increasing.

    The only issue I have with my "tests" is that the ambient conditions are very different from when I first noticed the overheating. The first time I noticed the overheating issue, it was 90, sunny & humid out. Today it was 76, partly cloudy & dry out. So I have no idea if I'll see similar behavior in hotter weather. But it still did overheat (just not as quickly) in similar weather today. I tried two days ago in 80, cloud/dry weather, and driving at the same speeds on the exact same route. The coolant temp hit 225, and there was no indication it had hit a ceiling.

    So ambient temps aside, I think the AFR is at least a significant contributor to the overheating issue. But 17 AFR at cruise & 15 AFR at WOT seems extremely high to me. Is this high? If so, is there some other underlying issue I should consider? This makes zero sense to me. BTW, higher AFRs should be causing overheating, not alleviating it, right?
    Last edited by JMG; 09-05-2016 at 12:51 PM.
    Trail: 1988 XJ, ZZ6 350 Chevy, 700R4, 35" MTs, Warn 1200, 4.11 gears, Detroit lockers, Hooker headers, Terminator EFI
    Daily: 2018 Grand Cherokee Trackhawk

  6. #6
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    Quote Originally Posted by JMG View Post
    So ambient temps aside, I think the AFR is at least a significant contributor to the overheating issue. But 17 AFR at cruise & 15 AFR at WOT seems extremely high to me. Is this high?
    Yes, 15:1 AFR is abnormally lean at WOT.

    If so, is there some other underlying issue I should consider? This makes zero sense to me.
    I think something is wrong with the ECU's AFR recognition. In Engine Parameters, ensure
    the "Fuel Type", "Wideband O2 Sensor" & "Actual System Pressure" is programmed correctly.
    http://forums.holley.com/showthread....ents-Read-This! (Initial Checks & Adjustments - Read This!)

    BTW, higher AFRs should be causing overheating, not alleviating it, right?
    Yes, that's usually the case with lean AFRs.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

  7. #7

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    Thanks. This is driving me insane, just doesn't make sense. I'll double check, but I'm pretty certain I set it to wideband O2. I'll double check the fuel pressure setting.
    Trail: 1988 XJ, ZZ6 350 Chevy, 700R4, 35" MTs, Warn 1200, 4.11 gears, Detroit lockers, Hooker headers, Terminator EFI
    Daily: 2018 Grand Cherokee Trackhawk

  8. #8
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    Quote Originally Posted by JMG View Post
    I'll double check, but I'm pretty certain I set it to wideband O2.
    All three "Wideband O2 Sensor" parameters are for WBO2 sensor types. Ensure they're programmed correctly. Maybe the WBO2 sensor is defective.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

  9. #9

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    I had thought the same thing, but haven't tried replacing it. I'm using the Bosch sensor that came with the kit. I bought a new replacement sensor last week, but it's sitting in my garage. I was grasping at straws. I thought maybe when I installed the differential, maybe the welding damaged the sensor. I'll swap it out one of these nights. Other than select the proper model sensor, what exactly do I need to do to program it? I don't remember any programming steps in the instructions.
    Trail: 1988 XJ, ZZ6 350 Chevy, 700R4, 35" MTs, Warn 1200, 4.11 gears, Detroit lockers, Hooker headers, Terminator EFI
    Daily: 2018 Grand Cherokee Trackhawk

  10. #10
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    Quote Originally Posted by JMG View Post
    I thought maybe when I installed the differential, maybe the welding damaged the sensor.
    This is also a strong possibility.

    Other than select the proper model sensor, what exactly do I need to do to program it? I don't remember any programming steps in the instructions.
    I'm referring to the "Number of Sensors" & "Sensor Averaging".

    EFI Software Problems:
    Often times, when EFI software related functions don't work properly, it's caused by a corrupted software download/installation.
    I suggest completely removing the Holley EFI software from the "Control Panel", "My Documents" (Holley folder) and
    the "C:Drive" (Program Files, Holley folder) and install a fresh EFI software download. Save your Global Folder somewhere.
    ECU Firmware Problems:
    Conversely, often times, when actual ECU related functions don't work properly, it's caused by a corrupted ECU firmware installation.
    Also, try completely disconnecting the battery for 20 minutes. This "resets" some unusual ECU issues.

    http://forums.holley.com/showthread....5760#post45760 (Determining EFI Software/ECU Firmware Versions)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

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