tbi to carb swap help

[crankenstein racing]

hi guys i have a 1987 chevy and i am looking at ditching the throttle body. is there anything i should know before i start swaping parts?

 

[HotRodPC]

Yeah, you should know unless you have a very damn good excuse, you shouldn't be swapping from TBI to Carb. Why give up durabilty and economy for a carb??? What's the purpose? Spill it !!!

 

[Jims86]

Yes, you should know that its a bad idea...unless you are going for all out racing of some sort, then you want a Holley Or similar carb.
Let me guess....someone said carbs are better?

 

[hinkv10]

I have an 87 thats been converted back to carb. I didn't do the conversion but if you need any pics. It appears to be a simple swap. A visit to the junk yard should get you everything you need.

I am interested in why you want to switch. I will say my 305 only got 10 mpg with a Edelbrock 1406. I just installed a Quadrajet and am hoping for a bit more..... If you plan on driving this everyday, it adds up quickly.

 

[Jims86]

I have an 87 thats been converted back to carb

Never was carbed. the only 87 to 91s that were carbed from the factory, were the HD trucks....very rare too.

 

[MrMarty51]

The only thing You need to remember,when removing Your TBI equipment,is to remove the complete wire harness related to the TBI,along with the ECM,and,send it ALL to MEEEEE.

I have an 87 thats been converted back to carb. I didn't do the conversion but if you need any pics. It appears to be a simple swap. A visit to the junk yard should get you everything you need.

I am interested in why you want to switch. I will say my 305 only got 10 mpg with a Edelbrock 1406. I just installed a Quadrajet and am hoping for a bit more..... If you plan on driving this everyday, it adds up quickly.

Please,keep us posted,on the MPG difference.
A Q-Jet tuned proper,I`m thinking will get some bettrer fuel mileage than the E-Brocks or the Holleys.Maby,Maby not,I dunno.

 

[Jims86]

The only thing You need to remember,when removing Your TBI equipment,is to remove the complete wire harness related to the TBI,along with the ECM,and,send it ALL to MEEEEE.



Please,keep us posted,on the MPG difference.
A Q-Jet tuned proper,I`m thinking will get some bettrer fuel mileage than the E-Brocks or the Holleys.Maby,Maby not,I dunno.

I have seen 22 mpg from a longbed with 350 with an SMI qjet. Engine had TBI heads, and a melling MTC1 cam, Full emissions equipment, Magnaflow 3" muffler.
similar truck got 23, but it had a bored out TBI, CFM Tech spacer.
Both trucks had 700r4' and 2WD.

 

[MrMarty51]

I have seen 22 mpg from a longbed with 350 with an SMI qjet. Engine had TBI heads, and a melling MTC1 cam, Full emissions equipment, Magnaflow 3" muffler.
similar truck got 23, but it had a bored out TBI, CFM Tech spacer.
Both trucks had 700r4' and 2WD.

That is what I would label as "Fine Tuning".
I`m looking for a 454 TBI for My 93 GMC 1500,350 and 700R4.I seen,somewhere,that someone had a demo. on converting the throttle shafts from the 350 TBI into the 454 TBI because of the differences between the two.

 

[Jims86]

That is what I would label as "Fine Tuning".
I`m looking for a 454 TBI for My 93 GMC 1500,350 and 700R4.I seen,somewhere,that someone had a demo. on converting the throttle shafts from the 350 TBI into the 454 TBI because of the differences between the two.

You would be using the 350 injector pod on the 454 base. the issue with the throttle shaft is the kickdown connection. there were no 454 700r4 combos.
you would be better off to send your throttle body to CFM Tech and have them port it to 2" barrels. You will need to open up the manifold to match as well.

 

[MrMarty51]

You would be using the 350 injector pod on the 454 base. the issue with the throttle shaft is the kickdown connection. there were no 454 700r4 combos.
you would be better off to send your throttle body to CFM Tech and have them port it to 2" barrels. You will need to open up the manifold to match as well.

Would You have a link to CFM tech ? I have three throttle bodies from the 89 to 90 versions,from the 350 engines.I would probably send them one of those as Mine pickumup is My daily driver.

 

[HotRodPC]

So as you can tell Crankenstein, it will be the popular here to keep the TBI for economy. Many of us don't drive our squares as often as we'd like due to economics and mpg.

I'll go out on a limb and guess you want to hop up the motor in the truck? Cam, headers, intake carb etc? If that's the case you're not concerned about mpg anyway. To go to Carb is fairly easy, but I'll suggest to carefully remove your ECM harness, intake TBI etc. There are guys on here that will gladly give you a few bucks to convert their carbed units to TBI. Shipping may kill the deal, or you might have someone close to meet in person, but point is, before you go hacking on ****. Take your time and remove it properly. We like good OEM harnesses in good shape.

 

[MrMarty51]

So as you can tell Crankenstein, it will be the popular here to keep the TBI for economy. Many of us don't drive our squares as often as we'd like due to economics and mpg.

I'll go out on a limb and guess you want to hop up the motor in the truck? Cam, headers, intake carb etc? If that's the case you're not concerned about mpg anyway. To go to Carb is fairly easy, but I'll suggest to carefully remove your ECM harness, intake TBI etc. to send to Martin to convert His carbed unit to TBI. Shipping wont kill the deal, but point is, before you go hacking on ****. Take your time and remove it properly. We like good OEM harnesses in good shape.

There,I fixeded it fuhr Yuh.

 

[Jims86]

I would like to see someone do that dual throttle body setup from Howell EFI.

 

[MrMarty51]

I would like to see someone do that dual throttle body setup from Howell EFI.

I have thought about doing a dual two barrel TBI using spare parts and pieces.
Like a two four barrel manifold with the four barrel to two barrel adapters,and I do have a couple of spare TBI units laying around.
Set it up with progressive linkeage to open one 1/2 way before it begins to open the secondary,then at full wide open thats the way both of them would be.
I do not know if it would work or not,might be a PIA to figure it all out as far as the ECM is concerned.
I guess it would be a version of the poor mans four barrel TBI.

 

[Jims86]

I have thought about doing a dual two barrel TBI using spare parts and pieces.
Like a two four barrel manifold with the four barrel to two barrel adapters,and I do have a couple of spare TBI units laying around.
Set it up with progressive linkeage to open one 1/2 way before it begins to open the secondary,then at full wide open thats the way both of them would be.
I do not know if it would work or not,might be a PIA to figure it all out as far as the ECM is concerned.
I guess it would be a version of the poor mans four barrel TBI.

I would get the harness and chip from Howell at that point...they have it all figured out.