What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

350 to 454 Help please

H

HSBlazer

Registered Member
Joined
Mar 28, 2010
Posts
30
Reaction score
0
Location
Bay City, MI
Great Forum... any input from you guys will be greatly appreciated. I have a 1991 K5 with a stock 350 TBI. I just replaced the tranny with a 700R4 that has been beefed up to handle extra HP in anticipation of a new engine. The current engine is tired and I have decided to have a 454 BBC built with a carb.

Here is my question.... (please forgive my ignorance). I assumed, perhaps erroneously that I will no longer need my computer since I wont be using the stock TBI. Now I am thinking, what about the speedometer that works off the VSS and the computer ? I read on another thread that my ABS is also run off the computer (I didnt even know I had ABS). I am now wondering what else I have overseen.

Have I screwed myself by going the route of this engine build ?

Thanks in advance for the input.
 
the speedo is feed off the tcase sensor. and can be setup to run stand alone.

the drac= speedo box is cliped to a bracket behind the dash just below the raido. and its a white plastic box. pic of the drac posted with lid opened to show modifyed to let you set speedo correct with pip switch mod i do. and the black bracket that holds them under the dash.

also the abs is not the best syystem at all on these trucks. its a rear abs only. if you bypass it prob no big loss.

and dont forget the bbc will require the brackets for bbc on the h20 pump/alt/power steering pump. exaust will be diffrent. . the true bbc from the factory used bbc specific motor mounts. but dont worry sbc stuff will work as others have used this in the past.

as to bbc swap in with carb that fine. just use a reg hei dist and feed it 12 volts with key on and in start position.

you can use the tbi gas tank and pump. use a fuel pressure regulator to drop the pressure to 3-5 psi and return the rest to the tank . wire it up so its also 12 volts with key on and in crank.

otherwise good luck. and welcome to the site.

drac mods done 001.jpg
 
Why not keep the TBI? It is a pretty painless swap from SBC to BBC and as long as you have a BBC TBI unit all you'll need to do it repin the IAC motor and maybe the TPS switch depending on which TBI unit you have. All you need then is a new chip for a BBC and you're done. Oh, like Brett said all of the accessory brackets will be BBC specific regardless.
 
and if you decied to keep tbi . we got used good computers . post a wanted add in the sale section.

otherwise like scott said sbc to bbc swap is easy as long as you got a computer friendly cam in the bbc.

and thay make cheep 4 barrel to tbi adaptors to bolt you on and go.
 
Thanks for the great info...very much appreciated. I spent a lot of time thinking about which engine to have built and carb vs TBI. My engine builder convinced me to go with the carbs and the ones he had in his shop were all carb'd and they ran so smooooooth. Not like the carb days I remember as a young guy. And I was also influnced by the TBI troubles I have been experiencing on my current 350 TBI. I just wasn't all that impressed with my current TBI. That plus, the simplicity of the carb set up is what made me decide to go carb.

My Blazer is super straight and clean, 100% rust free and is a real sweet ride. I decide this is a keeper for the long term and hence I decided to put the money into having the 454 BBC built (425 HP, 500 ft lb torque)and installed vs throwing a crate 350 back into it. My thinking was also that if I was unhappy with the carb set up, I could go back to TBI.

Again, many thanks for the great forum. I'll report back with the progress of my build.
 
Perhaps I have been overthinking this.... does anyone know if I install the new engine with the carb (thus disconnecting the EFI from the ECM), will the ECM still function for the other truck needs such as the VSS and ABS, etc....or does the ECM go tits up ?

I'm thinking of just leaving the ECM installed and live with the "check eng" light or disconnect the light.

Comment ?

Thanks much.
 
The ECM is needed for the lock-up convertor of the 700R4 although you can buy a stand alone lock-up kit. The DRAC module is all you really need in order to keep the speedo working and also the cruise control working (assuming you plan to keep the cruise control). I just converted from a mechanical speedo to the DRAC system and can tell you how to wire it up to keep the speedo and cruise control working but like I said you would need to buy a stand alone lock-up kit for the trans.
 
HSBlazer said:
?.. influnced by the TBI troubles I have been experiencing on my current 350 TBI. I just wasn't all that impressed with my current TBI. build.
Click to expand...

What sort of issues are you having with your current TBI system?
 
man i miss my old fuel injected blazer:(, its funny most people love the tbi as far as i can tell. i ran into a guy at the hardware store who had a ratty looking 89 k5 that he switched to a carb. he hates it and wishes he left well enough alone. seeing as how youre in florida i cant see the downfalls of a carb and benefits of a tbi really affecting you such as cold weather start ups, warming it up/choke issues, tuning for seasonal changes, etc. what kind of carb you plan on running? is this your daily driver?
 
Sorry for the delayed reply...just returned from Lousianna where I went to pick up a cherry International Scout for my best bud. OK, back to this thread....

The carb I plan on using is the Holley 770 CFM Avenger 4x4.

The issues I am having with my current 350 TBI is an intermittent surging / stalling at idle. I researched the heck out of this but still have the issue. The code (32) I am throwing tells me it is the EGR circuit. I have replaced the IAC, EGR, O2 sensor, wires, plugs, distrib cap and rotor, every vac hose and fitting I could find, PCV, fuel filter, TBI gasket (and re-checked for leaks). The surging continues.

After doing more research I have learned the VSS feeds an AC analog signal to the DRAC which converts the signal to DC digital to the ECM. I have not done anything to the VSS, DRAC or the ECM. I know the ECM controls the EGR and IAC setings so perhaps the there lies the surging/stalling issues...not sure. I know there are other areas to check like the coolant temp sensor, etc but I have been focusing on a replacement engine as of late so my surging investigation as been put on the back burner.

Anyway, all of this in consideration that I want more power and the current 350 is tired with 140k miles, I decided to go with the BBC and carb. Down the road, I would consider a stand alone EFI but thats a few $grand later. I have talked to countless fellow enthusiasts and trusted mechanics.... it seems a 50-50 split between recommendations for carbs vs EFI.

I obviously need a stand alone lock up kit for the torque converter... anyone know where this is available ?

Thanks again!
 
painless wiring makes a nice kit for lock up control. i researched it for my 71 cutlass (was gonna go with a 200-4r) and it seemed to be the best value for the buck. bowler also makes a nice kickdown set up and also a lock up kit that may be worth your time to look into
 
I had the surge/stall issue like you mentioned. Tested everything and it turned out fine. Got pissed and rebuilt the TBI and started throwing parts at it.

After much time and money, the problem was found. The new fuel pump I had installed a few months prior ended up being bad. The fuel pump wasn't maintaining pressure and the problem was very intermittent.
 
yep lots of people dont kep a ye on pressure if thay have a weird problem.

i wont have that problem tho.

i got this http://www.autometer.com/cat_gaugedetail.aspx?gid=3303&sid=7

also had a customer were i use to work. had funny problems. he requested we install a gauge for him. 2-3 hrs away from shop on work trip he had a problem. that gauge paid for its self right then and there. found a split hose in the tank were pump to sender hooks up. bleading pressure off.
 
You must log in or register to reply here.

Latest Posts

Top Bottom