Engine dies 4 barrel carb

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Dadaluma
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Engine dies 4 barrel carb

Post by Dadaluma »

Ok here is the situation. I have a 63 monza pg car with a holley 4 barrel carb brand new. When I first put carb on out of box idles great revs great. And I can drive around ok except when i get on gas abruptly it would backfire out carb and stall. I read on forum to fix this problem put on the 50cc pump kit so I did, now it dies when I try to drive it at all but it doesn't backfire it just idles down and dies. Any thoughts or suggestions
joelsplace
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Re: Engine dies 4 barrel carb

Post by joelsplace »

There are accelerator pump cams and different squirter sizes also that need to be dialed in. Maybe someone here will can tell you what they used.
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Jerry Whitt
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Re: Engine dies 4 barrel carb

Post by Jerry Whitt »

Carburetors have ratings related to how much air can flow through the carburetor. The term used is CUBIC FEET PER MINUTE, or CFM.
As the carb was purchased brand new, a rating was probably mentioned on the original box.

There is a formula you could use. Cubic inches divided by 2 multiplied by the rpm and then multiplied by efficiency of the intake system.
164 cubic inches divided by 2 because it takes two complete revolutions times the rpm max around 5000 times .8 . That gives a number of 328,000 which is now divided by 12 cubed. This will give an approximate cfm rating. This number comes out about 190 cfm.

Some carburetors will have a much higher CFM rating. This then means the air flow thru the carburetor is slow. When the air flows relatively slow,
the fuel is not atomized very well, and could cause stalling.

Please let us know what the cfm rating of your carb is.
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Dadaluma
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Re: Engine dies 4 barrel carb

Post by Dadaluma »

600cfm vacuum secondaries
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Re: Engine dies 4 barrel carb

Post by Jerry Whitt »

Way too large a carburetor! I suggest replacing it with a carburetor somewhere around the 200 cfm mark. Higher velocity thru the ports will make the car run a lot better.
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bbodie52
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Re: Engine dies 4 barrel carb

Post by bbodie52 »

:goodpost:
Dadaluma wrote: » Mon Nov 11, 2019 9:01 pm

Ok here is the situation. I have a 63 monza pg car with a holley 4 barrel carb brand new. When I first put carb on out of box idles great revs great. And I can drive around ok except when i get on gas abruptly it would backfire out carb and stall. I read on forum to fix this problem put on the 50cc pump kit so I did, now it dies when I try to drive it at all but it doesn't backfire it just idles down and dies. Any thoughts or suggestions
600 CFM is much too large for any Corvair — especially a small valve head 145 CID early Corvair engine like yours! Even the four carburetor 164 CID 140 hp engine had much larger intake valves, larger exhaust valves and exhaust ports with dual exhaust, and a performance camshaft to help the engine take advantage of the improved 4 carburetor breathing capacity. (The secondary carburetors also used a progressive linkage). The aftermarket center-mount 4-barrel manifold was designed for the 140 hp big valve engine only, and even then the recommended carburetor was a 390-450 CFM 4-barrel unit.

The center mount configuration also had some problems with running in cold climates, as no engine heat reached the isolated center-mount carburetor. Some tried to correct for this by modifying the carburetor mount to include a oil reservoir directly beneath and part of the intake manifold casting. Hot engine oil was routed into this reservoir to conduct some engine heat to the manifold.

Any size carburetor would idle OK with the throttles closed, but as soon as you opened those extra large 600 CFM carburetor throttles the engine will drown in too much air and very little gasoline. Carburetors depend on moving air velocity through the carburetor venturi in each barrel to draw in and mix fuel and air. The main jets and the venturi size and design must be matched to the size of the engine. The little 145 CID Corvair engine cannot provide enough airflow to function properly with the over-sized carburetor.

Accelerator pumps in carburetors attempt to compensate for an initial lack of venturi airflow with its associated fuel mix when the throttle is first opened. Initially when the throttle is opened there is some delay before the liquid fuel catches up and begins to mix properly with the newly started airflow in the venturi. By mechanically activating a pump plunger or diaphragm to inject a squirt of gasoline into the primary airflow, the result is to briefly enrichen the air/fuel mix to a usable percentage. The venturi airflow action ultimately creates a low-pressure region in the venturi that pulls gasoline from the float bowl. The accelerator pump helps to reduce the lean fuel/air mixture that would cause a power lag until the gasoline can catch up and start moving needed gasoline into the venturi. Even with the help of an accelerator pump system, a street engine could not handle all four barrels simultaneously. So the carburetor capacity is divided between primary and secondary barrels, with only the primaries opening initially and the secondaries opening only when the engine airflow and RPM can handle the added carburetor capacity. But the 600 CFM carburetor on the Corvair engine will never function properly on such a small displacement 145 CID engine. The 600 CFM four barrel carburetor would be much-more at home on a 350 CID V8.

Image


As far as I know, the 4-barrel center-mount manifold unit that had 4-runners was designed ONLY for the 164 CID 140 hp 4x1 engine. It was designed to mount a 4-barrel carburetor (originally a Carter AFB or Holley 390 or 450 CFM 4-barrel). The units designed to fit on a 2 carburetor Corvair had a mount for a smaller 2-barrel carburetor. This smaller unit more-closely matched the pumping and breathing restrictions of the 145 CID small-valve, low-performance camshaft engine with a single muffler exhaust system.

Image

Left-click the image below to enlarge for better viewing. Click a second time for maximum enlargement...
IECO Corvair Catalog Center-Mount Carburetor Manifolds.jpg
bbodie52 wrote:I think you are on the right track. On the little Corvair engine, would you rather have a 350 CFM 2-barrel open up all at once, or would you want a 390 CFM 4-barrel that divides the airflow between the primaries and secondaries, starts with a smaller primary 2-barrel, and then uses a vacuum-actuated 2-barrel secondary that opens on-demand by the engine, when rpm and airflow demand is adequate to open the secondaries?

Image 350 CFM
Image 390 CFM w/Vacuum Secondaries
Electric Choke Carburetor
4160
:link: https://www.holley.com/products/fuel_sy ... rts/0-8007


WATCH VIDEO: How To Choose A Carburetor


Holley does offer factory refurbished carburetors which could save you some money over the cost of a new unit.

:link: https://www.holley.com/products/fuel_sy ... rburetors/

Holley 4160 New: $575.95 PART# 0-8007
:link: https://www.holley.com/products/fuel_sy ... rts/0-8007
Holley 4160 Used: $299.99 PART# FR-8007
:link: https://www.holley.com/products/fuel_sy ... ts/FR-8007
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flat6_musik
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Re: Engine dies 4 barrel carb

Post by flat6_musik »

A lot of great input from the group here. All I would add is that.....these center 4-barrel setups are already a bit finicky and problematic, what with the proper carb sizing being so important and then their "freezing up" issues. And to install one on a PG car even accentuates this. I think that getting the center 4-barrel "ram effect" working well (good drivability) depends on getting a bit of RPM going, as with a stick shift car. You can probably make it work on a PG car with a smaller carb and some heat applied to the carb mounting base. Fortunately, the 600 Holley you're running is most likely a vacuum secondary, so you'll be running mainly on the primaries. It's still too big though..... :sad5: Hope you didn't drop a lot of $$ on that carb.

Oh yeah, another point....be aware that carb tuning requires a bit of time and testing for proper jetting and power valve selection. But don't give up! BTW, I believe you can actually make this 600 Holley work. There are "harder" vacuum diaphragm secondary springs you can install to keep the secondaries from opening up too early, effectively making the carb a 2-barrel for most of the time. Read up on Holleys! It's interesting!

If you start to doubt yourself, just look at this video of an Olds cutlass running 4 quadrajets.....LOL

https://www.youtube.com/watch?v=Hy8rufA6Pyw
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doug6423
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Re: Engine dies 4 barrel carb

Post by doug6423 »

I appreciate all the input too. I bought the single carb setup for a 140 I have. Just haven’t installed it yet.


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Dadaluma
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Re: Engine dies 4 barrel carb

Post by Dadaluma »

I was aware of the carb being large for the application it was quite a good deal though. I do believe it can work though.
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Re: Engine dies 4 barrel carb

Post by bbodie52 »

You could disconnect the secondary throttle linkage and essentially turn your 600 CFM 4-barrel into a 300 CFM 2-barrel that would more-closely match the capacity of your engine. With some experimentation with jet sizes and the tuneable Holley accelerator pump system you might be able to make your street machine more drive-able. But with the internal restrictions in engine design, including the limited cylinder heads, camshaft, and single exhaust the 145 CI, 102 hp engine will likely not produce much more power. The over-sized Holley 4-barrel will likely continue to impair drive-ability on the street, without adding horsepower.. The 2-speed Powerglide transmission is another limiting factor in performance tuning and driving.

Early Corvair performance tuners opted for a 4 Rochester carburetor modification that was later adopted by GM engineers in their 140 hp engine. But that engine received improvements and upgrades throughout the cylinder head including larger valves and ports, a better camshaft design, and a dual exhaust system. A comparison between the 140 hp and 110 hp engine cylinder heads is shown below. Both engines shared the increased 164 CI displacement, a 9.0:1 compression ratio, and the same camshaft grind. But the 110 hp engine retained the small valve heads, 2 carburetors, and single exhaust system.

Image
:link: https://ssl.corvair.com/user-cgi/catalo ... ow_page=63

Image

Part number C8607: OTTO 4 X 1 CARB KIT-CHANGES 2 CARB* HEADS TO 4- AIR CLEANER KITS ARE REQUIRED

Weight: 6 lbs 0 oz
Catalog Page(s): 63,OT-18(RM19)
Price: $ 386.35


Image

This will give you some idea of the differences between the 140 hp engine and the 110 hp engine.

140 hp vs. 110 hp...
  • Same high-performance camshaft on both 140 hp and 110 hp engines. Low performance camshaft in the 95 hp engine.
  • Same 164 Cubic Inch displacement with same bore and stroke on all 1964-1969 engines.
  • Stronger, nitrided crankshaft on the 140 hp and 180 hp turbocharged engines. (Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface).
  • On the 140 hp engine, a 4x1 carburetor arrangement, with two primary and 2 secondary 1-barrel carburetors, connected with a progressive linkage to open the secondary carburetors as you approach full throttle. (Equivalent to a 4 barrel carburetor on the 140 hp engine, vs. a 2 barrel carburetor (2x1) on the 110 hp and 95 hp engine).
  • Dual muffler, dual exhaust with larger exhaust ports and larger exhaust manifolds on the 140 hp engine. Single exhaust on the 110 hp and 95 hp engine.
  • 9.0:1 Compression Ratio in both 140 hp and 110 hp engines. 8.0:1 CR on the 95 hp engine.
140 hp Heads...

Image

Image

Image

It's all about better breathing at full throttle at the high RPM ranges. At lower RPM the big valves and dual exhaust don't make much difference, and the secondary carburetors are not open for business.


110 hp Heads...

Image

In addition to the factory shop manual, this book contains a great deal of performance information about the Corvair. As a teenager I read the earlier version of this book in 1970 and found it to be very valuable and informative. It is a personal favorite.
:link: https://www.amazon.com/Performance-Corv ... +to+hotrod
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===========================================================================================

:idea: The books shown below made a lot of difference to me when I was starting out with working on Corvairs as a teen back in the late 1960s. I was trying to follow the shop manual, but there was still a gap in my basic knowledge that often prevented me from really grasping what was going on. I discovered this series of books that was published by the people who published Hot Rod Magazine. I really devoured the contents of each book, and as I did, the "light" came on for me in understanding how electrical systems, carburetion and ignition systems, etc. really were supposed to function. If you are interested, these books can often be purchased used on Amazon.com, eBay, etc. for only a few dollars. If you are willing to invest some reading time, you may find them to be helpful. The book series is old, but they match the technology found in vintage Corvairs and other older classic cars.
bbodie52 wrote:Classic cars had a different way of doing things in the 1950s, 1960s and earlier, when compared to modern techniques utilizing sensors and computer technology to control fuel injection and ignition systems. There was a series of books that were published in the 1960s and 1970s that focus on basic principles of automobile design and function. These books covered basics associated with carburetors, ignition systems, suspension and brakes systems, etc. When I was a teenager I read through many of these books and they gave me a good understanding of the principles and functional designs that were common in the cars that I was interested in, including the Corvair. Once I read through these books, the shop manuals made a lot more sense to me as I began to understand how things function and what I was trying to accomplish in working on my Corvair. This series was published long ago (1960s-1970s) by Petersen Publishing Company, which was also associated with Hot Rod Magazine. With titles like Petersen's Basic Cams, Valves and Exhaust Systems, Petersen's Basic Ignition and Electrical Systems, and Petersen's Basic Carburetion and Fuel Systems, I was a teenager that found myself devouring much of the series to teach myself the basics that could be applied to most 1970s and earlier vehicles. The material in those books are now somewhat dated because of the change to computer-controlled electronic fuel injection and other sophisticated technologies that have been introduced in the subsequent decades. But I do feel a Corvair owner or any classic car owner could benefit from the material in these books. Many of them are listed as available on Amazon.com. If you would like to consider the possibility of reading through some of this material, the following link may help you to find what you're looking for. The cost of these books is low, and the investment in time that you might make in reading them may help you to develop a foundation of knowledge that will help you to leap ahead in your DIY maintenance efforts on your Corvair.

:link: https://www.amazon.com/s/ref=nb_sb_noss ... automotive

ebay :link: https://www.ebay.com/sch/i.html?_odkw=b ... c&_sacat=0

ImageImageImageImageImage
Brad Bodie
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Image 1966 Corvair Corsa Convertible
bowtyebob
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Re: Engine dies 4 barrel carb

Post by bowtyebob »

I may be a bit late in offering my two cents worth, however I have had a LOT of experience with what you are trying to make work ...and work well. Almost everyone who has attempted using a 4bbl carb (me included) has chosen one that is just plain wrong for this application. There really is ONLY ONE 4bbl carb that will work ...or at least come close to working properly. If you haven't already resolved your problem, the 390CFM Holley 6299 is really your only good choice. On a thoroughly warmed up engine the throttle response ,overall driveability and idle are good. Notice that I said "On a thoroughly warmed up engine".
Regardless of which intake manifold you use the carburetor is a looong way from the cylinder head making any (sufficient) carb heat non-existent. No carb heat is not much of an issue with a completely warmed up engine ...IF the ambient air temp is at least in the 65 -70 degree range. Keep in mind that the carb will be directly above the cooling fan. ...which is just fine for max horsepower, but not such a good thing on a cool morning when carb iceing and/or fuel mixture loss of atomization can happen. This is usually a warm weather application sort of thing.
A 6299 out of the box will be pretty close to the having the correct primary and secondary jets and the proper power valve and setting the idle is a whole bunch easier then attempting to get those Rochester H or HVs in sync.
IF this is for a two carb engine it is important to know that you MUST (or at least ought to) use a flexible coupling(fuel resistant hose) somewhere on the runners to the the head because there is a strong likelihood the a crack will develop at the plenum to runner attachment because of heat expansion/contraction and vibration)
Good luck. I hope that I might have been of some help.
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