LD4B OR LD340 FOR 273?? Coil mount?? Need pics

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4spdragtop

4spdragtop

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Mulling some ideas around here....Dad n I always wanted to put a LD4B on his 273, BUT we didnt like the thoughts of mounting coil on firewall or inner fender. We like the stock look, so we always stuck with the stock cast iron 4bbl carb.

I dont know why, but I never thought about my LD340, its just sitting in my shop on the shelf. It has provision for choke and for mounting the coil.

Here are specs on engine as it is now

Comp cams kit with 270-s cam n lifters, 901-16 springs, comp dbl roller timing chain
Eddy 1405, but we got elec choke for it.
Torque converter is new approx 2800(not sure of stall tho)

Is the LD340 usable on Dads 66 date coded 273??

OR has anyone got pics of an LD4B bolted on and where did they mount coil.

Im thinking that maybe I could make a coil mount that utilizes the 2 rear carb studs? Anyone tried this?

Thanks all!
Steve
 
What heads do you have on the 273? LD340 ports will be too big and overlap the OEM ports. But more importantly, 273's came with 2 different heads and I don't recall when the changover occurred. Early ones had different size & angle intake bolts and an LD4B and LD340 wouldn't work anyway. I believe a D4B would have the correct bolt angles. Later 273 heads would accept the LD4B or the newer Performer intake.
 
Couple of issues using the LD340, 1st the intake to head bolt holes on, IIRC, pre '67 273 V8s are drilled at a different angle than latter small blocks and 2nd the runner sizes on the LD are much larger than the intake ports in the 273 heads (LD = 340/360 large runner, 273/318 = small runner). This would cause quite a disruption in flow. The 1st issue can be resolved with re-drilling the manifolds bolt holes at the correct angle but #2 would be a performance killer.
 
Thanks for the input guys. Dads 273 is for the 67 model year, which would mean heads would accept the LD4B. The heads are cast iron stock, with the new comp springs, no machine work.

LD340 is a no-go, thanks for the info.

So Im thinking of trying to come up with a coil mount for the LD4B that would utilize the rear 2 carb mounting holes. Anyone tried this?? Or any other mounting ideas??
$$ is more than tight and I dont want to go ahead and purchase a LD4B just yet without having a plan for the coil. Also anyone see any hood clearance issues with LD4B and Eddy 1405?

Thanks!
 
The bolt angle is a bigger deal than the port mismatch. The mismatch is one of those overblown things in the SB world.

Maybe a bracket that use two of the manifold bolts? I don't like hanging coils on the firewall or fender either.
 
crackedback said:
The bolt angle is a bigger deal than the port mismatch. The mismatch is one of those overblown things in the SB world.

Maybe a bracket that use two of the manifold bolts? I don't like hanging coils on the firewall or fender either.
Click to expand...

I agree with the mismatch being over blown. But the LD4B will fit with my setup. Im sitting here with a pad of paper and scribbling. Im not at home with everything at my hands to be able to "test", so Im going with my brain here...LOL

Here is what Im thinking.
Make a rectangular plate that runs behind the carb and mounts to the rear carb studs. Runs side to side basically maybe slightly larger than the "spread" of the rear carb studs.
Deep enough to lay a coil on it and keep the coil oriented side to side.
Bottom of the rect plate would have a nut or 2 welded to the bottom. The coil "lays" on top of the plate and a strap with either one or 2 bolts to hold it down?? I know heat would be an issue and eliminating as much metal/heat from plate would be a must.

Sorry Im no good at drawing on computer or I would attempt to show what I mean.
 
While the port mismatch isn't the end of the world, an LD340 is still a "big" intake for a dual plane. This is only 273 cubic inches that has to suck through a larger volume intake. That's why I recommended an Edelbrock Performer or even a dual plane M-1. (Not sure how the overall volume compares between an LD4B and LD340.) Gotta keep the velocity up, especially on the street. What could be considered an "economy/torque" type intake on a 340/360 would be more performance oriented on a 273/318. Same principal applies to camshafts. What works best on a 340/360 would be bigger than needed for a 273/318 in the same application.
 
Locomotion said:
While the port mismatch isn't the end of the world, an LD340 is still a "big" intake for a dual plane. This is only 273 cubic inches that has to suck through a larger volume intake. That's why I recommended an Edelbrock Performer or even a dual plane M-1. (Not sure how the overall volume compares between an LD4B and LD340.) Gotta keep the velocity up, especially on the street. What could be considered an "economy/torque" type intake on a 340/360 would be more performance oriented on a 273/318. Same principal applies to camshafts. What works best on a 340/360 would be bigger than needed for a 273/318 in the same application.
Click to expand...

Thanks LM, I thought the LD340 might be a bit big for it. I am planning on doing some of my own backyard porting stuff to the heads, to clean up flashing etc on them.

Thanks!
 
I agree that the size of the runners are a bigger issue than the port opening. The LD4b has runners almost on par with an LD340.

The Performer 318/360 would be a good choice for a 273.
 
what about a plate to go under the carb with mounts on the side for the coil? It could be made of aluminum and would not need to be very thick to get the job done. JMO
 
I've got a D4B which I wold be interested in trading for the LD4B if interested, just let me know.
 
1968dartman said:
what about a plate to go under the carb with mounts on the side for the coil? It could be made of aluminum and would not need to be very thick to get the job done. JMO
Click to expand...

Thats what Im thinking John. But Im thinking mounting on TOP of the carb mount plate, I think that would be easier than mounting under the carb.
Im sure someone has done it, I just havent found any info or pics

marksmopars said:
I've got a D4B which I wold be interested in trading for the LD4B if interested, just let me know.
Click to expand...

Sorry, I dont have either D4B or LD4B, Im pretty sure what I need is LD4B
 
What about cutting a couple of aluminum bosses off of a "donor" intake and having them tig welded to the LD4B in the stock location?


We replaced an edelbrock performer and holley intake for a LD4B and edelbrock carb with electric choke and it ran great. Stock 71 318 2 bbl engine with a 4 bbl and dual exhaust. It ran great off the line with no hesitation. Much better than the performer.


I would be worried about mounting the coil off the carb base studs, as the vibration may cause the carb to leak in the long run.
 
krazykuda said:
What about cutting a couple of aluminum bosses off of a "donor" intake and having them tig welded to the LD4B in the stock location?


We replaced an edelbrock performer and holley intake for a LD4B and edelbrock carb with electric choke and it ran great. Stock 71 318 2 bbl engine with a 4 bbl and dual exhaust. It ran great off the line with no hesitation. Much better than the performer.


I would be worried about mounting the coil off the carb base studs, as the vibration may cause the carb to leak in the long run.
Click to expand...

Thanks Karl, not sure if any of my buddies have a TIG, also no donor intake for the bosses. I thought it would be worth a try with some "adapter" plate.

Maybe dbl nutting the plate down on the back carb studs to help "firm" it up??
 
4spdragtop said:
Thanks Karl, not sure if any of my buddies have a TIG, also no donor intake for the bosses. I thought it would be worth a try with some "adapter" plate.

Maybe dbl nutting the plate down on the back carb studs to help "firm" it up??
Click to expand...


We have a local welding shop that just specializes in welding.


There is also a guy that has a business going out of his house that has good capability.


My oldest son is taking a TIG class this summer in Community College.
 
My duster had the coil on the firewall when I bought it (its still there) well yesterday I went to the pull a part n got an electric distributor from a 74 valiant that still had the coil in the stock location, talk about a pain!! I eventually wanna buy the HEI kit from Trailbeast so I won't have to worry bout the coil but if I were staying with the stock ignition I wouldn't put it back on the intake!
 
4spdragtop said:
Thats what Im thinking John. But Im thinking mounting on TOP of the carb mount plate, I think that would be easier than mounting under the carb.
Im sure someone has done it, I just havent found any info or pics



Sorry, I dont have either D4B or LD4B, Im pretty sure what I need is LD4B
Click to expand...

Sorry, See where I misread now. FYI, it is my understanding that the LD4B is a 340 manifold and the D4B is for a 273. I am putting a 340 together and have a D4B, looking for a better fit for my 340, which is why I chimed in. Good luck!
 
marksmopars said:
Sorry, See where I misread now. FYI, it is my understanding that the LD4B is a 340 manifold and the D4B is for a 273. I am putting a 340 together and have a D4B, looking for a better fit for my 340, which is why I chimed in. Good luck!
Click to expand...

No sweat, I know for 100% that the LD340 fits all year 340's, I have that for my 69 340, but looking for an intake for mine and dads 273.
For 273, there are a couple variations on that, as there was the D4B, LD4B. D4B is for an 65 and down 273, its no biggie, but the intake to head bolt hole is angled ever sooo slightly different. Mods can be done by hollowing out the hole slightly and voila you now have an intake for 66 and 67 273.
That D4B is worth $$ to some, maybe post it up in the trader section??

Does your D4B have mount bosses for a coil??
 
Ok, there seems to be some confusion here.


D4B - is for the smaller port with the special angle intake holes for the 64 & 65 273 heads.

LD4B - is for the smaller port 273/318 heads from 66 and newer. It does not have mounting bosses for the coil in the stock location.

LD340 - is for the larger port 340/360 heads and has the bosses to mount the coil in the stock position.


The LD4B or LD340 will fit his 67 273.



Steve:

Since you plan on porting the heads, why not go with the LD340 that has the mounting bosses for the coil and open up the ports in the heads to match the intake, or match both to the gasket. Done deal, no special mods needed...
 
Thanks Karl, Im not at home to chk on port size on the LD340....If I do the porting to the heads, and I decide to change back to stock intake, or go LD4B later on do you see any issues??
 
4spdragtop said:
Thanks Karl, Im not at home to chk on port size on the LD340....If I do the porting to the heads, and I decide to change back to stock intake, or go LD4B later on do you see any issues??
Click to expand...

The only issue would be port matching if you decide to go LD4B later, but you could always port that to match the heads also.

I think that you would be happy with the LD340 and port the heads to it. Then you will have the stock coil mount location. I doubt that you would want to change to a LD4B and have to deal with mounting the coil.
 
..............Steve, the LD340 is way too big 4 a 273.............u can buy a heat shield for a Holley carb that u can mount ur coil too, in fact I have 1.......kim....
 
beside the coil mounting discussion... if tried to use and tune a LD340 on a 273 with ported 318 heads... result: not what i would call a good set up, wasted a lot of time to get the carb in a proper running condition. and lost a lot of power at the bottom end.

as long as you not going to rev the 273 up to the sky... a LD340 will make no sense.

personally, i will make a switch to an stock 340 4bbl intake an add a TQ

btw... i´ve mounted coil and ECU right under the dash to get it away from heat
 
krazykuda said:
Ok, there seems to be some confusion here.


D4B - is for the smaller port with the special angle intake holes for the 64 & 65 273 heads.

LD4B - is for the smaller port 273/318 heads from 66 and newer. It does not have mounting bosses for the coil in the stock location.

LD340 - is for the larger port 340/360 heads and has the bosses to mount the coil in the stock position.


The LD4B or LD340 will fit his 67 273.



Steve:

Since you plan on porting the heads, why not go with the LD340 that has the mounting bosses for the coil and open up the ports in the heads to match the intake, or match both to the gasket. Done deal, no special mods needed...
Click to expand...

Agree with you. Even if not porting, the ld340 does perform well on a 273. Had a friend who ran one for years. He couldn't find an ld4b, but his dad had the ld340 in the shop. Was a noticeable bump on the lower end and mid rpm range.
 
I would buy a 440+6 coil bracket and modify it for the bolt spacing of your small block intake. It would be easy to do with very little welding. I don't know what I was thinking? Just buy a 340+6 coil bracket.
 
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