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Thread: New install running hot.

  1. #1

    Default New install running hot.

    Hi All. I'm new to this forum and looking for some assistance on a fresh install. I have a 1977 Corvette with the MSD Atomic EFI with timing control, electric fan MSD controlled and while on longer drives? She get hot REAL hot.

    First off I live in California(bay area) and with this particular project have to deal with smog…hence why the purchase of the CARB approved Full MSD Atomic kit fuel pump to T/B.
    The project is my neighbors DAILY DRIVEN 1977 Corvette, now before I got involved with helping him with this he had the car “restored” and part of that restoration was removing the original SBC and replacing it with a BONE STOCK L31 vortex 5.7 BUT because of smog concerns they decided to put all the original fuel and smog equipment back on the vehicle IE, QuadraJet, EGR, air pump, PCV, exhaust valve?, cat, crap exhaust, etc.
    After the install of the engine, he had problems with the car passing smog, took it to a “reputable” local corvette shop and had the tech tune the car up.
    After watching him start this car everyday with a procedure that I could only compare to a steam locomotive. Long crank time, popping, black smoke, and just plain running like crap, I offered to take a look at the car for him. I got the car running pretty good enough to pass smog, but I was afraid that the old carb and HEI spark systems would just cause problems for him down the road, and me coming from the Fuel Injection world I recommended a T/B kit like the ATOMIC. Also keep in mind that this guy is not about the Horsepower. I know weird, but whatever who am I to judge, he just wants a smooth running reliable smog passing cool car.
    The install:
    The install went AWESOME!!!! Thanks to Holley and MSD for making a pretty good kit! Of course I had to improvise a few things but all in all the kit went in and with only a couple calls to TECH support to confirm my install only cause I have never done one of these before.
    ***Also note that I have also taken advantage of the timing control option of this kit, so I have removed the HEI distributor and replaced it with a 85551 similar locked out distributor with the adjustable rotor set 15° in the opposite direction of rotor rotation, 6al similar spark box, and standard Blaster type high output coil.***
    But even with that little bit more complexity? The car started instantly!
    After doing all my post start check, water level, oil, timing lock out, check and set, the car seemed really good. She would come up to operating temp 190°F, idle nice and smooth, rev real nice all of it I thought I was good. I took the car out for some short drives around the block and all felt real good. I was comfortable enough to to drive it to work, to help the system to “Learn”…about a 20 mile drive one way, cruise in the morning, and stop and go in the afternoon on the way home. perfect for what MSD recommends the system to learn.

    OK so on my drive to work I noticed what felt like a misfire at cruise and that the temps started to rise…. To high! only after say 12 miles in 60–65°F ambient air temps. I had to pull over let the car idle, turn on the heater and get the temps as low as they would go (237!) A/F are always good and timing seems good and active? Fuel pressure at 43-45 psi
    I got the car home and started to check some basics.
    Plugs looked lean, I confirmed timing, by locking the timing control and using a timing light set the distributor to 15°.
    Checked the radiator cap cause the coolant is just boiling, it's hot!
    I tried to fatten up the cruise mix from 14.7 to 12.5? No change
    I tried to adjust the timing advanced and retarded with no change.

    Fan replaced with 1500 cfm electric replacement controlled buy MSD.
    duel plane chevy intake manifold, recommended to keep in place by MSD tech support
    Smog Equipped with EGR,
    air pump (blocked),
    exhaust valve,
    water temp vacuum valve for EGR and Air pump.
    Stock short air filter housing with OEM cold air ducting.
    Non-vacuum advance distributor connected to MSD,
    aftermarket spark box and high output coil.
    2-1-2 exhaust with carb approved after market cat.
    New wires

    ENG DIS: 350
    NoC: 8
    FUEL PUMP TYPE: PWM with regulator, 40-45 psi.
    AIRPUMP: no
    REV LIMIT: 5000
    TIMING CONTROL: enabled
    FANS: fan1 175
    IDLE 14.6
    CRUISE 14.6
    WOT 12.1
    BOOST 12.9?
    IDLE 1000
    TOTAL 3000
    TOTAL 21
    VAC ADV 10
    VAC TYPE: ported
    PUMP SQUIRT: 20%
    POWER VALVE: 19%

    DASH: 2.0.7
    ECU: 1.2.14
    P/MOD: 1.0.9

    What I would like is any recommendations on timing settings?
    And spark plugs recommendations? It has been my experience while they will work for a bit, plugs made for a carb motor don’t work as well in a fuel injected motor and vice versa? But this is a weird mix of technology so any input or experience would greatly appreciated.
    AGAIN THIS CAR NEEDS TO PASS SMOG. If that means I have two different settings I can share for the owner that is fine, but I need both. One to pass smog one to enjoy the car more.
    At this time It is my feeling that the timing is contributing to the over heating? Since this car NEVER over heated with the carb, HEI and smog settings.

    I will very honest I have been working on cars for a very long time but my world is 4 cylinder turbo applications, I regret to say I am not a V8 guy but I'm a car guy, I believe in them all and an engine is an engine with subtle differences. I started on Air cooled VW with dual carbs and non-vacuum advanced distributors but that was over 30 years ago. I just don’t have enough experience with mixing new world technology with old world theory, I hope that makes sense. To end this long winded explanation, I just wanted to make sure you all had as much info as possible. Thanks all!
    Last edited by 23tuner; 06-16-2021 at 05:34 PM.

  2. #2


    I don't have any experience with SBCs as I have a 351 Windsor/427 Stroker. But after looking at all the settings I'd say that you need more total timing. 21° is not very much. I'd think somewhere around 32°-34? would be more like it. You did say you had tried to adjust it, so how much timing did you try? If the engine pings you could start walking it back down a degree at a time until no ping. Took me awhile to find the sweet spot for my setup, and it was total timing of 30°. My cruise Target AFR is at 13.8. Idle is the same.
    Make sure the adjustable rotor didn't move, use Loctite on the screws. Find out what the old distributor had for mechanical advance if you have to, and use that as a guide. If it didn't run hot before, then it has to be fixable by duplicating the former mechanical settings. I hope this helps. Take care, Ed

  3. #3


    @ak7an: Thanks for the input.
    It was my understanding that total timing was initial, plus total, plus vacuum advance? Which equals 38° in my case? Also, do you run ported or non-ported vacuum advance? I tried non-ported yesterday and it seemed to run smoother at idle telling me it definitely needs more timing?

    I did try 10° in either direction with no change.

    I did double check the rotor, and yes, did use a drop of blue to make sure that screw didn't back out.

    And I tried to find the curve for the distributor that was in it and Accel doesn't provide that info on there site for the old distributor, BUT they did for the replacement distributor I have, so I used that as the basis of my IDLE 1000 TOTAL 3000 ignition curve settings?
    And I agree with duplicating the previous conditions will help find the issue, I just wanted to make sure I wasn't too far off base with my setting to compound the problem.

    I'm gonna go one more step mechanical tonight and do a compression test to see if I can find a problem cylinder. It's my mechanical opinion that I have a soft cylinder which at revs and at the edge of lean fuel control 14.7:1 causes a lean misfire. The MSD is so quick at reacting to the WBO2 sensor that it leans the mixture for the rest of the engine to compensate, and there for causes the engine to run even leaner and consequently hotter. The car probably had this soft cylinder before with the carb, but had so much fuel it didnt show it as bad? Just a theory though, I'll l start the process of confirmation tonight. Thanks again for your input, it does give me food for thought. 23tuner

  4. #4


    I run ported vacuum. Total timing is just that, Total. Initial timing is what the Atomic sets for idle. So set your total timing to what you want it to be at whatever RPM you want it all in. Try this with the timing setting, set your total for 32°, then set your vacuum advance to zero, start the engine and slowly rev it to the total timing RPM. You should see the timing increase until it tops out at 32° at the total RPM. Now go back and set your vacuum advance to your 10° setting and rerun the test. You'll see the timing increase to a level higher than before, but not more than 10° more. A healthy engine with no load will run fine with 40° of timing. Under a load the vacuum advance will not be as much due to the lesser amount of vacuum.

    I'd decrease your Target AFRs (enrich), and see if that overcomes the lean misfire. My engine runs great at 13.8. Checking compression is a great idea as it'll show the overall health of the engine. Good luck, Ed

  5. #5


    Ed, ported? OK just wondering, I did change to non-ported and the idle smoothed out, telling me it needs more timing. I also bumped up the initial to 15° from the smog sticker 8°. As well totally makes sense on the timing thing it was a misunderstanding on my part. As well did a compression test and found 210-200 psi all the way across.

    Also when doing so I found plug #6 a little different from the VERY lean rest, so I started focusing on that. I swapped #6 & #8 wire and when for a drive. When I got back I and check #6 & #8 plugs again there was a difference. So focused on the plug wires then when inspecting the plug end of the #6 wire I found a bubble in the silicon cover, and a pin hole! I changed the end after spending all morning at the parts store trying to find a plug wire set (just give this project a fresh foundation) and I swear I can't find the proper lengthed set! Arg! I can't use a standard SBC length set because of the smog LOG manifolds. Anyway, found a spare boot in the shop as a temporary and went for another road test,

    This time I fattened up the idle A/F ratio to 13.0 and cruise to 12.0 and things smoothed out. But I'll do some more timing research and trials. Again thanks for your help. Lars

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