Just looking to get some opinions on a setup that I have in mind for my car. I've already made up my mind on my buildup so I'm looking for any possible problems that might arise with my plans. I plan on putting a set of AFR 195's on my 355, with a JET stage 2 QJet (non-CC), Edelbrock Performer RPM spreadbore, Comp Xtreme Energy 274 (.487" 230* int, .490" 234* exh 110LSA) with roller rockers, MSD Pro-Billet HEI, SLP 1 3/4" headers and full 3" exhaust, backed by a 2400 lockup TC and 3.42 gears. The idea is 400HP, decent gas milage and STREET DRIVEN EVERY DAY.

Idle problems? Vacuum? Anything else I'm not aware of?

 

SHOULD BE GREAT THE ONLY PROB I EVER HAD OUT OF Q JET WAS KEEPING ENOUGH FUEL ,THEY SEEMED TO STARVE VERY EASY ! CAR WAS RUNNING 12:20 @109 MPH TOOK OFF STOCK JUNK QJET HAD A FEW MODS I HAD LEARNED OVER THE YEARS OF RUNNING THEM, WENT TO A HOLLEY 750 DP CAR PICKED UP 1 TENTH SAME MPH WE WERE SHAKING OUR HEADS DAMN QJET NOT TO BAD GREAT IDLE GREAT MPG JUST NOT VERY PRETTY AND NEED A GOOD PUMP AND REG

 

Get yourself a copy of Doug Roe's book "Rochester Carburators" and make a few of the modifications suggested.

Q-jets suffer from float bowl envy. You can make a few modifications to the float, and there are suggestions pertaining to the correct size needle and seat, and he also recommends large diameter fuel line cause Q-jets don't like high pressure, but if you can keep the bowl full at high rpm with 4 psi, that is the ticket.

Just what I can recall at 1 am.

 

I already have that book, which is why I'm buying the Qjet from JET. All of the suggested mods have already been performed, and JET assured me that as long as I have 3/8" line from tank to inlet that I would have no higher RPM starvation problems. I already have them now

Oh, and I absolutely refuse to put a Holley on - or Edelbrock or Demon for that matter. QJet only!

 

Why?

 

Q-jets are the closest thing to fuel injection you can get with a carburator.

Excellent fuel mileage, if you keep your foot out of it.

Capable of flowing enough cfm to feed any street motor.

And when the secondaries open up BWAAAHHHHHHH ! ! ! !

Nothing like the sound of a Q-jet unhailing the world

 

1. Its a daily driver. EVERYONE who has put a standard squarebore carb on their car gets **** for gas mileage. I do not want 10-12 MPG highway as is typical with a Holley. Don't even go there with a DP. Why run a squarebore carb with a OD trans and highway gears? That's dumb.

2. The QJet will bolt right up. No throttle cable changes, no TV cable changes, no vaccum line and fuel line rerouting. No special brackets needed.

3. Because that's what I want. So a Demon might make a few more HP. But the better drivability and much, much better gas mileage is worth a few HP. Sounds cool too

4. Everybody says you can't go fast with one. I'd just like to shut those critics up.

5. Holley is old tech and overrated. Demon proves that and are nice, but quite pricey. Edelbrock should stick to just intake manifolds.

6. I want at least mid 12's @110 on DR's, 20MPG+, good street manners, and no costly FI.

 

Yeah, that's very true. Everytime I have a problem with mine (E4ME) someone always pipes up and tells me to get a Holley (Hi Jester!). However, I did run a 13.96@101.85 with it bogging off the line. I'd like to see TBI do that

 

When you start making serious HP and launching hard in 1st gear I've found it's difficult to keep a carb fed (ANY carb) using just a block-mounted mechanical pump sucking through a 3/8" line.

The pump may have plenty of capacity but the long draw from the tank under hard acceleration will often (almost always) cause fuel pressure to take a nose-dive at the top of 1st/bottom of 2nd gear.

Fortunately, it's easy to fix. Just run a Carter low-pressure street pump (5 PSI) back close to the tank IN ADDITION TO the block mounted mechnaical pump. The combination of the two will outflow either one of the pumps indvidually, and it will be super-consistent in delivering fuel at a constant pressure both during a hard launch and running through the traps on the big end.

I've taken this exact setup into the high 11s on a nitroused 400 and now on my blown 383. Fuel pressure is rock steady at 6PSI under any and all conditions.

Advantages:

1. No regulator required. Since the electric pump is of lower pressure than the block-mounted pump, the mechanical pump IS the fuel pressure regulator.

2. No return line required. See #1, above.

3. Redundancy. You can limp home on either pump alone if something goes haywire with the other.

4. Reliability. My Carter pumps (both the electric and the block mounted mechanical) are going on their 5th year of flawless service. My car is not a daily driver, but it could be and sees regular weekend action cruising, racing, and even towing my boat.

Holley now makes a low-pressure street pump, too. I've installed it on one of my friend's cars in an identical configuration, still using the Carter block-mounted pump on the engine and have had equally good results. I'm impressed with the slightly higher volume of the new Holley unit as well as it's quieter operation than the Carter. You'll never hear it over a performance exhaust system.

As for running a QJet, it's well known that I'm boased towards QJets since that's what I know best. But I'll put one of my home-tweaked QJets against any 750 vac sec carb on the market, performance wise and just KILL them for daily drivability and fuel economy.

 

Another vote for the Qjet here ! Only got one pass in at
the track (see signature) and no starvation yet. We will see
after a few more runs on this new motor.

 

I have a 350 that puts out about 390hp with milder parts and a CC Qjet, so its not a problem getting the power. It will be a big problem getting good mileage out of a non-computer Qjet as the carb will not adjust itself to deliver good economy-it must be done manually (a lot harder to do). I get 12 city/22 hiway with the same gears and converter, I wouldn't expect more than 10/18 with a regular Qjet. You can expect 425hp with that motor combo though.

One thing about using mechanical pumps: it does not give you the psi upon launch becuase of g-forces, the car sucking fuel... Even if you have an electric pump, the mechanical one regulates the total pressure, which may be as low as 3 psi at launch with a load. I say ditch the block pump (I did) and go electric near the tank (I did that). I run the race Carter and reguated it down to 5psi and it works great (it is noisy), even with a 150hp nitrous hit through a stock fuel line. I don't use a return line - it is capped off.

As for driveability, my car runs great - cold or hot, dry or wet. It is also very consistent compared to the injected cars that run worse when the weather is warm and the motor is hot. The car runs its absolute best when coolant is 200-210 deg, compared to 160-170 with TPI/LT1 motors. I never have to cool it off at the track and it runs exactly the same there as it does on the street (one great advantage of the CC Qjet).

Idle is almost stock, vacuum is unknown - but the idle is good, so it must be good.

Two things I would absolutely recommend:
Edelbrock A/F guage for tuning
3-1/2" exhaust (with the headers you mentioned), a 3" is too restrictive at the power levels you will have.

You may also want to go with a fresh air system (as opposed to an open element), but since you didn't mention it... Carb cars typically run better at 200 degrees, so run a 180 thermostat and have 2 electric fans (one at 200 and the other at 210) to keep it cool. If your trans is stock, it won't be for long - you will make a big choc milkshake the first week or two.

The Payoff
Mid 12 second timeslips (or better)
Decent mileage
Being able to floor the car at 50 and bark the tires
Looking stock under the hood

 

paul_huryk -
So even with a non CC QJet I wouldn't get the mileage I'm looking for? JET built a QJet for someone I know for his 490HP (dyno'd) 454 and with a TH400, 3500 RPM converter and 3.73's he was getting 15 highway with his. I understand that you have Edelbrock's Micro-Plus correct? I've been looking for one for years! The car will run like crap without one, so old style QJet is my only choice - unless of course, you'd like a $150 check in the mail

I have an Edelbrock Performer mechanical fuel pump now and figured it would be enough. However, it looks like the Carter electric is the setup I'll switch over to. Damon does recommend the mechanical in addition though - and he knows his QJets too.

As far as the exhaust, I'll keep my 3" for now (cut-out for track). When my wallet recovers (still saving for the AFR's) I'll go for a custom dual 2.25" system that runs side by side along the factory routing. The hi-po exhaust shop that will do it has done a few others and its very clean! Best looking dual setup I've ever seen on a Thirdgen - pricey though. I was quoted $900 from my headers back, mandrel bent with H-pipe and 2 chamber flows.

Trans? See sig - Built by Darrel Young less than a year ago. Supposedly good for 600HP. I should be OK.

OH! Good thing you brought up the cooling issue. I've got a dual fan setup from a 97Z just waiting to go in. This should be enough with a Stewart pump and stock type radiator right?

Hopefully I'll have the heads by winter so next spring I can surprise a lot of people. I just bought a set of ZR1's with Nitto DR's so I might be after New Years.

PS - I've had your website on my favorites list for years

 

I just replaced my semi-CC QJet with a non-CC Qjet and I lost about 1 mpg around town. That's on my 86 305, from 17.5 mpg to around 16.5 mpg.

I doubt it would even be very noticeable on the highway.

 

Hey Paul, looked at your web page an noticed the pictures of the
L69 dual snorkel air cleaner. In light of all the recent posts on
air cleaners (none vs dual vs open element) can you add any info
on what you use at ther track? Your good track times carry a lot of credibility so I am sure a lot of people would like to hear
from you.....

 

The only thing I would do is use a smaller camshaft.
If 400hp is your goal and fuel consumpion is a concern than
you'd do better with a Comp XE268H-10. Also consider the Crane HMV278.
You want to use just enough camshaft to get the job done.
With your planned combo , your cruising speed on the HWY
will be right about 1900 rpm. To low for the XE274. It will still drive ok but no mileage.

The XE268H will match your converter better too.

The Xe274 will exeed 400hp but will not be near as good on gas.

I'd go right along with Damon on his fuel system recomendations.

The carter elec + mech pump combo is easy to live with
and works on the street/strip....

www.compcams.com
www.cranecams.com

 

On your exhaust. Stick with the 3" main pipe or go to 3.5".

The dual 2.25" pipes are a pain and will not make more HP.
The 2 pipes have more wall friction than 1- 3" main pipe.
and will flow less even though the combined area is bigger.

I have custom made (by me) mandrel bent welded 2.5"
duals like you discribe with twin ganged turbos behind the axle.
It works but rattles a bit. Just not enough room.
No advantage over a well done two into 1,,, 3" system
and a 3.5" system will out perform it at way less cost.
Trust me on this one.

I already got the T-Shirt

 

I think it is humurous to listen to all the whining about Q-Jets and misinformed persons suggesting to throw them away! I would like to offer a suggestion to the feeble minded who cant make a Q-Jet work!..........Go to an NHRA event, look under the hood of virtually EVERY GM powered Super Stocker and what do you see?
( Just food for thought!!!!)

 

F-BIRD'88 - I originally wanted the 268, but I already have the 274. Got a real good deal on it Besides, the extra duration will help with the sound of the idle

The converter is just fine. I've driven cars with 2800-3000 RPM converters and hated it. It stalls at 2300RPM now, and flashes to 2500, so with the better engine it'll do OK.

I was tossing around the idea of the duals because they sound SO MUCH BETTER than any single I've ever heard. I didn't want a 4" Mufflex. I didn't know someone made a 3.5" system. Who sells one - none of the local muffler shops can do 3.5 pipe.

And as far as cruise RPM...
I - can't drive - 55... Most highways around here are 65MPH zones, and I usually do the complimentary extra 5-7