1970 Mk III hot engine, hard to start

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Originally Posted By: clinebarger
Originally Posted By: sasilverbullet
Yes, me again with another issue with my newly overhauled 460. I didn't realize that I needed to be an automotive engineer to get all this stuff to work! I don't know that I'd do this over if I knew about all the hassles.

Car starts and runs great except when hot and sits for 15 min or so. Starting it takes quite a few cranks and when it fires, it seems to be running on two cylinders. I have to baby the gas pedal and get the rpm up to about 2500 for about 5 secs, then it runs fine.

I used a laser temp gauge on the Edelbrock 2166 manifold, right below the carb is about 204, and the Edelbrock 1406 carb right above the phenolic spacer is about 185 degrees.

The engine shop says I need to trash the Edelbrock and put a Holley on there.

What do you guys think?



The 1406 is a 600cfm? That wouldn't feed a smog era 460 truck motor with 4 degrees of retarded valve timing, The '70 Lincoln 460 is pretty hot. The 1406 is calibrated to a mild 350 Chevy for economy.

Jegs has a Chevrolet Performance 4160 Holley 770cfm, Electric choke with quick change vacuum secondaries for $431.99....That is CHEAP for a 4160.

ALL Edelbrock AFB carbs are designed to run NO MORE than 5.5 psi of fuel pressure, I run them around 5psi, Adjust float level...Which is always to high, & Use an isolated gasket or a small phenolic spacer....Do all this & the hard hot start will go away.



I disagree with the assertion that a 600 won't feed a 460. It's relative I say. A 600 is usually within the range that most carb selection tools will recommend. Heck, Holley recommends a 390ish CFM for up a 360 in engine. If the OP isn't goin racin, then a 600 will give nice crisp throttle response and return decent economy. As for fuel, the OP had his engine dyno'ed prior to installing it, so I would HOPE the place the dyno'ed it checked/set fuel curves. I know the OP said they set timing...

I do very much agree with you that the float level needs to be verified. That was my first thought as I have run into it many times with Holley carbs. Different carb, same symptom, and likely the same cause.


OP- try cracking the throttle open when you attempt another hot start. I bet she comes to life a bit easier.
 
the carb he has is going to give excellent throttle response set up correctly yes a mechanical carb like a holley 750 hp or ultra series would likely give him 10 or 20 hp at 5000 rpm or above but its in a Lincoln.The problem he suggests sounds like float level or way out of adjustment period.
 
Since it only acts this way on hot start ups you like do need to make sure the exhaust crossover passages are blocked on the intake manifold and that the fuel like is not too close to anything really hot like your exhaust manifolds or headers. If you have headers wrap them and it will help the under hood temp. The cooler the air under the hood the more power you will get.

I had a problem with stubborn hot starts in summer on my small block chevy. All the things I recommended above I did and it helped quite a bit.
 
Originally Posted By: sasilverbullet
My neighbor has this on his car, fixed his problem. I'm going to get one and see if it fixes my problem.

link to heat shield


That means you have fuel percolating out of the carb into the intake during a hot soak. This makes the engine WAY too rich at startup, and it runs fine after it clears the excess fuel.

Check tailpipes at start for black smoke puff. Adjust float level lower. Regulate the fuel pressure. Pay no attention to the 'biggger carb' idea, you'll have FAR better driveability with the lil' Edelbrock.

It's called 'tuning', and it's a lost art...
 
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Originally Posted By: SteveSRT8
Originally Posted By: sasilverbullet
My neighbor has this on his car, fixed his problem. I'm going to get one and see if it fixes my problem.

link to heat shield


That means you have fuel percolating out of the carb into the intake during a hot soak. This makes the engine WAY too rich at startup, and it runs fine after it clears the excess fuel.

Check tailpipes at start for black smoke puff. Adjust float level lower. Regulate the fuel pressure. Pay no attention to the 'biggger carb' idea, you'll have FAR better driveability with the lil' Edelbrock.

It's called 'tuning', and it's a lost art...


lol! Yep, totally agree. I'll start with the heat shield and "tune" from there.
 
Originally Posted By: Skid
Hot rods... been a looonnng time.... Looks like this manifold has the exhaust ports crossing over underneath for better warm up.... that was OK with iron intake manifolds, but was awful with aluminum. I'd block those ports.

This would be a very good idea, especially where the OP lives. I have done this very thing on several cars. The only down side to doing this is that the car will idle rough until the engine is fully warmed-up. Also, unless you have a crossover pipe (X-pipe, H-pipe) in the exhaust system, it will make your exhaust sound kind of funky at idle. Buy a set of the correct heat blocker intake manifold gaskets if you want to do this.

Originally Posted By: SteveSRT8
Heat soak can be a bear.

If the carb is on a spacer that should not be a problem, though. Could be that the level is set too high and you actually are over rich on start up due to fuel percolation.

That would be most likely.

Don't fall for the bad mouthing on the carb. I have run them and they are great street carbs, just trickier to set up...

I agree with Steve. The Edelbrock/Carter AFB carburetors are excellent and are my personal preference for the street and cars used as daily drivers. But, you can't just take one out of the box, bolt it on, and expect the car to run perfectly. In addition to the float level, you need to check the choke adjustment and also how you have the choke connected to it's power source (as well as how it is grounded). A common mistake that many people make is to connect the choke to the + side of the ignition coil. The problem with this is that this connection is AFTER the ballast resistor and the choke will only get 8 to 9 volts, not enough to warm it completely up. You need to take the air cleaner off to see what the choke is doing when you try to hot-start the car. It should be FULLY open. If it is closing even part way, you found your problem.
 
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I forgot to mention that, in addition to the choke being wired to a good ignition-on 12v power source (BEFORE the ballast resistor), your Pertronix ignition module also needs it's + wired to the same 12v power source (NOT to the coil +). You didn't mention what kind of ignition coil you were using. If it is mounted on top of the intake manifold (in a traditional Ford location), IT could be getting heat soaked and causing a misfire after a hot restart. Also, if you are using the hot Pertronix coil, regardless of what Pertronix tells you, it MUST have a ballast resistor or it will overheat. I use a 1 ohm ballast resistor with this coil (JEGS 40103).
 
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The RVP of E10 gas that is available today presents the problem of fuel percolation in the carb that was not a problem in 1970.Do you have any stations near you that can supply a source of 100% gasoline? It will make a difference. FWIW

Oldtommy
 
Originally Posted By: 2oldtommy
The RVP of E10 gas that is available today presents the problem of fuel percolation in the carb that was not a problem in 1970.Do you have any stations near you that can supply a source of 100% gasoline? It will make a difference. FWIW

Oldtommy


Nope. No E0 available anywhere in Texas that I am aware of (except AVGAS at the airports).
 
Originally Posted By: 2oldtommy
The RVP of E10 gas that is available today presents the problem of fuel percolation in the carb that was not a problem in 1970.Do you have any stations near you that can supply a source of 100% gasoline? It will make a difference. FWIW

Oldtommy


Nope, not close by, 80+ miles away.
 
Originally Posted By: wag123
Originally Posted By: 2oldtommy
The RVP of E10 gas that is available today presents the problem of fuel percolation in the carb that was not a problem in 1970.Do you have any stations near you that can supply a source of 100% gasoline? It will make a difference. FWIW

Oldtommy


Nope. No E0 available anywhere in Texas that I am aware of (except AVGAS at the airports).


There is a company in the are that sells barrels of "racing fuel", but it's very expensive and i have to store a 50gal drum of fuel and pump it into the car.
 
Sounds like flooding. When the engine sits hot, gas will rise and flood the engine. Simply press the gas pedal a little when cranking and keep it pressed until the engine starts running smoothly.

The same problem happens in my car because the charcoal vapor canister is too old and can't store the vapors and fuel tank overpressures, which sends the gas into the engine. I don't know if you have a charcoal vapor canister.
 
Originally Posted By: Gokhan
Sounds like flooding. When the engine sits hot, gas will rise and flood the engine. Simply press the gas pedal a little when cranking and keep it pressed until the engine starts running smoothly.

The same problem happens in my car because the charcoal vapor canister is too old and can't store the vapors and fuel tank overpressures, which sends the gas into the engine. I don't know if you have a charcoal vapor canister.


Nope, too old for a canister.
 
Originally Posted By: Chris142
i agree with the engine shop. i gave up on edelbrock carbs years ago. plus a holley gave my truck 30 more hp and 90 more ft lbs of tq than the edelbrock did


While I would agree that a Holley is easier to tune I think your post implies that an Edelbrock/Quadrajet style carb cannot make high horsepower. Definitely not true.

IME there have been very high horsepower street cars and trucks, some making north of 600 crank HP that had excellent driveability with a Quadrajet on top. IMO for a real street cruiser like he has the Edelbrock has the potential to deliver better mileage and manners, he just needs someone who understands the design to set it up correctly.

Plus the most common mistake folks make is buying too big of a carb, his is actually fine for street, he isn't interested in the absolute biggest numbers...
 
Originally Posted By: SteveSRT8
Originally Posted By: Chris142
i agree with the engine shop. i gave up on edelbrock carbs years ago. plus a holley gave my truck 30 more hp and 90 more ft lbs of tq than the edelbrock did


While I would agree that a Holley is easier to tune I think your post implies that an Edelbrock/Quadrajet style carb cannot make high horsepower. Definitely not true.

IME there have been very high horsepower street cars and trucks, some making north of 600 crank HP that had excellent driveability with a Quadrajet on top. IMO for a real street cruiser like he has the Edelbrock has the potential to deliver better mileage and manners, he just needs someone who understands the design to set it up correctly.

Plus the most common mistake folks make is buying too big of a carb, his is actually fine for street, he isn't interested in the absolute biggest numbers...


+1

Would a bigger Holley give him a bit more peak power?

Probably, but would worse manners on the street and mpg. Don't get me wrong Holley makes a great product and are simple to work with. We run them on most of our engines, however I don't care about street manners. quadrajets have better response and fuel mileage (generally) from the small primarys, and the secondaries are very large for power.

GM spent a boatload of cash designing these carbs. Anybody who calls them "QuadraJunks" or "QuadraBogs" doesn't know much about carbs. They have a bad rap due to a few issues (throttle shaft bushings, warpage) but are overall a great carb.

Carb tuning is a lost art now days it seems. Find someone who knows how to tune it.
 
Originally Posted By: SteveSRT8

While I would agree that a Holley is easier to tune I think your post implies that an Edelbrock/Quadrajet style carb cannot make high horsepower. Definitely not true.

I thought an Edelbrock carb was more like a Carter AFB than either a Holley carb or a Q-jet.

But I'm not sure because I hardly ever encounter an engine that doesn't have EFI.
 
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