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dumb simple question. will a holley carb fit on my current manifold?

Tim Chavez

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hey gents.
i've got a 340 with a stock mopar 4 barrel intake manifold( i ran the casting numbers once and it came back as a 73 360 manifold).. it currently has an Edelbrock manual choke carb and i want to switch to a Holley. will i have to change my manifold to or will the holley fit right on?
 
I wanna say the bolt pattern is different, but someone who is more versed in the small block newer manifolds can confirm. Either way, they make a conversion plate you can use for the different bolt pattern that'll let you bolt your holley on that manifold.
 
I think 91r/t is right. I believe one is a spread-bore pattern and the other is a square-bore bolt pattern, so the Holley will not bolt up. If you have the height clearance though, you can use the adapter plate 91r/t mentioned. I believe the Edelbrock intakes are tapped with both patterns, but I could be wrong.
 
A 73 manifold will have a spread bore pattern. A holley will not fit with out an adaptor, as stated above.
 
Guys are right, I personally don't care for the adapters but I have used them until I could change the intake. They are available from any good parts store. (square bore carb to spread bore intake). If you haven't already bought the holley, I would find a good thermoquad. You can find rebuilt ones pretty reasonable
 
Guys are right, I personally don't care for the adapters but I have used them until I could change the intake. They are available from any good parts store. (square bore carb to spread bore intake). If you haven't already bought the holley, I would find a good thermoquad. You can find rebuilt ones pretty reasonable
No purchase made yet. Im just getting tired of this edelbrock. After the second rebuild it still doesn’t seem to run correctly. I was looking to eliminate the carb as a variable by just buying new and if I buy new I wanted to go with Holley.
 
I would change the manifold if going to a Holley. Back in the day, I built an engine with the stock spread bore manifold, adapter, and a Holley. Never could get it to run well. I put on an Edelbrock manifold, and with just minor carb adjustments, it ran great. My theory is the manifold mismatch ruined the flow of the air\fuel. This could be your issue with the AFB. If you don't want to change the manifold, a thermoquad would be your best bet.
 
Holley makes a spread bore, if you prefer holley. I think the biggest one is a 650.
Yep, Mopar had stock 650 Holley single-feed, double pumper, spread bore Holley carburetors stock on '73 440's I believe....I have one. So, your options are:
a. Thermoquad
b. Holley spread bore
c. Holley square bore with adapter
d. Holley square bore with new intake
 
Back with the dumb questions what are the chances that this carb spacer is causing my no idle issue? The intake is spread bore the carb is square bore and the spacer is just an open square. Which correct me if I’m wrong is basically turning my dual plane manifold into a single plane? What do y’all think?

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well, i see a couple of issues.
Adapter plate definitely wrong, get at least a 4 hole spacer, square bore or spread to square.
I have had good results with a 1/2 inch 4 hole phenolic adapter, keeps your fuel cold. Even on a spread bore manifold.
i hope you connect the large vacuum port to the brakes or PCV valve?
i also see the vacuum ports plugged for the distributor. you should connect it for your vacuum advance.
 
well, i see a couple of issues.
Adapter plate definitely wrong, get at least a 4 hole spacer, square bore or spread to square.
I have had good results with a 1/2 inch 4 hole phenolic adapter, keeps your fuel cold. Even on a spread bore manifold.
i hope you connect the large vacuum port to the brakes or PCV valve?
i also see the vacuum ports plugged for the distributor. you should connect it for your vacuum advance.
Yeah ignore the ports, I disconnected the Pcv hose for the picture and capped off the vac ports to eliminate that from the possible vac leak equation. Power brake is capped off with a bolt.
 
That carb is dirty. Dirt is your carbs enemy. After cleaning, inside and out, try resetting your timing, Adjust air mixture screws to highest rpm/vacuum. reconnect the vacuum advance, and see how it runs. a lot of times, it's the little things that make all the difference.
 
I think purplebeeper lined it up correctly with your options. With that said, I can tell you I have run a Holley 600 on my spread bore manifold with the correct open adaptor plate, and it ran just fine, however, the Holley always had a problem with the floats sticking open. Now, I am running the large thermoquad and once I got it dialed in, it runs great, idles great, and runs wide open great. Only issue with thermoquad is trying to find one that doesn't have worn out throttle rods.
 
Had a few seconds to get the carb off and get a better view, needless to say I’m not sure what the previous owners had in mind with this setup

C97ADEB9-79F2-4D20-892D-BAEE6DEB4F28.jpeg BD8417FD-2C0F-48EF-B41B-F6ED909EE0A7.jpeg BBA0D4D4-9699-4C22-A129-9335931DE3D3.jpeg
 
So did you do the last rebuild, or two?
I did. But I’m not afraid t call my self a rook at this engine stuff. I didn’t even realize it was a spacer until just the other day when I looked up the casting number of the manifold and saw that it should be a dual plane not a single plane. As it appeared when I pulled the carb off the first two times.
 
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