Carb/Intake swap

by Damon23 Thu May 05, 2016 9:49 pm

I'm having a issue with my car. It is a 350 2bbl completely stock. When it is cold it idles up fine and warms up. Sometimes if I hit the gas to disengage the choke it will pop. Not all the time though. Well today I took it out on a 40 mile run and after about 5 miles I slowed down to make a right hand turn and gave it gas after the turn and it stumbled and popped (not a loud backfire but a pop) then it accelerated smoothly down the road. The more I drove the more I noticed the idle get rough and just sitting at a stop sign for a minute I watched the temp creep from 180 to 190 in that short minute. If I got on it from a stop is stumbled and a couple times popped and died but fired back up, but if I eased into it the car was smooth as butter. I got the car home and hooked up a vacuum gage. It was at 18 then bounce to 16 and back to 18. Looked at the carb I noticed the right rear bolt missing and the front left bolt missing. I didn't have time to fool with it further cause all I could see is gasket so I'm thinking when the PO rebuilt the carb they probably snapped off the bolts.

So to make a long story short I think it has a vacuum leak cause of the two bolts missing and if they are broke off their is no need to mess with the 2bbl carb and intake so I should just swap it out. I'm thinking a 2101 intake and standard 1406 carb. If you've done this swap what all will I need? Different brackets, adapters, fittings and whatnots? I'll have to pay to have this done and I want to get everything cause I know a mobile mechanic and I want to have everything here when he comes to swap it out.

by bigredlaguna Fri May 06, 2016 1:29 am

You can verify a vacuum leak by spraying carb cleaner, wd40, or even unlit propane or map gas near or on the suspected areas of vacuum leak. The engine will rev up when the fuel is pulled in through the leak.

As far as stuff for the swap, you will need an air cleaner for a four barrel carburetor. You can get aftermarket brackets that hold all of your cables (throttle, kickdown, cruise, etc) as it is unlikely that the two barrel carb brackets will fit properly. New throttle return springs.

Intake, distributor, and carburetor base gaskets, and possibly valve cover gaskets. I would also recommend using a phenolic plastic spacer under the carburetor to reduce the chance of boiling the fuel in the carb when the engine is hot. This carburetor is prone to do that, so whatever you can do to insulate it from the manifold will help.

I also recommend getting a jet and rod kit for the 1405 carb. I read many complaints about the factory setting of the 1406 being too lean. A lot of people re-jet their 1406 to the 1405 settings. Yours may run fine with the factory installed jet/rod combo, but I would rather be ready for the possibility of needing to adjust drastically than not.

by bracketchev1221 Fri May 06, 2016 6:55 am

Are you saying the carb is only bolted down in 2 corners?

by Damon23 Fri May 06, 2016 8:46 am

Yep. Pretty scary. But a friend told me that my problem sounds more like ignition rather than vacuum. I did smother the carb and the car died so a leak may not be the problem.

by 73ss Fri May 06, 2016 12:51 pm

2 bolts is correct. The other 2 holes are probably not even drilled or tapped on the intake. GM started this in the mid 70's. who knows why. the last 2 barrel I worked on only had 2 holes in the base gasket as well.

by Damon23 Fri May 06, 2016 3:55 pm

Alright. Then that takes that off the table for right now and I can focus on the ignition.

by builtnotbought Fri May 06, 2016 5:35 pm

Have nearly the same problem. On my new 383 I have edelbrock EPS performer intake + edelbrock
600 CFm carb with electric choke, 1405 or 1406 model.

I think that car have stock throttle cable with tube on the end and stock cable bracket but I'm not sure.
Cable
Carb/Intake swap S-l16012

Bracket

When I decided to install old bracket and cable to new intake it appeared that when cable is fully loosed and pedal up it can't close the carb flap to zero position - bracket is too far away from carb.
I rewelded bracket and move it 2cm closer to carb - but only after that I noticed that now cable fully strained (pedal on the floor) can't open carb's flap to full throttle.
Don't know what to do. It appears to be that my cable travel is too short for my carb application. The only way is too use longer cable and remake bracket as it was... I can't find any useful info of what cable bracket combo I can buy/use with EPS+1405/1406 + 74 elco firewall.
I can't contact Edelbrock to ask because they allow only phone calls - no email.

Another question is - Should carb rocker to what acceleration cable is connected travel to it's edge position to make full throttle? Because the design of this cable on photo (with tube on it's end that will hit the bracket in the end position) doesn't allow carb rocker to reach it's end position anyway. Travel of the cable is shorter than travel (turn) of the rocker...

If anybody have any info I will be very pleased. Thank you!

by Damon23 Fri May 06, 2016 8:37 pm

I don't know the answer to your questions but one would think as long as these cars have been around and having the intakes and carbs swapped that someone would make a bolt on bracket to hold everything properly.

by bigredlaguna Fri May 06, 2016 9:38 pm

builtnotbought wrote:

When I decided to install old bracket and cable to new intake it appeared that when cable is fully loosed and pedal up it can't close the carb flap to zero position - bracket is too far away from carb.
I rewelded bracket and move it 2cm closer to carb - but only after that I noticed that now cable fully strained (pedal on the floor) can't open carb's flap to full throttle.
Don't know what to do. It appears to be that my cable travel is too short for my carb application. The only way is too use longer cable and remake bracket as it was... I can't find any useful info of what cable bracket combo I can buy/use with EPS+1405/1406 + 74 elco firewall.
I can't contact Edelbrock to ask because they allow only phone calls - no email.

Another question is - Should carb rocker to what acceleration cable is connected travel to it's edge position to make full throttle? Because the design of this cable on photo (with tube on it's end that will hit the bracket in the end position) doesn't allow carb rocker to reach it's end position anyway. Travel of the cable is shorter than travel (turn) of the rocker...

If anybody have any info I will be very pleased. Thank you!

Sounds like you just need to move the post the cable attaches to on the carburetor closer to the shaft. You could measure your total travel of the cable while unattached, then find a place on the carburetor linkage that matches that distance from idle to WOT.

by pila Sat May 07, 2016 12:03 am

My '74 Malibu originally had a 2bbl on it, and I had to buy a throttle cable for a 4bbl. The local Chevy dealer searched one out for me.
If you measure the full length of the 2bbl cable you have, maybe someone here will have the longer on for the 4bbl....
I believe I have one here, but not sure which carb it's for......

Bill

by chevellelaguna Sat May 07, 2016 5:38 am

Yup, Bill is correct. What you have is a two barrel carb cable. You'll also have to modify the trans kick down cable.. Or get one off of a 4 barrel car as well.

by 77mali Sat May 07, 2016 7:43 am

http://www.jegs.com/p/Edelbrock/Edelbrock-Carb-Linkage-Adapters-Studs-Cable-Extensions/753856/10002/-1?itemPerPage=60&pno=1

This may work also depending on your carb/intake set up.

http://www.summitracing.com/parts/spe-24283/applications/carburetor-manufacturer/edelbrock

I bought the Ededbrock adapter that has the throttle/kick & cruise(you still may have to make mods to the base to get it to fit on the intake)

by chevellelaguna Sat May 07, 2016 9:38 am

He still can't use the 2 barrel cable, with any of those brackets.

by bigredlaguna Sat May 07, 2016 4:06 pm

chevellelaguna wrote:Yup, Bill is correct. What you have is a two barrel carb cable. You'll also have to modify the trans kick down cable.. Or get one off of a 4 barrel car as well.

What is the difference? The only place I found cables that were anything other than 23.75" long was at Rockauto.com where they also have one that is 24.5". They do not specify 2bbl vs 4bbl.

My original 74 chevelle had a 2bbl that I eventually changed to a holley 4bbl. It was able to fully open with the original throttle cable. The Edelbrock carb may just simply have predetermined spots for the cable to attach that are further away from the shaft than the original carb. If the cable is the limiting force, then perhaps just trimming the outer sheath that blocks adequate travel would fix the problem.

My daughter's 74 came into this family with an Edelbrock 1406 already installed. I was just cruising in it last night and while it felt snappy from a stop, it just didn't feel like the secondaries were opening. I'm going to check this out today.

by chevellelaguna Sat May 07, 2016 5:44 pm

Itl like you said, edelbrock has the provision for different mounting points on the linkage. Holley does not. The 2 barrel cable will not generate WOT. I don't think you can cut the sheathing either, because of its design, also the cable needs to be longer. A cable system from Lokar would work.
The two barrel trans kickdown slot needs to be lengthened by about 1.5" when using a Holley.

by bigredlaguna Sat May 07, 2016 8:26 pm

Just checked my daughters car. It opens the carb all the way. I do believe the cable has been modified. There is no dust cover on the carburetor end.

by bigredlaguna Sat May 07, 2016 8:47 pm

by bigredlaguna Sat May 07, 2016 8:51 pm

It needs a new cable anyway, the part that holds onto the bracket is worn and the pedal feel is a little sticky.

by 77mali Sun May 08, 2016 7:59 pm

My car was an original 305 but had a swap to a 350. I'm pretty sure that the calbe is original to the car. Did 305's come with 4 BBL carbs?

by ant7377 Sun May 08, 2016 8:50 pm

My 77 monte has its original one too and came with a 305 2bbl. I have a holley on it now but use edlebrocks cable bracket.
Hey Paul! Happy Mothers day! 305 came with 4bbl in CA only in Monte Carlos at least. Ive seen one.

by 77mali Sun May 08, 2016 10:29 pm

After reading through the last few posts, now I'm wondering about it...

What's up Ant! Are you insinuating I'm a Mother______? Lmao
I'm a bad Mother (Shut yo' mouth!) I'm talkin' 'bout Shaft!

by builtnotbought Mon May 09, 2016 5:39 am

So many info Shocked

, thank you.
I will look again at my setup

My tv trans cable was also connected to pedal, not to the bracket on intake.

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