Knot 4 Me

I'm helping a buddy out with a fuel leak on one of his '97 7.4L motors. A prior owner ditched the stock Webers for a set of Holley double-pumpers. They have mechanical secondaries and no choke towers. They appear to be full-race carbs (4150's?). The leak appears to be around the rear fuel bowl or the rear accelerator pump on the starboard motor carb. Once I pull the carb, where are the identifying numbers located on it to determine the exact model and CFM? My gut tells me these puppies have no business being on stock 7.4L motors but I have no idea how they are jetted or what, if any changes have been made to the metering blocks. Thanks in advance for any help anyone can give me.

rmbuilder

Knot,
This will get you started.
Bob
http://www.holley.com/TechService/ListNumber.asp
http://www.mortec.com/carbs.htm
http://www.holley.com/data/TechServi...%20Listing.pdf
http://www.teufert.net/carbs/holley-cfm.htm
http://www.bob2000.com/carb.htm

David

The list numbers are stamped into the choke tower, unless they are dominators. Post a pic.

Knot 4 Me

Absolutely it will. Thanks!!

Knot 4 Me

No choke towers. They look like this --> http://www.holley.com/types/4150_HP_Series.asp
No j-tubes so for now I'm assuming they are not marine carbs.

SB

iTrader: (1)

4150's have metering blocks front and rear.
4160's have metering block in frt and metering plate in rear.

Almost all DP's are 4150's. Vac secondary can be found as 4150's and 4160's.

Measuring throttle bore + knowing booster type (annular, dog leg) usually can help tell you which cfm carb you have.

Marine carb's have j-tubes.

rdoactive

If they run well dont worry about size, jetting, etc.
As for rebuilding. Take the old gaskets with you to the auto parts store. There are only a few different metering block gaskets used. Get the blue ones, they are reusable.
There are 2 sizes of accelerator pump diaphram. BTW, I've sen a lot of these tear and leak.
And dont forget the 8 bowl screw gaskets.
Gary

Knot 4 Me

It runs good but with the absence of J-tubes, I'm concerned this is a street carb that someone just tossed on these motors without rejetting them. I guess once I determine exactly what carb it is, then the question becomes is it safe (and the proper size) to use on these stock 7.4L motors? How many CFM were the stock Webers? I would think at a minimum to turn an automotive DP into a marine DP you would have to install J-tubes and fatten up the jets. What other differnces are there? Any differences in the metering blocks, power valves, air bleeders, etc.? After fixing the fuel leak, would a plug check be in order to see where we are at? Thanks again for all the help! It's been years since I dorked with carburetors.

rdoactive

Oh, missed the part about J tubes.
For liability purposes, get some marine carbs.
BTW, the square bore Webers were pretty much the same as the old Carter AFBs, 750cfm. Edelbrock now sells these as a marine carb.
Gary

Knot 4 Me

Finally got a chance to get down to the dock last night to pull the carb in question and get a better look at what it is. I can verify it is not a Dominator. It is a 4150 street double-pumper that someone cut the choke tower off of! Since the list # is located on the choke tower, I won't be able to cross-reference it to determine exactly what we've got. After seeing the cobbled up mess he has, the owner wants to go back stock (I don't blame him). The original Webers are pricey so it looks like a replacement marine Edelbrock might be the way to go. Now the question is do we go with the 600CFM or the 750CFM?

http://www.jegs.com/webapp/wcs/store...tegoryId=10271

Or, do I go with something like the Holley 80559 600CFM marine double-pumper since modifications to fuel lines, throttle cable brackets, etc. have already been made to accomodate a Holley double-pumper?

http://www.jegs.com/webapp/wcs/store...tegoryId=10271

Any other suggestions would be appreciated. Thanks!