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Posts posted by WayneC

  1. My guess is the brake booster is likely the reliable indicator, but is the master cylinder cap original to the M/C or did someone add that Dot 3 notice?

    If the M/C has been changed at some point, the cover may have come with that notice.

    Dot 5 should not harm a system designed for Dot 3. Either will work, but they cannot be mixed; the question is: what is currently in the system?

    Since brake fluids seem to change/lose color after awhile, the purple color of Dot 5 is probably no longer an indicator.

    Perhaps by taking a bit of fluid from the master and dribbling it onto a painted surface... Dot 3 will likely damage the paint if left on the surface a day or two. Dot 5 will not harm paint.

    From the internet: "Another way to tell between DOT3/4 and DOT5 is to put some of the fluid in a glass jar and add a few drops of water.

    Water will mix completely with the DOT3/4 but won’t mix and will remain as a separate blob in the DOT5."

    As for preference, I use Dot 5 in my Avanti's. If switching from Dot 3 to Dot 5, you should remove all remnants of Dot 3 with a thorough Dot 5 flush of the entire system. I made the switch on my '71 when I did a brake system rebuild and was replacing all 4 cylinders.

    BTW, what are "slugs"?

  2. Nice discussion between folks who have done it before, glad it worked out for you... the rest of us are left completely baffled because no pictures, no links to hardware, and very brief cryptic verbiage (and I consider myself mechanically-inclined).

    Bill, wish you'd have taken my prior comment to heart, I'd have liked to learn something about doing a swap from this thread, but I didn't. Opportunity missed.

  3. Needing a 33 and having to use a 34, anybody know if the speedo will read fast or slow?

    Considering that the DRIVEN gear is 34 teeth instead of 33, that means the driven gear will make slightly fewer revolutions (than a 33-tooth driven gear) as compared to the number of revolutions of the driving gear in the transmission, so the speedometer will read slightly slower than actual.

  4. I agree that engine appears to be a 1971 engine with a VIN stamped on it.

    To be more certain, other numbers can be checked.

    There is a casting number in raised characters on the top left rear of the engine, on the "collar" for the bell housing to bolt to, and similarly, a casting date on the right rear. Those numbers might give more corroborating clues. My casting date information covers up to about 1971, but I expect it carries forward to later years.

    Very few casting numbers bridge the timeframe from 1971 to 1976, those few being...

    3911460 1969-80

    3932388 1969-76

    3970010 1969-79

    3970014 1968-76

    6250425 1968-76

    Note that none of those ranges include a 1971 and 1981 possibility, nor a 1976 and 1966 or 1986 possibility,

    so if one of those casting numbers had a date code string (see next paragraph) ending in 6, it would have to be 1976,

    or if it ends in 1, it would have to be 1971... so a 2-digit year code (see below) is not necessary to determine the year.

    The date code string should start with a letter (A=January, B= February, etc) followed by 2 to 4 digits: depending on the day of the month (single digit or 2 digits), and year (single digit or very rarely 2 digits, depending on the casting foundry):

    B1274 was cast on February 12th of 1974

    F124 was cast on June 12 of (probably) 1974

    C14 was cast March 1st of (probably) 1974

    Here's a sample of the smog plumbing you should likely see atop your engine:


    It would also have an exhaust catalytic converter, and possibly an exhaust manifold air injection system (pump and tubing, but

    that air injection system may have only been required on cars sold in California).

    Here is a current listing on eBay for an emissions equipment shop manual that might be of interest to you:


  5. Here's a whitewall in 205/75-15 that looks nice, but not highly-rated:

    http://tinyurl.com/leuyd5z and http://tinyurl.com/qyse9h7

    If you can stand blackwalls...


    And, 215/70-15 is also a possibility (I use them on my 1971 Avanti)

    http://tinyurl.com/mejr956 (whitewall, low price and highly-rated)

    http://tinyurl.com/l3lafww (whitewall, but not highly rated)

    http://tinyurl.com/2esycue (blackwall)




    On the links above that go to TireRack, click on the "Surveys" and "Reviews" tabs near the bottom of the page to see how users rate them in various ride categories.

  6. Anyone know of a source for the "proportioning valve" below the brake booster (or specific info on what other vehicles used that same "valve")?

    Actually, I do not think it is a proportioning valve, but rather a junction block with a switch that activates a dashboard light if pressure is lost in either the front or rear brake lines.

    I found some Chrysler and Corvette junction blocks on eBay that are quite similar to the one on my '71 Avanti, but they are not exact matches.

    Update 2/2/2015: it appears to me that the junction block is most likely a match to the '68-'69 Camaro block (Camaros got front disk brakes with the Z28 option in late 1967).

    I haven't ordered one to check it to see if pipe threads are a match, but it looks very much like my '71 junction block.

  7. Here is some info I've collected in the past (I don't really know much about the industry standard numbering system, and it's possible even the standard numbers have changed over the years, but a good brake supplier/distributor can probably make sense of them, even ones that changed):

    rear brake shoes: Industry standard #173 through 1971 Avanti serial 1661, Industry standard #228 after serial 1661 (but I also have conflicting info saying all '63-'83 Avanti's have a Spicer 44 axle and use EIS #ES449R shoes)

    rear wheel cylinders: 78-86 Ford Fairmont wagon, or 62-63 Mustang & 73 Fairmont sedan, or Wagner F37782

    rear springs & other hardware are 66-73 Jeep CJ with 11" drums: EIS# H7137

    rear brake flex hose: NAPA #11146 or EIS SP948

    I expect the Avanti parts suppliers may be the safest source.

  8. Not an expert here, but the serial numbers may denote differences in adjustments made at the factory, jet sizes, and differences in the throttle linkage and/or an extra vacuum port to accommodate a method of downshifting the automatic transmission when you stomp on the gas pedal (like a throttle valve cable).

    Also, when a car maker produces many thousands (or millions) of cars, minor differences between carbs can save them money by eliminating things not needed on some models, like extraneous vacuum ports, while providing those things on other models.... so for example, a carb intended for an automatic may come from the supplier (ie, Rochester or Holley) with a cable clamp on the accelerator linkage that is not present on the otherwise identical manual trans carb, which has an empty hole where that clamp would go (may be a bad example, the clamp might come on the transmission cable assy instead, or the hole may be absent on the carb intended for a manual tranny).

    I suspect a carb meant for a car with an automatic transmission can probably be used on the same model car with a manual transmission, but the opposite could be problematic. It should be possible (don't ask me how, though) to find the specs for jets/accelerator pump, float levels, choke, etc and purchase correct parts for the carb variation you choose, thereby transforming that carb to match the specs of the carb that was originally used on the car you have.

    Each new model car is tested exhaustively and tweaked/altered by carb experts to get best balance of driveability and economy under many driving conditions before the car goes into production. If the tuning items are anywhere close to correct, most of us would never know the difference (we'd just ignore the stumble that only occurs when we goose the throttle while going about 45mph up a hill). A Rochester carb for a Silverado probably needs very different calibration than one for a Chevy Nova, even though the same basic 4-barrel carb model is used for both, and both vehicles may have a 350ci engine. If you buy a carb with different serial numbers than the one used on your car, you ARE the carb test engineer, since the carb was not tuned/configured specifically for your vehicle.

    Carburetor overhaul companies, like recarbco ( http://www.recarbco.com/) can probably find the correct carb and/or rebuild yours to factory specs based on the serial number. I had them rebuild my '71 Avanti carb some years back and was pleased with the work.

  9. You said: "So today i moved the accelerator pump linkage from the middle spot to the top. It made the car bog a little, and if I blipped the throttle it would almost die before regaining idle. So i went to the bottom hole and it got better off the line. But still not perfect."

    ...I thought I understood that when I read it, but on re-reading I am not certain I did... is the "bottom hole" on the lever closest to the carburetor pivot point or furthest away? I expect the hole closest to the carb pivot point gives the earliest & longest squirt.

    If the bottom hole was best (furthest from the carb pivot point), that would give the softest squirt, but that still apparently wasn't soft enough. Am I understanding correctly that you had the best result with the rod in the furthest hole from the carb?

    Did you adjust the idle mixture in accordance with the Edelbrock pub? (see "Idle Mixture" on page 6 of the Edelbrock manual linked in my prior post).

    Out of curiosity, have you tried simply removing the linkage rod (to the accelerator pump lever) for a test?

    In perusing the manual I linked in my prior post, it appeared to me that it is possible to change the jet size for the accelerator pump, although that manual does not list other available sizes (there is a chart showing the accel pump jet size that comes standard in each Edelbrock carb type, and the 1405 uses the smallest/leanest size). Can you see a strong fuel stream from the accelerator jets when you blip the carb linkage off idle in the garage?

    A vacuum leak can give similar "stumble" symptoms at low rpm, so you might check for gasket leaks or loose vacuum hoses.... Vacuum leaks usually result in an uneven/rough idle, too, but not always, because you may have masked that while adjusting the idle. You can use a propane torch (valve opened a bit without lighting it, and pointed away from the carb, air cleaner removed) as a method of finding leaks, by directing the propane flow closely and slowly around the seams at the base gasket of the carb, around the outer edges of the intake manifold, along vacuum hoses, etc, listening for the engine idle rpm to increase noticeably when the propane stream passes a leak. Do it outdoors so the propane gas doesn't collect in your garage

  10. I don't have much sweet knowledge to lay on you, I've never played with an Edelbrock carb.

    But, it seems to me you are on the right track with the accelerator pump, considering the car seems to only have an issue off a dead stop. I would not fool with those metering rod springs until you get the stumble fixed.

    You might check to make sure the choke is properly adjusted.

    4 degrees advance timing at idle (with vacuum canister vacuum hose disconnected and plugged) should be fine.

    Is your idle set at 600 to 700rpm in drive, engine warmed up, tranny in Drive, with the brake on?

    There are a number of Edelbrock carb tuning videos on youtube, have you perused those?

    And, do you have this:


  11. I can't tell you much about the differences, except to say that all quadrajets are not the same, even for the same make and model car. There are many variations, even among Corvettes, because the carbs were tuned/tweaked by engineers from Rochester for the specific vehicle configuration during extensive driving at the GM test track prior to production. Variations include transmission type, jetting and adjustments, mixture rods, type of choke, fuel entry point, vacuum take-offs, etc, and I recall that some early smog-era carbs (1973 and later) even had plastic caps over the mixture screws that had to be broken to change the mixture (so smog station inspectors could spot carb-tuning violators). The stamped number reflects all the specifics of that particular variety. I never associated better gas mileage with post-smog carbs; my recollection is that mileage degraded rather than improved, as did driveability, but much of that may have been attributable to added smog equipment rather than the carb itself.

    I will try attaching some photos of my carb, as it looked when returned by the rebuilder:


  12. My 1971 Avanti (T400 trans) carb reads 7028208 DB.

    The "28" says it is a 1968 ("41" would be 1971); this carb would have been correct for a 1968 Corvette (Avanti Motors used base Corvette engines).

    I believe it to be the original carb, but I'm the 2nd owner of the car (purchased about 1979). I did send the carb away for rebuilding in 2006, and I was unable to find any old records to determine whether I'd recorded the number I found on it before I shipped it to the rebuilder... I seem to recall that I sent it out because it had a leaking/stripped fuel filter inlet (I normally rebuild my own carbs), and I did find an email from the rebuilder referring to having tested my carb on a test engine and that the filter housing helicoil didn't leak during the test, which bolsters my belief that the carb returned to me is the same one I sent him.

    This link has a code breakdown that might be helpful:


    Corvette carbs (base engine with automatic trans) for:

    1968... 7028208

    1969... 7029202

    1970... 7040202 (and later in the model year: 7040212)

    1971... 7041212

    Probably any of the above would work fine.

  13. I've not done the repair, but there is some good info on Bob Johnstone's website:


    Also, I copied info posted by "Billy" some years back about repairing the separation of an '87 Sky Top moon roof,

    and made a Word document from that. I cannot find anything on this forum now on that subject.

    I'm a bit uncomfortable about posting something here that was written by another forum member.

    Click the Avanti photo to the left of this post and send me a personal message via this forum with your email address and I'll send you that 284kb file.

  14. Not necessarily.... when Stude went out of business they still had a large parts stock, probably ordered in large lots for expected mass production. Altman bought the factory and the parts along with the rights to produce the car; there may well have been enough parts to last for many years.

    The Avanti power window switches of the 60's and 70's (maybe even early 80's) were also Ford parts, used on T-Birds.

  15. For backspace, if 4 1/2" backspace fits, worst case you'd need 1/4" spacers on the wheel studs, which isn't optimum, but might

    work. Stock wheels were 3 3/4" with 6" rim, Magnum 500 wheels were 4 1/8" and later wire wheels were 4", I think.

    But, it seems to me the wheel width is an even more serious issue, as it may very well rub the wheel opening lip in the front, not to mention the frame, during turns, especially if you hit a bump at the same time.

    Just for the heck of it, I went to the Coy website and didn't find a 19" wheel in that C67 style.

    Here is a writeup done about wheel fitting, but it doesn't directly answer your question...


  16. To get #7 (closest to firewall on driver side) I jack up the left front and with my upper body positioned below-left of the belhousing, I use a spark plug socket with a hex end (at the rachet end), placing the socket on the plug by hand and using a box wrench to turn the socket (ratchet box wrench would probably work even better than a regular box wrench, can't remember if I tried one). Remove the socket as soon as the plug loosens and turn it out by hand.

    IIRC, I get #5 and the others from the wheel well by using a long extension on the ratchet.

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