carburetion issue??

[Stuart F.]

Re: carburetion issue??

Installing an "anti dieseling solenoid" is not that big of a deal, and I'm sure it can be done w/o butchering your wiring harness. Making street modifications that enhance your driving pleasure do not have to be irreversible. I've done a number of things to my 63, all of which can be changed back to stock in a reasonable period of time. I never damage or destroy any of my original parts.

Stu Fox

[Leif A.]

Re: carburetion issue??

Installing an "anti dieseling solenoid" is not that big of a deal, and I'm sure it can be done w/o butchering your wiring harness. Making street modifications that enhance your driving pleasure do not have to be irreversible. I've done a number of things to my 63, all of which can be changed back to stock in a reasonable period of time. I never damage or destroy any of my original parts.

Stu Fox

Stu,

The holes are pre-drilled in the carb base just below the linkage to accept the solenoid so this carb base must have been used on other applications where a solenoid was required. Haven't totally written it off...just as a last resort if all else fails. Other than ethanol in our gas today, the setups from 47 years ago should, hopefully, still apply. I just don't remember ever having these issues back in the day. I know these cars were new then and they're old now but mine is "all new" again.

[Duke W.]

Re: carburetion issue??

Before you spend time and effort/money installing an idle-up solenoid, follow my recommendations and you will probably find a satisfactory solution. If it idles a little higher when the compressor is off, so-what. Apply Occam's Razor - the simplest solution is usually the best.

Consider the HEI versus the TI. The circuit diagrams are essentially the same, but improvments in technology allowed the remote amp and harness to be replaced with a thick film hybrid circuit inside the distributor with the coil mounted directly to a distributor. It's a complete integrated system and a very elegant design that can be completely overhauled with all new readily available electrical parts for less than a hundred bucks, but it's amazing how many guys throw them away when they fail (after 30-40 years of service) thinking they are "junk" and load up their car with a bunch of overpriced aftermaket ignition system parts.

Your VAC is definitely suspect (but we need the stamped numbers and start stop test results) since mechanics who replace them don't understand the Two-Inch Rule and replacements are often not properly matched to idle vacuum (Hey, they all look the same - parts is parts!), which causes all kinds of problems, and guys often end up spending hundreds of dollars trying to "fix" the problem when it may be nothing more than an incorrect ten dollar VAC.

Ethanol has nothing to do with overheating, but percolation is a problem due to the reduced 40-60 percent boiling point of E10 compared to most straight gasoline blends.

About a year ago I helped a local chapter member evaluate his recently purchased '65 FI that was running hot. It took me some time - about two minutes - to find that Bubba had plugged the VAC line with a BB. The original MS 236 16 VAC still met spec as did the centrifugal advance - 24 deg. at about 2350. I set the Total WOT advance at 39 at about 2700, blipped the throttle to about 6000 to verify that it did not overadvance, connected the VAC, and went through the idle speed/mixture adjustment procedure.

It ran cooler, but still hotter than it should, and I told John he should budget for a new DeWitts to replace the nearly fifty year old original, which he did, and coolant temperatures are now normal - usually no more than 180 except when stuck in a traffic jam in hot weather, but there is now plenty of cooling margin.

Including setting up/tearing down the test equipment it took a total of about 15 minutes to diagnose and correct the problem and optimize the spark advance map, and the parts cost was zero!

Duke

[Leif A.]

Re: carburetion issue??

Duke,

That's absolutely brilliant and, truly, is what I am planning on doing with mine. Step by step, inch by inch, just as you have described. Will certainly take me more than 15 minutes but I'm in no rush...just want it to be as perfect as I can get it. I hope I have the opportunity before the week is over to attempt your process on my car. Just as an aside, there have been over 800 "silent" views of this post...something tells me that there are a lot of other owners benefiting from all this sharing of knowledge. Thank you!!!

Leif

[Leif A.]

Re: carburetion issue??

First report back after getting my hands on my car after install of DeWitts 941 radiator. Duke, you're going to stroke out here but bear with me...I need to crawl before I can walk and I'm crawling. The vac canister currently on the car is a B1 (I know, "boat anchor") that starts coming in a 8"hg and is all the way in at 20"hg (I have new in the box B26 4"-12" & B28 4"-8"). Manifold vacuum, measured at the base of carb, is 14"hg at 850RPM. With A/C on RPM drops to 600 and 12"hg. As we say here in Texas, it's fixin to get better. The A/F screws on my Holley list 3810 are fully seated and the car runs as smooth as silk...no hesitation, detonation, run-on or anything. Smooth take aways from dead stop...purrs like a kitten. Carb was just rebuilt...supposedly. After gathering this information I thought it might be a good time to stop and report in before I even attempt to do anything, because I don't know where to start. Everything according to what everyone has told me is completely wrong yet the car runs smoothly. How can this be? How can the carb function with both A/F screws bottomed out? I attain 10"hg with the screws all the way in and the mercury doesn't change as I open the screws all the way to 1 1/2 turns each. Only idle comes up approx 100RPM. Tell me where to start. Car, also, has Lectric Limited's BREAKERLESS-SE ELECTRONIC IGNITION CONVERSION.

[Duke W.]

Re: carburetion issue??

The boat anchor has no business on ANY Corvette engine, so there's no point doing anything until you swap it out. Because you have A/C for the reasons I stated previously, suggest you install the B28.

Assuming you have about 8-10 degrees initial advance the total idle advance should read about 24-26 with the A/C compressor engaged at 600 and maybe a couple of degrees higher at 850 if the centrifugal starts below this. In any event, it should be steady except for a little spark scatter due to typical excess distributor end play.

It's very odd that the idle mixture screws seem unresponsive, but do one step at a time. Install the B28 and go from there. Trying to set the idle speed/mixture with incorrect total idle advance is a waste of time.

The breakerless system is likely not part of the problem.

You should check the centrifugal curve against specs, and since OE is real lazy, lighter springs should improve overall performance.

Duke