BRAAP

My first question is why do you want to alter the AFM for tuning purposes? Our tinkering over the years and testing on the Dyno revealed many things, and one is that the AFM is not really the place to perform electrical alterations unless you are trying to tune out/in something within the range it functions, which to date, we still have not found a situation for. With that said, here is what we have found. 1) Water Temp sensor; In altering the resistance at the water temp sender offers a linear AFR change across the entire RPM range under all conditions. As stated above, the only way to get “leaner” with the OE EFI is to use the resistor/potentiometer in place of the water temp sensor itself, but then you loose the coolant temperature compensation. I’m sure a savvy electrical engineer could build an electronic doodad that reads the water temp sender and then alters that return signal to the ECU both above AND below that of the water temp sender resistance. 2) TPS; The OE TPS is like a single pole double throw switch. Idle is one circuit closed, WOT closes the other circuit, (actually kicks in at approx ¾ throttle opening), everything in between idle and ¾ throttle is “open circuit”. I tried a FIAT TPS years ago that closed the WOT circuit only at WOT, so at above 3/4 throttle position, the engine surged and had flat spots till the WOT switch was closed, at WOT. Discovering that demanded playing with a manual switch in the cockpit hooked up the TPS to see how the ECU uses that TPS switch, i.e. the throttle no longer actuated the TPS I did with a switch. a) The idle circuit is a richer mixture and will only allow the engine to rev up to 3200 RPM, then as the RPMS drop, the EFI kicks back on at 2800 RPM. This is a VERY violent rev limiter! Many of you have found this after washing your engine bay and the TPS connector gets wet. This is incorporated for high RPM when you drop the throttle to closed, under deceleration conditions, the ECU shuts off fuel delivery to the engine completely for emissions. If you have a very free flowing exhaust, and depending on how rich your AFR’s are to begin with, will notice a slight to moderate ”POP” in the exhaust as the fuel is turned back on as the RPMS drop down through 2800 RPM, but only at closed throttle during decel. b) The WOT switch alters how much influence the AFM has on the fuel map. Open circuit, mimicking part throttle cruise, the AFM has tremendous influence on the injector pulse widths. At WOT, it has substantially less influence and the pulse width is mostly based on the ECU dedicated map, though the AFM does still have an influence, remember, it is substantially less of an influence at WOT than it does at part throttle. Also, the when the WOT switch is closed, the base fuel map is fattened as well. 3) Thermo time switch AND cold start injector; The Thermo time switch function is to allow the cold start injector to dump more fuel into the intake via the cold start injector during start up only and only for a couple seconds, when it really really cold outside and the engine is really really cold. Without the cold start injector and/or Thermo time switch, if the EFI is in good tune, the out side temp is REALLY cold, (around the freezing point) and the engine is also cold, the engine may take a few more revolutions to fire off during cranking. That is the only side affect of eliminating the cold start injector and Thermo time switch. 4) Inlet Air Temp sensor; The IAT is in the front of the AFM, looks like little white pencil eraser of sorts. It reacts to VERY quickly to temp change, (tested a few of them from freezer to heat gun using an OHM meter). The ECU uses that to adjust for air density based on Temperature. The IAT functions just the same as the water temp sensor and by altering its resistance has the same effect on AFR as the water temp sensor, just on a much finer scale, not as drastic as the water temp sensors affect. 5) AFM; This complex electro-mechanical device is a well engineered, durable, intricate piece of antiquated equipment, and performs its intended job VERY well! It functions is tell the ECU how much “volume” of air the engine is ingesting, hence the name Air Flow Meter, (MAF stands for Mass Air Flow sensor and MAF’s measure the MASS of the air the engine is ingesting, which is more accurate as the engine actually needs fuel added based on the mass of the air, not the volume). At WOT, the AFM actually tops out, full open between 4000-4500 RPM! After that, all fuel delivered to the engine is based on RPM, water temp, and air temp. The AFM has NO affect on the injector pulse width above 4500 RPM at WOT, (which is the main reason why I question wanting to “tune” the resistances within the AFM) The air flow flap opens as the “volume” of air pushes it open against the return spring and then passes around it on its way into the combustion chamber. Attached to that flap at 90 degrees to it, (see pic below), is the damper flap which is cushioned by the air space above it. Engine acceleration enrichment is delivered by the “over swing” of the flap in the AFM. The flap is also counterweighted. Altering the damper flap by drilling a small hole in the upper flap and/or removing mass from the counter weight, will allow the flap to over swing further, thereby fattening the acceleration enrichment. Loosening the AFM return spring also has the same effect, but also richens the mixture within the operating range of the AFM. Of all the L-series OE EFI tuning I have ever done, I have not found a need to alter that acceleration enrichment of the OE EFI above and beyond what adjusting the return spring for good cruise AFR has delivered. As an aside. Back in the mid ‘90’s, I had the wild idea of eliminating the AFM from the air stream altogether. I sacrificed an AFM and cut up the body, connected a bicycle brake cable to the damper flap, bolted this AFM to my intake manifold plenum and connected the other end of the cable to my throttle linkage. The idea was to use the AFM electrically, but actuate it with the throttle, not the air stream! Also had the TPS switch in the cockpit so I could manually trip the WOT circuit during this testing. WOW what a learning exercise that was! To drive the car without the engine stalling completely or at least drive it somewhat smoothly, the throttle pedal had to follow the RPM. With the TPS in cruise condition, (open circuit), that range of pedal position to RPM was a very narrow range. With the WOT circuit closed, I had much more leeway in the throttle position to RPM range before the engine would let me know it didn’t like it, hence the WOT circuit not relying on the AFM so much for calculating fuel delivery. Also, just to drive the car I had to accelerate the same at the same rate all the time and finding that constant cruise condition to maintain a given speed that the engine would like was, oh so difficult. I even added holes along the length of the flap to alter the rate at which it was being actuated. In short, I found the AFM works as originally designed and works INCREDIBLY well, and due to the narrow range that it functions, which is only below 4500 RPM and mostly under cruise conditions, the only tuning or alterations I perform to the AFM is to adjust the spring tension. Outside of that, tuning the AFR’s is done with water temp sensor. Oh, one other point. My particular L-28, with the water temp resistance first set for max WOT performance, then the AFM adjusted for best cruise conditions, while at idle, the CO adjuster would allow the flap to close enough to allow a lean enough mixture at idle. So I used Dremel tool and ground a small trough in the floor of the AFM just under where the flap rested at idle to allow that air to enter the engine and not be registered by the AFM, (just as the CO adjusting screw does) there by allowing the AFM flap to close a little more leaning out the mixture, but only at idle. One other down side to that mod is if the fuel switch is in the AFM, (early EFI), sometimes the AFM would close just enough at idle to turn off the fuel pump. Fuel pump triggering had to be hard wired to the ignition.

Dan, Sorry to hear this. Truly a frustrating situation for sure. The inconvenience of loosing transportation, the feelings of being violated, etc. Sucks!!! Let us know if there is anything we can do from up here. Take care, Paul

The debate has been covered for pages on this forum. The link below covers that topic with tests, arguments, pics of busted blocks with core plugs still intact, testimonies, links, etc, of how and why Freeze plugs are NOT freeze plugs, but are indeed Core plugs, Soft Plugs, or Expansion plugs. If you are bored and want some entertainment and to learn some history on the core plug and how the misnomer freeze plug came to be give it a read. Click ME for one of the infamous Freeze Plug threads. So Garret is a freeze plug dealer? No, I didn't say a “Freeze dried drug dealer”, I said a “Freeze plug dealer”! Even has a little baggy stash of freeze plugs for his own consumption? PLUGGY!!!

This one was around for a while…. A recent thread prompted this!!!

Don't take this personal, the term "freeze plug" is totally an inaccurate term for the CORE PLUG, and for me any how, is just one of those never ending saga's. This is more for the rest of the membership that have followed my rants on that subject over the years here, as I'm sure they'll get a kick out of it. I give?!?! UNCLE!!! Freeze plugs it is then.

Yes, a P-90 will work, though your compression ratio would be VERY low. I found your head. ’75-’76 head, (your car is ’75 so this is the same exact head, N-42 casting) Rebuilt ready to bolt on and at an INCREDIBLE price! Buy it if you can… http://forums.hybridz.org/showthread.php?t=130600

Only the Q-45 came with 3.54 ratio short R-200 and larger beefier output shafts, (same as the Z-32TT R-230 output shafts). The N/A Z-32 came with 4.09 ratio short R-200 and weaker output shafts.

Alan, Thank you for being so tactful in your replies. Well done. By the way, do you mind if I use your slight digression quote? Racers poetry ... Love IT!!!

The only thing out of the ordinary that stands out in your pictures is the rust pitting on the #6 cylinder wall and of course the broken head bolt. The oily carbon in the chambers, etc is typical of any high mileage old engine with God only knows what sort of upkeep during its life. To remove that busted bolt that is protruding out of the block, heat up the block surrounding that bolt with a torch, then smack the top of the bolt like you are trying hammer it back into the block, smack it good and HARD! (Do NOT hit the block deck surface as that will dent/mar that surface.) Next immediately grab that bolt with a pair vice grips and rotate the bolt out of the block while everything is still hot. Or just take the block down to the local automotive machine shop and they will remove it for you. As for the one busted below the deck surface, you are better off taking the block to a machine shop and have them remove that bolt as they will take care in not destroying the threads and if the threads are damaged, they have the means to repair/replace that threaded hole to as good as new. All the other threaded holes in that particular block should also be dressed as well. If you are not into rebuilding that engine, you could try to source a used running engine in known good condition to drop in the car. Good luck, Paul

Yes, the L-series is an interference engine. So when this valve “pops” back up, the cam lobe for that valve, (#2 exhaust), is pointing up or at some other point than being in contact with the rocker? Possibly the piston is pushing up enough on the valve as it comes to TDC that the spring can then take over and seat the valve? With the valve all the way up, is the top of it still lower than the rest of the other valves that are all the way up?

Your gasket is on the way, 2nd day. Should be there on Wednesday. Check your PM.

Broken spring maybe?

Stony, Sure did. Sorry I didn’t reply yet. The gasket will ship out Monday afternoon. I’ll PM you the shipping cost after it ships. If you have any special requests regarding shipping such as 2nd day etc, just let me know. Otherwise I plan to ship it just plain ole UPS ground Take care, Paul

What exactly are you describing? We can’t make out any thing you just said. Your terminology does not make any sense of what could be taking place. When talking about engine internal parts, or any form of communication at all, we need to be speaking the same language for both parties to fully understand each other. Internal engine parts all have names and we all know those parts by those names. If you are calling those parts by names other than what we know them as or making up names for them because you don’t know what to call them, we have absolutely no idea what you are saying or trying to convey. Here is a list of the parts of the valve train for each valve, starting at the valve and working our way up to the to the rocker pivot. The Valve itself. Valve spring. The valve spring retainer is the disc on top of the valve spring. The keepers are inside the retainer and hold the retainer on the valve spring. There is lash pad that sits on top of the valve stem, in side the middle hole of the retainer, under the rocker tip. Then there is the Rocker arm itself, the cam lobe “wipes” across the rocker wipe pad on the rocker, then the rocker pivot which is height adjustable and is used to adjust valve lash at the cam to rocker interface. Now, using those parts description as listed above, could you please rewrite what is taking place so that we can better understand what is you are trying to convey?

John, Are your intake runners ported or as cast? For some reason I always thought your runners were extensively ported which helped boost your HP numbers a bit compared to your torque. At any rate, Phil, whatever John says works, you can take to the bank. Not only does he have the experience, but also the background and a mentor that is not afraid of the edges of any envelope, no mater how sharp those edges are!

At first this thread seemed destined as a “377 is the only option” thread. I applaud your patience in keeping it going and not just giving up. This is a GREAT technical subject. Rod to stroke ratio will have an impact on combustion efficiency and sensitivity as you stated. Now does the 377’s greater rod to stroke ratio offset the 406 displacement? That is a good question and I honestly don’t know for sure, but I am willing to bet it will get you part way there at least. I do feel strongly that the shape and design of the combustion chamber will have even greater impact than the rod to stroke ratio itself. Also, the piston dome/dish matching the chamber shape and squish will help in taking advantage of the attributes a longer rod to stroke ratio offers. The 406 can make 375 lbs of torque at that RPM at a lower BMEP than the 377, due to it displacement advantage, which we all have agreed to and have beaten to death. So basically, as I understand this, the question is, does the rod to stroke advantage of the 377 working at a higher BMEP, to produce 375 lb feet of torque at 4000 RPM going to offset the shorter rod to stroke ratio 406 working at a lower BMEP, in regards to TBO? Hmm… I’m inclined to think we are splitting hairs and personally would lean towards the 406 from a practicality stand point, but from a “wanting something a little less common”, might lean towards the 377. So what sort of “white water” jet boat are you building? A race boat?

Phil, Swapping just “one part” and retuning should net an honest 50-75 more HP on the same dyno, and depending on that part, could be as much as 100-125 more HP, at the same boost levels, no other changes! INTAKE MANIFOLD!!! A “other than OE L-28 EFI” intake manifold and your HP will DRASTICALLY increase, even with your current cam and no head work!!!!! Those small diameter intake runners are fine for torque and don’t restrict torque production, but are choking the living daylights out of your potential HP! Yours and Chris Torque and HP numbers at those boost levels is the most PERFECT example of this! OE intake manifold runner cross-sectional area is only 53% the area of the stock intake valve itself! Head work will help just a little, but your HP restriction right now IS the intake manifold itself. Even if you go to the extreme of cutting up an OE intake and opening up the runners, that is where your HP will come from. If you design a new intake, if you keep similarly length runners, just larger diameter, your torque shouldn’t suffer to much if at all, but make tons more HP! Of course this will require extensive retuning, but I have lots of faith in your tuning abilities. After the intake swap, head work would be the icing on the cake, and I just happen to know a custom cylinder head massager…

Phil, you are running an OE EFI intake manifold right? Can you also give a rundown on the power plant Chris is running, including intake manifold, etc?

Jason, The low speed cooling issue most typically is the result of inadequate air flow though the radiator therefore not removing enough heat from the coolant. Higher vehicle speeds, more air flow = more heat transfer from the coolant through the radiator fins to the atmosphere. As for how and why removing the rad cap allows the engine to cool at idle vs when the cap is installed, the only thing I can think of is the water-pump is out-pacing what the thermostat can flow, subsequently collapsing the upper hose to the point it is severely restricting coolant flow. By removing the rad cap, the pressure inside the upper house then becomes equal to atmospheric, un-collapsing the upper hose allowing coolant to flow through it. (See below for more on the upper hose collapse issue). Suggestions for low vehicle speed cooling; 1) Improve air flow to and through the radiator as best you can. Study the Aero section of this forum as there is some REALLY good info on just this topic. 2) Be absolutely sure your thermostat is indeed opening all the way, (boil it in pan of water and visually note the amount of opening), and that there is enough room in the thermostat housing beneath the thermostat for it to open down all the way, (seen that in L-series with high flow thermostats). As for your hose collapse. My initial gut instinct is that it sounds like the high flow thermostat is not allowing enough flow to keep up with the pump. That would put everything between the low pressure side of the pump and the top of the thermostat, including the radiator and both hoses, at lower than atmospheric pressure causing the hose/s to collapse. Your lower radiator hose should also be experiencing similar pressures. Typically, the lower radiator hose has a coil of spring wire inside of it to help prevent it from collapsing and it also is generally a stiffer/thicker material which also helps resist collapsing. Bends in the hose also stiffen the hose. Suggestions for upper hose collapse; 1) Verify with a pressure gauge the pressure In the upper hose/radiator/lower hose. 2) Be absolutely sure your thermostat is indeed opening all the way, (boil it in pan of water and visually note the amount of opening), and that there is enough room in the thermostat housing beneath the thermostat for it to open down all the way, (seen that in L-series with high flow thermostats). 3) Check to see if the upper radiator hose is just too soft to begin with. 4) Possibly install and upper hose with the coiled spring in it or install a coil in yourself to keep it from collapsing, or a rigid upper pipe. At this point, that is all I can think of. If anything else comes up that might be of help in diagnosing this, or you perform any testing, be sure to update.

VERY cool. Thank you for sharing. I didn't see any reference to the year of your car, but from that video or your stunning clean and gorgeous 280, it looks to be a '76? Thank you again for sharing.

That sounds like you have the R-180 differential. The link shows the R-200 which is similar, just larger.

Then change the pump! I don't understand. If you are shooting for a certain HP at a certain “impellor” RPM, which this impellor you are talking about just so happens to fit your 377 mold, why lock yourself into only one impellor? If you are locked into that one impellor and have sold yourself on the 377 filling the role of “best power plant for that impellor” for the all the reasons you stated, why entertain other engine options? I am pretty sure a different combination of impellor and nozzle is available, or at least attainable, that would allow you the same thrust and speed characteristics you desire, though at a lower engine RPM, allowing you to build the larger engine. If the engine longevity is, or at least one of, your main criteria in the design of this project, Impellor pitch and diameter coupled with the nozzle sizing acts similarly to gearing in car. In other words, focus on your main criteria of building the longer TBO power plant and then figuratively speaking, “gear” the impellor to deliver thrust and speed commensurate with the engine, or use the impellor you are talking about as your main criteria and build the power plant around that, which you feel the 377 fits perfectly, then build the 377 and enjoy.

Stony, Don’t let the Schmuck boys spin you out. I happen to have a new intake/exhaust gasket that fits the carbureted intake manifolds, square exhaust port, i.e. 240/260. You can have it for $5 plus whatever actual shipping comes to from Sandy Oregon. If you are interested, PM me your shipping address and I’ll get a shipping quote. We accept all major credit cards, PayPal, money order, first born, and only right arms and legs at this time. We have too many lefts in stock right now. Let me know if you are interested. Take care, Paul