Hei Swap Woes what to do?

[71Longbed]

hello did the very popular hei swap today but it seems to me the truck feels gutless i can pound the throttle down and its not very responcive however it does run smoth and idles smooth and the vaccum advance is working properly any ideas? also timing is set at 10 degrees

[GMC AMI]

Maybe a tooth off? My lifted 68 the PO had the HEI a tooth off and it had the same gut-less feeling with little power. The Vac. adv nipple should be pointing towards the
upper rear pass side valve cover bolt at between 8-10 degrees if in correct position.

[71Longbed]

a tooth off the gear? also mine is timed at 10 and it is pointing in the spot you mentioned

[VDOG]

Installed my HEI 2 years ago had that same gutless feeling, and it did not run smooth. I said this before, but when I installed my Tach to the HEI, everything change. People that I have talked to said it should not make a difference. My truck now runs smooth, fires up the first time, and has better power. I say that to ask do you have a tach set up?

[VDOG]

My truck ran bad also after the HEI swap. Had it for two years, installed headers, got a lil bit better, but nothing major. Added a Tach and pluged into the HEI Tach side of the distributor, my truck now fires up on the first try and it runs smooth. I also seem to have found power.

[pjmoreland]

Maybe the mechanical advance mechanism isn't working properly. With the vacuum advance disconnected, you should see your timing advance a little over 20 degrees past your initial idle advance setting when you rev your engine up to about 3000 RPM (a total of a little over 30 degrees total advance). Also try removing your distributor cap and make sure you can twist the rotor about 30 degrees clockwise and have it snap back to the original position when you let go.

[68haywagon]

Did you replace the wire coming from the fire wall with a new one?

Mike

[67ChevyRedneck]

Set at 10 degrees? Do you have a high HP engine? I believe 350's should be somewhere between 4 and 8 degrees. I believe stock is set at around 4. You may be off a tooth on the dist. gear. If it idles good at 10 degrees a tooth off, it will run real good at 6 degrees with the correct dist. position.

Edit, are we talking about a v-8 or six banger???

[lilred67]

if you can advance the distributer up to 10 deg btdc you are not a tooth off.how far can you retard the timing?

[flip66]

as pj states make sure you check the time with the vacuum advance disconnected should be about 10 also make sure you have both grounds in the cap hooked up

[Radman]

Theres a lot of misinformation here about the ign swap. (1)... you need a full 12 volts going to the distributor. not the wire that was orignally used for the points.(2.)... you need to recurve your distributor. either buy a msd recurve kit or moroso. You want the curve to come in asap. (3)... your initial timing will be between 12-14 degrees... as much as your stock starter can handle.. if it is hard to roll over back it off a degree or 2. (4).... Your TOTAL timing has to be between 34-36 degrees..At about 2800-3000 rpm. This is with no vacumn advance.

This will give you a performance curve. Your engine will be very responsive. If you don't know how to do the curve take the distributor to a performance shop with a distributor machine or to a speed shop and get them to install the weights and springs. This is assuming that you are using a hei that is in great shape. If it is worn out(bushings) or excesive end play then some times it is cheaper to buy a mallory or msd distributor complete..

Your vacumn advance must be hooked up to a ported fitting on carb. This means no vacumn at that port when the vehicle is running at idle. As engine revs up and there is constant rpm (1500-2000 rpm) there should be vacumn.
Then check the curve. have someone check timing while some one revs the engine check it every 500rpm up to 3500 rpm that will tell you your curve.Check it with NO vacumn advance hooked up.
The old way was inital timing at 4-8 degrees and vacumn at idle. My way will give you better low end torque. If you experience a little pinging just back of inital timing a degree or 2.

[Robert1970C20rstbukt]

The stock setting should be 6 degrees before TDC. I run mine at 8 and I never had a problem.

[smokekiki]

I agree,Radman,Most make the mistake of not having 12volt to start with.The stock wire only has around 9volts.I run 12 degree on my 2wd suburban,my blazer runs real good at 14 degrees.I am running the light springs from Moroso.Also run 045 gaps in the plug with a HEI.With a "hot" coil and good plug wires You can run more gap.

[71Longbed]

its a v-8 i have the setup a lil diffrent than wut is told in the hei swap faq im runing a msd cap with a mallory ciol cap that lets you run an external coil im using a 10 gauge wire from the starter to the + on the coil would getting a cure kit make it run alot better also i noticed then on any little incline it stumbles and shuts off and seems its running hot

[pjmoreland]

The wire that runs from the outer terminal on the starter (originally a yellow wire) only provides voltage to the coil when the engine is being cranked over by the starter motor.

[71Longbed]

then what shall i do? do i need to run a new wire ? and time it as suggested above at around 12 degrees?

[pjmoreland]

Do you have the stock white ignition wire that comes out of the big square connector on the firewall connected to your coil as well? Does the Mallory coil adapter have a place where you need to connect 12 volts for powering the components inside the distributor? Did the Mallory coil adapter come with a wiring diagram?

[71Longbed]

pretty sure its a no on the white wire the mallory coil adapter does not have one but im running the pink wire on the dizzy to the + on the coil and the wire from the starter also on the plus the brown wire is on the - of the coil the wiring i beive was as i described above pink wire to + on coil brown wire on - of coil and black wire not used the then spark wire from the coil comes in to the mallory adapter for the coil

[68 Stepside]

All I did for my HEI swap was run a 10 GA. wire from the IGN UNFUSED spot on the fusebox, to the power spot on the HEI, never had a problem with it.

[pjmoreland]

I just took a look at the schematics in the FAQ section. The white (resistive) ignition wire that comes from the large square connector on the firewall T's into two yellow wires: one goes to the + terminal of the coil and one goes to the outer terminal of the starter motor. The white wire has high resistance and drops the voltage down to the appropriate level for the stock coil. That means your hei distributor is operating on lower voltage than it was designed to run on. Maybe this isn't a problem since you aren't using an HEI coil, but I don't know. Personally I think you'd be better off replacing your stock coil with an HEI coil. Then you could connect the distributor directly to a 12V source (Ignition Unfused terminal) using 10 gauge wire.

[71Longbed]

im running an MSD Blaster 2 Coil Taylor wires MSD cap Mallory extarnal coil adapter but im am going to swith to the new wire from the fuse box do i need to run a fuse once i run that wire or not?

[Radman]

You NEED A FULL 12 VOLTS!!!!! Run the wire from your ign switch directly to your distributor. you have old wiring and it cannot be trusted. Use a multi meter on your ign switch to find out witch terminal has a full 12 volts with the ign on. Run a 10 gauge wire. Hei ign's thrive on voltage. I have even run 16 volts and the plugs were like arc welders going off!!!!! Run good plug wires (msd) good plugs (ac delcos) gapped at .045 or .050.
Try my timing set up, your eng will rock!!!!

[pjmoreland]

I'm concerned that the coil you are using right now cannot handle 12 volts. I'd be hesitant to connect 12 volts until you get an HEI coil.

[cdowns]

maybe you shpuld call the msg people at thier tech line to find the required voltage for this setup/// to me it's confusing?? really just sounds like it's a tooth off in the distrib

[71Longbed]

soon as i get a chanc im gonna change it to 12 volts about your timimg setup radman wont that cause me to have to use 91 octane?