GM made millions of cars with Quadrajet carburetors that have mechanically actuated secondary throttle valves. There is a secondary well separate from the float bowl with a metered amount of fuel supplied from the fuel bowl. When the secondary throttle valves are opened suddenly, a timed/metered amount of fuel is provided to the secondary throttles as an "accelerator pump" to cover the lean condition before the secondary fuel nozzles begin to flow. (Look at the front wall of the secondaries right above the air valve, you'll see two small holes which is where the secondary "accelerator pump" shot flows from as the air valve begins to open.) A common modification is to increase the size of the orifice feeding the secondary well if off-on-off-on throttle application frequency is quicker than the well can refill. The Quadrajet is technically a mechanical secondary, double-pumper carburetor with an air valve to limit air flow to the demand of the engine...it will easily provide accurate fuel metering and excellent drivability across whatever RPM spectrum you want.

The Quadrajet's only limitation is the amount of HP you can make with it's single inlet needle/seat...the fuel flow rate will only provide enough fuel to support about 500 HP continuous (much more HP for very short bursts). If I was drag racing, I would increase the float level and run it up to 800 HP but my application was Ocean Racing in Cigarette type boats where you have the throttles firewalled for extended periods. If anybody ever provides a method to increase fuel flow to the float bowl (I have a design, never implemented though), an 800 CFM Quadrajet could easily make the same HP as an 800 CFM Holley. The other alternative is to run two Quadrajets with a progressive throttle linkage for the street.

 

Very True. If we were to go to the Persian Gulf we would need to re test the Delta T and make sure we still had our 30 degs. If not then we would need to adjust the orifice. With the warmer water temps out side the hull we would need to slow down the flow even more. If we were not able to get the 30 degs then we would need to increase the surface area of the heat exchanger.

No I'm not a degreed engineer. I have a 1600 gt Master of Oceans, DDE Unlimited HP. Issued by the USCG.

 

Regarding the "stay in the radiator longer to cool": If the fluid travels 2 times faster it is in the radiator twice as often.
10 / 1 = 10.
20 / 2 = 10.
The coolant speed has zero effect on radiator dwell time.

 

No. Coolant speed has nothing to do with radiator dwell time. If coolant travels twice as fast it is in the radiator twice as often. Coolant speed has nothing to do with radiator dwell time.

 

So, please explain this:

My 79 starts fine when its cold but cranks slow for a couple of seconds when its hot. Its got a new batttery, new starter, but the passenger side exhaust pipe hits the starter as it goes by. Would you claim that if I re-routed the exhaust so it doesn't hit the starter I'd still have hot start slow cranking?

 

I am. I asked my husband who's a long time mechanic about the claim that heat soak doesn't make a starter crank slow and after he laughed and rolled his eyes he explained to me the specifics of why it does.

 

Hi Priya,
First of all, you asked a simple question to a real mechanic. Good for you!

So what's the difference between someone who works on cars for a living and a "proclaimed" educated mechanical engineer (the OP)? The mechanic has real world experience.

(No disrespect intended to the real, actual mechanical engineers on the forum)

 

You should have seen the thread I posted on a Sharkbite Rear Suspension kit I put on my car. I had more armchair engineer retirees informing how it simply wouldn't work.

Well, works great. Adjustable ride height. Adjustable compression and rebound. Works like its supposed.to work.

I can remember hearing the story about the guys wife who always cut her roast in half before putting it in the oven. Her husband asked her why she did this. She didn't know, only that her mother did the same thing. The son in law asked his mother in law why she cut the roast in two pieces before placing it in the oven. Her reply was that her mother always did, so he went to his wife's grandmother and asked her. "Why silly, she replied, it's because my oven was too small so I had to cut it in half".

So now we know how myths get started and carried on for generations....

 

Yes we do.

 

Just read the Sharkbite thread. Not quite sure what to say about it but I definitely won't say it on this thread.

 

Here's what my husband explained to me. As the temperature of a wire rises so does the resistance in it and that means less electricity can flow through it. So while its true the solenoid will lose magnetic strength when its coil winding get heat soaked, the same is necessarily true of the starter itself. If the problem in heat soaking the starter was that the solenoid loses magnetic strength then the solenoid wouldn't engage the engine and the starter would just spin when the ignition key is put in the cranking position. That doesn't happen when we see a heat soaked starter. What happens is the windings in the starter increase in resistance, this means less electricity gets through and the magnetic field that turns over the starter isn't as strong as it should be, the starter generates less horsepower and so the engine cranks slowly when hot. It takes a lot less power for the solenoid to engage the starter than for the starter to turn the motor so heat soak in hurts the operation of the starter, not the solenoid.

If, as toobroketoretire says, the heat soak affects the magnetic strenght in the solenoid then he has to accept that it also affects the magnetic strenghth in the starter and makes it crank slowly - you can't have one without the other.

 

Why would you think that Mechanical Engineers have no "real world experience"?

And yes, I'm a Mechanical Engineer.

 

This Corvette stuff is complicated. I just wanted to drive a cool car and tinker with it. Do I need to go to MIT? Should I just sell it now? Does my oil need to be at an exact temperature before it will flow from the oil pan? At one time, someone used the ashtray, will this affect my timing? What have I got myself into now?


Oh, woe is me!

 

You husband nailed it! He gave you a theoretical and real world explanation. You should keep him around! lol

 

You misunderstood the comparison I was making between just the OP and Priya's husband.
I was referring only to the OP. Do we have any proof he really is a mechanical engineer? That's why I said "proclaimed". I have yet to see a single thing he has posted that shows any form of intelligence or education.

 

Your husband sounds pretty sharp. My compliments. I do, respectfully, disagree with your wording in the bolded section, as the starter motor won't/can't turn if the solenoid plunger doesn't move/engage. The moving plunger moves the internal copper disc that connects the battery voltage to the motor windings. No solenoid/plunger action, no motor activity.

 

Oh yeah, he's a keeper!

 

Yes, my husband didn't say that, I was assuming based on my experience with Ford starters.

 

It's treads like this that make me limit my posting, and asking questions.

For someone to say "ignorant people who believe these myths" is calling EVERYBODY ignorant.

Everybody uses their cars for different things and is setup differently. To make blanket statements about setting timing or which water pump to use (or any setup) depends on the individual car, and how it will be used. To call them "ignorant" for not following your advise is offensive.

BTW, If i want to drive in figure 8's in a parking lot, I am going to do it. If you don't like it, then don't watch.

In Before The Lock

 

Priceless!