Hey, i was just wondering what it would take to take my 305 out and put a 350 in and still be able to use my TPI. im going to build a mild 350 for it and still want to use my tpi system. so will i need new injectors? will i need a new ecu or can i just get a chip burned for a 350 and still use th 305 ecu?
i was thinkin about usein the 305 heads also cuz i heard that bumps up the compression? if this is true thatd be cool, otherwise no big deal. any help you guys could give me would be AWESOME! thanks alot guys!
i was thinkin about usein the 305 heads also cuz i heard that bumps up the compression? if this is true thatd be cool, otherwise no big deal. any help you guys could give me would be AWESOME! thanks alot guys!
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Did the same swap when I first started. Larger injectors, L98 (or custom) chip, and velocity port, and match everything for flow (your going to need all the help you can get if you use the stock TPI system). 305 heads are optional, however, I would look into a decent set of used aluminum L98 heads, and have them worked (you'd be surprised what you can come across these days). Good luck.... Originally Posted by my89iroc
Hey, i was just wondering what it would take to take my 305 out and put a 350 in and still be able to use my TPI. im going to build a mild 350 for it and still want to use my tpi system. so will i need new injectors? will i need a new ecu or can i just get a chip burned for a 350 and still use th 305 ecu? i was thinkin about usein the 305 heads also cuz i heard that bumps up the compression? if this is true thatd be cool, otherwise no big deal. any help you guys could give me would be AWESOME! thanks alot guys! 
BTW, welcome aboard....
what size injectors would i need? and explain velocity port? and yea, imma port match everything b4 it goes together. what would be the advantage of a set of 305 heads?
KrisW
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Jul 17, 2025
The 305 heads are great budget pieces to use. They flow as well as 350 heads but with a smaller combustion chamber you can bump up the compression some. You can have 1.94/1.60 valves installed as well.
You need stock L98 (350 TPI) injectors (22 pounds, I think???) and an L98 ECM chip. I don't know what velocity port he means, but you should also have the 350 EST module and knock sensor.
Good luck!
You need stock L98 (350 TPI) injectors (22 pounds, I think???) and an L98 ECM chip. I don't know what velocity port he means, but you should also have the 350 EST module and knock sensor.
Good luck!
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The shape of the orifice to a conduit dictates volume and velocity. If he's going to utilize the stock TPI system, an extremely limited system at that, he'll need to concentrate his efforts on velocity, the rate of speed in which air is brought into the combustion chambers. Port matching is always a good thing, but velocity porting in itself is equally important, if not more so, than actual flow numbers themselves. Shapes and measurments at very key areas is the key... Originally Posted by KrisW
I don't know what velocity port he means.... 
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im sure it would still work great if you used the stock setup without any mods , an youde also have a better chance if you used the 305 heads, a 305 an a 350 is basically the same ,
awesome thanks guys! im ready to build this motor the ole 305 just isnt gonna work i have a feeling!