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Thread: Poor Performance When Hot

  1. #61
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    They used to ice the intake (besides just cooling the engine overall) in an attempt to get as cool of a charge as possible. The theory was good, but I'm not sure if it made much difference since the A-F mix went through the ports so fast. Also, when the fuel mix comes out of the bottom of the carb it cools things anyway. If you ever run a tunnel-ram you can watch the outside of the top piece of the intake actually start to ice up after running for awhile.
    X2 on that. There is a tremendous cooling effect due to the pressure drop through the carburetor venturis. It's there on a standard manifold, just much easier to see on a tunnel ram.

  2. #62
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    Quote Originally Posted by chasracer View Post
    On those crossover ports, we used to take heavy duty aluminum foil and make balls of it about the size of the crossover passage and just keep filling it and cramming them in until we couldn't put anymore in there. The stainless steel plates are probably a better idea.
    It's a little harder doing that on a BB because of the weird crossover port shapes. As you said it does work though.

    I did something like that with a twist before. I took the foil and crammed it down into the head to make a dam, then I filled the rest of the way up with epoxy. Much later I had a wrist-pin issue so I pulled the motor apart. Inside those ports the foil was completely gone and burned up looking. I guess the foil burned up and passed though the exhaust just fine, because I don't remember having any noticeable problems.

    The best way to solve it is to run a newer-better head that don't even have those useless crossover runners in the first place. The second best is to get an intake without them. The third best is obviously to run good gaskets with the block-offs. Money is always an issue with the first two though for most street guys.

  3. #63
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    Back in the old days I had a pair of iron heads prepared by the late Lee Shepherd. He had a little dam that he built for the exhaust port so that he could melt down old pistons and pour the aluminum into the crossover passage. It served two purposes - one it blocked the crossover and two it "fixed" the exhaust port that connected to the crossover so that it looked like and flowed like the other exhaust ports. We set a record with that engine and NHRA had us tear it down to certify. Got scolded because Lee did "too nice of a job" and they told me to remove some of the metal in the port to crossover joint. They didn't take away the record or make me fix it that day, just told me not to come back with it that way. I don't miss that nit picking.

  4. #64
    Registered Member chasracer's Avatar
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    Oh yea, I raced a '55 Sedan Delivery with my partner in IHRA/NHRA SS/OA for a few years. I was at Budds Creek for an IHRA national event and on my second qualifying pass, they backed me off saying I had dumped fuel from the tank on the burn-out. This was a 3400 pound car that didn't exactly shake the ground on a burn-out. We went back to the pits, tore everything apart around the fuel tank and couldn't find any evidence that we were leaking, put it back together the way it was and ran the rest of the race and more after that without hearing about it again.

  5. #65
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    There is no programed retarding of the timing for starting. What I thought was a delay/retard I believe I was mistaken reading it and it was 18 cold and hot. I turned it to 16.

    I used a fixed, and a dial back light, both with the same results.

    The *miss* wasn't it jumping around, the light(s) would skip a flash. I did this on 3 different cylinders.

    The initial timing is (now) 16. The advance *at 1500rpm* takes it to 28 total (no vacuum), all in is 38 (no vacuum). I was asking if that advance at only 1500rpm is too early and I should change one spring to a little stronger one, but from what I see that isn't too much too soon. I don't think so anyway?
    Tony

    1955 Bel Air Sport Coupe

  6. #66
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    Well Tony I just got home from MWR it was high 90s with triple digit hear index's where a friend of mine and I double teamed my 3800 pound [ driver on board] SBC Z28, a little off from the fall about a tenth. No real issues thank you VP, get some and try it
    Last edited by markm; 06-16-2018 at 07:57 PM.

  7. #67
    Registered Member chasracer's Avatar
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    So 1500 rpm you have 28* then 38 total at what rpm?

    I think the 16* initial is okay and starting around 1500 rpm to say 2600-2800, like to see it all in at maybe 34*-35* total. Not sure of your fuel but 38* might be pushing it a bit and if you have 28* by 1500 rpm, that's maybe too much too early. But on the other hand, you need to find out what the engine wants too, so I wouldn't hesitate to swap springs and weights with test shots to see where the engine performs best.
    Last edited by chasracer; 06-16-2018 at 08:27 PM.
    Remember the "13"


  8. #68
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    Houston, we have ignition.

    Long story short, I replaced the MSD/R2R distributor with an Autotronics/MSD distributor that is from the 70's or early 80's and I feel a big improvement in power. Not sure if I'll spend time tweaking it, or buying a different new distributor. MSD stopped supporting it 20 or so years ago. Last I talked to someone at MSD about it they basically told me it was a piece of crap.

    Anyway, it was late and not hot out, BUT my A/F gauge never read as steady as it does now, a major difference. My timing light(s) were a LOT more steady. I don't know if it was the new smooth road, all in my head, or for real, but it felt like it was running smoother.

    Tomorrow it's forecast to hit 90F, I'll sweat my ass off and take it for a ride. This is without the multi spark box hooked up yet either. Maybe I'll hook that up in the morning.

    Let's say I'd like to use something more modern but not an MSD, any suggestions?
    Tony

    1955 Bel Air Sport Coupe

  9. #69
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    Also, I had swapped gears from the R2R to the old one. If I get a new one, is a melonized gear compatible with a roller cam? Or bronze, or composite.
    Tony

    1955 Bel Air Sport Coupe

  10. #70
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    Today I bypassed the electronics on the very old MSD distributor and fed the magnetic sensor signal directly to the 6AL multi spark box. It idles better than I ever remember. I took it out when it was just under 90°, then again at 94° and it ran great! No, not like when it's cold, but how you would expect it in the heat. So after years of it not running good when it's hot, I think it's finally fixed. This problem started out in extreem heat but was getting worse and worse, glad I think it's cured.

    I'm not sure if I want to send the billet R2R in for repair or not. I could open it up and bypass the electronics in it also, but it's not just plug & play like the old distributor. I'd have to do a little more work on that one.
    Tony

    1955 Bel Air Sport Coupe

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