kal

I completed a v6 to v8 engine swap (LG4) and I have a non-cc Q-jet. It runs fairly decent but I think it needs tuning. I have searched but I haven't found any posts that tell how to do a complete carb tune. I have a vacuum gauge and air fuel gage but I'm not sure what exactly to look for. I just read that you can't tune a carb without on. THe a/f gage lights up almost all the stoich bars at idle but while driveing sometimes it's rich and sometimes it is very lean and won't read on the gage. Is this normal. I guess I would like a step by step guide on how to tune a carb, like first here's how to set the idle mixture, then you set this ect... Thanks.

Sonix

iTrader: (1)

just making sure, you have the non-cc dist right?

Then you want to set your idle mixture first, use your vacuum gauge, hook up to manifold vacuum, should be showing ~18" vac (in that range say...), then turn your mixture screws out (even left to right) until you get max vacuum, as you're going, reset your idle to a reasonable level (lumpy cam?)....
You can lock out your secondaries, then tune your primary jets and rods....


How's your timing set?


If you want a step by step guide, start searching, i'm not typing that much....

wait a sec, is this basically a stock LG4 ? geez, setup the tune to stock LG4 specs and you'll be fine. What are your rods and jets in their currently?

five7kid

iTrader: (14)

North Carolina and non-cc q-jet don't equate to "stock LG4".

What did the carb come off of?

Project: 85 2.8 bird

I've found the book " Rochester Carburetors" by Doug Roe & HP Books to be very informative. LINK

swimster

People gotta stop just immediately posting a question right off the bat and start learning how to research something. THis board is OVERFLOWING with information that almost NO ONE does a search for. instead they just start posting questions. 9 out of 10 times, it's always the same people answering them.. who are the same ones who awnsered the last same question. doesn't it get a little tiring having to write out the same crap over and over again?

I see it in my kids at home and in my customers at my store.. people these days just do NOT know how to use their brains. It's DEFINITLY no longer taught in schools.. Look at some of these kids running around today. Anyways.. that's a whole new issue that needs to ahve a book written on it. ALL these forums are heading the same way.. I go to the cadillac forums for my eldorado and the same transmission questions are asked almost daily.. no one does a search for the info they need first.. Every forum I've been on.. It's no particular age group or anything.. It's just looking like a sign of the times.

I have NO problems with helping someone out on a problem they are stuck on, but if I've ALREADY written about a problem and the person asking the question is asking for the same info that is already published, well, htat just tells me they are lazy. Knowledge is NOT free.. many of us have had to find out what we know the HARD way or pay for that knowledge.

At LEAST you bought that book.. I ahve the same book.. very informative. But this site could have saved you the $18.95 you spent on it and got you in business if you had searched out the answer.

five7kid

iTrader: (14)

Personally, I don't think this Board replaces the book. It can help if you don't understand something in the book, or if you run up against something that isn't covered in the book.

But, the book will have information that you can have at your fingertips without spending the time searching this Board for the info.

As a side note, before Al Gore invented the Internet, I was a mechanic in the U.S. Army. I was the top in my class in "Advanced Individual Training" in the mid-70's, because I had an understanding of the basics from working on our own equipment and cars back on the farm, so AIT was just information about the specifics of the Army vehicles. Out in the field, the best mechanic I knew, who was better than me FWTW, was a guy who didn't know how to change the oil in his car before joining the Army. I asked him once how he got to know so much, and he answered, "When I got to my first assignment, I was clueless so I would take a TM (Tech Manual - Army version of shop manual) for the vehicle we were working on to the barracks with me every night and sit on my bunk and read it. I did that until I got through all the TM's on the shelf."

People knock "book knowledge", but when you read the book and then do the job, that's called "experience". Doing the job without reading the book is called "hacking".

Buy the book. The Haynes "Rochester Carburetors" is also a very good book. I have and would recommend getting both.

swimster

I'm all for the books too.. I have over a hundred tech manuals and such as well as the carb books, how to do this or that to your small block chevy, etc etc etc... On my trofeo's, I was lost without my service manuals. I too was in the military. I scored int he top 2% on the ASVAB test in the mechanical aptitude section. I, however, entered into communications electronics. Wanted something different. It was a good time.. had alot of fun and learned ALOT. My time was served from 94-98.. just the 4 years.. that was plenty enough for me.. The Army might have bene diferent when you served, but these days, the ones running the show (in the divisions I were in) in there are the ones who could not possibly make it on the outside.. The decisions some of these people made were mind boggling. It didn't matter if you were the best at your job as far as getting promoted goes. If you could memorize a book and afford to pay to ahve your uniforms done up perfectly was what was going to get you your promotion. I could go on for days abotu the military.

I apologize, Kal, for the bashing. I'm not in any way insinuating you have a lack of intellect. I just hate reading the same questions over and over. I've done alot of Q-jet work in the past. My pride n joy Q-jet I have setting on a shelf. it flows almost 900 cfm. It's too big for any engine I have at this point, but we did run it on my uncle's 455 pontiac drag car a few times.. I couldn't believe it worked as well as it did.

Anyways.. Hope you get your motor all worked out.. Start by tuning the idle.. do one screw at a time.. you can do it without a vaccum guage. just use your tach. Adjust one side until the RPM's stop climbing.. then turn it back a half turn. same with the other side. lower your throttle back down to 700-750 and if needed, adjust your idle screws again as above. once that is done, you'll want to start adjusting your transition point. you're gonna have to drive it for this.. you ahve ot make sure your vac advance is hooked up to the right port as well or this will all be dumb. ..

almost forgot.. make sure SURE your timing is set correctly. and make DOUBLE sure your vac advance is not connected when you set it or check it. and make sure the vac advance port is plugged.

There's a hundred other tricks you can do.. hope this gets you int he right direction. also.. depending onw hat 1-jet you have, you're more than likely gonna want ot adjust that secondary air valve to suit your needs.

kal

I'm sorry about posting this but I did search for a while and found tuning for the cc Q-jets. Nobody had a guide for Doing a complete tune. I think that it would be helpful to alot of us to make a tech artical for the non-cc q-jets. Thankyou for helping anyways. I did buy the Doug Roe book but it dosn't really tell how to tune it, it just tells how it works and how to rebuild them. But mine was bought rebuilt so I didn't want to take it apart and mess it up, I just want to make it run good. It is almost a stock LG4, it has hooker 2055's ceramic coated and the 3" hooker catback with a magnaflow 3" cat. The carb is off a 79' Cadillac Coupe Deville The list/OEM # is 17059230, Heres a link to it here I also have a mallory 85 distributer. So I think it has a little bit more power than stock but not much more. Also how do you adjust the transition point? I'm asuming this is when the secondaries open up.

I'm still in the Air Force as an F-15E Crew Chief, and we have Technical Orders (TO's) not TM's so if we get caught skipping a step or not wearing goggles or gloves we get paperwork and weekend duty. And you are so right about the promotions. There are guys that have put in 10 years of 12 hour shifts in the rain, sleet, snow and heat just for a pilot to make a training sortie and the people handing out towles at the gym are getting the promotions and a college degree on there 2 hour lunch break. It sucks. Well sorry bout the rambling I just got off another 12 hour shift. Thanks for all your help it is much appreciated.

five7kid

iTrader: (14)

Well, the carb looks clean enough from the outside.

There's a tech article linked from the TGO home page about getting the most out of a q-jet. It talks like it's about CC q-jets, but most of what it says is common to both (tells you to get the book for the CC stuff).

Most likely, that carb is an early emissions type, which means late mechanical type, that was pretty severely hamstrung for performance. Most likely better rods & lower letter hanger, along with AV tension adjustment, will take care of it. A quicker opening pull-off may also be needed.

A 305 can't use most of the q-jet's potential, especially a mostly stock LG4. But, it can be improved with these adjustments.

Rejetting the primaries requires pulling the airhorn. You can also tune out the off-idle dead spot a lot of q-jets have by adjusting the primary rod depth out. Primary rod spring rate is another tuning trick that I've never pursued.

Keep 'em flying for us!

(I won't comment about promotions, because 1) I've been out for 23 years this month; and 2) I moved up fairly quickly.)

swimster

Heeeey FLYBOY.. niice.. My uncle retired recently from the AF.. was an F-16 crew chief for YEARS until he went to Nellis AFB.. Then in '88, thanksgiving, he was home for a while.. Sitting watching the news one night, they say the AF is going to let out some "secrets" about the new F-1117a... My uncle **** a brick!.. He jumped ont he phone using code words and trying to get thru some sort of sattelite link to "Nellis" to find out what the FU-K his plane was doing on TV...

He was senior crew chief for a team of six of those puppies when they went to the Gulf. promtply thereafter, he put in for a desk job and 6 years after, retired from Hill AFB in Ogden, UT.

Nice to see some fellow soldiers out here. My hat's off to you my friend and may you be fortunate enough to never end up in the ****.

Your q-jet MAY be larger than a 750.. like an 800cfm.. Mine was also off a 79 caddy motor.. 7.somethin liter engine I know that.. My carb is a genuine 800 cfm carb. you can tell by the primaries and the lack of buldges. That air valve is going to be your biggest tuning aid. I had an 85 Monte SS with a CC'd 750 Q-jet. A 305 could never take in a whole 750 cfm of air.. so tuning that secondary air valve opening rate will turn your stock underpowered lg4 into something to at least be reckoned with. My monte went from 15.10's in the quarter to 14.8's That's ALOOOT of improvement for a 305. But int he long run, you have something that you can put onto a 350 should you get one and somethingt hat is MUCH nicer to have than a CC carb. Setting all these performance items up on your q-jet is going to be a long trial n error process. no 2 people's setups are entirely the same. and your driving style will also dictate much of what you need to do. there's ways to go for all out racing, there's other ways to go for economy. But once you konw what you're doing on a q-jet, you'll be tinkering with one of the finest fuel metering devices ever made. The air valve is an ingenious device. One carb, 50 different applications.. just make a few adjustments. You'll have some fun with this and I hope ya keep it around for your 350.

When I decide to put a turbine engine in my car, can I get some advice from you?

Take care man!!!

Project: 85 2.8 bird

that's why you break out the grease pen & checklist

Guess I'll have to search for this deadspot mentioned, and alsosee about fixing te carb (when running) to keep the stomp bog from happening.

swimster

if it bogs when you floor it, you need to adjust the air valve to not open so fast as well as adjust the pump shot. I'm wanting to say that you would need more of a shot, but since that carb came from a MONSTER motor to begin with, I think you should tighten up that air valve first. Whqat's happening is, you're giving the motor way too much at once. You're gonna want that air valve to open alot slower based on the engine's needs. Kind of progressive. that way the engine can keep up with it. You'll see a HUUUUGE difference when you ahve that air valve set up right.

Let us know how it goes.