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Scrapping TBI, looking for carb recommendations

R

Russ

1/2 ton status
Joined
Feb 17, 2000
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Location
Piedmont AL
I have decided that I do not have the smarts or the patience to try and tune the TBI to my engine so I plan to remove it and set up a carburetor instead. Any size/brand recommendations would be appreciated. I am thinking 750 CFM but not sure?
Engine is a .030 over stroked 454 (489) running 10:1 pistons and XM270HR cam. Edelbrock large oval port aluminum heads with roller rockers. Longtube headers with dual exhaust.
Truck is my 88 crewcab dually that is used primarily as a farm truck with occasional towing (approx 10K).
Thanks for any help,

Russ
 
I agree, I think the Q-jet is the way to go. It should get good mpg when driven reasonably. Ratzila had a Jet (Stage 2) q-jet on a fairly healthy 454 and it drove really nicely.

That said... How you doin Russ? I hope the move to Tn went well. Look for a thread titled "crew cabs" and post a pic of yours. :wink1:
 
I've got a holley 4050 on top of my 496. no choke, not very nice to drive but man will it run!
 
That Jet quadrajet is fairly expensive. I was looking at the Holley 4150's and 4160's as they are a little more reasonable. I am planning on running a vacuum secondary to keep it a little more street friendly.
I am just hoping for something with a little less aggravation than I have had trying to make the TBI run right on this engine for the last six months.
Mainly I was curious if the 750 would be big enough or should I be looking at an 850 carb?

John - Tennesse is a great place to live and I am enjoying retirement. Hope all is well with you. I don't believe I can post pictures of my truck as I am not a paid member anymore.
Thanks for the help,

Russ
 
You might try contacting "Thunder" (I'll try to find his email), he seems to be really good with fuel injection and trouble shooting. :wink1:


Russ said:
I don't believe I can post pictures of my truck as I am not a paid member anymore.

Russ
Click to expand...

Oops, forgot about that - I'll fix it. :thumb:
 
I have run a Holley Street Avanger 770 on the 427 in my blazer for the past 3 0r 4 years with no problem. I will use the same on my 454 I am building for my chevelle.
 
Russ said:
Mainly I was curious if the 750 would be big enough or should I be looking at an 850 carb?
Russ
Click to expand...

Mine's an 850 but it's a pretty stout motor and has nitrous on it. 750 I'm sure would be plenty.
 
Thanks for the help everyone. It looks like 750 is the size to go with. Now I just need to round me up an intake and distributor and thin out my wiring harness.

Russ
 
I don't know about 454 TBI but a 350 TBI is something like 470cfm. 454 probably a bit higher maybe in the 500 range. 650 or 750 I would think would suit you fine.

I just pulled the harness out of my truck last weekend. It was scary at first but thanks to Beater_K20 i got it out.
 
I have had a truck avenger for a few years now. I love it. replaced my quadrajet with it. runs at crazy angles that the last carb would stall at. great right out of the box to. all I adjusted was the electric choke.
 
SkysTheLimit said:
I don't know about 454 TBI but a 350 TBI is something like 470cfm. 454 probably a bit higher maybe in the 500 range. 650 or 750 I would think would suit you fine.
Click to expand...
the TBI 4.3 up to 350 had a 670 cfm throttly body, i believe the 454 had a 770 or 780. not exactly sure on that.

im either going with a 770 truck averger or the 795 qjet on my bigblock.
 
Edelbrock 1406

dont look or think about anything else. It's the simplest, and the ez'est.

this is waht happened to me with experimenting

2264063_10_full.jpg
 
big83chevy4x4 said:
the TBI 4.3 up to 350 had a 670 cfm throttly body, i believe the 454 had a 770 or 780. not exactly sure on that.

im either going with a 770 truck averger or the 795 qjet on my bigblock.
Click to expand...

I stand corrected. I got the x70 part. Meatloaf said "Two outta three ain't bad".
 
makovai said:
Edelbrock 1406

dont look or think about anything else. It's the simplest, and the ez'est.
Click to expand...

yes, your grandmother can tune an Edelcrap, BUT when it comes to getting off camber, the thing is a piece of crap. i had one on my TA, and the thing would act funny when launching hard, a can only imagine what it would do on any sort of real incline.
 
If I were you I would keep the TBI and get it to run right. The stock throttle body is plenty large, but the stock injectors probably don't flow enough fuel at full throttle. Also, you will definitely need a recalibrated prom. You will probably spend the same money as a good carb, but driveability and gas mileage will be better. If you're dead set on a carb, I say QJet as a 1st choice, and an AFB as a 2nd choice. The AFB sucks when operated at wierd angles, but since you said it is mainly a tow rig this shouldn't be a problem. AFBs are also cheaper and easier to tune than a QJet, but a properly tuned QJet will have the edge in mileage and driveability IMO. 750-800CFM is plenty for that motor.
 
The TBI doesn't run terrible, just bad enough to be aggravating. Plus I believe it is leaning out when I am towing. I have an overbored throttle body on it with AFPR, new injectors, fuel pressure gauge, two high flow fuel pumps etc.... All sitting on an edelbrock TBI manifold that I port matched to the heads. I have had a custom chip burned for it twice and have done a lot of tweaking on the fuel pressure, TPS and idle myself but just cannot get it to idle below about 1500 rpms if I bump the fuel pressure up enough to keep it from leaning out. I installed a 3 wire O2 sensor on it, but it doesn't want to stay in closed loop. As soon as I let of the gas when driving it goes back to open loop. I thought I may have a bad O2 sensor (Bosch), so I replaced it with a GM AFS74, but it does the exact same thing.
I know my only logical step from here is to try and start datalogging and burning my own chips, or switch to a carb. I am more mechanically inclined rather than electronically so I don't think I would be very successful at trying to burn chips.
Thanks for the help,
Russ
 
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