Rochester Quadrabog
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Re: Rochester Quadrabog (Rhys)
I've worked on Q-Jets in cadillacs and vettes. I like them. I would put good money on a bet that your problem isn't the carb, but an incorrect vacuum connection to the timing advance diaphram. There should be little or no vacuum to the distributor at idle. People that have performance increase and eliminate bog when they install a Holley simply have plugged their distributor into the correct port on the Holley (there's a diagram in the Holley instructions telling you where to plug it in) and not that the Holley is better. If I can get a 15.248 second 1/4 mile out of an L48 with a Q-Jet then I'm sure you could get an L82 or better to get there with a Q-Jet.
The vacuum fitting for the distributor is on the drivers' side. There is a diagram in the Chilton's manual that incorrectly shows timing advance being connected to manifold vacuum. Timing requires ported vacuum so there is little or no vacuum at idle, then rising up to 12inHg or 17inHg depending on engine and carb number.
The vacuum fitting for the distributor is on the drivers' side. There is a diagram in the Chilton's manual that incorrectly shows timing advance being connected to manifold vacuum. Timing requires ported vacuum so there is little or no vacuum at idle, then rising up to 12inHg or 17inHg depending on engine and carb number.
Le Mans Master
Joined: Oct 2000
Posts: 6,563
Likes: 2
Re: Rochester Quadrabog (Rhys)
Rhys,
Be careful- The same thing happened with the 850 Holley that came with the ZZ/502 crate motor. It was from hell. As many people or more have had Holley problems! NOBODY seemed able to fix it, and I replaced it with an Edelbrock 800; no more bog, idles MUCH better, better low-end response. It loses a little on the top end vs. the Holley, though.
Be careful- The same thing happened with the 850 Holley that came with the ZZ/502 crate motor. It was from hell. As many people or more have had Holley problems! NOBODY seemed able to fix it, and I replaced it with an Edelbrock 800; no more bog, idles MUCH better, better low-end response. It loses a little on the top end vs. the Holley, though.
Melting Slicks
Joined: Apr 1999
Posts: 2,675
Likes: 13
From: Sudbury MA
Re: Rochester Quadrabog (Rhys)
Rhys,
I enjoyed reading this thread as I removed my Holley Dual Feed double pumper and purchased the correct Rochester carb for my car. Sold or gave the Holley away. Haven't mounted the Rochester yet as the engine isn't finished.
I wish you were around a year or two ago when I purchased my Rochester for $1,000.00 and then paid $250 to have it professionally rebuilt.
If you think it is junk, someone who needs that type of carb with the right numbers and date codes will pay good money for it, so be careful what you throw away. Mine isn't worth $1250.00 but that was the price tag to get the correct part for the car. Think twice before you throw away once.
I enjoyed reading this thread as I removed my Holley Dual Feed double pumper and purchased the correct Rochester carb for my car. Sold or gave the Holley away. Haven't mounted the Rochester yet as the engine isn't finished.
I wish you were around a year or two ago when I purchased my Rochester for $1,000.00 and then paid $250 to have it professionally rebuilt.
If you think it is junk, someone who needs that type of carb with the right numbers and date codes will pay good money for it, so be careful what you throw away. Mine isn't worth $1250.00 but that was the price tag to get the correct part for the car. Think twice before you throw away once.
Racer
Joined: Apr 2001
Posts: 395
Likes: 0
From: Shoreline WA
Re: Rochester Quadrabog (Rhys)
Rhys,
I would be happy to pay you a $100.00 for it if it is the correct numbered one for my '78. If you can check and report the ID number off of the carb, I'll let you know if it is what I need. Quadrajet for '78 L-48, Auto with AC, late design. Early '78 design was manufactured by Carter for Rochester.
Thanks,
Mike
I would be happy to pay you a $100.00 for it if it is the correct numbered one for my '78. If you can check and report the ID number off of the carb, I'll let you know if it is what I need. Quadrajet for '78 L-48, Auto with AC, late design. Early '78 design was manufactured by Carter for Rochester.
Thanks,
Mike
Thread Starter
Platinum Supporting Dealership
Joined: Dec 1999
Posts: 6,425
Likes: 1
From: Traveling the US
Re: Rochester Quadrabog (Rockn-Roll)
Mine appears to be conntected to the right port. Like I said before, when I remove the bottom part of the air cleaner, problem solved.
I have zero experience with Q-jets and Holleys, so I really have no beef against either. I just want something that works and works well.
I have zero experience with Q-jets and Holleys, so I really have no beef against either. I just want something that works and works well.
Melting Slicks
Joined: Oct 2000
Posts: 2,268
Likes: 0
From: Roanoke Virginia
Re: Rochester Quadrabog (Rhys)
Hang in there, and give Lars some time to work with you. I think he's in Mexico right now enjoying the beach and brews, but should be back next week.
If you're interested, I have a square bore Holley 650 double pump I'll sell you with the fuel line. Gauranteed to keep your mileage under 10 mpg or your money back :D
If you're interested, I have a square bore Holley 650 double pump I'll sell you with the fuel line. Gauranteed to keep your mileage under 10 mpg or your money back :D
Drifting
Joined: Nov 2000
Posts: 1,361
Likes: 0
From: Honolulu Hawaii
Re: Rochester Quadrabog (Rhys)
Sounds like you have accelerator pump plunger problems. Watch the plunger shaft when you crank the throttle. Sometimes the plunger sticks in the bore, especially soon after a rebuild. It did that on mine. Try putting the air cleaner back on to get a bog, then look at the plunger to see if it is hanging up.
If you still have the bog & if you have the energy, try installing a carb mouth spacer between the cab & air cleaner and try to see if the bog disappears. If you have a large diameter worm-drive band clamp, they make a good temporary spacer.
If that fails too, try retorquing the carb mounting bolts evenly & lightly at first to see if the carb behaves the same as it does now. Hope this helps.
If you still have the bog & if you have the energy, try installing a carb mouth spacer between the cab & air cleaner and try to see if the bog disappears. If you have a large diameter worm-drive band clamp, they make a good temporary spacer.
If that fails too, try retorquing the carb mounting bolts evenly & lightly at first to see if the carb behaves the same as it does now. Hope this helps.
Drifting
Joined: Nov 2000
Posts: 1,361
Likes: 0
From: Honolulu Hawaii
Re: Rochester Quadrabog (Project76)
I have offered repeatedly to trade two quadracraps for one Holley and have never been accepted. That should tell you what absolute pieces of $H!T they are. I have only heard of one quadra$hit that worked, and I don't want to jinx it by looking at it or mentioning the owner's name.
Buy a Holly or Edelbrock and use that quadrajunk as a hammer or wheel chock. :cool:
Buy a Holly or Edelbrock and use that quadrajunk as a hammer or wheel chock. :cool:
Your offer is tempting, BUT I can't shake the image of the 2 qjets that you have. In my mind, they have been tossed, slammed, dropped, etc. Maybe others have the same image in their minds, so that may be the reason nobody has taken you up on your offer.
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Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Re: Rochester Quadrabog (Rhys)
Anyone need a 1978 Q-Jet rebuilt by Holley? It is number 17058204 2367 BHT. Check the Black Book.
Yes, it is a Carter version of the Rochester Q-jet.
[Modified by paul79, 9:02 PM 8/8/2001]
Yes, it is a Carter version of the Rochester Q-jet.
[Modified by paul79, 9:02 PM 8/8/2001]
Drifting
Joined: Feb 2000
Posts: 1,607
Likes: 0
From: Clarksville,Tn,USA TN
Re: Rochester Quadrabog (paul79)
I have 2 quads here at the house if someone needs a certain one. One is a new rebuilt bought from a parts house 17057204 0217 AYN
and a 17058228 3327 BJM
Neil in Tenn
[Modified by Nomad78SA, 9:02 PM 8/8/2001]
and a 17058228 3327 BJM
Neil in Tenn
[Modified by Nomad78SA, 9:02 PM 8/8/2001]
Racer
Joined: Jan 2000
Posts: 491
Likes: 0
From: florida
Re: Rochester Quadrabog (nunus79)
I have a quadrajet. I get nothing but wheel spin when I floor it. You have to understand that these q-jets are set up for stock engines. when you start putting intakes, cams and headers on these engines, you have to modify the idle circuits, rejet the primaries, secondaries, metering rod hangers, and the air valve spring adjustments to compensate. I think q-jets get a bad rap because engines are modified, and these carbs are expected to perform with out the modifications required to perform with the engine upgrades. lou
Safety Car
Joined: Mar 2000
Posts: 4,078
Likes: 27
From: Northeast South Dakota
Re: Rochester Quadrabog
Well doesn't everyone just come out of the woodwork when somebody says something bad about a q-jet. :D I have the computer controlled q-jet on my 81 and love it......now. That carb and I had a slight misunderstanding for awhile there, but then I learned how to tune it properly, and now it works great. It's all a matter of knowing the right thing to mess with. :chevy :yesnod:
Race Director
Joined: Jun 2000
Posts: 10,046
Likes: 675
From: FL
Re: Rochester Quadrabog (Alwyn678)
OK, I went looking for Lar's thread on my tuning session but it has disappeared. Here is some tuning info I picked up from the master.
1. Start engine. Remove pin from accelerator pump arm. Blip throttle. If the bog disappears, then you are running rich in the main jets.(this was my problem).
2. If you hold your hand over the primaries and rpm increases, then you are running lean.
I had richened mine from 72/46 primary rods jets to 75/48. This was way too rich. We tried 73/46 which was too lean, then settled on a 74/47 combination. Note that the difference is still .027" but the area is changing.
This combo works real well for my mods. I can break the tires loose anytime I start over 1800 rpm. I also pulled down 19-20 mpg at a constant 70 mph on the highway taching 3000 rpm.
Anyway, don't give up the Q-jet just yet.
If anyone needs Lar's jetting info let me know and I will forward my copy. Lars email is:
lars.grimsrud@lmco.com
but I guess he is on vacation right now.
1. Start engine. Remove pin from accelerator pump arm. Blip throttle. If the bog disappears, then you are running rich in the main jets.(this was my problem).
2. If you hold your hand over the primaries and rpm increases, then you are running lean.
I had richened mine from 72/46 primary rods jets to 75/48. This was way too rich. We tried 73/46 which was too lean, then settled on a 74/47 combination. Note that the difference is still .027" but the area is changing.
This combo works real well for my mods. I can break the tires loose anytime I start over 1800 rpm. I also pulled down 19-20 mpg at a constant 70 mph on the highway taching 3000 rpm.
Anyway, don't give up the Q-jet just yet.
If anyone needs Lar's jetting info let me know and I will forward my copy. Lars email is:
lars.grimsrud@lmco.com
but I guess he is on vacation right now.
Instructor
Joined: Dec 2000
Posts: 192
Likes: 0
From: Blythewood, SC
Re: Rochester Quadrabog (79MakoL82)
Nunnus,
Both quadrapoopys are on running small blocks. Neither idles worth a crap untill they warm up. Neither one gets off the line, just a bog. They both suck ford and have not been off the car they are on. I have not had the opportunity for creative experiments with explosives since I can't justify wasting money on a carb for the 305 in the 69 RS/SS since we are going to put a 427 in it, and I am trying to sell the vette, but no one wants a deal on an easy project I have lost interest in.
Doesn't matter, no one here is interested in a running vette for $3500, why would they want a trade one get one free deal for a carb.
Both quadrapoopys are on running small blocks. Neither idles worth a crap untill they warm up. Neither one gets off the line, just a bog. They both suck ford and have not been off the car they are on. I have not had the opportunity for creative experiments with explosives since I can't justify wasting money on a carb for the 305 in the 69 RS/SS since we are going to put a 427 in it, and I am trying to sell the vette, but no one wants a deal on an easy project I have lost interest in.
Doesn't matter, no one here is interested in a running vette for $3500, why would they want a trade one get one free deal for a carb.
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
Re: Rochester Quadrabog (Project76)
Another happy Quadrajet customer here. I have had no problems with mine, runs awsome, choke works great in cold weather. Good response on the throttle... of course I know someone who knows how to tune it. He said that most people who don't like quadrajets just don't understand them and cannot get them to work. They buy a holley cause its easy and it will work out of the box. I can understand your frustration with something that you can't get to work. And I cannot blame you for getting a holley there is nothing wrong with that either. Im sure it will work fine. There is just something about having the original carb that works great. I wonder if people who own old ferrari's swap out original carbs ?
http://www.web-cars.com/gto/135-28.html
http://www.web-cars.com/gto/135-28.html
Race Director
Joined: Feb 2001
Posts: 10,787
Likes: 0
From: My own state of mind
Re: Rochester Quadrabog (Rhys)
I have a computer controlled QJet (thanks GM!(yes...I am being sarcastic)) on mine and I replaced the accel pump and also switched to a pair of "DR" secondary metering rods. The accel pump got rid of the hesitation and the "DR" rods give some more fuel to the secondaries. I like the combo right now. But as soon as the emissions man will let me I'm sticking a 600 cfm vac secondary Holley on there because I'm more acquanted with them and think they're easier to work on IMHO. The QJet has one advantage though. It has a crisper feel (at least to me) than a Holley does because of the little primarys. Also check out http://www.thirdgen.org/cgi-bin/mess...=20&LastLogin=
This is where I've gotten all of my Carb tuning tips. (That and the C3 forum)
Matt
This is where I've gotten all of my Carb tuning tips. (That and the C3 forum)
Matt
Team Owner
Joined: Jun 2001
Posts: 43,136
Likes: 155
From: Thomson Georgia
Re: Rochester Quadrabog (flood)
Hey Flood there is a guy on the Forun that paid 1000 bucks for a matching numbers Qjet and another 150 for a rebuild...But to him it was worth it cause of the ncrs aspects......I have decided to have my q-jet rebuilt by Lars hopefully and stick it back on the vette in a couple of months :smash: ..That dude that paid a 1000 bucks is on this sam thread isn't he