carb swap questions
 

i have never done this before but as i am a hardware man i figure its not too hard to do, plus i work at Ace Hardware so i can get my parts cheap if i need them. i am ordering the new carb tonight and want to make sure its all i need and how hard it is to swap.
Currently have stock 350 with Rochester quad in my 76.
So i am ordering 3 parts from Summitracing.com:
1) EDL-9913 Rebuilt 750 cfm Performer carb (new is 1411)
2) EDL-2697 Adapter plate for Edelbrock carb to Rochester quad intake
3) EDL-8135 Fuel line adapter kit since mine has the metal line with flare connection to carb.

I am not looking for great performance, just a good carb that wont give me major problems like this Rochester has.
As I've never done this before, one of my concerns is if the accelerator rod (from gas pedal) will connect up without problems to the new carb. Since i am getting the adapter plate (Edel carb to Roch intake) it should be a matter of taking off the 4 old bolts (looks like the 2 rear may be missing), disconnecting the fuel line and accelerator rod and vacuum hoses. Putting down the gasket, plate, gasket and new carb. Will i need 4 new short bolts to tighten down the plate to intake? Hopefully the carb will come with the long ones to tighten the carb to the plate. Everything else is a matter of hooking it back up and i didn't see any vacuum intake holes on the new carb so i hope that doesn't mess anything up.

Let me know if i am missing anything...
also if you know a reliable resource with some step by step instructions online with pictures, that would be a tremendous help.

Sounds like you have everything you need but you might want to rethink the carb. The Edelbrock carb is great but on a basic 350 the 600cfm will be good. I have a warmed over 350 and the 600cfm does great on mine. You also might want to get a Carter tuning kit for the size carb you get. The tuning kit from Carter is better than the one from Edelbrock with more items (rods, jets, springs) but will interchange. If you don't have emissions where you live you can get away with alot of the vacuum lines gone with this swap. I just have the brake booster, PCV, and the HEI hooked up to mine. Everything else I eliminated. On the adapter plate you are getting it should come with the bolts to hold it down.

the reason im going with the 750 is i expect it to be a bit quicker on the road, better response time and also the rebuilt is $5 cheaper than the 600...
or will i just be sucking more gas with the 750? whats the pros and cons?

Sucking more gas running worse. Go with the 600.

ok i placed the order last night and i went ahead and got the 600cfm. I talked to another good friend of mine whose baby bottle was filled with motor oil and he confirmed what yall said.
I shoudl have the parts Thur or Fri

What, you didn't believe us? Sort of hurts my feelings. :p

You will be happier with the 625 CFM carb (actual size), The 750 would give you an outstanding topend running condition, but would make a lousey driving condition for normal everyday driving. The 750 works great on a lighter vehicle, such as a Camaro or a Nova, but for a heavy truck you want to keep the airflow up to get more efficiency in the carb throat. The 625 will curb your upper end power slightly, but it works quite well otherwise. I have a 625 on a 383 stroker motor and previously had a 750 in it's place, I witnessed the pain of sloppy acceleration from the carb, also when we rebuilt the motor, the intake valves were coated with deposits, from the fuel. You can buy the Edelbrock internal parts cheaper than the Carter parts, since they are essentially the same "Weber" bodied carb. Play with the needles and jets to get the best acceleration and fuel ecomomy, it is worth it.

the fuel line adapter and intake adapter plate will be here the 6th and the carb the 10th even though it was one order, the carb is coming from CA.. so i hope that distance doesnt hurt it with all the bumping from shipment
the closest i could find locally was a 600 rebuilt for $550 plus the adapter plate for $120... no thx

i hope you didnt pay too much cus you can get a brand new 600 from shucks for 250 or off of ebay for <200

i got a warrantied rebuild 600 from summit parts for $229

ok got it finally (it took 7 days from the ship date) and swapped out today since its my only day off work. took awhile since ive never done it before but it was successful. I got rid of most of the vacuum parts although im wondering if anything is suffering because the vacuum valve just above the fuel pump isn't attached to anything now.. if it wasnt for this damn rain i would still be out there.
The second thing is the gas pedal is half the distance it was from the floor now, i know it is because the line is pulled tighter due to the forward pump drive link... i was wondering if theres a way to fix this or just learn to live with a shorter pedal distance...

Also, you didn't need the adapter plate. The Edelbrock performer carbs are drilled with both squarebore and spreadbore patterns. Just use a Rochester Quadrajet gasket and use the inner bolt holes. I've done it a few times with success. If you were dealing with an "ultimate performance" engine, a disruption may be created by the somewhat poor transition between the squarebore carb and the spreadbore manifold, but in a realitively stock engine, it wouldn't make much difference. At least it doesn't with aftermarket spreadbore manifolds.

oh well its already on there and i would prefer the adapter plate for proper airflow...
I'd still like to know if theres a simple way to get the gas pedal back in the original location.

doh nevermind i found a throttle cable extension kit that will take care of my problem. (Edelbrock #8012)

I have the 750 AND the 600. the 600 is good on the 350, but the 750(i had to change the rods a tad leaner for cruise, 2 stages richer on primary jets, and 8 leaner on secondary jets, as well as lighter vacuum springs), it idles well, part throttle and cruises well, and WOT is W00T! But if you want a good all-around you won't really have to mess with, go with the 600. btw, did I mention I lightened the secondary butterfly too?

I've been thinking about rebuilding the q-jet on my stock 76 Sierra Classic 350. Would it be better to go to the 600 cfm Edelbrock? If so, what is the part number for the one you guys would recommend?

Thanks,
Mike

Personnaly I would stick with the Quad. $14 for a rebuild kit. Might need to have a machine shop sleeve the shafts. As long as sombody didnt; mess with it allready and overtighten stuff and warp the casting why change?
Stock q-jet will hadle 750 if you can build the motor to do it but if you motor only needs 500 then it will only provide 500. That's the great thing about them. They adjust to engine demand. I got Rochesters on three right now and the new one is still 20 years old. If I'm driving the truck daily it starts first try. It starts better then my Fuel injected Suburban.

Thanks for the info....I'll just stay with my q-jet.....

Mike
:gmc:

after going to the Edelbrock 600cfm (part #1400 available from www.summitracing.com ) i will never go back to a Q-jet. yes my truck would start first time everytime... unless the engine was warm, then it would take 10 minutes to never to start. Thats why i needed to replace it, as soon as the engine was warm, if i shut it off, came back to try to start it 30 mins or 4 hours later, 95% of the time it would NOT start.
I got this Edelbrock with adapterplate for Q-jet intake, i have close to twice the power, speed and response that i did before with the Qjet. It is quick of the start and quick to respond in traffic. I have Michelin 31x10.50 XTC tires (made for off road) and it spins them on dry pavement. Never did that before with old carb, had to be wet before those tires spun.
My personal suggestion based on what 95% of what everyone else has said, definately go with at least the Edelbrock carb. If you want part numbers for summitracing.com let me know and i will give them to you. It cost me about $310 for carb, adapter plate and chrome aircleaner/filter. I did it myself and have NEVER done any engine repair myself before and it was easy enough for me. To have someone do it locally, it would have been $600 for the same parts plus labor.

Hey screwball,

What did you do about the fuel filter? Isn't is different on the #1400 than on the Q-Jet (attached to the carb)?

Kewl $300 + for a Edlebrock to solve a choke problem that may have cost nothing to repair. :metal:

What kind of choke problem?

the 750 is not worth it. i would go with the 600. i get great get up and go with it. you are jsut sucking like double gas other wise.
just my cent
thanks shane

The adapter plate also came with the fuel line adapter that allowed me to connect the regular rubber fuel line to the steel line and it included a standard fuel filter that attaches inline with the fuel line, not on the carb.


As it was a 28 year old carb i would rather replace it now and be done with it rather then continue screwing around with the old one again and again and again just trying to get it to work properly.

Alpha, I already have it, its been installed for over a week now and is doing awesome!!!

thnaks for the help everyone!

O.k., I have a Q-Jet #17085290 in my 1986 GMC K2500 pickup. I sent an e-mail to Edelbrock and they are telling me that my carb is computer controlled and Edelbrock doesn't make a replacement Q-Jet for that type of carb. I asked because I couldn't find my carb on their cross-reference sheet.

Will the #1400 work on my truck? I'd like to go with the 600cfm. My baby needs a new carb NOW and I'm at a loss. Your help is greatly appreciated!

The Rochester on my 70 Pontiac I have ever done more then change the fuel filter. Ran great! The quad on my 75 I rebuilt because it sat and the accelerator pump rubber got stuck to the bore and pulled off. That was 5 years ago and I haven t touched it and it's sat for a month. I know it will start just fine when I take it wheeling this month.

I stand by my statement. New doesn't mean better. The only two big problems Rochesters have is the shaft wear (an thats all carbs have that same problem and even FI has it) and the rest is usualy error on the part of those working on them. Overtighten them and they warp the castings and are forever screwed. Other wise sitting and dirty gas are the only things that cause issues and that's is a accross the board problem as well.


Now I also offroad and the Carter is pain in the butt off road. The quad is far better. I am so sick of my one boddies ford running a carter. to get it to run off camber he has it so rich it makes me want to puke. On the street they don't suffer that problem.

well it seems that when my truck is parked with the front end lower than rear end such as on a slight hill or parking space, even after sitting for 8 hours, it either floods it or starves it of fuel, not allowing the truck to start like tonight... with starting fluid it almost catches but doesn't start. ?Next is to replace the fuel pump, probably my next day off, Sunday. I am sure it was the combination of carb and fuel pump to begin with, a trusted mechanic said that is the most liekly scenario and hes sure thats the problem.
I got the new carb already and running good (when running) and now need the fuel pump. Just going for stock replacement from AutoZone or Advanced Auto... i tend to have better luck with Advanced locally.

If this doesn't fix it then i am totally stumped as to why it will start while still warm but wont start on a decline. Next i would guess the distributor???
Whats the suggestion from y'all?

ok i dont know what the hell is going on, it started fine this morning and drove/ran fine going to work. I started it on ym luch break without a problem, i started it 45 minutes before leaving work just to make sure its doing ok... i tried starting it when i got off work and it wouldn't start. Tried starter fluid, no change. Why would it start at 5:45 and not at 6:30??? this is really pissing me off about this truck. My next step i was going to try was the fuel pump but im not sure that will fix this problem.
Maybe the distributor? Maybe needs complete rebuild because its not getting the compression to start? Maybe fuel sending unit in the gas tank since my fuel gauge bounces and it always displays 1/4 tank higher? This is just bugging the hell outta me.

Earlier someone said a choke problem.. well now its same problem but with new carb and electric choke. What else could it be? its a basic engine so not much should be able to be causing this problem.

Id like to know this too.

I don't see why it wouldn't. You would lose the "computer controlled" aspect, but I don't think that would be much of a downside. Do the ESC mod on www.73-87.com and lose that headache at the same time.

if you look at http://edelbrock.com/automotive/carb_index.html it says for the 600cfm:
"600 cfm Carburetors
Street Legal, Electric Choke
50-state street legal for all 1980 and earlier General Motors V8s (E.O. #D-215-10). Calibrated for maximum fuel economy. Includes timed vacuum ports, EGR and fuel vapor outlet. Not for computer- controlled engines. Comes with the following jets, rods and springs: Metering Jets – Primary .098, Secondary .095; Metering Rods – .073 x .047; Step-Up Spring – orange (5" Hg). Includes carb studs and hardware."

For alot of the mid-80's vehicles especially GMs, they had a carbureted engine but had an electric throttle body, basically a carb with the standard jets removed and a computer controlled external injector on top or just inside... The computer balanced the O2 sensor, intake, amount of air and fuel in the system and a few other things to continuously adjust the fuel flow making it richer or leaner depending on the needs. If you were to put on a new standard Edelbrock carb, you would have to remove the computer completely including the O2 sensors and anything else that is hooked up to it.
A better suggestion for you might be to get a replacement QJet, remove the jets and use your existing (or new) throttle body injector...

I cannot complain about a 750. My 350 is going to be running a 750 Q-Jet that has been totally rebuilt. It will be mated to my Edelbrock Performar intake. I hope to get at least 10 MPG. I am running 58cc heads and a 443/443 cam. Should do okay.

1986 non-california is not computer controlled.
 

Edelbrock told me the same thing about my truck and they were wrong. My 86 has a M4ME quadrajet and it is not computer controlled. The M4ME has a dual capacity fuel pump that is controlled by a thermastatic switch, so there will be a electrical connector at the top of the carb, this is not computer control. Take a close look at your carb and identify it before you take Edelbrocks' word that it's computer controlled.
It took a lot of research, but I talked to a carburetor design engineer at Magneti-Marelli in Sanford NC and they told me that the Edelbrock 1904(which they designed) could be used on my truck. By the way Magneti-Marelli also designed the Quadrajets for GM, this guy read me the jet sizes and other specifics off the spec sheet after I gave him the GM part number.
I purchased a 1904 off of ebay but have not installed yet. The 1904 does not use the dual capacity fuel pump, so the thermostatic switch connector is not used, but based on what I have read I am sure it will bolt in with no problems.
As Swervin and others will tell you, the 1904 is a good Qjet replacement, reliable and tunable.

new replacement OEM QJets are suitable replacements but i wanted soemthing better than just a simple replacement carb. I am very happy with mine but it is still a personal decision...