gm hei question

[Wilson_WWSC]

I have a 73 240z with a small block 327 with a points distributor right now. I have more than 1 inch of clearance between the dizzy and the firewall right now. How much extra space will I need for a GM HEI unit? I've read that 11/16's is how much closer the HEI unit will be to the firewall. How about vertical clearance?

Also, the wiring seems very confusing, especially integrating it to the 240z side. Can anyone give me a guide through this process? I know that my tach will probably not work after this, so I will also need to look for new one. And if I take my dash off, I'm going to want to replace all the gauges. What is a good value set of gauges?

Thanks,

Wilson

[deja]

Sorry, I don't know how much clearance you need.

If you have calibrated your tach to work on a 8 cylinder engine already it should be fine with the HEI. It gets connected to the TACH terminal on the HEI.

The +12v from the ignition switch or relay needs to be present in both run and start positions. It will hook to the BAT terminal on the HEI and needs to be a #12 or #10 wire, anything smaller is going to restrict the current the HEI needs. Do not use a ballast resistor or a resistor wire. Remember the coil is now in the HEI cap, not external like you have now.

If I remember correctly there is a third terminal on the HEI and it is not used.

[Pyro]

that is right, your 240 tach will not work with an electronic ignition system.

 

A 5" Autometer will slide right into the stock tach location. No need to pull out the dash.

 

a little cheesy, but a little black rtv will hold the 5" Autometer tach in place.

[rsicard]

I have a 73 240z with a small block 327 with a points distributor right now. I have more than 1 inch of clearance between the dizzy and the firewall right now. How much extra space will I need for a GM HEI unit? I've read that 11/16's is how much closer the HEI unit will be to the firewall. How about vertical clearance?

Also, the wiring seems very confusing, especially integrating it to the 240z side. Can anyone give me a guide through this process? I know that my tach will probably not work after this, so I will also need to look for new one. And if I take my dash off, I'm going to want to replace all the gauges. What is a good value set of gauges?

Thanks,

Wilson

 

The Autometer Tach is somewhat on the expensive side. If the 327 was installed with the JTR engine mount kit, then the hood latch mount needs to be replaced such that the HEI distributor can be installed by pulling the hood latch and mount, installing the HEI and putting back the mount and hood latch. Check with Speedhut on their Tachs as they are 1" smaller in diameter. Then the factory tach can be removed with the dash in place, remove the guts of the factory tach saving the metal backshell. The gut the metal backshell and have a circular adapter ring made to fit the Speedhut tach and inside the metal backshell. Tack weld this adapter ring into the metal backshell at an appropriate depth and feed the wires through the back of the backshell and hook up same. The Speedhut tach illumintes through the dial as this is not always the case with the Autometer Gauges. Just hook up the backlight to +12v all the time the key is in the run position. New VWs have max bright on gauges all the time day or night and it provides VERY GOOD VISIBILITY.

[kamikaZeS30]

He will also need to do something about the turn signal indicators if he's going with a SpeedHut tach.

 

I probably would've used a GM HEI if I had the room, but I pushed my motor so far back a standard magnetic pick-up type barely fits.

 

If I were you, I'd look at a magnetic pick-up distributor (either mechanical or vacuum advance)a la MSD, Accel, or hell, you could probably get away with the $60 Procomp unit, that's what I'm using and it works fine (it's an exact copy of the MSD magnetic pick-up unit). Then run an external coil and a CDI box. Crane, Mallory, MSD, Procomp, whatever, they're all made in the same factory in China, now anyway. The basic 6A/6AL units, at least. $200 tops on eBay. I like magnetic pick-ups because you never have to worry about them, they're less finicky than optical units and worlds better than points.

 

Another option is one of the aftermarket units that's basically a Ford Duraspark inside (I think most companies call them like "ready 2 run" or standalone units). That way the only thing external to the distributor is the coil and you can run the tach off of the coil negative (or is the stock tach loop through, I don't remember)

 

Either way, depending on how your motor is mounted (as in my case) you'll probably have to remove the hood latch temporarily to install.

 

The HEI unit is nice, but it's basically just a way of integrating all three components (trigger, control unit and coil), which to me just makes trouble-shooting and maintenance a pain.

Edited May 13, 2011 by kamikaZeS30

[grumpyvette]

small cap distributors measure approximately 4" in diam.

LARGE cap distributors measure approximately 5.25" in diam.

[kamikaZeS30]

So, using basic geometry:

 

Small cap radius = 2"

 

Large cap radius = 2 5/8"

 

GM HEI distributors range anywhere from 5" to 7"

 

So you're looking at radii from 2 1/2" to 3 1/2"

 

There's a thread (I think it was when bjhines was looking for a dizzy) where a member used an MSD p/n 8570 and that's one of the smallet GM dizzies I know of, it has a 3 1/4" total diameter and total height of 6 1/4". That one, however, is mechanical advance, not vacuum.

[rsicard]

He will also need to do something about the turn signal indicators if he's going with a SpeedHut tach.

 

I probably would've used a GM HEI if I had the room, but I pushed my motor so far back a standard magnetic pick-up type barely fits.

 

If I were you, I'd look at a magnetic pick-up distributor (either mechanical or vacuum advance)a la MSD, Accel, or hell, you could probably get away with the $60 Procomp unit, that's what I'm using and it works fine (it's an exact copy of the MSD magnetic pick-up unit). Then run an external coil and a CDI box. Crane, Mallory, MSD, Procomp, whatever, they're all made in the same factory in China, now anyway. The basic 6A/6AL units, at least. $200 tops on eBay. I like magnetic pick-ups because you never have to worry about them, they're less finicky than optical units and worlds better than points.

 

Another option is one of the aftermarket units that's basically a Ford Duraspark inside (I think most companies call them like "ready 2 run" or standalone units). That way the only thing external to the distributor is the coil and you can run the tach off of the coil negative (or is the stock tach loop through, I don't remember)

 

Either way, depending on how your motor is mounted (as in my case) you'll probably have to remove the hood latch temporarily to install.

 

The HEI unit is nice, but it's basically just a way of integrating all three components (trigger, control unit and coil), which to me just makes trouble-shooting and maintenance a pain.

 

The Speedhut Tach already has turn signal indicators within the tach. Thats more than Autometer does.

[kamikaZeS30]

Their speedometer has turn signals, not their tachometer.

 

Unless they started offering that as an option on their tachometer since I ordered mine back in January.

[Wilson_WWSC]

So, I got the MSD Hei distributor installed, and MAAAAN is it NIIICE. Easy to install. I have enough clearance to the firewall, but I cannot use my JTR hood latch mount. The plunger from the hood smacks into the ignition coil unit on top of the distributor cap.

 

Now, I'm looking for hood pins. Anybody have suggestions on where to mount them exactly? Also, what are some good value hood pins? I'd like them black, but I can paint over any other finish.

[kamikaZeS30]

I would recommend finding ones that lock.

 

Last thing you need is another weak-point as far as vehicle security.

[DavyZ]

So, I got the MSD Hei distributor installed, and MAAAAN is it NIIICE. Easy to install. I have enough clearance to the firewall, but I cannot use my JTR hood latch mount. The plunger from the hood smacks into the ignition coil unit on top of the distributor cap.

 

 

This is interesting...any idea if the dimensions of the MSD unit are the same as a stock Chevy HEI? I would venture to say that they are close. Can you estimate how much space you would need to make it work? I wonder if the difference is the "bump steer spacers" that go between the body and the front crossmember? If you didn't install the spacers JTR mentions, that may be the trick...or just go hood pins like you mentioned.

 

Davy

[Wilson_WWSC]

i believe the msd is the same diameter and height as a stock unit. You can get a HEI unit with a separate ignition coil and that will give you enough clearance for the JTR hood latch. If you don't think you have enough firewall clearance, there are even HEI units on a small base, with a separate coil. These are the same (or very similar) size as a points distributor. Make sure you relay the HEI unit when you convert as you need much bigger wire. I probably need another inch or so for my plunger and safety latch to fit. I ordered some locking carbon fiber hood pins from auto zone for 27 bucks. Probably going to end up painting them black.

 

So, now that my tach doesn't work, I'm gonna need new gauges. How do I get around the turn signals on the speedo? And I've heard it is possible to take out the tach without remove the dash. How?

[kamikaZeS30]

There are wing-nuts on the back of the gauge housings holding the gauges in the dash. What I did when I put my SpeedHut gauges in was unscrew those wingnuts, and then the gauges literally just "pop" out of the front of the dash. It helps if you remove the steering wheel, but I didn't (I have an aftermarket steering wheel, so I think I have a tad more clearance).

 

Be careful, you might want to disconnect as much of the gauge as possible before popping it out, the wire harness doesn't have a whole lot of extra wire.

 

If you're going with the 5" autometers, they fit snugly within the insets of the dash. The 4" SpeedHut gauges will fit inside of the stock metal housings, but you might want to remove some material from the back so that the wiring can go through more easily.

 

SpeedHuts are, in my opinion, the "best" option. They're easy as hell to wire-in, have built-in indicators (brights and turns) and do not clash with the rest of the 1970's interior. You could probably source the Autometer ultra-lites for a little bit cheaper but they don't look as nice IMO, plus they're really noticeable outside the car. You can get the GPS revolution speedo w/turns and the matching 8K tach for less than $500.

[leopard_125]

So, I got the MSD Hei distributor installed, and MAAAAN is it NIIICE. Easy to install. I have enough clearance to the firewall, but I cannot use my JTR hood latch mount. The plunger from the hood smacks into the ignition coil unit on top of the distributor cap.

 

Now, I'm looking for hood pins. Anybody have suggestions on where to mount them exactly? Also, what are some good value hood pins? I'd like them black, but I can paint over any other finish.

 

I ground My plunger down a bit so it would clear the cap.

Is the MSD cap larger than the stock cap? It seems to Me the high performance coils are the same size under the fancy cap, maybe you could swap the two.

[hwvigo]

You could be having The same problem with the tach I had when I switched to the hei before spending all the money on a new tach wire in a 10k ohm resistor in the tach wire that fixed mine and only cost 1$. If u need a how to on the resistor wire in I have all the pics

[Wilson_WWSC]

You could be having The same problem with the tach I had when I switched to the hei before spending all the money on a new tach wire in a 10k ohm resistor in the tach wire that fixed mine and only cost 1$. If u need a how to on the resistor wire in I have all the pics

 

 

Pics would be great. Definitely worth a try. Thanks

[hwvigo]

ok here you go

 

what u will need

 

cut the wire in to 5 inch lenghts

 

strip the wire back 1 inch

 

fray the exposed wire in to 2 sections

 

 

now incert the 10k resistor in the middle of the split wire

 

 

now twist the wire around the end of the resitor

 

now repeat on the outher side

 

now just heat shrink

now just take the unit and install it in the wire from the distrubitor to the tach

Edited May 23, 2011 by hwvigo

[LLave]

I would solder that, or you may end up with a lot more than 10k or resistance.

[hwvigo]

That would be good idea I do solder most things but for this how to I wanted to make this as easy as possible