Hello, i am trying to make up my mind weather i should put an 85 tpi 350 in a 84 vette, or just try to find a complete 84 engine and make things alot cheaer and easier on myself.
Anyways on to my fuel pum question, i know i would need an 85 pump to make the 85 swap work, but would i also need to change the sending unit also?
And if anyone has a complete list of changes i would have to make to make the 85 work that would be great, so far i have a lit of parts i know i will need , and its getting pricey real fast.

 

control system, sensors, the whole wiring harness, ECM, with any/all dash mods to make the new harness work.

The pump is a stright up swap. Same sender. 84 is a 15 psi system. 85 is closer to 40 psi BUT many folks use the 85 pump to feed the 84 CF motor.

 

You might consider going to the 86 rather than the 85. The main reason is that the 85 is the only year with the 870 computer. You will find it more difficult to get someone that knows how to tune the 85. 86 and up use a different chip and you will be happier. Most of the parts for the 85/86 are for the most part the same. There are some minor differences. If you get the later 86, it will have aluminum heads a great improvement over cast iron.

 

The 85 has a one year only (becoming more expensive everyday) burn of module behind the breadbox on dash, unless you have the complete wireing harness ecm, burn of module and all sensors with the engine go for a later model.

As per ECM speed and car performance before i modified my 85 she would do 14.4 quarters, a standard 91 would do around 13.9 but they do not have the MAF and have a bigger air intake duct.
There is not much in it between the TPI years in performance and with headers adjustable fuel pressure regulator set fuel pressure to 45 psi they will go around a second quicker than standard. Note the 85 had 24lb injectors and that may be the reason why they only ran around 30 psi standard. If it is the original 85 engine they have TRW forged pistons standard so may be good if it is a low mile one?

Note you can fit the 85 but due to the early TPI setup having a cold start injector you may want to fit a later TPI intake .... or put a later TPI intake on your 84 engine and just replace the fuel pump and get the corresponding year wireing harness and burn of relays with all
accessories. Mafs esc spark retard controllers are also different for some years, so you need to get the whole loom and all engine sensors including maf and spark retard modules.

So it doesnt really matter what engine just realise the late 86 went to a one piece rear main seal so you need the correct oil pan and fexplate.

Later years had other goodies like roller lifters but be ware look for corrosion if the engines have not been maintained and coolant was not changed every two years.

With slight changes over the years you may want to double check the ecm will work with your dash? you may have to modify the loom to get everything working.