Thanks again Don. I hadn't seen a lot of these photos so I am enjoying your bringing us up to speed. I know your "up to date" but maybe you could scrounge up a couple more?? LOL..
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Thanks again Don. I hadn't seen a lot of these photos so I am enjoying your bringing us up to speed. I know your "up to date" but maybe you could scrounge up a couple more?? LOL..
Attachment 57485Attachment 57486Attachment 5748434-40 you may be the only one interested in my project but I can add two lesser problems. In the case of runningboards I got tired of working while sitting on the painted runningboards trying to avoid scratches. What I came up with is sheets of aluminum diamond plate which is flashy but maybe also trashy? I usually ask folks what they think of the running boards and they usually like them so I am not going to try and put rubber covers on the runningboards in the forseeable future. A more complicated problem is the pulse generator for the digital speedometer. In the transmission pan photo you can see two narrow black plates fore and aft. That is the transmission mount hanging from the first crossmember. There is a gap between the hanging trans mount and the side of the transmission where the speedometer cable comes out the side of the transmission. When you add the pulse generator it will not fit in that space! After looking around I found a unit which has a right-angle gear which allows the pulse generator to just barely fit in that space as "bent around the corner". Then the pulse generator needs a small bracket to hold it steady in its orientation and you can see that the space is really cramped in that area! The right-angle pulse generator is visible at the top of the transmission pan photo. The unit on the left of the board is the plastic speedometer cable port which broke easily when I over tightened it. On the right is an optional metal unit which you have to hunt for in a junk yard or try to purchase from a transmission shop. The center unit is what I used.
Don Shillady
Retired Scientist/Teen Rodder
Great pics Don!!!! Hope you have them in an album to take along to the car shows this summer, people love to look through pics of the build process!!!!
BTW, came up with a great idea for you for the summer----How's about you just cruize around the countryside and stop by to give us all a ride in the roadster????
I'll second Dave's idea! I'm closer so you gotta come here first! :LOL: To sweeten the deal, you can take the 34 for a spin! :eek:Quote:
Originally Posted by Dave Severson
I doubt I'm the only one looking. The count goes up by more than just me. Not everyone is as chatty as me I guess! :HMMM::rolleyes::)
As an aside, I just bought a new set of Classic gauges and instead of using the pulse generator I picked up their GPS transmitter that supplies the speedo / odometer with a signal. Tucks right under the dash!
Don, if you come visit me first, I'll buy you a nice slice of apple pie with ice cream and a cup of coffee!!!! Then I'll let ya make a pass in the drag car!!!! That should be more fine then riding in some old coupe, right??????:LOL::LOL::LOL:Quote:
Originally Posted by 34_40
PS---That would be hot apple pie with cinnamon ice cream!!!!!
HMmmmmm.. I'll give ya a full tank a gas! Now that surely beats a quarter mile sprint and some pie w\ ice cream!
Wow, either jaunt would be a long trip for me but I appreciate the offers. First I need to get some short runs in for road tests. Dave that is a good idea about an album. I recently discovered that Target has a print service where each picture is only $0.10 and you can get them in a few minutes so I could/can print out enough for a show album. For the time being I will start with a local Friday night meet at Chic Fila and then work up to Culpeper Va for a July 4 meet.
Don Shillady
Retired Scientist/Teen Rodder
It has been a while since I was here last. Time has passed because of problems with my transmission. Due to my GM700R4 only having low gear and third gear a series of tests at a local Transmission shop determined that I had left the trans dry for about five years during my build and the main valves in the transmission had rusted shut. Phil of a local Mr. Transmission shop first rebuilt the existing transmission and then talked me into scrapping my Zip Riser water pump set up for an electric water pump. He also talked me into purchasing a higher grade Monster 700R4 in case other parts of my previous low level street grade Monster had accumulated additional rust (even though he put it through a complete strip down wash and added new clutches). Phil is locally regarded as an innovative mechanic and he improved my car several ways but the car was in the shop over a five month period first checking the 700R4, rebuilding the rusty trans and then replacing the transmission with a new higher level Monster 700R4 along with a complicated modification of the water pump and installation of two cooling fans. I was not keen on going to an electric water pump (Meziere 35 Gallons/min) and I am still worried that the new 90 amp alternator will be able to supply the water pump, headlights and TWO 8" 1600 CFM fans but in recent tests in 95 F July traffic jam idling heat the car has not overheated. One fan comes on when the ignition key is on while the second fan is controlled by a thermostat set to 185 F. The combined 3200 CFM of the two fans is greater than any single electric fan we could find and the nose of the Meziere pump is too long for a single fan as well. I still want further summer heat tests before I plan any trips longer than a quick jaunt through areas with plenty of back up stopping points for cooling but it looks like Phil and his crew did solve the heating problem. I still like the Zip set up and can sell my unit to any interested party but I note some of the other successful installations were on small motors like a 283 SBC and others run without a hood or hood sides. So far I am able to keep the full hood look that my wife wants for a "cute" Model A and cross my fingers regarding an electric water pump. At present most of my summer time is spent working/teaching to pay for the new replacement Monster transmission. I will say that 700R4 low gear is a lot of fun even with my rather high ratio 3.55 rear and the sudden shift to second is a real kick in the pants. I picked the 3.55 rear gear so that even if I am not running in OD I may get reasonable mpg. So far I have to restrain myself at a light since that low gear is a real Jack Rabbit! Now can anyone tell me how to insulate the alternator wire from the front of the SBC left head? The wire fits in a narrow space that can't be more than a 1/4" wide between the back of the alternator and the front of the 882 head. I am thinking of trying a piece of electronic circuit board between the head and the back of the alternator but have not completely figured it out yet. Does anyone make a small fiberglass sleeve for this situation?
Don Shillady
Retired Scientist/Teen Rodder
Don,
I'll offer a comment on your fan control. I would not want one fan running all the time, as when you're running down the open road you shouldn't need any electric fan help. The velocity pressure through the radiator is more than enough. I would trigger the first fan to come on at ten degrees above your thermostat setting, and the second fan about fifteen to twenty degrees higher than the first. My single fan runs two speeds, and with a 180F stat I start low speed at 195, and high speed at 210. Running down the road I run about 185F, and no fan runs.
I don't think I'd worry too much about that alternator wire. There's not way for you to get any movement of the alternator apart from the head, so your 1/4" should be just fine.
Hi Don. Good to see your updates and glad your making trips with the car. Although it was expensive playing with those trannies I bet!!!
Like RSpears, I don't run any fans until the motor hits 190 degrees. And that only happens sitting in traffic, once underway, the forward motion feeds enough air through the radiator and the fans shut off.
I also don't think you need to worry about that wire. As long as it has clearance (1/4" is fine) and isn't allowed to rub against anything, you should be fine.
I seem to remember a specific wire end and terminal on some alternators to encapsulate and insulate that alternator wire
Jerry, you're right Summit has them;
http://www.summitracing.com/parts/rnb-85684
Jerry and 36 Sedan, Thanks for the link. For $5 it seems like good insurance for that alternator wire. Rspears, I want further tests in summer heat before I turn off the initial fan. I think my dash thermometer reads high because it gets up to 220 F quickly without any sign of overflow in the catch can and an Infrared gun says the temp is lower than 220 F. 34-40 thanks for your continuing interest in my car. After seeing the interior parts of the 700R4 and the two rusted valves I understand the four combinations of the valves now which are key to the four forward gears. The other bee bee check valves are more complicated but they are some sort of plastic (Teflon?) and not subject to rust but the sliding valves have a close tolerance fit which is easily messed up with rust.
Don Shillady
Retired Scientist/Teen Rodder
Don,
I think if you do some research you'll find that a running fan tends to block air flow more than a freewheeling fan at highway speeds when the fan is not needed. This is the reason for thermostatic clutches on mechanical fans. Regarding actual temperatures measured by infrared gun, your engine will have temperatures varying over a significant range depending on what you shoot. For example, my dash gauge reads right at 180F running down the open road, sensed on the thermostat housing, but the ECU input is a second sending unit in the water jacket as it exits the head, and that point reads between 186F and 192F (ECU display is incremental, not by degree). If your dash display is reading significantly different than the infrared measure of the sending unit base I'd think about investing in a new sending unit to see if that fixes the discrepancy.
There will be a speed(mph) vs rotational RPM where a constant rpm fan(or propeller) will actually push the air flow backwards!!!!!!!!!!!might be a little difficult to grasp, but think about it a little(don't loose any sleep over it)
Jerry, The reason I am on this board is to get advice from experienced folks like you and actually this is more your thread than mine! I have ordered the little boot for the alternator connection and that should reduce one worry. Do you have any comments about the Meziere electric pump? Relatively few folks run them on the street but the Meziere engineer says it should be good for about 50,000 miles and I am carrying a spare set of brushes. Rodger, I appreciate what you say and I would like to recover some amps to the battery after starting while the engine warms up but I will have to figure out the wiring Phil put in for the fans. The easiest modification is to simply put a manual on-off switch on the first fan and then remember to turn it on when the temp reaches 180 F or above. Assuming I don't forget to turn on the first fan a break in the line to that fan is my simple way to avoid adding another thermostat and relay. Until I can figure this out I will run it the way it is now. I have enough history in making changes that make things worse to be cautious in further modifications even though I would like to turn off the first fan at highway speed and before the engine reaches 180 F.
Don Shillady
Retired Scientist/Teen Rodder
Jerry thanks for the useful comments. You and Rodger remind me that I would like to recover some of the starter amps to the battery while the engine warms up but I will have to study Phil's relay circuit. One easy way might be to simply put a switch into the power to the first fan. There is a guy near me who recently moved East from California with an absolutely beautiful 1926 Ford coupe with a 283 SBC and an electric fan which he switches off when running on the road and then turns on manually when in traffic. His setup is simpler than mine but he told me that his fan runs down his battery when it is on all the time. Again there are many variables to consider but maybe the simplest idea is for me to break the line to the first fan with a switch. I will have to check and see if that would turn off both fans or just one. This is something to consider but requires further study to understand the circuits Phil put in there along with several relays.
Don Shillady
Retired Scientist/Teen Rodder
IMHO, the safest way to operate the fans is through a thermostat. If you feel you need more control, you can add a bypass switch to operate the fans manually at any time without the thermostat. Fans wired to a manual switch only is asking for trouble when you forget to turn them on and are not paying attention to the gauges.
If you think you have to have one fan run when the engine is on, wire that fan relay to the accessory part of the ignition switch, this way the fan does not operate with the starter and allows for easier starting (more amps to the starter). The down side to this is the fan operates in the accessory position when you’re listening to the radio with the motor off.
I have dual fans wired through a thermostat with a manual bypass switch that kicks the fans on whenever I like, and when I shut the motor off if the thermostat is calling for cooling the fans will continue to operate for an additional 20-30 seconds before shutting off.
I am totally against the use of electric water pumps unless its on a drag car where you need to circulate the coolant for cooling while between runs-----------
Use a oem type water pump run at the rate the factories built the engine with---do not use underdrive pullies at all, if anything overdriving is a better way to go, but a proper flow rate cooling systen based on the engines rpm is necessary-------
Jerry, I totally agree with you and you are the fourth "Pro" to tell me that. I certainly wanted a belt driven water pump but the transmission shop insisted on the electric water pump against my wishes and would not guarantee the trans unless I improved the cooling system. The Zip set up was on the ragged edge of overheating with the full hood in December so it was questionable how it would behave in July. This was very frustrating to me but all I can say is that it does run cool now and I will try it for a while. I still have the Zip setup and could go back to it.
Don Shillady
Retired Scientist/Teen Rodder
Don,
I'll second the statement about manual switches on cooling fans being a bad idea. It is sooooo easy to overlook a temp gauge until it it pegging out, especially if you're coming into a traffic situation where you need it. I'm using a SPAL programmable controller on my SPAL fan, along with a SPAL temperature sensor input. The beauty is that you can adjust the On & Off set points (low speed/high speed on mine) independently over the full range of the temperature sensor.
I also agree with Jerry that IMO an electric pump is generally not a good idea for the street. Now if you had a rear mounted radiator and needed more system flow head than an OEM provides you might need one, but I prefer the OEM style pumps.
If your new friend is telling you that his fan runs down his battery he needs to install a higher capacity alternator. My 100amp alternator keeps the system voltage at about 13.5V under all conditions.
With that I'll back away and let you enjoy figuring out what works best for you & your car. Have fun!!
Well as rspears notes the car is set up now with the electric water pump which was installed pretty much against my wishes and I will live with it until something breaks. I only wanted to get my car back from the transmission shop which had it from February till May. First they did try to repair my rusted 700R4 with various special fluid soaks, then they took it apart and cleaned it, put it back but then would not give any guarantee unless I replaced it entirely AND THEN the shop would not guarantee the new transmission from Monster unless I installed a cooling system that would not endanger the new trans! Thus I just wanted to get my car back but I am glad to have the improved Monster 700R4. Then over the summer I planned to use my summer salary for a professional interior but our home heating/cooling system went bad so I just took the summer check and gave it to the air conditioning man! As a result of working over the summer and having my car in the shop all Spring I only now got around to calibrating my speedometer. The speedometer is part of the instrument set I got from TPI-Tech about six years ago but they are now out of business, although I still have the instruction sheet. Anyway the speedometer was reading an outrageous factor of 2x high. I got some help from my son who is more confident with digital gadgets and we finally found a measured mile on Route 301 just south of Bowling Green VA which is about 25 miles north of my home. Although I live within 200 yards of I-95 with 0.1 mile marks, I-95 is not a place where you can pull over and pause to mess with a digital speedometer! The weather was great and we appreciated the Lexan windscreens running along during a period of very little traffic. We set the speedometer on the measured mile and had lunch in "downtown Bowling Green" near the only traffic light. Now with an accurate speedometer/odometer I can check the mpg of my A roadster which was set up with a low rpm cam and a 3.55 rear, depending on the 700R4 low gear for acceleration and I do have a noticeable chirp in the shift from low to second so I hope for a good compromise of low gear performance in a light car and maybe 20 mpg(?) due to the 3.55 rear and the 700R4 OD. Watch this space for a report on the mpg. Compared to my wife's big cushy 2008 Impala, the A roadster rides a little rough and the short wheelbase with the Vega steering requires almost total attention on the road. I am sure my wife will not like the primitive riding conditions but it was a real time machine experience for me! Due to my 2" chopped top frame I got one of those prisms to look up for the light and it works.
Don Shillady
Retired Scientist/teen rodder
That's good news Don! PROGRESS!!! I hope you can enjoy the remainder of the season and get some cruising in.
Vega Box Review?
My steering already has a small amount of slack in it and it has been tightened on the adjustment quite a bit so I am looking at replacing it. The prices for Vega Steering boxes range from $200 to $950 and Flaming River has not always had good reviews. My Vega Box was bought from Flaming River when I assumed the quality was good but now I wonder. Part of the problem is that I originally installed the drag link upside down and had to reverse it, thereby probably messing up the tapered spline. So can my problem be solved with a new $200 Vega box and a new $50 drag link or do I need a higher quality steering box and what make is recommended? Also what is this business where some vendors say the Vega Box is only good for vehicles under 2000 pounds while others say for under 2500 pounds?
Don Shillady
Retired Scientist/teen rodder
Don, have you discussed these problems with Flaming River? And yes, the "intended" weight of the vehicle needs to be discussed when selecting a steering box. There is a load rating.
34-40, yes I had a good chat with a Tech guy at Flaming River named Kevin. I can/may send the box back to them for inspection and possible repair. I think I will leave that go while my arm strengthens since I think part of the problem is that I have a 13" track racer steering wheel so I can enter the car more easily and the effort to manhandle the smaller wheel in parking maneuvers requires more effort than on a larger wheel with more leverage. Now for the Good outcome of what might have been a disaster. About a month ago I went to a nearby store with the right door ratteling and when I got to the store I closed it tight. Along the way the vibration was enough to partially break the steel tubing link between my gas tank and the fuel line! It turns out that the Bebops body just sits on the floor pan without a seal and gas ran forward and slopped off into the front fender well. I never saw the gas because it was on the passenger side so I did not see it until the next day. By that time heat under the running board apron due to a trans heat exchanger had severely blistered the paint on the base of the right front fender and the forward part of the running board. Well the good news is that I wanted to fix a mold mark at that spot that had not been smoothed before paint. Now I had a good reason to repaint that spot and smooth the mold mark which should have been taken care of originally. I realize now I had a close call with a possible fire so I am lucky in that but it did cost a pretty penny to repaint that part of the front fender. I was so shocked over how I almost had a fire that I did not take a picture of the big blisters in the paint but I do have a shot of the original annoying mold mark as well as the new repaired section. Discussion with several shop guys say the trans cooler under the running board alone should not spoil the paint and that it was that I let the gas puddle up over night on a hot spot and that blistered the original paint. Well anyway I am probably just talking to 34-40 and Roger anyway but I will document the pictures of the trans cooler and the before/after pictures since the folks on this Forum like pictures. Well the pictures are in the wrong order with the NEW RUBBER HOSE between the 13 gallon tank and the line that runs forward from the fuel filter to the engine along the right frame rail but I think you can see how the problem is now fixed as long as the rubber hose lasts and allows some vibration without leaking. Roger need not worry over that tank seat belt since the rumble seat area is now a "trunk" holding a tool bag, extra Prestone, extra engine oil and trans oil and the side curtains (in the summer) so there really is no room for anyone to sit anyhow. The Trooper who put the title plate on the fire wall said nary a word about that seat belt.
In edit mode it may be worth mentioning that the 1" square tubing skeleton of the Bebops roadster body has little rigidty when the door is open and apparently that flex was enough to stress the former steel tubing between the fuel tank and the fuel filter which is bolted to the quarter panel. Lesson: Keep the door latched and hope the rubber hose will flex with possible vibration. The front buggy spring is very firm but the rear coil-over shock suspension makes the ride reasonable and allows softer up and down motion of the rear of the body, hence the vibration when a door is open.
Don Shillady
Retired Scientist/teen rodder
Sorry to hear of these recent troubles Don... sounds like you missed a bad scene by the narrowest of margins! Fuel leaks are nothing to mess with, besides the gas being so expensive it can be dangerous. I don't understand how you achieved that much of a flex to break the metal connection of the fuel line and the sub structure to the body, but it did so the rubber line should eliminate that problem from returning.
I thought your steering had some play in it? Did they (Flaming River) address that issue?
34-40, I am going to track down some slack in the steering. It may be in the spline at the top of the column or the wheel itself. Then there is the universal joint in the column before the steering box. I need to find the main cause of some relatively small amount of slack. I am going to enjoy driving the car for the last warm part of the summer before I pull the steering box off. Thanks for your interest in my foibles.
Don Shillady
Retired Scientist/teen rodder
Don, why don't you move that fuel filter underneath the car where any leak will drip on the ground instead of saturating the interior???Looking at where its mounted in relation to the tank and not seeing the metal line you had on it---------OEM type systems of any hard lines that change directions orcomponent mounting will always have some flex zones built in( a loop) to allow the flex of the structures without breaking the lines--------A good example of what I'm saying is evident on probability of every persons cars if you just look at the brake lines up near the master cyl/frame/body---------loops, curls,etc
Car looks nice---enjoin the good weather!!!!!!!!!!!!!!!
Thanks Jerry,
That is a good suggestion. Maybe I should scrap the replaceable filter and use a smaller in-line filter (also replaceable) that would hide under the running board apron. I had a set up like that on a restored MG midget money pit I used to own but I got carried away with the idea of this larger filter and could not see a better place to put it but a smaller one would fit underneath. I don't want to go through the fire hazard again along with the cost of another paint repair. However I would like to get in a few more cruise-in events and then do some mechanics later in the Fall. I will know "when" I can't run without side curtains due to cold! The top shop that made my top from scratch is presently adding a zipper to the left side curtain (like a Jeep) so I can adjust the left outside mirror with the door closed. The best news of the day is that my wife had her first ride in the car and did not find in/out a problem so that opens up the possibility of attending local cruise-in events. Today I won a raffle for a nice nylon T-shirt at a cruise-in at a local Pontiac-Buick agency and last night I attended a Chick-fil-A cruse-in where there were almost 150 cars! I'll try a few more of these local events before I start messing with the changes over the winter.
Don Shillady
Retired Scientist/teen rodder
That's great that "the BOSS" can enter/exit easily and you can share the experience together. My wife went for a short cruise last week, we went for a short ride and then stopped for ice cream. Later went over to some friends and she said that she did her annual ride and that's enough 'til next year.. :eek::LOL::eek::LOL:
I don't really mind tho.. as she talks the whole time she's in there! takes all the fun out of the cruise for me!!:eek::eek: So I'm good 'til next summer! :D:D
Well 34-40, since my last post "we" had a break down coming home from a local cruise-in but the wife still likes the car because she rode home with me from another local drive-in two weeks later. Due to the tight placement of my electrical coil under the simulated tank eyebrow on the fire wall, the top of the coil broke with bouncy vibration and the problem was mysterious for a while until a crack in the neck of the coil was noted. Replacing the coil fixed the problem but I added a foam rubber "nest" between the new coil and the fire wall to soak up future bouncing vibration. The coil spring rear suspension gives mostly a good ride but the front end is subject to bumps and on the way to the cruise-in we crossed a long one of those new slab-type bridges with a bump for every boundary edge. That is probably what bounced the coil up and down? Now for a promised report on the mpg. The results are disappointing since I had hoped to get to 20 mpg. The stock specs for a 1977 Z28 (3828 pound car) were 14-17 mpg and my mild 350 is basically a 1976 350 built to 1977 Z28 specs with slightly more compression. Sooo, I took a short 63 mile jaunt from home near Glen Allen to Bowling Green Va and back again and the AV8 used 4.201 gallons of 89 octane (10% ethanol). Thus (63/4.210)=14.9964 rounded to 15 mpg. I checked this with my 1998 Sunfire and got 32.1782 or almost 32.2 mpg over the identical route. Parts of the course were traveled at 65 mph but most was at about 55 mph. Noting the tach showed most of the time it was between 2000-2100 I was probably traveling in the 0.7 4th gear of the 700R4 trans.
700R4 0.70 trans 4th gear
3.55 8" rear gear
P235/75 R15 rear tires (fairly wide and large)
Tach Reading over most of trip: 2000-2100 rpm
15 mpg over mostly a rural black top road (Route 2 north, Route 1 south)
I guess when you consider a V8 engine as two 4 cyl engines the near 2:1 gas consumption makes sense but I thought I was deliberately building a "conservative hot rod" with a high ratio rear, OD and big rear tires for a mild V8 in a light car. The acceleration performance of the car is fun but I had hoped for better mpg with the 700R4. In any event I put the side curtains on the car for the winter yesterday and will have time over the winter to think over the range of driving to local meets next summer.
Best Wishes,
Don Shillady
Retired Scientist/teen rodder
Postscrip: I went out to Sonic for a snack and noted one rear tire looked a bit low. Checking showed both rear tires were at about 10 psi! maybe that hurt the mpg a bit but I doubt that it would bring the mpg up over 17 mpg so I will just tell myself its 16 mpg until I can run it around the course again.
Don Shillady
Retired Scientist/teen rodder
Low tire pressure adds a lot drag and could effect the milage drastically.
and that thing has a terrible drag co effient----------------
Hi Don! Thanks for the update(s).. 15 for a pretty conservative build is poor mpg. But having the tires at 10 or less surely dragged it down, but by how much? I'll be curious as to the next measurement results.
And breaking the coil tower is curious. I don't think the material between the coil and firewall is helping, I'm thinking it may allow movement but I'm not holding it in my hand(s) so it's only my imagination of what it looks like (Hint / Hint /Hint re; pics)....
One of my last trips out my car just died! I wasn't far from my shop and my uncle came out and flat towed me home. I later found I had run out of gas! The gauge says I have a 1/2 tank, but when I dipped the tank with a stick.. It was dry! Lousy TPI Gauges! I've had enough of them.. I just ordered a new set of Classic and wil replace them over the winter.
Jerry is correct again. A "flying brick with a 2 inch chop" is still a "flying brick" aerodynamically! For reasons I don't remember I had a 3/16" spacer between the coil and the firewall allowing the mount to flex and pushing the top of the coil toward the lip of the firewall eyebrow. Removing the spacer and adding a foam rubber pad (pipe insulation) reduces the mount flex. I will rerun the test as soon as we get some clear weather here and I can pump up the tires to the 35 psi maximum. I think the 1st-to-2nd shift is too sharp with almost always a tire chirp which may have loosened the seal of the tubeless tires to the rims. Hopefully using the 35 psi pressure will seal again or maybe I will have to remove the tires and apply some sort of sealer to the rims or use tubes as a last resort. I'll post new results when I can run the course again with better tire pressure. The interesting thing is that the car is light enough so that even at 10 psi the tires were barely noticeable as underinflated. Another chore I need to do is to weigh the car but I expect it to be in the 2600 pound range. This kind of open-ended discussion with experts is what makes this Forum valuable!
Don Shillady
Retired Scientist/teen rodder
Don,Quote:
Originally Posted by Don Shillady
Running 35psig may give you better mileage, but it will also prematurely wear out your tires due to them running "crowned" with only a portion of the tread pattern contacting the ground fully. To get the best mileage plus the best wear you need to chalk the tires, drive a short distance (100' is enough) and look at the chalk line. Raise or lower pressure until you see the whole line disappear at the same point, showing you that the whole tire is in contact with the road. You'll then get the best of both performance and mileage from those tires. I'd venture that about 20 to 24 psig will be the right numbers for the back.
Don S., I'll agree with what RSpears said. 35 PSI is going to be to much. The car will ride harsh also. I started at 35 and did the chalk thing. I think I'm at 25 / 26 now.
But, I'd be curious as to what the MPG totals at that pressure!
34-40 and others, Thanks for the suggestions. I did the chalk trick but only at 30 psi. It may be slightly on the high side but I want to favor mileage. Anyway you can see from the chalk pattern that the whole width of the tread is present. I also saw a suggestion on a Corvette web site to just use 5 psi less than the max rating. I also saw other suggestions ranging from 22 to 33 psi. Anyway the pattern looked good to me so I used 32 psi in the front tires and 30 psi in the rear tires and took the identical 63 mile trip as before including a stop at the same spot in a McDonald's parking lot and a quick lunch. This time I used only 3.889 gallons of fuel (WaWa 89 octane) so this run gave (63 miles/3.889 gallons) = 16.19954 mpg or about 16.2 mpg for an improvement of about 8.02%. Thus I will have to keep checking the tire pressure and 32psi front with 30 psi rear looks like about all I can do to optimize the mpg. Of course this little experiment was fun because I got to drive on rural roads but I did keep the speed roughly between 57-62 mph since I saw some traffic pull over tickets along the way. Again the Tach stayed under 2100 rpm the whole trip. On the previous run I hit 70 mph a few times but that is about the top speed with the top up due to vigorous flapping of the top at speed. I also recall seeing a wind-force curve versus speed somewhere and it is pretty steep after about 35 mph. When the Model A body was new most highways had a 35 mph limit so the flying brick aerodynamics was no problem then but when you get up to 60 mph the drag coefficient becomes important as Jerry noted. As far as the ride goes the choice is between "harsh" and "harsher" anyway although most of the trip was on smooth roads. However there is one pothole in Route 1 just north of Ashland that I forgot about and when I hit it again this time it almost took out some of my eye teeth! Well I did not even get to 17 mpg and 20 mpg seems impossible even with my 0.7 4th gear. I do note that the 1977 Z28 had a 3.42 rear gear compared to my 3.55 rear ratio. Thanks to several of you for suggestions as well as some unknown folks on Corvette chat rooms. I look at the Corvette comments because technically my engine is from a 1976 Corvette. The first picture is for 34-40 as to the new padded mount for the coil. I am not happy about all the wires which resulted when relays were added for my dual fan setup and the plug wires could be hidden better but you can see the edges of the black foam around the back of the coil and the mount is now flush with the firewall. The second picture shows the chalk pattern for 30 psi in the rear tires as Roger suggested. One good result is that I was toying with the idea of changing to smaller rear tires for better acceleration but obviously this experiment shows that I better stay with the 235/75r15 tires!
Don Shillady
Retired Scientist/teen rodder