Click on image for the lowdown. 
====
| | | Forums66 Topics128,077 Posts1,056,019 Members48,433 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | An after thought makes me think of a possible variable.
Throttle position.
If HEI provides better SFC then it has to create a situation that will provide for lower SFC. That would be HEI at 1,401 RPM should need less throttle to achieve the same 1,401 RPM as when running with points.
Same thing at the higher 2,568.5 RPM
Deve, should try to mount a protractor to see how the throttle position changes. | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I can record throttle position, no problem, but why again? 1400 rpm is what is needed no matter what ignition system you are using? Its a required level? | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | | | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | I can record throttle position, no problem, but why again? 1400 rpm is what is needed no matter what ignition system you are using? Its a required level? I said you should test at three speeds. Idle, which I guess is 500 RPM, RPM that your engine would to at 30 MPH and 55 MPH. | | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | If you can tell me the RPM it takes to go 30mph with no load and no transmission or rear end, let me know what that number is. Same for 55. Please let me know cause that makes sense. (although now we are talking about TWELVE tests). I feel idle is just slightly too slow for the test because of the erratic behavior of a points distributor at very low rpm. That's why I suggested bumping it up, but not enough to trigger the mechanical or vac advance. I wish you could be here to see what I am talking about when using a high tech timing light. You asked for RPM equivalent and that's were the numbers I gave you are for. Load does not matter for your truck to drive 30 MPH it will have to do 1,401 RPM's. For the engine will have turn those RPM's to turn your drivetrain to do that speed. Load only comes into place in that when load increases the throttle position has to increase to maintain engine RPM to maintain MPH. Your engine is in a stand and there will be no change in load once you hit target speed. | | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | I can record throttle position, no problem, but why again? 1400 rpm is what is needed no matter what ignition system you are using? Its a required level? Because engines just do not run at idle. But idle provides a base point where there is not timing advance and load on the engine is the lightest. I think that the Idle test will show that there will be no to very little improvement of HEI over points. Because vacuum and mechanical advance do not matter and lowest cylinder compression pressure. Testing at 1,401 RPM puts you at a road speed fast enough to be in 3rd/direct drive. Also more air and fuel enters the cylinder increasing cylinder compression pressure making the ignition system work harder. Testing at 2,568.5 RPM is where you would have to be doing 55 MPH. Again further increase in air and fuel, further increasing compression pressure making the ignition system have to work harder still. This increase in cylinder pressure does not make up for not having a dynamometer tough it will make for a more valid comparison of how HEI and points as ignition system has to work harder. Also the 30 MPH and 55 MPH to me sort of breaks your testing in city verses highway driving. Your testing then would show if HEI shines best at one, two, or all three engine RPM operating ranges. Jeffrey
Last edited by 32vld; 07/18/2015 8:48 PM.
| | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | Stock Ignition System Tests will be as follows: ◦Test One: Stock Ignition System at 650 RPM with spark plugs gapped to .035 ◦Test Two: Stock Ignition System at 1400 RPM with spark plugs gapped to .035 ◦Test Three: Stock Ignition System at 2500 RPM with spark plugs gapped to .035 ◦Test Four: Stock Ignition System at 650 RPM with spark plugs gapped to .040 ◦Test Five: Stock Ignition System at 1400 RPM with spark plugs gapped to .040 ◦Test Six: Stock Ignition System at 2500 RPM with spark plugs gapped to .040 Your stock ignition test is what I would do though I based on my limited knowledge. And it will settle the oldtimer debate you mentioned where some hold the opinion later stovebolts ran better with the larger SP gap as the earlier stovebolts. Though did the oldtimers realize that when GM reduced the SP gap the point gap was reduced as well? High Energy Ignition Tests will be as follows: ◦Test One: High Energy Ignition System at 650 RPM with spark plugs gapped to .045 ◦Test Two: High Energy Ignition System at 1400 RPM with spark plugs gapped to .045 ◦Test Three: High Energy Ignition System at 2500 RPM with spark plugs gapped to .045 ◦Test Four: High Energy Ignition System at 650 RPM with spark plugs gapped to .050 ◦Test Five: High Energy Ignition System at 1400 RPM with spark plugs gapped to .050 ◦Test Six: High Energy Ignition System at 2500 RPM with spark plugs gapped to .050 For your HEI tests I would not do the .045 gap test. One it is to close to the .050 gap that you will not see enough change to make it worth your time. Instead I would use the .035 stock SP gap setting. The reason is when doing a test you want to enter one variable at a time. Thus changing from points to HEI and then testing with stock SP gap the results will be only caused by one thing, the HEI. I know money does not grow on trees. Though HEI has many reasons why it is better then points. Though HEI was designed to run with SP gaps of .060 to .080. When people put HEI upgrades on pre HEI cars they also switched to large gap plugs. I feel those larger gaps is the main reason why they got a big increase in MPG. So I still advocate for larger gap plugs though it is easy to advocate when it is not your own money being left on the parts counter. So I will endorse your tests with the .050 gaps. | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | Ok, I am still confused as to why I need to record the throttle position. It's arbitrary at best and these rochesters aren't exacting enough for very much precision. Explain in detail why throttle position (per test) matters. I wish I had a protractor type control, but the very best I can do is measure how far out of the socket the cable is with a tape measure. Is this still a good idea to you?
You NEVER EVER gap an HEI to .035. Its way too little gap and is totally not recommended. It would be like gapping a stock ignition to .025. It makes no sense whatsoever. If I don't understand it the way you do, explain?
THIS PARTICULAR HEI is totally different than anything else out there because of its 'small body' nature. The stock distributor cap, rotor and wires are used and there is very little room in that cap for the extra high voltage electrical impulses to fire without causing a crossfire condition. I know all this because its been fully explained to me by the guru. He says there is no worries of any of that with this system if it's set up correctly.
So what I CAN do is get a different set of plugs with larger gap characteristics and try them at .060 for starters. I am a little leary of getting too carried away with gap since that fire has to go somewhere, and if it doesn't jump the gap it can go back down the plug wires and do damage to something.
Can you recommend a spark plug that is the right threads and correct for wider gaps?
The codgers I am talking about are adamant that any engine from that era (1941 to 1962) runs better with .016 and .040 respectively. They say forget about the book, just do it and watch the difference it makes. This is a good time to see if they know something I don't. That part is just out of curiosity.
How did you compute the 46.7 rpm for every 1 mph? That would be interesting to put in the article. | | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | Ok, I am still confused as to why I need to record the throttle position. It's arbitrary at best and these rochesters aren't exacting enough for very much precision. Explain in detail why throttle position (per test) matters. I wish I had a protractor type control, but the very best I can do is measure how far out of the socket the cable is with a tape measure. Is this still a good idea to you?
Rochester or Jack Benny does not matter. You want to run each test at the same RPM's.
Changing plugs from .035 to .040 on SI or going to HEI can cause idle speed to change. To be testing for SFC the idle speed must be 650 RPM for each test.
So the idle speed screw may have to be adjusted to have the idle speed back to 650. For that 650 is the constant makes the results valid.
Yes you can measure throttle cable length changes. You can also count the number of turns of the idle speed adjusting screw needed to return the idle back to 650 RPM. Most likely in fractional turns 1/16, 1/8, 1/4, etc.
You can mark the pivoting centerline on the arm that the throttle cable is attached to with a magic marker. Then if you can mount a $.50 plastic protractor in front of that arm. As the throttle plate gets moved you will be able to see how much it moved in degrees and whether it was opened or closed.
Now when you are doing the all of the 30 MPH and 55 MPH (both SI and HEI) tests having the engine running at the correct RPM's will not be enough for say if the SI .040 SP gap is needing less throttle to hit the correct RPM and if HEI still needs still less throttle opening the tachometer will not be able to tell you this.
You do not just want to see that SFC dropped. You want to see a reason such as less throttle was needed and that is why SFC decreased.
You NEVER EVER gap an HEI to .035. Its way too little gap and is totally not recommended. It would be like gapping a stock ignition to .025. It makes no sense whatsoever. If I don't understand it the way you do, explain?
Never gap a HEI to .035 for it is not recommended? You are not setting up a pre HEI engine to run on HEI for use on the road.
You are testing how ignition system changes effect SFC. You want to see how SI compares to HEI. Well when you do a test you only have one variable at a time to get valid results.
So when you test SI with stock SP gap of .035 the first test has to be just running the HEI with the stock plug and gap.
Your test results will be valid because you have followed basic testing logic limiting your test to one variable. Then you have a valid 2nd base result to build further tests on.
Now with SFC between SI and HEI with stock gap you then can add a new variable such as HEI with the .050 SP gap. Then again this test's results will be valid because you had a base with one added variable.
THIS PARTICULAR HEI is totally different than anything else out there because of its 'small body' nature. The stock distributor cap, rotor and wires are used and there is very little room in that cap for the extra high voltage electrical impulses to fire without causing a crossfire condition. I know all this because its been fully explained to me by the guru. He says there is no worries of any of that with this system if it's set up correctly.
I do not know how important that space needed by a larger dist cap for I remember or think I remember that there were some GM HEI systems that had the smaller cap because the coil was not integral (GM's words to say the coil was separate from the dist cap) to the cap. Though your Expert probably knows more then me.
So what I CAN do is get a different set of plugs with larger gap characteristics and try them at .060 for starters. I am a little leary of getting too carried away with gap since that fire has to go somewhere, and if it doesn't jump the gap it can go back down the plug wires and do damage to something.
If I was doing the test I would be not feel the need to go past .060. The secondary voltage always wants to get to ground.
Back in the 80's the large HEI distributor's had a large round rotor that cover most of the HEI workings. When a SP wire would go bad that voltage not being able to jump across the plug would try to find a way to ground out to the distributor housing. As the secondary voltage would repeatedly flash over the rotor it would eventually weaken the plastic and burn a hole through the rotor and the engine would stop running due to loss of spark. New rotor and the car would start right up. However if the mechanic knew why the hole was burned in the rotor he would mostly find a bad plug or wire and sell a tune up with new plugs and wire set so there would be no come backs.
Can you recommend a spark plug that is the right threads and correct for wider gaps?
I can not recommend a specific spark plug. You need to get a AC Delco book or Champion book and find a plug with the correct reach, as close as possible to the same heat range that is designed to have a .060 gap.
Care must be taken to make sure that there will be clearance between whatever plug you put in and the top of the piston so they do not hit each other.
The codgers I am talking about are adamant that any engine from that era (1941 to 1962) runs better with .016 and .040 respectively. They say forget about the book, just do it and watch the difference it makes. This is a good time to see if they know something I don't. That part is just out of curiosity.
Well when the points were set wider on the earlier engines at .022 the time spent closed was less which resulted in less dwell time/coil saturation time then when gap was changed to .016. So it would appear that the later cars had more dwell time so they should of had a stronger spark. So the later cars then would of been able to work better with the .040 SP gap then the earlier cars did.
Though based on what I know those old codgers were right. Though we don't know what else GM changed besides the point gap on those later models and why they went with a smaller point gap.
How did you compute the 46.7 rpm for every 1 mph? That would be interesting to put in the article.
GM Heritage Center. For your year truck they give the stat that for every 46.7 RPM's your engine does will yield 1 MPH. I think the Power Glide was 44.something. So 46.7 x 30 = 1,401 RPM when doing 30 MPH. Deve, this much writing is too hard for my brain. If you like PM me and I'll give you my cell. Jeffrey
Last edited by 32vld; 07/19/2015 1:09 AM.
| | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | On the .035 gap for HEI issue, you are thinking it lessens the number of variables but what is not computing to me is that to set up any HEI test, you are changing coils, removing ballast resistor, installing the HEI module, etc. So I don't understand why .035 HEI gap, which is totally incorrect for its operation is going to tell us anything. I REALLY only want to do two gaps on each style ignition. To add three more tests really seems like alot for something that nobody will ever do. It isn't comparing apples to apples due to the coil change.
On the throttle issue.. Im still confused. Idle is (for example) 650 RPM. It's 650 RPM using the stock ignition and its STILL 650 RPM using HEI. Since I am starting with the stock ignition and it's weaker, I set the throttle for 650 RPM. When I go to the HEI I set the throttle for 650 RPM. What does the throttle movement differences tell us? I will NOT be changing ANY controls on the carb for these tests. That is messing with a control. Before testing I will make sure I can get down to 550 RPM just to make sure I have the ability to control the RPM in the range I want using both ignitions. Does that make sense? Or do you think it's okay to re-optimize the carbs idle circuit for each ignition? The idea was to see how changing just the ignition system would affect fuel consumption. Sincerely, thank you for the help.
| | | | | Joined: Feb 2000 Posts: 5,213 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,213 | I am with you on each test being the same, they have to be for accurate results. My point is, with no load on the engine, the test standards are so low, both should come out even since it doesn't take much to run on a test stand.
You cannot change anything except the distributors and plug gaps. The timing must be exactly the same, along with the fuel settings. I would suggest using gauge blocks placed between the throttle stop and lever. If the engine runs more or less rpm, you know it's the ignition and not the carb setting. By altering the speed after a change, you alter the parameters of the test. Change block thicknesses for different rpm test, not the set screw. Any change to the carb, no matter how small, fouls the tests. A different rpm only means the engine is performing better or worse on the ignition system, so let the rpm stand where ever it ends up using the same gauge block on both systems. With standard block settings for rpm change, the engine is receiving the same amount of throttle opening, so any difference in fuel usage should come from the ignition. Higher rpm means better mileage, since out on the road you should have to let out of the throttle to run the same speed you was before with more throttle.
And for a fuel system, install a T fitting with two shut off valves coming from two fuel tanks. For the tests, use a clear 1/2 gallon tank with bottom drain and a clear fuel line running to the T fitting. Mark a full line on the tank and empty line half way down the clear fuel line. Use the main tank to get the engine up and running and set, then shut off the main and open the test tank. Start the stop watch when fuel starts flowing, stop it when it hits the empty line on the fuel line. It may only take a quart of fuel, depends on how long you want to watch it run.
It will be interesting what you find. Don't forget to factor in break-in time. The more you run the engine, the looser the cylinders get and the better it runs. So will a newly rebuilt engine gain mileage as it finally seats in all the critical parts, or was it the switch in ignition systems? | | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | On the .035 gap for HEI issue, you are thinking it lessens the number of variables but what is not computing to me is that to set up any HEI test, you are changing coils, removing ballast resistor, installing the HEI module, etc. So I don't understand why .035 HEI gap, which is totally incorrect for its operation is going to tell us anything.
Think of it as one system compared to another system not the total parts and you are testing one variable.
We know that the HEI puts out a higher voltage. We do not know how much the larger spark plug gap adds to making the HEI better. Testing with the .035 gap with SI and then HEI allows us to test the one part that is common to both systems and we then can see how much importance SP gap has on how HEI functions.
If you had a Sun Distributor machine and an Analog Oscilloscope you could observe how secondary voltages change, see how RPM's effect timing advance curves and compare systems. I do not have or know how to use a Sun Distributor machine. My dad did and I still have a box filled with distributor weights and advance springs. And memories of my dad saying how with that box he could set up distributors to get maximum performance from an engine.
You do have the ability to test HEI at .035 and .040 to gain insight where HEI provides the effect.
I REALLY only want to do two gaps on each style ignition. To add three more tests really seems like alot for something that nobody will ever do. It isn't comparing apples to apples due to the coil change.
Again this is a test of SI system and HEI system not a test of individual parts.
On the throttle issue.. Im still confused. Idle is (for example) 650 RPM. It's 650 RPM using the stock ignition and its STILL 650 RPM using HEI. Since I am starting with the stock ignition and it's weaker, I set the throttle for 650 RPM. When I go to the HEI I set the throttle for 650 RPM. What does the throttle movement differences tell us?
It is one thing to prove HEI has lower SFC. By measuring the fuel used all you can prove how much fuel was used. You can not prove why SFC changed.
By noting HEI used less fuel by throttle position changes then you are proving that the superior spark of HEI is the reason for improving SFC. Not that just SFC got better.
I will NOT be changing ANY controls on the carb for these tests. That is messing with a control. Before testing I will make sure I can get down to 550 RPM just to make sure I have the ability to control the RPM in the range I want using both ignitions.
Turning the Idle Speed screw to make sure HEI runs at the same RPM's is not messing with any controls. The idle speed adjustment is not the idle mixture adjustment. Knowing how much the Idle Speed screw is turned to achieve the correct RPM provides a mechanical indication of how much the HEI allows the throttle to be closed and get the same RPM's.
Does that make sense? Or do you think it's okay to re-optimize the carbs idle circuit for each ignition? The idea was to see how changing just the ignition system would affect fuel consumption. Sincerely, thank you for the help.
No, put down that screwdriver and slowly back away from the Idle Mixture Screw. Touching the mixture screw is only adding variables to the test. Can HEI allow for leaner Idle Mixture settings, most likely some. But then you would be needing to start another whole level of tests. Best to keep things simple for now. | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | JoeH, check the link. I have the fuel test tank issue resolved. http://devestechnet.com/Home/HEIgnition/#fuelmileagetestingGuys, I have a digital tach in my timing light so I can get the exact rpm I want. I don't have to touch the carb except for the throttle control to get anything I want including idle. Its a stock AD cable style throttle that pulls out of its housing. I can measure how far the throttle control is outside of its housing. Would that work? JoeH, one of the controls is to keep the RPM the very same for both systems because it represents a particular driving speed. This is why I am questioning why I care about where the throttle is. I will record where the throttle is, but I just don't understand why. Call it Proud Kansas Farmer syndrome. There are just certain things we don't need to know! I spent several years working in the AF Weapons Lab at Sandia National Labs in ABQ, testing nuclear material for gamma. Controls, variables, clean rooms, very high tech top secret test equipment, etc. were just a way of life. So maybe I'm just getting old, but how does this have anything to do with the question.. Does HEI improve gas mileage. So, since I am not getting any answers on what spark plugs HEI users are using, I assume they are using stock plugs. You can't really make the stock plugs go over .050. So I will do one run at .050 and one at .035. The problem for me is the .035 test is a comparison test and I was hoping to get two gap tests in. If I have time I can up the tests to 15 and do a .045. Lastly, I disagree this is a moot test because its under no load. It will provide the very same quality of data a loaded engine will. The reason is because all tests are done the same. Your loaded test will be no more accurate since you cant control a persons foot. I see this on powerblock TV all the time. Lab testing will not provide the same result outside. But I am not concerned with outside! Just the comparison between two systems under the very same conditions. My no load test will yield the very same fuel percentage results as your loaded test will providing the exact same conditions are met. Wish I had a dyno so I could prove it. | | | | | Joined: Feb 2000 Posts: 5,213 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,213 | Use the same plugs, just different gaps. The plugs don't care what the distributor is. I keep pointing out a no load test because, it takes very little throttle or ignition to run an engine this way. When loaded, the engine is working and the cylinder pressures are way different, this changes the way plugs fire, and this is where the differences are going to show up if there are any. The throttle is the key to the test, not the rpm. As you open or close the throttle, you add or delete fuel, so did the distributor change the fuel milage, or was the carb adjustment ? You changed to variables at once. Lets say you go from HEI to points. All you do is drop in the distributor and set the timing. The carb is exactly where it was with both units. The rpm is lower so you open the throttle to raise the rpm back to the HEI setting. You just increased the fuel usage, test over, HEI is more fuel efficient! You absolutely cannot change the carb setting from one to the other if you are checking fuel usage. The only way you will convince me of a true fuel advantage is taking two 100 mile test trips, one with each distributor, and each on the same route in similar weather. Read this is if thing pressure in the cylinder doesn't matter. http://www.camaroz28.com/forums/advanced-tech-38/cylinder-pressure-spark-gap-260024/Joe | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | Thats a good article! It helped me to understand the wisdom of the .035 HEI gap test. Check that one off. GTG!
Six of the tests I am doing, the Idle ones, are exactly the same because they are not loaded even in the truck. So the idle numbers will be very accurate. This is a great baseline and will tell us all we need to know if the fuel consumption rates are different. I am interested in seeing how different those tests are.
The cylinder pressures are much less and much more insignificant in our vintage motors, but point taken. But these tests represent the differences in only one aspect of our systems. The Ignition differences. I am only seeking to answer the question.. Is the HEI more fuel efficient and if so, by what percent. Straight line driving from point A to point B will not 'load' the engine that much due to having gears that alleviate much of those stresses. In any case, all points taken, this test will tell us a great deal about the system differences.
I want to simulate Idle, 35 MPH and 55 MPH. I cannot do that without the proper RPM to achieve that. I will record the throttle differences that it took to achieve that goal so everyone is happy?
The question is "How many ounces of gas does it take to do the very same work." If the question was "How much effort does it take to do that work", then we would have to look at throttle issues. You guys want me to measure effort as well as fuel consumption, and that's just fine. I will record throttle positions. I just wish I had an accepted standard to go by. Measuring the amount of gap between the throttle knob and the casing with a tape measure just doesn't turn me on as anything that will be of help to anyone.
Two people driving that same 100 mile trip will have two totally different results due to their driving style. This sort of test needs to be done where those variables are gone.
This hobby is fun and all, but not worth purchasing a Dyno over. We can achieve these repeatable and provable results without breaking the bank.
| | | | | Joined: Feb 2000 Posts: 5,213 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,213 | Deve, a simple dial indicator on the throttle lever will tell you where you are at.
What you need is a great big old box fan, flat leather belt, and drive pulley on the back of the crank. You would have your load, and be cool at the same time.
It would be just like the tractors use at the steam shows, just a good way to work the engine.
Joe | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I am going to set up a protractor arrangement off the throttle control on the carb and carefully write down the degree numbers. It will be more useful that way.
I had a nice talk with Tom Langdon today about this HEI setup. He was very encouraging and said it will work just fine. When I talk to any HEI guru I always ask about the Vac Advance because that makes me a bit nervous, but they all say the same thing, it will work fine.
Tom added that because the system works so cleanly, and the vac advance is so antiquated on these distributors, it IS the weak link because they can develop pin holes in them at no notice, but he recommended gapping to .060 on the plugs. I ordered a few sets from him (at $1 each and $5.95 Postal Priority Shipping how can I lose?) and I will run three gaps for the HEI. .035 for comparison purposes, .045 and .060.
Once fuel testing is complete, I will go to my Waterjet shop and get a bunch of stainless internal adapter plates made and start making up kits for people who are interested.
Before I can do ANY of this I need to get my test engine back in service. I made a serious mistake when rebuilding it in that I ordered a mild performance cam. I do that on every rebuild, but this time I used a different machine shop and he uses a local friend of his. Before this, they always sent it off to Comp Cams for the grind. This time, I got terrible idle, popping in the exhaust, soot everywhere, and 19 degrees of unnecessary advance with 15 inches on the compression gauge. I have no idea what happened but I have a new STOCK cam installed now and I am waiting on gaskets to get it back together. I will let everyone know when testing begins. Thanks!
The idle tests will be performed using the proper idle numbers out of the shop manual, NOT 650 RPM. In the case of our test engine, it's 500 RPM.
| | | | | Joined: Apr 2014 Posts: 924 Shop Shark | | Shop Shark Joined: Apr 2014 Posts: 924 | "On the .035 gap for HEI issue........ Best to keep things simple for now."(-Deve's long quote) Jeffery, when you quote you can also remove 99% of the irrelevant text & make it easier for everybody to scroll through the threads. Brad
Wrench Fetcher, PhD | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | Added the Protractor setup and got out the Barometer and made a cover for the HEI module. The placeholders that you see for pictures near the bottom are for the O2 Sensor. As soon as it comes in, I am ready to test. Thanks for all the suggestions! http://devestechnet.com/Home/HEIgnitionO2 Sensor is a Standard Motor Products SG5 (V14319). The idea of an O2 sensor sounds intriguing, but I do not know how controllable the fuel mixture is. It will be fun to play with! | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | Testing Begins! You can see the results of the first three tests here: http://devestechnet.com/Home/HEIgnition near the bottom. You will notice that the 30MPH test gets a little less than 30 mpg. Of course we know this isn't real life loaded in a truck with a few tons involved, so this is a baseline test to see how DIFFERENT the HEI system will be in the very same circumstances. The O2 Sensor is quite useful and I didn't really expect it to be. You can tweak your fuel mixture screw to get really nice balance. (before any testing, not during!). Of course, that mixture screw also changes proper timing and engine operation, so the best way to leverage the information is by changing the jet in the carb I think. (but it's still new to me) I have to get a steel pipe for my test stand to replace the rubber one.. it just gets too hot and starts smoking, so tomorrow I am going to the muffler shop to get a steel pipe THEN resume testing. Any observations? | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I noticed today that I was testing only 20 ounces of fuel instead of 24. It doesn't change the outcome other than I need to recalculate the results. I tested more today and should have all the results up by tomorrow late. I have to take my time on this and make sure the results are repeatable by anyone who wants to take a stab at it. Not to mention programming the web site for the results is time consuming. Stay tuned! | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I apologize for some of the long winded conversation that appeared to go nowhere, but its how I vet certain procedures and better understand the validity of each persons concern. Thanks for your patience. Testing is complete. After doing 21 tests in several different configurations, we now have THE DEFINITIVE answers we need about HEI vs Stock Ignition Fuel and performance differences. I even made sure to run tests on some popular setups that are not openly recommended. If there is anything else I can add to this document, please do not hesitate to let me know. I like complete and accurate information. Each test was done the exact same with no interference or changes in associated systems. I am confident that YOU can do this at home the same way with the same outcome. http://devestechnet.com/Home/HEIgnitionTesting starts in about the middle of the document. Hope it helps someone! | | | | | Joined: May 2015 Posts: 236 Shop Shark | | Shop Shark Joined: May 2015 Posts: 236 | THANK YOU Deve,
The results are interesting to scan through.
When time comes may have to look at the HEI ideas.
Side note interesting to know you work over at Sandia Labs.
Great group there.
Baking in the nice desert sun, breathing life back into a 48 3800 5 window.
| | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I haven't worked there in years, but they are great people. I loved Albuquerque and have threatened to move back there for years. It was so long ago, it was during the Reagan Star Wars era and we were irradiating transistors and IC's with gamma radiation to see how they would operate in space and other adverse conditions. Thanks for the kind words! | | | | | Joined: Aug 2012 Posts: 1,214 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 1,214 | re. star wars, looks like some of that technology worked out pretty good for the Patriot missile defense....
All kinds of great things have come out of our desire to explore the heavens, and defend ourselves.
Dave | | | | | Joined: Mar 2014 Posts: 4,485 Moderator, Electrical Bay | | Moderator, Electrical Bay Joined: Mar 2014 Posts: 4,485 | Thanks very much, Deve. Very interesting results and glad you took the time and expense to do this study.
Jon
~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
| | | | | Joined: Dec 2008 Posts: 319 Shop Shark | | Shop Shark Joined: Dec 2008 Posts: 319 | Nice work.
Next should be a simple "stealth" TPI using the Model B as a throttle body...
If you can't fix it with a hammer and screwdriver, you need a bigger hammer.1965 Chevy C10 | | |
|
|
