Slant Six Forum :: Progress update/accurate MPG?/best dizzy rebuild route?

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Progress update/accurate MPG?/best dizzy rebuild route? https://www.slantsix.org/forum/viewtopic.php?t=45145	Page 1 of 1

Author:	MattyBrown [ Sun May 29, 2011 8:27 am ]
Post subject:	Progress update/accurate MPG?/best dizzy rebuild route?
Hi everyone! First, I'd like to thank you all for all of the help that was offered to me a couple weeks back during my engine swap. I can't imagine how I would have done it without help from everyone on this board. You people are my saviors! Second, let me just update you all and let you know my car is running great! The trick ended up being replacing the coil with a better one. Adjusted the timing, adjusted the carb and HOLY CRAP this thing is purring like a kitten! The guy who I found on Craigslist, who was supposed to help me tune my car, ended up blowing me off. But it's okay, I don't really think I need the help at this point. My car is running REALLY GOOD. Also, there was some talk of my transmission not working properly. Turns out, I hadn't adequately replaced all the fluid after the swap (warmed up, in neutral). It is now shifting normally, so I think I'm in the clear (for now). Third, quick question: I understand the math used to calculate MPG, but what I'm wondering is, how fast are you guys going on the highway when you post your highway MPG's? Are you cruising around the speed limit (assuming let's say 65-70 MPH) or are you cruising at 50 MPH (which I'm assuming is the speed where it is most efficient)? I want to know how my car compares to the rest of yours. Fourth, I am interested in diving into my distributor and doing some maintenance. I doubt this distributor has been touched in the 38 years it's been on the road. What is the best route for me to take? I don't know anything about recurving a distributor but I've been reading old threads. Can anyone recommend a particular rebuild/spring kit? Not sure if I should use stock springs or not. Any recommendations? My car is: 1973, electronic ignition, stock cam, normal compression, 904 automatic, assumed 2.76:1 rear, NOS Holley 1945, EGR block-off. WHAT SHOULD I DO? Thanks!! -Matt

Author:	olafla [ Sun May 29, 2011 1:46 pm ]
Post subject:
Happy to see both you and the car, MattyBrown! Well, like always when you need info on anything slant six, turn to the 'engine' FAQ. There you'll find this thread, letting you dive right into your distributor. Do some reading and research, plan the disassembly in forehand, make notes, take a LOT of pics to help you reassemble again. One good starting point before removing the distributor: disconnect the battery, and turn the engine by hand till you reach the ignition mark, or TDC mark. That way you know the starting position for the reassembled distributor, and can turn the engine back to the same point if you have goofed up and have to do parts of the job over again. Before doing more, take a photo of the distributor with cap off, clearly showing which way the rotor and vacuum can points. Loosen the dizzy hold down bolt, and slowly turn and lift the dizzy, or pull the housing upwards while rotating the shaft with the rotor as a handle. It rotates app. 30 degrees anti-clockwise before it's gear is free of the cam drive. Just when you feel it is free of the drive, take another photo - again clearly showing which way rotor and vacuum can points - before lifting it out. That marks the starting point for refitting the dizzy later. A distributor spring kit for recurving can be bought form our member bigslant6fan, just send him a pm. I have just done the job, and I am sure you can do it, just work patiently. Good luck! Oh, and while you're at it, go HEI! See the FAQ again! Use a rainy day to sit down and read through all the links in the engine FAQ - you already know some of the contents, and there is a world of info there, but all at once may be a bit overwhelming! Olaf.

Author:	Reed [ Sun May 29, 2011 1:52 pm ]
Post subject:
+1 recommendation for the spring kit from bigslantsixfan. It is a good package for distributor recurvers. You also should verify that the timing mark on the out vibration dampener ring hasn't slipped. Make sure TDC on the dampener = true TDC on the motor. Use a piston stop tool and some white out to check. 55MPH is supposed to be the most fuel efficient, but I think this will actually vary depending on engine build and gearing choices. Best MPG will be achieved by running the engine at the optimal RPM for power and fuel consumption and this will depend on many variable of the motor. The speed that that will correspond to will depend on gearing and vehicle weigh and aerodynamics. Whenever I calculate MPG I just take the # of miles driven between fillups and the # of gallons filled. Divide miles by gallons and there you go. If you haven't already, I would bypass the OSAC valve.

Author:	Aggressive Ted [ Sun May 29, 2011 2:39 pm ]
Post subject:
Matt, If you can borrow or buy a dial back timing light it would be a tremendous help. I like and use Doc's re commendation of using a medium tension primary spring with a super stiff long looped secondary spring to limit the advance instead of two medium weight springs and welding the slots on your governor. In the recurve post you can see how much initial, mechanical and vacuum advance I am running and when each kicks in. On best mileage with a 2.76 rear end and automatic depends on your power output. If you are down on power you will be pushing it and the vacuum gauge will prove it. If you can run at 2200 to 2500 @ 16" of vacuum or more at cruise (55 to 60 mph), your on your way to getting some good mileage. What #jet are you currently running? Is your motor stock? The more you increase compression the more effect the recurve will make. With a 9 to 1 motor you can feel the difference. Recurving an old stock motor is not as dramatic.

Author:	ESP47 [ Tue May 31, 2011 11:24 am ]
Post subject:
I calculate my mileage by just running the way I normally do. You can do a flat run at 55-60mph to see what your max MPG will be. It's cool to know but its not very realistic and chances are you'll never do that again. I probably do 60/40 Highway to City driving. When I'm on the highway I typically do 60-80mph depending on traffic. City driving is normally 40-50mph as well until you get into a neighborhood. I usually get 21.5 MPG on most fill ups. Sometimes slightly lower and sometimes slightly higher.

Author:	MattyBrown [ Tue May 31, 2011 11:47 pm ]
Post subject:
Hey guys, sorry for the delay. Life got really busy! Olafla, thanks for the advice. I have contacted BigSlant6Fan telling him the specs for my car and asking what he recommends. The good news is, I actually have a spare distributor, same year and everything as the one on my car. That will afford me the pleasure of doing this at my leisure without taking my car off the road. I can recurve the distributor and when it's perfect, do a quick and easy swap. Nevertheless, I will definitely take your advice when it comes time to do the swap Learned a lesson or two about making note of proper distributor position during my recent engine swap. I'm not sure if I'm ready(or financially stable enough) to tackle the HEI yet, but let me ask you this: Does installation of HEI require someone to curve a distributor differently? Could I decide to do it later and just put the setup on top of the distributor I'll be curving now without altering anything? Reed, I have determined TDC on my damper. It is almost correct but seems to have slipped only about 2 degrees. Thanks for your input on fuel efficiency, I will keep it in mind. Disconnecting the OSAC setup was one of the first modification I did when I acquired this car, so no worries there. Aggressive Ted, I can't say that I know what a dial back timing light is. What is the benefit of it? I will definitely take your recommendations into consideration but I fear that my understanding of all of this is limited. I have looked at your graphs and understand the data but am not at a point of understand what makes good and what makes bad. I will keep reading though. Hopefully it will sink in. My motor is entirely stock, cam degreed at stock position. New piston rings, so good stock compression (all cylinders at or near 140). I don't know the # size of my jet. The carburetor is a NOS Holley 1945 and I believe everything about it is stock. It is supposed to be the final revision of the 1945, manufactured in 1989. ESP47, Thanks for your input, will take into consideration. The good news, regardless, is that my gas mileage has improved greatly with my "new" engine. Just want to make sure there's nothing I'm overlooking that could improve it even more. -Matt

Author:	Aggressive Ted [ Wed Jun 01, 2011 2:49 pm ]
Post subject:
Matt, Using a dial back timing light will show both rpm and timing at the same time. It much quicker to map the curve. Map the combination of initial plus mechanical first, then go back and map with the vacuum advance plugged in for total advance. Be sure you do this to document your baseline setting of your current set up. Then map each change you make. This process will help you document history of your changes. If you don't use a dial back timing light it will take much, much longer........ 21.5 to 22 mpg in town, 25+ on trips with a 1920 Holley. What mileage are you getting? and how punchy/responsive is your new engine?

Author:	olafla [ Wed Jun 01, 2011 6:01 pm ]
Post subject:
Switcing to a HEI setup just means you throw away the ballast resistor and the ECU - the unit containing the electronics that gets the signal from the dizzy and send them on to your old coil - that you also throw away, and replace them with a small HEI module and a new so called E-core coil. Nothing else need to be changed. See the FAQ for some facts, the HEI will give you a longer duration, more powerful spark, and is stable over a wide rpm range. As far as I know, the module is around $30 and a coil is $30-40 new, but you can pick up the parts cheaply from a wrecker. Olaf.

Author:	Aggressive Ted [ Wed Jun 01, 2011 6:44 pm ]
Post subject:
Matt, Click in the red link below my name and take a look at my ignition pictures. Another option or alternative is to eliminate the resistor and buy a 3 ohm coil and continue using your ECU module. You get a full 12 volts to the coil instead of 6 volts or less which really helps and the plugs and run very clean gaped at .045. This setup has been very stable at all rpms. It takes about 15 minutes to install.

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