87zz28

Hi,
So i am currently trying to gather parts for my winter project. I decided it was time to get rid of the lg4 305 and build myself a mild 350. The goal is a nice street car with get up and go. The car is an 87 z28 so it currently is running the factory computer controlled carb set up. So my question is, what will i need to run the car without using the computer to control the engine?
Thanks

danryanm

There isn't much involved in divorcing the engine from the computer. You will need a distributor with vacuum advance and just about any off-the-shelf carburetor. Of course, there may be other considerations depending on what you plan to do with the car (torque converter lock-up comes to mind if you have an automatic) but those two parts (or three if you change the intake manifold) are really all that's absolutely required.

pancherj

You also have to make sure to switch over your coolant temp sensor from the old 305 to the new 350 so the fans will run (or, put in a different switch and circuit to run the fans). Also, the oil pressure sending unit is tied into the fuel pump circuitry. You either need to keep it or rewire to bypass it.


Get the correct bracket and geometry corrector for the carb so the TV cable works correctly.

danryanm

Thank you for that, pancherj, I forgot about the geometry corrector. However, 87zz28, since your car is already carbureted, you most likely will not have an electric fuel pump to worry over (some carbureted cars had both a mechanical and an electric pump, though that setup appears to be uncommon.)

For my application, I didn't want to take any chances with running hot (bored .060 over and living near Hot-lanta,) so I ran a wire from the IGN port on the fuse block to a relay, which in turn sent power directly from the battery to the fan so it will run as long as the ignition is switched on. No muss, and easy to tell if my fan is working or not.

87zz28

Sorry forgot to mention that my car is a manual and not an auto and it is also a mechanical pump. With being a mechanical pump what role does the computer play in that.

danryanm

Absolutely nothing.

87zz28

After a little more looking around it turns out my car has the in tank helper pump along with the mechanical pump seems that only 87 lg4s had it to help prevent vapor lock or it was installed on earlier year cars that had a vapor lock problem. Anyone know if running no computer will cause a problem with the in tank pump?

five7kid

iTrader: (14)

Not a problem.

The only carb type that would make this worthwhile would be a Holley-style double-pumper, and only because you have a manual transmission. If you're thinking Edelbrock or vacuum secondaries, you might as well keep the factory CC q-jet and save yourself a bunch of money.

87zz28

I was planning on a Holley 600cfm. set up will be an edelbrock performer intake and 292 turbo heads

five7kid

iTrader: (14)

You will need an intake that accepts a squarebore carb. Most people would probably say to get a 650 DP, but a 600 DP would be fine for a mild 350.

292 heads aren't all that great compared to something like Vortecs, and might not have hardened valves & seats. Your 305 heads would probably be better, depending upon the shortblock you have (smaller chambers work well with dished pistons, for instance; and the 305 081 heads actually have decent ports). But, the 292s will probably be fine for a mild engine (and that's about all a T5 can handle).

I believe the in-tank helper pump has a dual power activation path, the computer, and the oil pressure switch. You probably won't have an issue, but if you remove the computer completely, it will only run once the engine has sufficient oil pressure.

87zz28

My research shows that ported 292 heads flow fairly well. About the same as vortecs would. Would I be fine letting the pump only run at high oil pressure or should I wire it to run off a switch all the time?

3rdgenmaro

iTrader: (9)

I wouldn't wire it to run all the time. It will be fine with it as is, but if the car sits for awhile it could make it harder to start. It may have to take time to pump the fuel up. But since you have a mechanical pump as well, it really wont make much difference.