Ok im building a heavy modded 305. Im in the process of figuring out what type TBI unit to go with. I know im not going with a holly unit because of past experences with Holly products. So basicly I have 2 choices. Take the stock TBI unit and do the ultimate TBI mods, bore it out to 1 13/16" or get a 454 TBI unit. I know im going to have to enlarge the holes on my edelbrock intake. What throdle body and injector combonation should I go with? Heres some basic specs of the motor:

305 borred .040 over
World Products S/R torquer heads
Edelbrock Performer TBI
Crane Cams Compu Cam 2030
Pro Magnum Roller rockers
Hooker Headers and dual exhaust

 

Go over to the DIY-Prom board and look at the Tech article on the front page for the Into to Prom burning. Learn how to burn chips and tune your prom before doing those mods or you will really regret it later judging by seeing guys on this board do similar mods and still have 15 second cars: not pretty.

 

I know I need a custom chip burned. What im looking for is what TBI system to run.

 

Hey welcome aboard. You will find most of your answers here. Just read through and you should see what you can't and can do to your 305.

https://www.thirdgen.org/techbb2/sho...hreadid=227281

 

Ok basicly what I gather is im proally want to go with the 454 throtle body if I want the full pontential of my engine. Now as far as what injectors to run im not shure. im debating between the 68# and 74#. I think I might need a computer and knock sensor from a 454 to use that throtle body ?

 

You only need the 305 knock sensor and computer. You will however need to burn a new chip for your combo. You can go with any injectors that were not found on TBI V6 or 305's. So any injector off of a 350 or 454 will work with the proper tuning.

 

I read on turbocity.com that if I get a 87-90 454 TBI unit I will need to modify the idle air passages in the base by grinding to equalize idle air to each manifold port? Is that correct? Anyone else out there runing a 305 with the 454 TBI unit?

 

After doing a lot of searching and reading im still wondering what to do as far as a TBI setup for my heavy moded 305. Ive seen many heated arguements about what to do. Basicly I see 2 arguements.

1) Go with the stock TBI unit, do ultimate TBI mods, Port it to 1 13/16" and upgrade injectors. Turbo City claims a ported one will do 590 CFM.

2) Use the 454 TBI unit, use #68 350 injectors.

Anyone out there with actual experence runing a heavy moded 305. Heres a link to the specs of mycam.

I would be interested to see what combonations other people are runing on their built 305's.

 

If it were me I'd go a step bigger with the cam up to the 2031, I liked that one. For the TBI unit check out This Thread

 

Fabbibg up a 454 unit or going with a holley unit would be the easiest. My buddy has a built to the hills 305 and we are fabing up his 454 unit to go on next week. He is gonna run the 85lb injectors that came with it but at a ver low PSI. We have to convert to the truck style IAC and moddify the throttle brackets a bit but nothing to serious. It is not a driect bol on but has the much needed 2" bores. There is a guy on ebay that bores the stock units to 2". That is something you may want to look at as well. That way you can just hook up everything to your TBI unit without any fab work.

 

Nice what are the specs of the engine. Ide be interested to see how it all turns out.

 

milled vortec heads, 97 LT1 cam, walbro pump, hooker headers. He has maxed out the stock TBI unit. He ran this combo on the stock fuel pump but he could not tune it becuase the pump could not keep up. Now that he has the fuel the stock TBI is maxed out.

 

would not a truck GM 350 TB be an option? the 454 may be overkill. going too big may be worse than too small. 454 is 660 cfm and 350 is 530. but dont compare to carb cfm.

 

A 350 TBI unit flows the same airflow that a 305 unit does because they are the exact same casts with the only difference being injectors.

 

If I were you I would go with the 2031.. Im running that in my 305 now with stock heads carb manifold and headers.. and it pulls pretty hard.... Im giving the cam to my friend over in daytona because im going with the zz4 cam hehehe IMO bigger is better... But look into the 2031.. its worth it, and it u go tpi its nice in that also

 

Ok I got a formula for figuring out how many CFM a engine requires. A 311 CI engine at 6500 RPM runing at 100% Volumetric Efficiency requires 585.942 CFM. I would think that a borred stock throtle body to 1 13/16 with a shaved shaft would flow enough to fuel my 311. I e-mailed the gentelman over at tbichips.com to see what he thinks.