TBI on a 472?

German_472 · #1 (**permalink**) 12-25-03, 05:55 PM

Hi!

I am new to this forum, but I have already found a lot of nice post while surfing here - lots of info on the 472s and 500s

Anyhow, I have a 1974 472 in my Coupe Deville and am planning on a massive upgrade after my US vacation in March

. Currently, the stock Q-Jet is leaking badly (fuel and air) and I was thinking about one of the following options:
- Get a new Q-Jet
- Get a new carb (non-Q-Jet, no clue what...)
- Get a 670cfm Holley TBI (2-Barrel)
or get a 700 cfm Commander 950 Holley TBI.

For that, here is my question: Has anyone installed either one of the TBIs on a 472/500? My goal is not (necessarily) to get much more performance, but a better running engine (better idle, smoother "pull" to, say, 4000rpm, and maybe even a little better economy) - The performance will come thru the new Edelbrock intake and the reworked heads. For that, I would like to know how hard the installation & setup was? Also, what additional parts were needed (distributor, etc etc??). Thanks!!!

Greetings & A Merry Christmas,
Andreas

MMNineInchNails · #2 (**permalink**) 12-26-03, 02:34 AM

Well it all depends on if you're a Q-Jet guy or not. Most will argue that Q-Jets are awesome and one of the best carbs out there, and some will not. I myself put a 750cfm Edelbrock squarebore on my 472 and like it a lot. My old Q-Jet was very beat up so I needed the new carb and went with non q-jet. I don't think I'd go with a 2 barrell for a big engine like a 472 though. I believe the stock carb on the 472 is a 750cfm (that's all that I found from researching on the internet), but some people say it's 800cfm. I still think that's a little too big for stock so I'm sticking with around 750cfm. Hope this helps you out.

German_472 · #3 (**permalink**) 12-26-03, 12:43 PM

@ MMNineInchNails:

Well, I admire the concept and function of the Q-Jet and was, so far, quite happy with it - it certainly operated good during the non-stop cruise from Phoenix to Miami last year. But as it is broken now and I really have no clue of how it actually works (with few shops in Germany to work on it), I was not looking at buying a new one. I am more of an electronics person and tuning a car with a laptop is easier for me than tuning a carb (me thinks).

Anyhow, I went to the other forum and posted my questions there. I just want to avoid buying a 1300 USD system and finding out the hard way that it wont work on the Cad.

Greetings,
Andreas

DaveSmed · #4 (**permalink**) 12-26-03, 04:26 PM

Those EFI setups are pretty expensive. Go with a new carb. Q-Jets are Ok, and some people build them, but I personally prefer an Edelbrock. It doesn't have the design issues that allow it to leak like the Q-jet does, and it doesn't have some of the maintence issues Holleys have. Take the money, and put it into other mods. Also, did your car come with A/C? If so, you might have some trouble installing that intake. I believe MTS (http://www.500cid.com/) sells a bracket that you can use with a different compressor to keep your A/C system.

P.S. Someone should know the rules better than that.

Angela Desmond · #5 (**permalink**) 12-28-03, 11:09 AM

Wie geht's German472? I run an Edelbrock 650 on my 350 Chevy and it has given me over 100,000 miles of trouble free operation. For my fairly modified 425 Caddy engine I'm using the Q-Jet that I modified to suit this engines needs. As for leaks, re-bushing the throttle shafts should get rid of any vacuum leaks and sealing up the plugs under the carb with some kind of liquid weld, like J-B Weld, should cure that. ( They're supposedly notorious for leaking fuel from those plugs.)...P.S. I could see that engine swapped into a great handling BMW or similar auto and speeding around Koeln at madcap speeds

German_472 · #6 (**permalink**) 12-28-03, 08:56 PM

Quote:

Originally Posted by Angela Desmond

Wie geht's German472? I run an Edelbrock 650 on my 350 Chevy and it has given me over 100,000 miles of trouble free operation. For my fairly modified 425 Caddy engine I'm using the Q-Jet that I modified to suit this engines needs. As for leaks, re-bushing the throttle shafts should get rid of any vacuum leaks and sealing up the plugs under the carb with some kind of liquid weld, like J-B Weld, should cure that. ( They're supposedly notorious for leaking fuel from those plugs.)...P.S. I could see that engine swapped into a great handling BMW or similar auto and speeding around Koeln at madcap speeds

Hi Angela. Mir gehts gut, danke

Well, I think I will go with a Q-Jet for now and keep my eyes and funds open for a future upgrade to some kind of Fuel Injection - I heard that CadCompany was working on a TPI-kinda setup. And for then, I will get a new Q-Jet. I wonder if a JET Stage II will already be sealed up?

The BMW idea sounds great, but I got an old Mercedes and the fourbanger in it is good for somewhere around 230 km/h - I think thats enough for Koeln

Greetings,
Andreas

vanaisa · #7 (**permalink**) 01-02-04, 06:46 AM

Hallo to Germany!
I find this book is very useful - maybe it helps you. It tells everything about q jets tune up....

Angela Desmond · #8 (**permalink**) 01-02-04, 12:45 PM

Another good Rochester book is the "Haynes" techbook series book on Rochester carburetors. Plenty of good Hi-Po modifications in there also...By the way, German472, I've gotten a speeding ticket on one of your Autobahns outside of Dortmund at 7:00 am on my way from Koeln to Berlin.I would be on one of the few Bahns to have a speed limit on it!

German_472 · #9 (**permalink**) 01-02-04, 05:54 PM

Quote:

Originally Posted by Angela Desmond

Another good Rochester book is the "Haynes" techbook series book on Rochester carburetors. Plenty of good Hi-Po modifications in there also...By the way, German472, I've gotten a speeding ticket on one of your Autobahns outside of Dortmund at 7:00 am on my way from Koeln to Berlin.I would be on one of the few Bahns to have a speed limit on it!

Jeez, Angela. How did you manage to do that? Anyhow, are you living in Germany or just visiting from time to time?

Early mornings and early evenings are bad times for speeding. But sorry to hear that you got a ticket. I hope it was not too much. I got a speeding ticket the first week I had my drivers license (doing 50 in a school zone might not be smart, but I was late for class

). But that was the last one never got caught again.

Oh, talking about books. Does anyone have Doc Frohmanders Big Inch Caddy book? I was trying to get it thru amazon, but they dont have it. I wanted to buy a few good Q-Jet books and that book, but it really is a pain to have to go thru multiple sources (shipping just multiplies...)

Greetings and hope you all have a good new year!
Andreas

Angela Desmond · #10 (**permalink**) 01-03-04, 03:12 PM

Actually I'm of german desent ( my maiden name was Reiss) and haven't gotten to visit since '92, but i do speak almost fluent german.The ticket was 20 marks but I noticed the ticket had 10 marks outlined in red, so I think the cops ripped me off for 10 marks. They took the money right on the spot. I have the "Big Inch Caddy" book and found it somewhat useful in my 425 re-build, but it's nothing special. It can be bought through "maximum torque specialties", the place where many of us purchase parts for our engines.

EastOfGratiot · #11 (**permalink**) 01-10-04, 03:54 PM

I purchased an Edelbrock 1910 and am thrilled with it. It is Edelbrocks brand new Quadrajet. It has 850cfm and an electric choke. It runs great on my '79 Seville with an Olds 455 engine and a Performer manifiold. It cost about $490 from Summit Racing. Don't ever worry about too large of a cfm rating with the Quadrajet. It only gives an engine what it needs and nothing more. The Edelbrock carb is a brand new Quadrajet with several performance enhancements. It also has the benefit of looking almost stock.

Angela Desmond · #12 (**permalink**) 01-11-04, 09:34 PM

I've been waiting to hear from someone using the Edelbrock Q-Jet. Glad to hear good things about it. If the original Q-jet that came off my 425 and I modified doesn't make me satisfied, I may go that route myself.

EastOfGratiot · #13 (**permalink**) 02-25-04, 11:49 PM

Angela,

Regarding your 425 build-up: My previous Caddy was a '77 Eldorado with a stock Quadrajet. It stumbled just off idle when floored. I rebuilt it to original specs. and it still behaved poorly.

I'm sure I could have fiddled with it to fix it, but I sold the car and never solved the problem.

The new Edelbrock 1910 was a perfect setup right out of the box for my 455 Olds engine. It works great at all throttle openings and at all RPMs. Surprisingly I never hear about anyone else using this carburetor. It is a bit pricey for a Quadrajet, but my time is valuable and I didn't want to mess with an old carb.

Good luck with your project.

http://hometown.aol.com/wadewmbryant/seville.html

Angela Desmond · #14 (**permalink**) 02-26-04, 08:01 AM

Sounds like accel. pump; the off idle stumble, that is. Did you put a new cup on the pump when you rebuilt it? I just got over a similar problem with the Edelbrock Performer series 600cfm, manuel choke. It did have 100,000 miles on it, which is a wonderfully long time for no problems with a carb, but I was getting the dead spot when flooring it off-idle. Rebuilt it ( easiest carb in the world to rebuild) and now I'll probably get another 100k out of it. It sits on top of a mildly modified 350sbc. For the 425 I have 2 Q-Jets. One is a stock re-build just to start the motor up. (Don't need problems trying to keep it at 1800rpm to break in the cam) and the other I changed jets and modified some circuitry. It will be a while before this engines done. I'm waiting for pushrods. Was sent the wrong length for the Ford type cast rockers.

Keith · #15 (**permalink**) 03-05-04, 07:53 PM

The leaking problems on your q-jet are not a big deal and can easily be fixed for much less than a new carb. The plugs on the bottom leak, but can be fixed by simply cleaning the carb (dipping), and applying Epoxy glue to the bottom of the plugs to seal them. As to air leaks, the usual culprits are the bushings on the primary circuit which wear the most, and can be rebushed (drill, resleave, reassemble) with the use a rebush kit. Doc Fromader's (sp?) book "Big Inch Cadillac" now has two chapters at the end devoted to the rebuilding of the q-jet and can be purchased from MTS at www.500cid.com.

Quote:

Originally Posted by German_472

Hi!

I am new to this forum, but I have already found a lot of nice post while surfing here - lots of info on the 472s and 500s

Anyhow, I have a 1974 472 in my Coupe Deville and am planning on a massive upgrade after my US vacation in March

. Currently, the stock Q-Jet is leaking badly (fuel and air) and I was thinking about one of the following options:
- Get a new Q-Jet
- Get a new carb (non-Q-Jet, no clue what...)
- Get a 670cfm Holley TBI (2-Barrel)
or get a 700 cfm Commander 950 Holley TBI.

For that, here is my question: Has anyone installed either one of the TBIs on a 472/500? My goal is not (necessarily) to get much more performance, but a better running engine (better idle, smoother "pull" to, say, 4000rpm, and maybe even a little better economy) - The performance will come thru the new Edelbrock intake and the reworked heads. For that, I would like to know how hard the installation & setup was? Also, what additional parts were needed (distributor, etc etc??). Thanks!!!

Greetings & A Merry Christmas,
Andreas