revving an engine to "warm it up"

Ya ya, they fall into the modified class in my book and I have helped a pile of those owners retrofit the heat pipes once they realized their carbs were turning into ice blocks come winter so they could use them year round. Along with a second set of rims and snow tires.... Most just parked them come cold weather.

Reply to
Mike Romain
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now that I think about it...I believe you are right. Many of the 70's year model cars had all kind of crap in the emission controls, and other junk. I think I do remember some type of valve in the exhaust manifold (one side) of my 78 z/28. Of course those went in the garbage (had to install headers). I believe it was a "butterfly" value in the exhaust manifold and had metal rod that operated it off a vaccum valve (is this right....anyone recall the GM Crap?)

I bought the car used and the first thing that went was that valve "thing" in the exhaust, and on went dual exhaust. Then the intake and the smog carb went away too. Dual plane and holley went on next.

I was wrong in my statement above... thats been a few years ago.

I know that "valve thing" does not do much justice to the item but maybe you'll understand :) Thats been 20+ years ago now.

Boy all that crap on those cars was about useless. I remember the smog pumps, and all the crazy vaccum lines. I think the stock 78 z/28 had about 180 HP...boy what a machine :)

The factory air clearner went out the door too. I had a lot of fun with that car....especially after it ate a rod bearing....re-built the motor / trans and added a mild stall converter. Pretty hot street machine then.

Long story short....I was wrong.

----------- Elbert snipped-for-privacy@me.com

Reply to
Elbert

Again here is the link which shows a GM engine from the '70s with exactly what Neil is talking about.

formatting link

Reply to
Stan Weiss

you are right.... I got caught up on the heat pipe to the carb and I clearly forgot about the other stuff. I spent a lot of time removing all that junk. It did not stay on the car long (the one I had at the time) back in my HS days. (early 80's)

Thanks for correcting me....I should have thought through my answer and done a little research prior to my post.

Elbert

----------- Elbert snipped-for-privacy@me.com

Reply to
Elbert

thanks for the link.... yea I clearly forgot all about that...

I remember telling the exhaust guy to through that crap away and put on some real dual exhaust.

You guys were right on.

----------- Elbert snipped-for-privacy@me.com

Reply to
Elbert

Without knowing what tempertures you see in the winter I cannot say. I know here in Philadelphia PA I drove my '67 GTO all year round in the late '60s as it was my only car. The only problem could be some water in the gas that would want to freeze and some dry gas toke care of that. Stan

Reply to
Stan Weiss

You must be use Obfuscate on your replies. Stan

Reply to
Stan Weiss

That's interesting I suppose, but it has absolutely nothing to do with the O.P.'s comment.

That setup was very common on cars up through the late 80's and early

90's. A shroud surrouds the intake manifold and an aluminum air intake hose connect the shroud to the front of the air cleaner. There is a temperature controlled air valve is used to direct air. Do a little research before making such a flat statement.
Reply to
John S.

Exhaust manifold.

Reply to
cavedweller

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Maybe on -some- makes of vehicles...certainly nothing I ever drove. IIRC, in the 80's and 90's I had a lot of *vintage* automobiles...nothing I paid over $200 for.

The one thing they had in common was amazing horsepower and an insatiable appetite for fuel. You could watch either the speedometer or the fuel gauge...sometimes it was hard to tell which was which.

I might still be driving something similar today if it weren't for the strict emissions tests run by the State of Illinois. Those vehicles wouldn't/couldn't Pass no matter what you did to them.

I did drive a 442 one summer, and watched that gas gauge drop like a barometer in a tornado. You could EASILY go through 1/4 tank of fuel in 10 minutes. An eighth of a tank in one acceleration ( that would glue you to the drivers seat...or rather IMBED you in it ). here is something to refresh your memory:

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400 cubic inches, 4-barrel carburetor, 2 exhausts

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That was a jet fighter. All it was missing was wings. 345 horsepower.

Compare that with the dinky shit on the roads today. They will not build another 442 in our lifetimes, I'm sad to say. Fuel has become too expensive for such a beast.

At the opposite end of the spectrum is the limp-wristed Eurocar, coming to a neighborhood near you soon.

Do I care about yesterday's vehicles? Only if I'm driving one. Not too many are. Show me a 442 on the road today...ANYWHERE.

Lg

Reply to
Lawrence Glickman

Which is absolutely NOT the same as the exhaust being "shut off."

The heat riser is spring loaded so that if you do get on the throttle while its still "closed" the exhaust pressure will swingit open and let the exhaust take its normal route.

Reply to
Steve

Two things can happen -

1) a "heat riser valve" will shut and direct exhaust away from its normal path of straight from the valves through the exhaust manifold(s) and out the exhaust pipe(s) to an auxiliary passage under the carburetor, to help the carburetor get up to operating temperature quickly. This valve will have a thermostatic bimetal spring to open it again when the appropriate temperature is reached. (something to check when a car has been sitting a while; this valve will often be rusted in the shut position causing vapor lock problems when warm)

2) a valve will close in the snorkel of the air cleaner causing the carb to suck its intake air not straight through the snorkel but from a little sheet metal "heat stove" strapped or bolted to an exhaust manifold, also to help the carburetor warm up quicker. Again, when warm, this valve will open to prevent the carb from overheating.

On a "modified" engine, it's entirely likely that some of the first modifications made were to replace the manifolds with tubular headers and the original air cleaner with some freer-flowing aftermarket unit, which will provide for better airflow and thus more efficiency and power under normal operating conditions, but will also eliminate both of the functions described above and tend to make the car a little "cold blooded" unless it's operated only in a temperate climate. This can be compensated for somewhat by adjusting the choke richer, but at the expense of economy until the engine is fully warm (and it will still prolong the period of time that the carburetor is operating in "warm up" or choked mode)

As I posted before, sometimes people with a really "hot" car will mill off the choke horn in the interest of improved airflow; when combined with the other mods mentioned above, this will make the car all but impossible to drive without revving the snot out of it to keep it lit until it reaches operating temperature.

I don't know how old "older" is, but any car I've ever worked on has at least a choke and the heat riser valve. I think the heat stove/snorkel valve was introduced in the late 60's or early 70's (depending on manufacturer.)

nate

Reply to
N8N

And if the cam is radical enough (lots of overlap) then even using the choke won't do much good since so little vacuum is developed in the intake manifold. That's really the reason most people eliminate the choke at some point- it stops being useful and is *just* in the way of air flow.

Reply to
Steve

Then they're those carbs without choke butterflies to begin with, but enrichment jets instead, like Strombergs and certain Motorcraft (Ford) models.

Pulling out the "Choke" lever on an old Volvo just slides a metering rod out of the auxiliary jet in each carb. :-)

Reply to
~^Johnny^~

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