Inliners International Forums General Discussion Engines Interesting Observations of 250..........Opinions

I've been running the 250 in my K-20 for a acouple of months now. Most of you guys know my setup, but for those that don't........'69 250, 4 brl heated clifford intake, clifford truck headers, staight exhaust with only a glass pak, but the rest of the engine is stock.

Anyhow, I've noticed some things........First, with the heated intake, the in cab heater doesn't make much heat when its 20 degrees out? Anyone else experience this? Doesn't really bother me because we don't drive long distances.......Usually start it up, let it idle, hop in drive 4 miles, hop out to start a tractor, leaving the truck idle, hop back in the truck, drive 2 miles, plug another tractor in, etc.
The second thing, which actually suprised me, I'd say this heavier truck(3/4 ton 4x4) does better on fuel with this setup, than our 1/2 tons with 250's did with the stock setup...........I haven't ran a kept track of the mileage/fill ups to see exactly what it is getting because 4-5 of us run it and everyone fills it up when needed. I probably put 50 miles on it on the interstate the past two days, and it may even do as well as my other 3/4 ton 4x2 did with a 305. The fuel gage didn't move much.......I was expecting it to be way harder on fuel.......50 miles with the 454 would have took a 1/4 tank

I am more tempted to try the Q-Jet on it this spring than ever!

TP, it's interesting that you bring this up because I just got my setup up and running and seem to be experiencing the same things. I have a Clifford heated intake and Clifford shorty headers, a stock Edelbrock 1405 carb. I have a T-5 in mine, but really don't get a chance to use the 5th gear much. Right now I can't accurately gauge mileage because the speedo gears in the trans are wrong for my 3.73 rearend (305 Camaro used a 3.08 rearend I believe). I do know it doesn't heat up too well in the cab though. I've recently cleaned out my heater box also. Oh, another thing I've noticed is that my temp gauge is usually at the 1/2 way mark with the occasional trip to the red and I've got a 180* stat in there. Once I bleed out all the air out of the system it'll probably stay at the 1/2 way mark on the gauge.

Put that Q-jet on. I'm VERY curious how it'll work out for you. I've been waiting very patiently for you to do this, lol.

TP.
What 4bbl are you using now?

Running a 500 CFM Edelbrock, 1404 I believe is the #...........

Brad, its been in the teens here in the morning, which is why I've been noticing the heating problem Not really a problem because I don't know what I can do about it to be honest

I won't play with the Q-Jet until late spring at the earliest, but I sorta can't wait to try it.

TP, what is the path of the engine coolant to the intake manifold and heater? Are they in series or parallel with each other?

Series, went by Cliffords own instuctions, intake then heater core.

TP
I think you will love a Q jet, I was a total believer in Edlebrock carbs till I switched to a Q-jet set up for a 4.3 V6 on my 250 (.030 over flat tops from a 307, comp cams 260H, MSD ign, and major head work with Stainless pro flow 1.60/1.94 valves). I noticed a 3+ mpg improvement over the Edelbrock I was running. I had switched several sets of jets and rods but it almost always ran rich (I have a air/fuel ratio gauge which allows me to know what my mixture is doing). I installed the Q jet and watched my mixture start to run the way it should plus the engine just ran better, more usable power and smoother. Most of my friends can't believe I switched because I was always an AFB/Edelbrock fan and never cared for a Qjet till I built this six.

I have a Q-Jet off a 305 V-8 and was thinking it should be darn close to what I need off the get-go for the 6..........Its just getting around to trying it. I have to rebuild it first however.

TP from Central PA,,,,
What size is that Q-jet you want to try out?

If you can,, try and find one of the smaller Q-jet carbs. Like a 650 or less?

MBHD

TP, I was just thinking about this post again today and realized that I never did patch up that hole after I swapped over to the cable style gas pedal. I'm sure I've got a few other holes around the cab, but even so it still doesn't seem to heat up as much as it did before I hooked up the lines to the intake.

There are only 2 cfm sizes for Q-jet carbs, 750 and 800. The 800 has slightly larger primary venturies. Doesn't really matter which one you use, the air-valve secondary design of this carb won't feed your engine any more air than it 'asks' for.

The Pontiac OHC-6 Sprint engines used the 750 cfm carbs.

Best book on Q-jets ever, you can learn everything about them and build up a good one with this for reference: Rebuild-Modify-Rochester-Quadrajet-Carburetors

Who ever told you that????? there is only 2 sizes??Know that the v6s used a smaller CFM Qjet.
I know a guy who is running one on his L6 which came from a v6 and is less then 600-650 CFMs If?
I remember right him telling me.

Larry
If memory serves me right wasn't there a 1050cfm Q jet that was used on big block muscle cars in mid to late sixties.

I believe the biggest spreadbore carb that came stock was a Carter Thermoquad(A.K.A. thermobog!)L.O.L.
850 CFM I.I.R.C.? If I remember correctly.
I also thought I read that the Pontiac OHC 6 had a 650 Carb.

MBHD

Basically the Rochester Quadrajet does come in 2 sizes , Doug Rowe's book on Rochester carbs will show that. The Quadrajet was used on such a wide range of engine sizes based on its internal bits ,mainly its metering rod and jet sizes. it was used on the Pontiac OHC engine too but GM simply limited the abilility of the back barrels to open 2 between 2/3 and 3/4 of wide open throttle position .

Hank
You guys are probably right that has been over forty years ago and I never liked or ran them I just thought I remembered a few guys claiming that they had 1050s. I always ran Daytona AFBs or Holley. I never saw a Q-jet that I liked until I bought my wife a new 1985 Astro Van, Drove it ten years and never had to touch it. Then I built my current 250 and had an Edelbrock on it but couldn't get it to lean out at low rpms (under 3000) changed rods, jets, & springs and never got it to suit me. A friend of mine that collects, rebuilds and sells carburetors handed me a Q-jet set up for a 4.3/5.0 chevy and said try it if you don't like it after 3 or 4 months bring back if you do pay me for it. To make a long story short I paid him for it.

The Q-Jet I have came off a running 305 V-8...........I am more excited now to try it!

Yeah as far as I know there only two Q-jet sizes: 1 3/32" 1 7/32" (primaries), but there are countless different cfm ratings calibrated by how far the secondaries open. And Big Bill is probably remembers right about the 1050's, I have a Q-jet book by David Vizard that shows how to bring them up to 1070+.

Dan

Yes some of the OLDER BB SS cars Had higher CFM Qjets The AFB also came as a pretty big carb/CFMs
On someof the Mopars.

(CFM Ratings)not so much as carb Size.

TP from Central PA, did you ever put your Q-Jet on? If so, how does it run? How's the mpg's?

Hey guys,, Im running a q-jet on my 250,,,
Larry will tell ya, Ive been fighting this thing for years,,, Ive used the Rowe book,, way to confusing,, the book to get is by Cliff Ruggles, awesome guy and company,,cliffshighperformance, basically you got it,, two different bodies to support desired airflow,,,only the early actual muscle car quads (oldsmobiles) came with giant cfm/fuel metering capabilities and some of gm 454 /427's all others are pretty d-tuned by gm.. my carb is a b.o.p. so the fuel inlet is straight in not at a side entrance like chevy,, and the air valve is modified with a set screw, and the factory table is ground off,,,so it opens much larger than factory intended,, quadra-bog is usually never to much fuel as thought, it is not enough,,in addition to the amount the fly opens there is a spring below that changes the speed it opens,,according to the vacume being pulled through the venturie, that is the key,, open to fast and you dump air without the right fuel creating a lean spot (bog)open it to slow and you create a rich dog,,once the carb is metered for the fuel,,and when you get the air valve worked out the carb will run great,,, on the trek to our buddy freddys annual breakfast, the car knocked down 24 mpg cruising about at about 70,,,

Now Now No fibbing You know that you was doing at least 110 LOL Just kiding.But that is pretty good MPGs at 70 mph. I'd be willing to bet it would come up at least another 1-2 mpgs @ 60.But bottom
line is it sure did sound Dangggggggggggg Good/Sweet.

hey Larry,, thanks for the word of reconition, it has been a long project,,,finally begining to take shape,,, for my demons we discussed,, the weekend test,,,oil 39-44 at start,,,gradual heat up cruising town,, traffic light, 214 temp, 2psi oil,,(yikes), pull away pressure back, mid 30's, got home,, inspection,,, 15" flex fan flattens out at idle way to much,,no air being pulled,,shut down at 227, no burp, no overheat, I'm going to pull the tranny cooler out of the rad, to fit a larger fan, I have a 16" flexalite,, haven't got a set of mechanical gauges yet,, still a little bit of faith in the digitals,,,(but not much...)

Fingersix, can you say for sure if your speedo is correct? That mpg sounds almost too good to be true, but if so....sign me up!!!

Could you provide me anymore details about your Q-Jet? For example carb #, what it came off of, is it a reman or specially built for your app, anything else I'd want to know? Thanks!

Its been a long time from tranny build till now,, but we used a calc chart form carcraft on tailshaft drive and driven gears,, we got as close as possible for my tire height and 3.08's,, I'll try to get out tonight and see the old fashion way and rpm at 70 on the highway,,,the car is a 65 chevy II, so with me in it, the car wieghs some 2800lbs I think. Im also using a 700r4 tranny,,so overdrive helps., The q-jet is just a junker I've collected over the years,, it is a mid 70's/80's and a b.o.p. body,,,that choice would be determined how you wanted to bring in your fuel line,,if you are going to mount the carb primaries out,, you want a chevy q-jet with the side inlet,,the front inlet with the filter tip and fuel line came to close to the shock tower in the nova,,basically you want a non-computer q-jet with an adjustable apt,, and with the tons of different throttle shafts you have to pick one that meets your needs,, from throttle to tranny linkages,,Hit your local bookstore and find the q-jet book by Cliff Ruggles,,it is worth its wieght over Rowes,
After I worked with the carb with help from Cliff over the phone,after countless times with a carb co out of St. Pete, I did send it to him for his rebuild,, He does so many, and is very familiar with the setup for sixes,,(even ohc sprints), he took my car/setup info and when I got it back, bolt on and go,, haven't touched it since

Your welcome fingersix =fsix Hum name sounds like a Cool Ride at a fun park HUH fsix LOL.

fingersix, does the Ruggles book cover how to prep a Q-jet for a blow thru setup with a turbo?
Lee

Lee, I dont believe it discusses prep for blow through,, but Im sure Cliff is familiar, I learned alittle myself reading the book,, the apt is vacume controlled and when it doesnt work tuning is difficult on the primary side, so I removed the factory plug, tapped the hole and reassembled the carb,, while running I found the apt did not work,,I called Cliff and he informed me that I had a base plate for a turbo application,, the vacume orfice is removed so it doesn't pressurize under boost,,somebody must have swapped it on without knowing (carb company from St Pete)..he instructed me how to drill it out, so I did,, I wish I had kept it cause Im interested in turbo apps..sidenote..those bases came off the early 80's turbo trans am's

Brad... I got out this weekend,, the speedo is correct according to the Santa Fe,,50 mph, 1500 rpm, 60mph, 1700 rpm, 70mph, 2000 rpm, 4th gear locked up,, the overdrive really helps gettin those mpg's.
I also got out Cliffs book,, it is the early pontiac carbs that were great stock performers,, not Olds' oopps,,but any carb can be made to work well,,even looking through it this time was great..