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John Strenk 06-10-2021 11:21 AM

Quote:

Originally Posted by Fourtrail (Post 41290209)
Covered in my post just before yours, come on keep up John...:grin2:

i t y p e t o o s l o o o w . . . . https://www.jeepforum.com/forum/cust...tar49393_2.gif

pedal2themetai 06-10-2021 11:32 AM

HI Ok.. I see that now the outsides of the barrels are the same distance and the oversize was taking to the center.. My bad... so maybe he needs to adjust the spring on the secondairs so they open..
good luck
tim

Fourtrail 06-10-2021 11:42 AM

Quote:

Originally Posted by Fourtrail (Post 41290071)
Wherein lies part of the issue, the Edelbrock carb does have mechanical opening secondaries, but there is a weighted air valve between the venturi and the butterflies in the base plate. If you are not creating enough vacuum on the secondary side of the intake, the air valve will not open and no fuel will flow through. With the larger runners on the secondary side of the offenhauser intake, it is possible that you just aren't getting enough vacuum signal to open the secondary air valve. One option is to drill a small hole in each weight to reduce the mass so the secondary air valve will open/open quicker. Just don't go too much, then you are ordering a new secondary air valve if it opens too quick and causes the motor to stumble.

https://www.jeepforum.com/forum/atta...dsc00181-l.jpg
Image is of the air valve that sits between the venturies and the butterflies.

Quote:

Originally Posted by pedal2themetai (Post 41290245)
HI Ok.. I see that now the outsides of the barrels are the same distance and the oversize was taking to the center.. My bad... so maybe he needs to adjust the spring on the secondairs so they open..
good luck
tim


Unless the OP has a Thunder AVS carb,which uses springs, the secondaries on the 500cfm performer are controlled by these weights and vacuum to pull open the air valve.

85Tuxedocj7 06-11-2021 02:02 PM

probably around 30,000 miles lol and ran until i parked it for 6 years. water jacket cracked outside the waterpump and i sealed it with 3M 5200 sealant and it held for 2 years of daily driving.

85Tuxedocj7 06-11-2021 02:17 PM

Quote:

Originally Posted by Fourtrail (Post 41290151)
Not sure what people are seeing, but the carb is a square bore edelbrock performer/carter AFB. Definitely not a spread bore carb.


85Tuxedocj7, can you get a picture/the numbers from this location on the carb? That will tell us the size and give a starting point to if the carb is too big or other suggestions.

It is a 1403

85Tuxedocj7 06-11-2021 02:20 PM

Quote:

Originally Posted by Fourtrail (Post 41290171)
Bad camera angle, that is an edelbrock square bore base plate. Plus any spread bore has an exaggerated difference between the primary and secondary butterflies.


https://www.jeepforum.com/forum/atta...wrong-carb.jpg


Edit: if it is a very early Carter AFB, there were a few that had slightly smaller primary butterflies, but they were still a square bore design and should work just fine with that manifold as the secondary butterflies are still smaller than the bore in the intake.

I think it's Square bore, the primaries are smaller than the secondary's but it fits a square bore spacer.

BagusJeep 06-14-2021 01:57 AM

A 1403 is a square bore so that is sorted. In fact it is the carb that Offenhauser recommend for this setup BUT they go on to say use one from 400 to 600 cfm for street to race applications.

I have never raced my Jeep so I am unsure about the 600cfm but my concern at a 1403 is that it is rated at 500cfm. WADR to Offenhauser, the physics suggest on a trail rig it is oversize.

The 258 will, on a good day, run to 4000rpm but unlikely you would want to go much above 3000rpm. At 80% volumetric efficiency this is 180 to 240 cfm, the carb is MUCH larger than a 258 in stock form needs, it would run fine on just the primaries.

Different manufacturers measure and rate their carbs in different ways apparently so it is difficult for complete comparison.

I took this from the Edelbrock manual as they write so well:

The Secondary Main System delivers fuel only when the secondary throttle blades and air valve are open. It ensures that fuel delivery varies with air flow.

The Secondary Throttles begin to open when the Primaries are about 65% open. The Primary and Secondary Throttles arrive at the WOT stop at the same time.

Air flow through the Secondary side is controlled by Air Valves. These valves are located in the secondary bores above the throttle blades. They are balanced against a counter weight and open to admit additional air flow only if there is enough air velocity to allow the proper operation of the Secondary Metering Systems.


In other words, you need to open the secondary throttles AND there needs to be enough air flow as Fourtrail set out above, and with low flows that is not as likely to happen. They could be sticking of course.

Have you checked the secondary throttle butterflies start to open at 65% of the primaries an dare open at 100%? There is a mechanical linkage which could be out of whack.

Then give the air valve a prod, it should swing smoothly.

Apparently even the factory suggests getting a 1/8" drill and taking out a hole in the big lug part of the counterweight to get them to open sooner.

BagusJeep 06-14-2021 02:29 AM

Offenhauser say:

"The Dual Port 360 can best be described by saying itís actually two separate manifolds in one. The entire manifold is divided from the base of the carburetor to the head flange. In operation, the primary mixture is fed into the bottom runners and the engine operates on this smaller port until the engine demand cuts in the secondaries (the top port). In the Dual Port, the primary system further restricts the air flow after passing the carburetor and increases it to the speed of sound. This means that even at low engine RPM, it offers near perfect aerodynamic efficiency, which means MORE HORSEPOWER!!! This intake can gain you fuel economy while also adding 15-30% more power!


This extra horsepower on the primaries comes from a more perfect mixture moving at near sonic speeds, a larger volume passing the intake valve and greater turbulence in the combustion chamber for a highly efficient use of fuel. The primary system being on the bottom uniquely provides two layers of manifold casting and a high speed mixture flow which acts as a perfect insulator for the secondary runners. And since the secondaries are insulated from engine heat, this means that when cut in, the secondary mixture will be colder and more dense, a further increase in performance. Then, when the secondary mixture gets to the end of the runner, it is picked up and rammed into the combustion chamber by the sonic velocity of the primary port. All of this means less fuel to gain more horsepower. Also, this intake is proven to lower emissions due to its efficiency in mixing air / fuel.

Uses standard 4bbl carb from 400 CFM to 600 CFM depending on whether itís for street or competition.

Works great with the Edelbrock 1403 500cfm carburetor!

**NOTES:

Works with stock exhaust manifolds, and also works with headers (except Borla or Clifford brand headers).
Includes linkage kit, which works with stock stamped steel bracket off stock intake.
The carb will be mounted sideways, and there is a cable and bracket to the carb included in the kit."



Heck, sonic primaries and ramming!!!!!

I don't suppose the OP has any vacuum measurements?

gutthans 06-14-2021 08:55 AM

1 Attachment(s)
Quote:

Originally Posted by BagusJeep (Post 41292811)
Offenhauser say:

**NOTES:
...works with headers (except Borla or Clifford brand headers).

Just because it's in print...doesn't make it so. Pic of Clifford headers with Offenhauser manifold. That's my 'go to' on conversion and stroker motors.

skypilot123 06-15-2021 05:53 PM

Quote:

Originally Posted by BagusJeep (Post 41289801)
I am surprised it even ran.

Amazing!

How did you do that???

It looks like you rotated it 90 degree's and got it to bolt up. Half your cylinders got no fuel and the other got it all. Hope you didn't wash away your rings.

gutthans 06-15-2021 07:44 PM

Quote:

Originally Posted by skypilot123 (Post 41294145)
Amazing!

How did you do that???

It looks like you rotated it 90 degree's and got it to bolt up. Half your cylinders got no fuel and the other got it all. Hope you didn't wash away your rings.

V-8 and I-6 manifolds are built differently...look at the supplied pictures closely. I-6 carbs are supposed to be rotated to face the valve cover...V-8's must sit straight.

85Tuxedocj7 06-16-2021 06:30 AM

What all have you done to the heads besides go with roller rockers? and where did you find all your parts?

85Tuxedocj7 06-16-2021 06:31 AM

Quote:

Originally Posted by gutthans (Post 41292989)
Just because it's in print...doesn't make it so. Pic of Clifford headers with Offenhauser manifold. That's my 'go to' on conversion and stroker motors.

What all did you do to your head besides roller rockers? and where did you find your parts?

85Tuxedocj7 06-16-2021 06:35 AM

Quote:

Originally Posted by BagusJeep (Post 41292811)
Offenhauser say:

"The Dual Port 360 can best be described by saying itís actually two separate manifolds in one. The entire manifold is divided from the base of the carburetor to the head flange. In operation, the primary mixture is fed into the bottom runners and the engine operates on this smaller port until the engine demand cuts in the secondaries (the top port). In the Dual Port, the primary system further restricts the air flow after passing the carburetor and increases it to the speed of sound. This means that even at low engine RPM, it offers near perfect aerodynamic efficiency, which means MORE HORSEPOWER!!! This intake can gain you fuel economy while also adding 15-30% more power!


This extra horsepower on the primaries comes from a more perfect mixture moving at near sonic speeds, a larger volume passing the intake valve and greater turbulence in the combustion chamber for a highly efficient use of fuel. The primary system being on the bottom uniquely provides two layers of manifold casting and a high speed mixture flow which acts as a perfect insulator for the secondary runners. And since the secondaries are insulated from engine heat, this means that when cut in, the secondary mixture will be colder and more dense, a further increase in performance. Then, when the secondary mixture gets to the end of the runner, it is picked up and rammed into the combustion chamber by the sonic velocity of the primary port. All of this means less fuel to gain more horsepower. Also, this intake is proven to lower emissions due to its efficiency in mixing air / fuel.

Uses standard 4bbl carb from 400 CFM to 600 CFM depending on whether itís for street or competition.

Works great with the Edelbrock 1403 500cfm carburetor!

**NOTES:

Works with stock exhaust manifolds, and also works with headers (except Borla or Clifford brand headers).
Includes linkage kit, which works with stock stamped steel bracket off stock intake.
The carb will be mounted sideways, and there is a cable and bracket to the carb included in the kit."



Heck, sonic primaries and ramming!!!!!

I don't suppose the OP has any vacuum measurements?

I know very little about vacuum on a carb, I did hook a vac gauge up to it and at idle it pulled 20" and when i throttled up it dropped to around 17"

gutthans 06-16-2021 06:48 AM

2 Attachment(s)
Quote:

Originally Posted by 85Tuxedocj7 (Post 41294437)
What all did you do to your head besides roller rockers? and where did you find your parts?

The one pictured is a 1987 258 block. Head is a 7120 casting from a 1995; used a SD530 head gasket. Headers are Clifford 3 into 1 dual exhaust.

I used to go with Clearwater conversion heads, but they stopped supplying 7120's exclusively. So I just scrounge and pick-up used ones. Do a clean-up plane of the surface .003 - .005, 3-angle valve job, cc the chambers, install full silicone bronze guides, stop up the water jacket steam pockets (pic) because up to '89 the pockets hang off of the block edge (NOTE: HESCO sells them now, but instead of welding, they use DEVCON...so I just do it at home with JB Weld and save $300)
. Use the CJ to early YJ oil pan with the middle sump.

Pretty much all stock parts except for performance upgrades (cam and etc.)


The time now is 10:32 PM.

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