Last post on Dec 11, 2001 at 10:20 AM
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Dec 05, 2001 (5:53 pm)
I don't know if you guys have ever driven a vehicle with the stove pipe removed but it runs like heck till it warms up, I have a 74 Dodge with that stuffed removed and it barely gets going in the morning, but my 81 Chevy pickup, starts right up and when I drive away it doesnt spit and sputter (as much lol)
Carb icing, I have experienced this about 2 weeks ago, I usually go 55 at the steepest part of the pass, my truck would only do 40, on the way back put some anti-ice stuff in the gas and no problem. Happened because I have two tanks, and one I only use once in a while I filled them both up for safety (get stuck in some sort of snow storm want to be warm) and I was using the tank I don't use to often so it was bound to have some moisture in it.
Dec 05, 2001 (8:14 pm)
Yeah I imagine a '74 anything would need all the help it can get to start on a cold morning, even when it was new. By '74 they were using every Michael Mouse smog control fix in the book.
I'm pretty sure my '73 Ventura still had the pre-heater and it started fine, but we hardly ever get below freezing. My '71 LeMans had all the pre-heat gear too, but I don't remember if the '69 GTO did. You'd think I would because I had to park it on the street and every night I took the Ram Air air cleaner off and put it in the trunk, then put it back on in the morning. I did this for months before I finally decided to take my chances and leave it on overnight. I'm pretty sure it still had the stove but '69s weren't nearly as leaned out and wouldn't have needed as much help starting.
I've always lived in warm weather states and it sounds like I should keep it that way.
BTW that '71 LeMans had kind of an interesting smog control, no vacuum advance once the engine reached operating temperature. There was a sensor in the intake manifold with a plunger that blocked off vacuum to the advance can once it sensed the coolant was warm. I always thought vacuum advance was a real useful innovation, right up there with the self starter, but I guess it fouled up the emissions somehow--just one more variable to control.
#47 of 54 OK, I'm confused.....
Dec 05, 2001 (9:28 pm)
Are we talking about vacuum advance on the distributor? I thought your car wouldn't run without it. My understanding (correct me if I'm wrong), is that at low RPMs the sparkpulg can fire when the cylinder is almost at TDC on compression stroke, and ignite the fuel. But at higher RPMs, the fuel's going to burn at the same speed, so to get it all burned, you have to advance the timing, ie fire the spark plug sooner, so that all the gas is burned when you get to top dead center. Otheriwse, you loose power, and gas is still burning into the power stroke. And when that happens, I don't see how it could be good for emissions, as you're burning fuel that doesn't help provide power. Wasting it, in other words.
#48 of 54 Rea98d...Even the Auto Engineers were Confused in the '70's
Dec 05, 2001 (10:25 pm)
You are correct about the fundamental engine speed and spark advance relationship, Rea98d, but the centrifugal advance rather than vacuum was the major element of spark advance control - and it was basically unchanged during the dark days of the '70's. Before '72, most vacuum advance systems provided little or no advance under conditions of high engine load because detonation would result from the high combustion pressures combined with high timing. At low engine loading, the increased manifold vacuum would provide extra ignition advance for improved economy. Thus, in general, vacuum advance varied inversely with engine loading and centrifugal advance varied directly with engine RPM.
In the '70's, as Speedshift indicated, there were several schemes for changing the ignition advance curves with engine temperature in the effort to reduce exhaust emissions. Some involved switching between ported vacuum and manifold vacuum when the coolant temperature reached a pre-set level. I agree that these spark-advance schemes, combined with the primitive EGR controls and low compression ratios, often caused stumbling or stalling during acceleration - and they consistently provided poor power and fuel economy.
Dec 06, 2001 (8:37 am)
Fuel0injection and computers saved cars from this fate. The 1968 VW squareback led the way.
Dec 06, 2001 (11:20 am)
I also seem to recall that the factory recommended initial timing, the kind you set by rotating the distributor, was retarded in the early '70s.
That '71 LeMans was a good indication of what had happened to musclecars by then since it had the optional 400/335 standard on the GTO that year. You'd think it'd be quick around town but part-throttle response was pretty flabby because there was no vacuum advance to bring in an extra 10 or 15 degrees of advance. The 8:1 compression ratio (down from 10.75:1) didn't help either, or all the weight intermediates had picked up by then.
Dec 06, 2001 (3:32 pm)
timing wasn't the only thing retarded on cars in the 70s.
#52 of 54 How about the three speed (manual)
Dec 10, 2001 (5:27 pm)
Just not enough in so many ways. Not enough low end in first. Too high of a ratio differential going into second. Gutless in third. Usually not a good ratio between second and third to give good passing capabilities.
Thank goodness that five speeds are now the norm, and six speeds are not all that uncommon.
#53 of 54 Mod tops....
Dec 10, 2001 (11:43 pm)
I think that is what they were called. Pretty flowers all over your vinyl top with a lovely matching interior.
Dec 11, 2001 (10:20 am)
I remember that Chrysler had a paisley pattern. What a beautiful fashon statement.