GM HEI ignition and 82 Impala 305

[iTurbo]

I'm working on my brother's '82 Impala with the 305/700R4 drivetrain. It's got HEI ignition with the coil in the cap, but the timing advance is computer controlled. My brother installed an Edelbrock Performer intake manifold and carburetor a few years ago and never hooked some things up. There is a MAP sensor that isn't hooked up and I can't seem to find a coolant sensor or a knock sensor anywhere so I doubt the computer controlled advance is working very well if at all.

Would it be possible to replace the distributor with this one from Summit and just have vacuum advance instead and not have to deal with getting the computer controlled advance and all it's parts working properly?

http://www.summitracing.com/parts/sum-850001r

[GLHS60]

Sounds like your brother replaced the feed back carb with a non feed back so there shouldn't be any problem as the ESC will now serve no purpose.

The 700 R4 is very, very sensitive to TV cable adjustment so make sure the new carb linkage is appropriate.

Thanks
Randy

From the internet:

I talked to some Chevy mechanics at my dealer about this and they told me how to bypass the spark control computer and keep the original distributor, something they claim is done quite often.
First thing to do is unhook the spark control computer lead from the pink wire and hook the pink wire directly to the dist. cap. Make sure you plug it into the cap at the BAT terminal. The second thing is to locate the 4 wire connector that feeds into the ignition module. There's a brown (D), green (C), white (B), and black (A) wire there. The letters in () are on the black clip that the wires come out of. You cut the green (C) and black (A) wires between this clip and where they go into the distributor. Then all you need to do is solder the 2 cut leads from the dist/ignition module together, i.e. the green and black ones, (make sure to tape the exposed wires) and now your HEI distributor will function just as a pre ESC model does. I did this and it has been running fine for well over a year now.

[iTurbo]

Thanks for the info Randy. I ended up buying the Summit HEI distributor (with vacuum advance) because the original electronic distributor was pretty rough. Got it installed today and it's running better than ever. I also bought the correct TV cable adapter for the carb linkage and learned how to properly set the TV cable. Seems to shift normally but I haven't had it on the highway yet.

[Aries_Turbo]

a friend of mine did this with his 85 camaro. edelbrock carb, summit dizzy, trick flow heads, a cam, and edelbrock intake and headers and upgraded exhaust on a 305.

it actually spins the tires now.

Brian

[marc]

One more thing the ecu controls is the converter lock up. I believe B&M has a kit for this. I don't know if you need lock up on a 700 transmission but it may run a higher temperatures with out it.

[GLHS60]

Right on Jeremy, I have a 1981 Parisienne, 400 SBC, T350, so I have some fondness for these units.

Thanks
Randy

[iTurbo]

One more thing the ecu controls is the converter lock up. I believe B&M has a kit for this. I don't know if you need lock up on a 700 transmission but it may run a higher temperatures with out it.

Thanks for the info; I did not know that. I just looked at the B&M kit at Summit and wow $$! So far the computer is still in the car and the wiring is plugged into the 700R4, but there are LOTS of unused connectors now that the Edelbrock carb has replaced the Q-jet and the Summit distributor has replaced the electronic distributor. All of the emissions have been deleted as well. The Check Engine light is lit, and I will probably just remove that bulb from the instrument cluster.

I *think* the ECU is still controlling converter lockup, but how do I tell for sure?

[marc]

There also away to wire it by using a pressure switch to lock the converter when in fourth gear. A lot cheaper to do and simple.

[iTurbo]

Car is running good, except there is a loud popping noise (backfiring?) at WOT. It happens when flooring it at lower speed and it downshifts from 3rd gear to 1st. It sounds more like a backfire than any kind of detonation I've ever heard.

I brought it to an exhaust shop to have the stock exhaust welded back up. They found that the valve on the end of the passenger side exhaust manifold was closed so they wired it open. It ran A LOT better after that, but that's when the popping started at WOT. I've told my brother not to floor it until we get it figured out.

It also has brand new Goodyear tires, and it spins them....a little bit.

[GLHS60]

A Chevy poping back through the carb is very often a sign of a worn exhaust cam lobe or lobes and the popping increases with engine speed, hot or cold, eventually even at idle.

A low speed carb backfire when floored is often the result of a weak accelerator pump, secondary's opening too soon or retarded ignition timing. These symptoms are typically worse with a cold engine and improve with a warm engine. Slowly flooring it will mask the backfire some what and mashing it will bring it on.

If it has good power at WOT / high rpm the fuel pump and filter are probably not at fault.

This shouldn't directly have anything to do with the heat riser getting wired open other than the engine will be slower to warm up.

All this assumes your ignition system is reliable.

Thanks
Randy

[iTurbo]

Thanks again for the info Randy. I know a little about GM small blocks now but they are still pretty new to me.

The ignition system should be good. It's a new Summit HEI distributor, with fairly new Accel spark plug wires. My brother put new spark plugs in it gapped at .035 and it still does it.

I will do some more testing when I see the car again. If it turns out to be a worn cam, I'm going to tell my brother to just get a Goodwrench 350 crate engine or LS swap (I wish but doubtful).

[black86glhs]

Definitely check the accel pump. Some cars backfire and others just fall on their face and suddenly pick back up. Possible you might need to redo the timing.