berlinettakid

I know how to bolt it in, hook it up, and set the timing. But what about the wiring stuff? My main worry is that the injectors won't fire. respond quick or I'll try it anyway

dimented24x7

iTrader: (2)

It can and has been done. I dont know the specifics, though. Youd need to get some sort of reference pulses to the ecm as well as, i think, some way of telling the computer that the engine is cranking so it gets fuel when your trying to start the motor.

berlinettakid

So does anybody in here know how to hook it up?

JokerRS

A fellow Iowan!
I gotta ask though, why do you want to do this swap?

1981TTA

The ECM is going to need to see a 4 pulse-per-crank-revolution signal. This is normally supplied by the computer controlled HEI module. One way out of this that I can immediately see would be a crankshaft mounted trigger wheel. But, most of those are pretty expensive.

I wonder if it would be possible to use a computer controlled HEI module in a non computer controlled HEI distributor. If you wired the module to stay in "bypass" mode, it would always spark when the pickup coil lines up (i.e. base mechanical timing). The non CC HEI uses the vacuum and mechanical mechanisms to physically move the rotor. So, this would seem like a good approach (on paper/electrons!). This would give you the ability to keep the existing engine speed interface to the ECM.

Here are some potential roadblocks :
1. Unfortunately, I don't know if the dwell calculations would be good at all speeds. The CC HEI is usually only in bypass mode at engine startup. After that, the ECM calculates timing and dwell. I don't know if the CC module has the brains that the non-CC module has regarding dwell calculation.......? If the brains aren't there, you'll likely roast the module and/or coil.

2. If this worked, you may have problems with your engine speed calculations giving you less than stable results. Because the relationship of the pickup coil will change with vacuum/RPM, the timing of pulses into the ECM will change, too. With no "real" engine speed change, the ECM will think the RPM is increasing as the timing advances because the pulses are coming "faster". The opposite would be true for retard. This might cause problems in other algorithms within the ECM that use RPM. But, this would only be the case while the timing is "changing". If the timing stays the same, the engine speed will settle to its true value.

The above being said, I wonder why you want to put in a "mechanical" HEI. With the CC HEI, you have the ability to do lots of adjustment to fit what the engine wants. Lots easier than swapping vacuum canisters and springs/weights.

berlinettakid

12 bucks and 15 minutes is eaiser than the 300 bucks it costs to start burning your own chips. And the reason for the swap is cause somethings screwy with the timing. I set it (yes i did it right) and it runs good very little throttle every where, and at full throttle above 2500 RPM but when you're at half throttle it feels like the ECM isn't advancing the timing anywhere near enough.

The engine has a slight rod knock, so It may be pulling timing to compensate for detonation. HMMM. Could I unhook the knock sensor to test this?

dimented24x7

iTrader: (2)

That will do it. There really wont be enough advance. In some cases depending on how its all set up there might be little or no commanded advance. Itll make the car run like a real pig. Combistion deposits causing detonation will really make a car run lousy as well. The knock routines are very agressive with a stock ecm.

berlinettakid

Could I unhook the knock sensor?

Dewey316

you would have to put a resitor in its place, to keep the ECU thinking it is attached. you will have no knock protection though. have you considered the possibilty that you do have legitiment knock besides just the rod knock, and that the sensor is actualy doing its job?

1981TTA

Or, just unscrew the knock sensor itself. You could then leave the wire "connected" to the unattached knock sensor. But, you'll want to tie the sensor *securely* to the most vibration resistant spot you can find. Maybe even wrap it loosely up in an old shirt or something. The sensor detects knock via vibration. If the unattached sensor vibrates via bouncing or rattling against something, it will do the same thing to your timing.

As Dewey mentions, I'd make sure that there isn't any "real" knock that's causing your problem. It does make the sensor's job harder as more noises are added during engine operation. And, a rod knock is certainly a good candidate for appearing like spark knock to the sensor.

Of course, if your attitude due to the rod knock is "spin it 'til it dies", I'd say go for it! If you have another engine planned for the car anyway, you probably can enjoy watching the death race to see if rod knock or spark knock ultimately destroys the motor..... I know I've had fun in both vehicles I've owned and friends vehicles in similar situations where we tried to get an engine to fail. Just make sure you're close to someone's house when you try just in case you succeed!

berlinettakid

it's deffinetly a rod knock, we are planning on a new engine and while we don't really care if we blow it up we aren't exactly trying to. We've got a 307 to put in it, and we're starting a 327 buildup that is gonna HAUL!

I unplugged the knock sensor and it still did the same thing. didn't unscrew the sensor though and didn't put any resistor in it.

I'm probably going to make it carbed and put a non cc HEI in it, but if i can get the bugs worked out I'm going to keep it injected.

Grumpy

Yes, doing things the correct way, can cost money. And if your building a hot 327 your going to have to learn how to burn chips to get it right anyway.

Just unplugging the sensor, sets a code. The proper way to bypass the K/S is in the code, ie burning a chip.

Yes, hook a scanner up, and then actually see what's going on. No need to unplug anything.

Does your Throttle Body have a ported vac source for the Dissy?, and is it actually for a dissy?. Just plugging and unplugging things to try and get something to run, really isn't a good habit to get into.

berlinettakid

i already scanned it and the only code it is throwing is the vss, And since it has a th350 and the speedo isn't hooked up that's why.

If we kept the TBI i would burn a chip for it, but first we have to get the bugs worked out. My little brother sold his daily driver to buy it, so we need to get it running soon, and if we can't work the bugs out we'll have to put on a carb and non-cc HEI.

If we can work the bugs out of it Then yes, i will be burning chips, which I would LOVE to do, but right now I don't have the money or time to do that, and I don't have any FI third gens, so I can't justify spending the money yet. (I say yet because I'm going to use a TPI system witha stealthram on my 79 berlinetta, and that is going to be a BLAST.

persa

I would also like to know how to use a non-stock distributor with the TBI system.
In my case it's because I´m converting an old Cadillac 390 engine from carb to TBI.
It would be so much easier if I could use a Pertronix Ignitor or something, so I can use my Caddy distributor, instead of the CC HEI.

I know it's a thirdgen board, but I hope someone can help me out.

stew'86MCSS396

AZFT9503 7.4L THM400 No VSS or TCC No ESC

Of course this would be for a '747 'puter...where did I see that...DIY_EFI I think...
stew'86MCSS396

Kenny g

Yes I have done it before and works fine hotter spark you have more control on the timing you just have to wire in another module of the original distributor mounted to the firewall and hook up your existing pick up in the HEI to the module and it will fire the module and the module in the distributor for the HEI that's how you get your signal for the injectors to work will work fine

Schurkey

[EDIT]Awww, ****! Got pulled into a necrothread fifteen years old![/EDIT]

Yup. This is crazy. There's no benefit to sabotaging the computer's engine-speed sensor system, then trying to patch it up again so the injectors fire.

There's a difference between reading the data stream, and reading codes. "Code readers" are not scan tools. They're cheap consumer-grade junk.

Codes can be useful. SOMETIMES they're as useful as the data stream.

Am I understanding this correctly? The computer/sensor system has already been tampered with? The computer is looking for a vehicle speed sensor, and there isn't one?

morgsie

iTrader: (1)

Not only did you bring up a 15 YEAR thread, but your information is incorrect. A big cap HEI does not have a hotter spark vs small cap ot vis versa. Unlike a mechanical distributor where you have to "settle" on spark advance with EFI you can set any timing at any load and rpm.

Kenny g

Take the module out of a throttle body injection distributor mounted to the firewall set your HEI distributor in Run 2 wires off the pickup as normally would run to the module the running from the module inside the HEI distributor to the module you will mount on the firewall out of the throttle body injection distributor it will work I have done this

gcdonner

Could you give a diagram to illustrate your description? Thanks

Schurkey

https://www.thirdgen.org/forums/tbi/...p-hei-tbi.html

Post #30 is about as good as you're likely to get. Ignore the earlier diagrams.