Holley carb fuel bowl mods

C

cadreamn67

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My new 670 cfm Holley Street Avenger carb will not fit on new Weiand Stealth manifold with new 347 motor installed. It fails to clear the rear of the engine bay by about 5/32 inch (half the thickness of a 5/16 carb mounting stud). Problem is the nub on the back of the secondary center hung float bowl. I do not want to notch the sheet metal. Here is my work around solution. Does anyone see any problems?

BTW, I have given Holley tech assistance three chances to help me. I am still waiting over a week since sending the third reply. At this point I think they are just ignoring me. To say they are incompetent is being way too kind.

My solution is to replace the center hung float secondary with a side hung float bowl. Gaskets and bolt pattern are the same for both.
To get the inlet on the same side as the avenger's primary, I am using a primary bowl from a 600cfm carb.
The 600cfm's primary cross tube port for feeding the 600 cfm secondary was hand tapped with a 1/8 pipe thread tap and the hole plugged.
A Fragola 90 degree fuel line adapter was used to connect a 3/8 fuel line hose to the side hung bowl. The front center hung float bowl is already set up for a 3/8 hose inlet. (I have run 3/8 line from the rear tanks and have a new Holley 125 pump in the trunk for delivery.)
The side hung bowl has its sight plug hole about 1/16 higher than the hole in the center hung float bowl, measured from the bowl floor. I intend to set the float in the new secondary at about 1/16 inch below the bottom of the sight plug hole in an abundance of caution.
Holley claims their center hung bowls have a 20 percent larger fuel capacity than the side hung bowls. I intend to use a 1.20 needle valve in the smaller secondary bowl and keep the 1.10 needle in the front bowl. Theory is that the 10 percent bigger needle in the now smaller secondary will help it refill faster than the primary, somewhat offsetting smaller capacity in any extended WOT condition.
I am also installing "whistles" in both front and rear metering blocks to deal with any potential fuel sloshing under hard acceleration and braking.

Does anyone see anything I have missed taking into account, or created a problem with in all of this?

Thanks in advance for any and all feedback.:)

Pics below.

Gene
 
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Why is your engine so far back? Do you have the engine mounts on the wrong side? My Holley Ultra HP with 20% larger float bowels fits fine with room to spare.

If you have the engine mounts switched, the engine will be ~1" too far back.

007-5.jpg
 
Hi Duke,

Pretty sure motor mounts are on correctly. We checked pretty closely during install. Also, motor is in car with trans attached and trans mount installed. I do not see how motor could be sitting 1 inch back from where it should be if trans and trans mount also installed and connected. Also, shifter is nicely centered in trans tunnel hole.

As I remember, your engine bay is notched at the back which would give you more clearance than me. As I said, mine would almost fit. Just misses by about 5/32 inch. Interference is right at the leading edge if that sideways "V" ridge that runs across the back of the bay. If it were not for that ridge jutting forward I also would have plenty of clearance.

Gene
 
Yes, a POs did notch my firewall. But if you look at these pictures, extending a straight line across where the original fire wall is, there is still clearance for the rear float bowel that is 20% longer than your center hang FB. I think your engine is too far back from the stock location.

002-57_zps0ee00338.jpg


001-55_zpsf22e6e7a.jpg
 
Hi Duke,

Just got through checking the dimensions on the 47 year old Ford Motor mounts in the cabinet. They are clearly marked with LH and RH molded into the rubber along with the part numbers and have a L and a H stamped on the metal pad that faces the hanger. I checked the distance from the center of the single stud to the center of the mounting hole on the long ear. On the LH mount, that distance was approximately 4 1/4 inches. On the RH mount that distance was approximately 3 7/8 inches. Not a 1 inch difference, but certainly meaningful. I then checked the mounts as installed on the car. I have them right.

Anyway, thanks for the suggestion of what may be wrong. It certainly was a high probability suggestion and definitely something that needed to be checked. I almost wish I did have the mounts reversed.

It then occurred to me that the only other variable might be where the carb mounts on the intake manifold w.r.t. the rest of the engine. I measured the forward distance between the center iof the nearest intake manifold bolt on the passenger side and the center of the rear most carb mounting stud hole on that side. It was about 3/4 inch on the Stealth manifold. I then went over to the F4B still mounted on the 260 motor. Same measurement was 1 1/4 inch! So the Stealth mounts the carb a full 1/2 inch further back on the motor than does a F4B. No wonder I have clearance problems...:(

So, since it is not a engine positioning problem after all, I guess I am back to the initial question. Anyone's knowledgeable critique of my work-around solution would be greatly appreciated.

Gene
 
Tiger Tamer,

Thanks for the picture of your installation. I am curious to know what intake manifold you have.

Also, it may be the camera angle, but does that rear most nub on the secondary bowl tuck under the sideways "V" protrusion across the back of the engine bay? With my Stealth manifold, they are essentially horizontal w.r.t each other.

Gene
 
cadreamn67 said:
Tiger Tamer,

Thanks for the picture of your installation. I am curious to know what intake manifold you have.

Also, it may be the camera angle, but does that rear most nub on the secondary bowl tuck under the sideways "V" protrusion across the back of the engine bay? With my Stealth manifold, they are essentially horizontal w.r.t each other.

Gene
Click to expand...

Gene, here is another pic at a lower level. It is pretty much level. The intake is an Edelbrock rpm.

I see in your reply to Duke that the carb mount is 1/2" further back, I was wondering if that was the problem. As for a fix apart from changing the intake, I can't help. But good luck.
Cheers Mal

023_zps24450f6a.jpg
 
Good, I am glad you found the variance.

Fix ='s a Weiand 7515 intake. I had 1/2" machined off of the carb tower to allow a spacer and hood clearance. I caution you using that smaller fuel bowl designed for a smaller carb. You run the risk of that bowel getting too low under full throttle due to the smaller volume of fuel and going lean. That 347 is gonna be sucking some serious fuel WOT at 6000 rpm.

weiand_7515.jpg


Tiger tamer - nice distro ;) MSD has a black cap available for it too.
 
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The carb mounting locations on many of these after market manifolds
vary so you need to be careful what you select as Duke pointed out.
I'm using this manifold on my 302 and with a 650 double pumper there are no
firewall issues...

Moondoggie
 
Holley carb

Mal's post shows an Edelbrock RPM intake which is a dual plane manifold. Check the Febuary issue of CAR CRAFT MAGAZINE. An Edelbrock RPM out performs a single plane Victor Jr on both average Torque and Horsepower which means more streetable. Why use a single plane manifolds? I tend to like the Edelbrock carb which does'nt leak from gaskets or blow power valves, and fits without interference with the firewall. My Edelbrock 289 Torquer and Holly double pumper required the big BFH.
 
Duke Mk1a said:
454 HP, 445 lbs/torque is why.
Click to expand...

February issue of Car Craft Magazine intake manifold test with the Edelbrock RPM dual plane on a Ford Performance Stroker crate motor made 473 hp and 456 lb of torque. The single plane Victor Jr. manifold produced 469 hp and 443lbs of torque. The test used an 800cfm Edelbrock Thunder carb.
 
motor mounts

In my humble Tiger experience, I've always thought the motor mounts fit better "backwards". In measurements taken on several of my Tigers, this puts the engine 5/8" farther forward as opposed to having the motor mounts in the factory positions. You do have to shave off the passenger side motor mount a little to get it to sit correctly on the driver's side, as it hits the block otherwise and you can't get the mounting bolt in the block threads.
Yes, it does put the fan that much closer to the radiator, but I've never had a strike.
Makes it a lot easier to get the valve covers off and that back drivers side spark plug out.
The carb on B9471705 (similar to Duke's) would be banging on the firewall if the motor mounts weren't in backwards.
To me, it also seems like the hangars fit better in the headers with the motor mounts reversed - in B9471929 the hangars hit the headers (very old set believed to be original LAT headers) and I couldn't get all three frame bolts in when I tried to "correct" the motor mount locations while putting in new mounts a while back. Gave up and put them in backwards again.
Bob K.
B9471705
B9471929
 
Duke Mk1a said:
Good, I am glad you found the variance.

I caution you using that smaller fuel bowl designed for a smaller carb. You run the risk of that bowel getting too low under full throttle due to the smaller volume of fuel and going lean. That 347 is gonna be sucking some serious fuel WOT at 6000 rpm.
Click to expand...

Not saying that there are not advantages to larger float bowls, but I have seen earlier models of even 850 CFM carbs with the same size float bowl as I have grafted on.

Also, I found some interesting facts in Bill Fisher's 1994 Holley carb book.

A 350 ci motor, with 100% VE would need about 210 lbs. of fuel per hour while running at a AF ratio of 12.5:1 at 6000 rpm.

If the VE is only 85%, the motor would need only about 175 lbs per hr.

A .110 fuel bowl inlet needle will flow 232 lbs of fuel per hour at 4 psi. Surprisingly at that fuel pressure the .120 I was initially considering is only slightly better.

My Holley 125 fuel pump is internally regulated for 7psi at output. If it can keep the psi at the carb (both inlets) at above 4psi, the physical bowl capacity would seem to become almost irrelevant. The delivery system can replenish fuel at a faster rate than the motor is consuming it. BTW did I not read somewhere that your pump was keeping pressure at above 4 psi at the carb under WOT? Not the same pump as mine but hopefully comparable.

As an additional thought, this 210 lb per hr. of fuel consumption is coming from two fuel bowls, the primary and the secondary. At anything close to a 50/50 split, it would seem my risk of running the "replacement" secondary bowl dry under WOT is extremely remote. "Seems" is of course the operative word.

I am very new at all of this, which is why I am asking. Am I missing something in all of this?

Gene
 
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Gene,

I have the same headers from CAT and my hangers were also close. I had to grind off a corner of the driver's side motor mount, but my hangers cleared... barely. The headers may have some variation set to set.

I don't think I swapped hangers like Bob suggested.

Gary
 
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