Original 1985 HEI
Thread Starter
Burning Brakes
Joined: May 2013
Posts: 768
Likes: 24
From: Valrico Florida
Original 1985 HEI
Just curious.
I am still running the original HEI coil, rotor, ignition module that came from the factory in 85.
I was considering doing a summit tune up kit http://www.summitracing.com/parts/sum-850030 but don't want to waste the money if it really wouldn't be of any benefit.
Car runs a little rich but I am pretty sure that is due to a possible crappy (Hyper, Jet, whatever) aftermarket chip... I have yet to open up the ECM and look but I am pretty sure as temps are always below 180 and fans kick on at 175... That and the previous owner had cut the air lid, K&N, put in an air foil, and I am pretty sure a 160 thermostat.
Car has 25K original miles if that factors in to it at all.
I am still running the original HEI coil, rotor, ignition module that came from the factory in 85.
I was considering doing a summit tune up kit http://www.summitracing.com/parts/sum-850030 but don't want to waste the money if it really wouldn't be of any benefit.
Car runs a little rich but I am pretty sure that is due to a possible crappy (Hyper, Jet, whatever) aftermarket chip... I have yet to open up the ECM and look but I am pretty sure as temps are always below 180 and fans kick on at 175... That and the previous owner had cut the air lid, K&N, put in an air foil, and I am pretty sure a 160 thermostat.
Car has 25K original miles if that factors in to it at all.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
25 K and someone did all that stuff to that engine ???? Must have been a high school kid. Why would anyone mess with a new engine like that? That's crazy.
if you want to keep it and keep it alive, you need to un-do some of that bolt-on garbage before it damages the engine.
#1 airfoil. Useless as lips on a wood pecker. Big marketing scam. has ZERO value to the way that engine runs. How often do you run it for extended periods of time at WOT???
They have been known to crack, jam the throttle and cause it to stick, not to mention the potential for sending broken bits of metal or plastic (whatever its made of) directly into the engine.
#2. Chip The off the rack chips do 3 things.....alter the curve of timing advance vs rpm, it will richen the fuel by adding duty cycle time, and it tells the fans to come on TOO soon. I can tell ya right now that running rich and too cool results in sludge in the engine, AND worst of all, the cylinders are getting a rinse each stroke with the rich/excess fuel and loosing the lube. That causes the ring wear to accelerate. Running too cool does not let the oil get hot enough to burn away moisture that collects EACH nite after its been run to hot temps. If the oil cannot get to near boiling, it collects water and forms sludge. IF you allow the engine to operate as it was DESIGNED at the normal temp range of 195 to 225...the oil stays cleaner and so does the engine. That's also got a little to do with the rich smell....The ECM thinks its still cold so its adding fuel. Adding WEAR is what its doing...
Now, as far as the HEI is concerned, a stock engine really does not benefit from a bunch of costly aftermarket ignition stuff.. Its MARKETING hype that sucks everybody in to buying stuff that promises Mo' Power ! Mo' Power.
Its just marketing BS designed to separate YOU from YOUR money....that's all.
Anyway, the HEI is a pretty hot ignition and fairly reliable. ALL it needs is one thing........
repair/replace with REAL Delco modules/parts and it will remain good. If you were to come across a small cap HEI for under $100 that would be a good upgrade....A local speed shop had a case of those selling for $60 a couple yrs ago... I missed out on that deal. Complete HEI ready to drop in. All it needed was to be connected...$60.
I messed up missing that deal.
Seriously, you have an opportunity here. A low miles stock motor that's still tight. IIWM, I'd work to keep that good GM feeling as long as I could and keep that thing stock, reliable, and original ! Undo some of that junk....that's all it is and some is even BAD for the engine as previously stated. The 160 stat HAS to go asap. That engine was designed to run hot and that stat is letting it stay cold for TOO long....once its reached op temp the stat is irrelevant as it is only a MIN temp control, but running too cool for too long each morning just accelerates the wear. It needs to get hot and stay that way for many reasons.
These ain;t 1960's muscle cars. They are computer managed engines that use heat to aid in the engines performance AND in its longevity. Heat keeps the oil clean and that keeps the engine clean.
If you want to have REAL power upgrades, get rid of the stock 85 exhaust manifolds, install some LT manifolds or shorty headers, a cat-back exhaust system, keep the K&N, dump the hyper-chunk chip and have a REAL tuner burn you a chip that's appropriate for your region and your list of mods and go from there.
The generic chips are junk and they can actually do more harm than good. The single best place to start and NOT do a bunch of damage is the exhaust. The stock L98 exhaust manifolds are smaller than the ex port on the head, so anything you do there is an upgrade.
Oh yeah, the other reason it runs rich is because the injectors are JUNK. If it has the stock injectors they are sticking and leaking because they have been damaged by the alcohol blended fuels. Those injectors were NOT designed to run this fuel.
Bosch-III inj are not expensive, about $300 from FIC and THAT will give you a real boost once the engine is being fueled properly again. Without knowing anything else, the age alone tells me it needs injectors regardless of the miles. Its the alcohol that kills these cheap injectors.. and time.
What a great find ! A near NEW, original engine. Keep it that way and it will serve you for 200,000 miles or more...easily. Start messing with it and you can cut that in half.
Good luck and enjoy your car !
if you want to keep it and keep it alive, you need to un-do some of that bolt-on garbage before it damages the engine.
#1 airfoil. Useless as lips on a wood pecker. Big marketing scam. has ZERO value to the way that engine runs. How often do you run it for extended periods of time at WOT???
They have been known to crack, jam the throttle and cause it to stick, not to mention the potential for sending broken bits of metal or plastic (whatever its made of) directly into the engine.
#2. Chip The off the rack chips do 3 things.....alter the curve of timing advance vs rpm, it will richen the fuel by adding duty cycle time, and it tells the fans to come on TOO soon. I can tell ya right now that running rich and too cool results in sludge in the engine, AND worst of all, the cylinders are getting a rinse each stroke with the rich/excess fuel and loosing the lube. That causes the ring wear to accelerate. Running too cool does not let the oil get hot enough to burn away moisture that collects EACH nite after its been run to hot temps. If the oil cannot get to near boiling, it collects water and forms sludge. IF you allow the engine to operate as it was DESIGNED at the normal temp range of 195 to 225...the oil stays cleaner and so does the engine. That's also got a little to do with the rich smell....The ECM thinks its still cold so its adding fuel. Adding WEAR is what its doing...
Now, as far as the HEI is concerned, a stock engine really does not benefit from a bunch of costly aftermarket ignition stuff.. Its MARKETING hype that sucks everybody in to buying stuff that promises Mo' Power ! Mo' Power.
Its just marketing BS designed to separate YOU from YOUR money....that's all.
Anyway, the HEI is a pretty hot ignition and fairly reliable. ALL it needs is one thing........
repair/replace with REAL Delco modules/parts and it will remain good. If you were to come across a small cap HEI for under $100 that would be a good upgrade....A local speed shop had a case of those selling for $60 a couple yrs ago... I missed out on that deal. Complete HEI ready to drop in. All it needed was to be connected...$60.
I messed up missing that deal.
Seriously, you have an opportunity here. A low miles stock motor that's still tight. IIWM, I'd work to keep that good GM feeling as long as I could and keep that thing stock, reliable, and original ! Undo some of that junk....that's all it is and some is even BAD for the engine as previously stated. The 160 stat HAS to go asap. That engine was designed to run hot and that stat is letting it stay cold for TOO long....once its reached op temp the stat is irrelevant as it is only a MIN temp control, but running too cool for too long each morning just accelerates the wear. It needs to get hot and stay that way for many reasons.
These ain;t 1960's muscle cars. They are computer managed engines that use heat to aid in the engines performance AND in its longevity. Heat keeps the oil clean and that keeps the engine clean.
If you want to have REAL power upgrades, get rid of the stock 85 exhaust manifolds, install some LT manifolds or shorty headers, a cat-back exhaust system, keep the K&N, dump the hyper-chunk chip and have a REAL tuner burn you a chip that's appropriate for your region and your list of mods and go from there.
The generic chips are junk and they can actually do more harm than good. The single best place to start and NOT do a bunch of damage is the exhaust. The stock L98 exhaust manifolds are smaller than the ex port on the head, so anything you do there is an upgrade.
Oh yeah, the other reason it runs rich is because the injectors are JUNK. If it has the stock injectors they are sticking and leaking because they have been damaged by the alcohol blended fuels. Those injectors were NOT designed to run this fuel.
Bosch-III inj are not expensive, about $300 from FIC and THAT will give you a real boost once the engine is being fueled properly again. Without knowing anything else, the age alone tells me it needs injectors regardless of the miles. Its the alcohol that kills these cheap injectors.. and time.
What a great find ! A near NEW, original engine. Keep it that way and it will serve you for 200,000 miles or more...easily. Start messing with it and you can cut that in half.
Good luck and enjoy your car !
Last edited by leesvet; Jul 2, 2014 at 10:43 PM.
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 275
From: Melbourne, Victoria, Australia
Hi
Leesvet is spot on.
The aftermarket chips are garbage and can easily be overwritten by a scanner and put the stock tune in, i have had a performance chip in my 85 and it made no difference just lower engine temps.
Headers (long tube) are the best bang for buck, when i got my vette 16 or 17 years ago i ran the quarter in standard form 14.4 sec in the 1/4 mile.
Next week with long tube headers fixed the Y join before the cat for better flow , adjustable fuel pressure regulator (set to 45 psi) cut the air filter lid open gave her new plugs leads and tune with more advance and she ran 13.2 in the quarter mile.
The distributor is a good one leave it alone, just replace the cap, leads and put some new plugs in. Check the air filter and best replace the fuel filter as well, you can check your TPS with a multimeter (throttle position sensor) check the top and middle wires and make sure it is at 0.54 volts d/c, you can set it to 0.6vdc for better throttle response.
Check your fuel pressure, it should be 32-38 psi (the 85 uses 24lb injectors so ran a lower fuel pressure. A blocked fuel return to the tank can force more fuel thru the injectors. You may have a previous owner fit an adjustable fuel pressure regulator, i know the higher fuel pressure makes a richer idle.
Do you have any codes (check engine light) the ecm will let you know what is wrong and the stored codes are accessible for diagnostics.
The engine burns fuel cleaner at higher engine temperatures for better emissions, there are minimal benefits with cooler running engines.
Remember the water pump will blast cold water on the front cylinders that will make them run a little rougher, having the standard 195F thermostat open keeps a stable coolant temp flowing through your engine and the cooling fan cycles to keep the temp around 230F.
My engine ran supercharged for six years before upgrading to a 383, she had 170,000 miles on the clock and only because the rings were not sealing well. The 85 has TRW forged pistons standard and is pretty bulletproof, she would have done many more miles naturally aspirated.
Leesvet is spot on.
The aftermarket chips are garbage and can easily be overwritten by a scanner and put the stock tune in, i have had a performance chip in my 85 and it made no difference just lower engine temps.
Headers (long tube) are the best bang for buck, when i got my vette 16 or 17 years ago i ran the quarter in standard form 14.4 sec in the 1/4 mile.
Next week with long tube headers fixed the Y join before the cat for better flow , adjustable fuel pressure regulator (set to 45 psi) cut the air filter lid open gave her new plugs leads and tune with more advance and she ran 13.2 in the quarter mile.
The distributor is a good one leave it alone, just replace the cap, leads and put some new plugs in. Check the air filter and best replace the fuel filter as well, you can check your TPS with a multimeter (throttle position sensor) check the top and middle wires and make sure it is at 0.54 volts d/c, you can set it to 0.6vdc for better throttle response.
Check your fuel pressure, it should be 32-38 psi (the 85 uses 24lb injectors so ran a lower fuel pressure. A blocked fuel return to the tank can force more fuel thru the injectors. You may have a previous owner fit an adjustable fuel pressure regulator, i know the higher fuel pressure makes a richer idle.
Do you have any codes (check engine light) the ecm will let you know what is wrong and the stored codes are accessible for diagnostics.
The engine burns fuel cleaner at higher engine temperatures for better emissions, there are minimal benefits with cooler running engines.
Remember the water pump will blast cold water on the front cylinders that will make them run a little rougher, having the standard 195F thermostat open keeps a stable coolant temp flowing through your engine and the cooling fan cycles to keep the temp around 230F.
My engine ran supercharged for six years before upgrading to a 383, she had 170,000 miles on the clock and only because the rings were not sealing well. The 85 has TRW forged pistons standard and is pretty bulletproof, she would have done many more miles naturally aspirated.
Last edited by gerardvg; Jul 3, 2014 at 05:34 AM.
Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
There are probably only 2 upgrades to the 85 dizzy setup that are worth doing,
getting a decent cap (MSD etc) as these are a wear item,
getting a decent high voltage coil (Mallory / Accel) ,
I wouldnt worry about the rest, I did get one of those red rotors from Summit when i put the cap on, I went for a test drive, revved it out in 2nd, bang !! the clip came off the rotor, $80 tow home, cleaned up the standard one and put it back in and its been going strong ever since.
The Mallory coil works well but get the hacksaw and file out to make it fit !
getting a decent cap (MSD etc) as these are a wear item,
getting a decent high voltage coil (Mallory / Accel) ,
I wouldnt worry about the rest, I did get one of those red rotors from Summit when i put the cap on, I went for a test drive, revved it out in 2nd, bang !! the clip came off the rotor, $80 tow home, cleaned up the standard one and put it back in and its been going strong ever since.
The Mallory coil works well but get the hacksaw and file out to make it fit !
Thread Starter
Burning Brakes
Joined: May 2013
Posts: 768
Likes: 24
From: Valrico Florida
Great info from everyone.
The car runs just fine, I am not trying to fix an issue beyond the fact that it runs rich mainly at low RPMs and I am pretty sure running rich is what took out the catalytic converter so before I put in a new one I need to resolve the rich condition. Looking at BLM's on a laptop it's only rich at low RPM, but still.
Car has no codes, again, no real issues. Shortly after purchase and clearing out the clogged cat I had a compression and leak down test performed and the results showed the engine was in perfect shape. I currently only drive it once every 1-2 weeks just to exercise the engine.
I am only the 2nd owner, however, the first owner had the car since purchase in 85 and then let his son drive it from Iowa to Florida. That son let his son drive it and my guess is the grandson is the one that added the K&N and chip.
I think to start I am going to take a look in the ECM and confirm the aftermarket chip... pretty sure it's aftermarket.
Where can I pick up an original prom for my auto 85? Can I assume they are all the same regardless of rear gear ratio and options as my car is a Z51 with 3.07 rear.
My brakes are also not working great at the moment so I have new pads and a flush/bleed happening next week. I can't lock up the brakes/tires, braking is too progressive and weak. Going with pads and bleed first though I think the booster or master could be a problem as well, going to work through it cheap parts to expensive until it brakes better.
leesvet, thanks for the writeup, everything sounds spot on.
gerardvg, I will see if I can get a peek at the regulator but I think the last time I had the dizzy apart I looked at it and it was a stock one.
Longtubes and full exhaust will be my first real $$$ investment (besides the repaint I already did, Florida sun killed the original paint).
The car runs just fine, I am not trying to fix an issue beyond the fact that it runs rich mainly at low RPMs and I am pretty sure running rich is what took out the catalytic converter so before I put in a new one I need to resolve the rich condition. Looking at BLM's on a laptop it's only rich at low RPM, but still.
Car has no codes, again, no real issues. Shortly after purchase and clearing out the clogged cat I had a compression and leak down test performed and the results showed the engine was in perfect shape. I currently only drive it once every 1-2 weeks just to exercise the engine.
I am only the 2nd owner, however, the first owner had the car since purchase in 85 and then let his son drive it from Iowa to Florida. That son let his son drive it and my guess is the grandson is the one that added the K&N and chip.
I think to start I am going to take a look in the ECM and confirm the aftermarket chip... pretty sure it's aftermarket.
Where can I pick up an original prom for my auto 85? Can I assume they are all the same regardless of rear gear ratio and options as my car is a Z51 with 3.07 rear.
My brakes are also not working great at the moment so I have new pads and a flush/bleed happening next week. I can't lock up the brakes/tires, braking is too progressive and weak. Going with pads and bleed first though I think the booster or master could be a problem as well, going to work through it cheap parts to expensive until it brakes better.
leesvet, thanks for the writeup, everything sounds spot on.
gerardvg, I will see if I can get a peek at the regulator but I think the last time I had the dizzy apart I looked at it and it was a stock one.
Longtubes and full exhaust will be my first real $$$ investment (besides the repaint I already did, Florida sun killed the original paint).
Thread Starter
Burning Brakes
Joined: May 2013
Posts: 768
Likes: 24
From: Valrico Florida
Found this on Ebay...
http://www.ebay.com/itm/85-Corvette-350-TPI-Automatic-PROM-Computer-Chip-HLH-/360413442105?pt=Motors_Car_Truck_Parts_Accessories&hash=item53ea50b039&vxp=mtr
I am guessing this would work.
http://www.ebay.com/itm/85-Corvette-350-TPI-Automatic-PROM-Computer-Chip-HLH-/360413442105?pt=Motors_Car_Truck_Parts_Accessories&hash=item53ea50b039&vxp=mtr
I am guessing this would work.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
The hei set up puts out more juice then your car would ever need There would be no way in he?? I would mess with it. It is time proven to be one of trhe mopst reliable systems out there. With the mileage you stated I would not mess with the cap, rotor or coil age does not affect them. If I was going to do anything I would replace the wires age does get to them. I would also put the correct stat in the car and get the fans to come on at the correct temps.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Oh yeah,
Glad someone mentioned replacement caps...
when shopping for new caps, ONLY use the brass contacts. There are usually 2 options available in caps.......
aluminum post/inside contacts --------------burn away quickly and also have questionable conduction.
Brass post/contacts-------------------------good as it gets. brass last longer, conducts energy with minimal loss to resistance.
the brass will cost a few dollars more BUT it will last 3 times longer.
Same goes for the rotor.
Buy yourself a tube of heat-sink paste as well. The module needs to be laying in a glob of the stuff. If that module gets too hot it acts funny and sometimes fries itself. The paste helps carry the heat away.
I pull my dizzy annually and sterilize the thing. Its not a big deal. Take it apart, wash the pieces, reassemble and drop in.
Oh yeah, the coil contacts need to be cleaned and rust removed so the ground post/bar can make good contact.
Look at the wire pins/blades and make sure none are loose or broken. That's a good mystery misfire or no-run situation...a broken white coil wire in the dizzy cap for the plug-in... Those coil wires are fragile, so look at them and secure them somehow if they are able to move or get pinched. It don't take much to break one off and like I say, it can turn into one of those mystery problems that takes forever to figger out.
A clean dizzy is a happy dizzy !
Glad someone mentioned replacement caps...
when shopping for new caps, ONLY use the brass contacts. There are usually 2 options available in caps.......
aluminum post/inside contacts --------------burn away quickly and also have questionable conduction.
Brass post/contacts-------------------------good as it gets. brass last longer, conducts energy with minimal loss to resistance.
the brass will cost a few dollars more BUT it will last 3 times longer.
Same goes for the rotor.
Buy yourself a tube of heat-sink paste as well. The module needs to be laying in a glob of the stuff. If that module gets too hot it acts funny and sometimes fries itself. The paste helps carry the heat away.
I pull my dizzy annually and sterilize the thing. Its not a big deal. Take it apart, wash the pieces, reassemble and drop in.
Oh yeah, the coil contacts need to be cleaned and rust removed so the ground post/bar can make good contact.
Look at the wire pins/blades and make sure none are loose or broken. That's a good mystery misfire or no-run situation...a broken white coil wire in the dizzy cap for the plug-in... Those coil wires are fragile, so look at them and secure them somehow if they are able to move or get pinched. It don't take much to break one off and like I say, it can turn into one of those mystery problems that takes forever to figger out.
A clean dizzy is a happy dizzy !
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Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Found this on Ebay...
85 Corvette 350 TPI Automatic Prom Computer Chip HLH | eBay
I am guessing this would work.
85 Corvette 350 TPI Automatic Prom Computer Chip HLH | eBay
I am guessing this would work.
It might be worth a try as long as t here is some kind of return policy JUST in CASE...
That's why we hate generic proms...there could be Pi to the 10th saved on that chip and not one bit of data that's applicable for your yr model. I have a half doz stock 87 proms....somewhere around here, but they will not work for your 85. If they did, I'd give ya one so you'd know whats in the ECM at least and what to expect. I have a custom that I run most times and I will swap ECMs with a stock PROM to do some testing since its the benchmark for all the basic engine function.
Pro
Joined: Jul 2012
Posts: 707
Likes: 147
From: St. Petersburg Florida
There are probably only 2 upgrades to the 85 dizzy setup that are worth doing,
getting a decent cap (MSD etc) as these are a wear item,
getting a decent high voltage coil (Mallory / Accel) ,
I wouldnt worry about the rest, I did get one of those red rotors from Summit when i put the cap on, I went for a test drive, revved it out in 2nd, bang !! the clip came off the rotor, $80 tow home, cleaned up the standard one and put it back in and its been going strong ever since.
The Mallory coil works well but get the hacksaw and file out to make it fit !
getting a decent cap (MSD etc) as these are a wear item,
getting a decent high voltage coil (Mallory / Accel) ,
I wouldnt worry about the rest, I did get one of those red rotors from Summit when i put the cap on, I went for a test drive, revved it out in 2nd, bang !! the clip came off the rotor, $80 tow home, cleaned up the standard one and put it back in and its been going strong ever since.
The Mallory coil works well but get the hacksaw and file out to make it fit !
Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
