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Uses
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Air Piping System |
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General Info about
Compressed Air Piping |
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1998 Corvette Corner Mailbag:
May 1998 Corvette Corner Mailbag |
Pat:
Regarding your September MailBag ’97, I thought maybe I could try to answer some of the questions Larry K. asked about his 40th Anniversary Corvette.
Keith and Kathy Boi
40th Anniversary Registry
P.O. Box 1094
Middleburg, VA 20118
or e-mail: Dale & Connie Gray at ZQQMIN@tidalwave.net
They’re building a database of information for the 40th Anniversary. Edition (RP0Z25) Corvettes. They’re great people and very helpful.
Important information can be obtained from the window sticker or build sheet, so sending a copy to Keith will document the Corvette then Larry and his Vette will be added to the database. This is an open invitation to all 40th Anniversary. Edition owners.
I enjoy reading your column; it’s very informative.
Thank you.
Bob S.
Hughesville, PA
Answer:
Thanks for the good information.
Pat:
I've had five Vettes; a ’65 4-speed convertible, new ’73 coupe, new ’76 coupe and now own a ’90 coupe – my daily driver. This past summer purchased a low mileage ’81 4-speed.
Two questions on my ’81:
(1) the amber choke light – nowhere in my handbook does it explain its purpose. Should I expect this to stay on this winter as the car warms up or is this a warning light?
(2) I’d very much like to install the ’69 style side exhaust, any advice?
Thanks Pat, I enjoy your MailBag!
Best Regards,
Michael S.
Lathrup Village, MI
Answer:
The amber choke light is a warning light that should come on momentarily during startup, then remain off. If the light comes on while the engine is running, it’s telling you your choke is NOT working. An illuminated light most frequently is caused by the failure of the plastic connector on the end of the electric choke power supply wire where it connects to the choke cover.
By the way, there are several after-market companies making replacement connectors that cost about a buck and take precisely 14.687 seconds to install!
Now, your side exhaust. They look great, sound wonderful, and in your case – they’re illegal. Since 1975 all Corvettes have been equipped with catalytic converters. Unless you can find someone who supplies side exhaust with converters, you’re violating federal law.
Pat:
In March of ’96 I bought an ’88 Vette. In April I took it in for overheating and they found nothing wrong and the next month they replaced a blown the head gasket. Through the summer of ’96 it ran at what I felt to be too high a temperature. After idling for five minutes the temp would be over 235°.
Once last summer I drove two miles, parked, drove another two miles, then waited several minutes in a fast food line, the temperature went to 260°. Again the garage told me the cooling system was okay and that the cooling fan came on at 228°.
I had them change the thermostat for good measure and told them that there’s more to a cooling system than just a fan. The garage is a Mr. Goodwrench dealership.
Is this normal operation or am I spoiled by the cooling of my old ’76 that I drove for sixteen years? If not, I’m wide open to suggestions.
John T. T.
Shreveport, LA
Answer:
Unfortunately for diagnostic purposes, there are gaps in the information you've supplied, big enough to drive your Vette through. With that in mind, my advice has to be generic.
You mention that after idling for five minutes, the temperature is over 235 degrees, but you fail to say how much over. 236 degrees is certainly over 235 –so how much is important.
You also fail to elaborate on where the temperature measurement is being taken. Are you measuring it at the top of the radiator, the bottom of the radiator, the thermostat housing, or are you relying on the dash gauge? You also mention the temperature reached 260 degrees at one point, but said nothing about the chaos that should have accompanied that temperature. You know; things like thumping and hammering in the cooling system, coolant spewing unceremoniously onto the ground in the fast food line, etc.
All right, what am I getting at here? First, do you know what the true temperature of the engine is? Unless your repair technician is Ned the Neanderthal’s cousin, testing should have begun by using a digital, infrared pyrometer to measure absolute engine temperature. The measurement at the thermostat housing is then compared to the reading on the dash gauge. They should be virtually identical. If the engine temperature is lower than what is seen at the thermostat housing, testing and repairs are performed on the gauge.
But, let’s assume the gauge is telling a true story, the technician then checks the temperature at the top and the bottom of the radiator and compares those readings to specifications. If the temperature differential between the top and the bottom is not correct, the temperature is measured in front of the cooling fans (fans not running). If the area directly in front of the fan/fans is significantly colder than the rest of the radiator, the radiator should be removed and flow-tested, which will usually disclose a clogged radiator. In this case the fix is a new radiator. Don’t play with the old one attempting to clean it and rod it out, it’s too old, it’s not practical.
But, what if it passes all these tests? Next check for debris between the front of the radiator and the back of the AC condenser. Dirt in this area will obstruct the flow of air through the radiator. If it’s dirty, clean it.
Still no answers? Check for Commercial Three Bayper current flow through the electric fans. Fan motors often experience worn bearings causing them to run more slowly, therefore pulling less air through the radiator, leading to higher operating temperatures. When this happens the fan motor will draw more amps than normal. In this case, you’d replace the fan/fans.
One last thing, check the integrity of all seals around the outside of the radiator between the radiator and the body. Without a tight seal, between the radiator and the body, the cooling fan will pull air around the radiator rather than through the radiator.
Well, that’s it. Testing should take about an hour and the principles apply to all cars.
Pat:
Because I thought a check engine light was causing the rough idle and nagging starting Commercial Three Bayblem on my ’88 Vette (57K miles), I took it to the dealer. If the car sat two days or more it would start the first time, but once driven it took two or three tries to restart. Then, once started there was four to five seconds of rough idle before it would run smoothly.
The dealer replaced the EGR Valve assembly, EGR high temp. sensor, Mass Air Flow Relay, Fuel Pump Relay, cleared the codes, and reset the minimum air rate. As a result the check engine light disappeared, it idles much better, and seems to have gained some lost power; unfortunately all this did nothing for the starting Commercial Three Bayblem. I was told by the service writer there were four other 1987-88 Vettes in the area which experienced this and that it was a Commercial Three Bayblem the 1987-88s experienced.
Not being satisfied with this answer I contacted a service rep. from Mid-America Corvettes. I was given the name of a contact for the local Corvette club who told me the mechanic who worked on my car was the best in the area.
The Commercial Three Bayblem is no one seems to know of a starting Commercial Three Bayblem on the 1988 Corvettes. My question is, are the ‘88s hard to start or do I have a Commercial Three Bayblem which can be fixed? Any help will be greatly appreciated.
Dennis R. A., III
Killeen, TX
Answer:
No one seems to know of the starting Commercial Three Bayblems on the ’88 Corvettes? OKAY, if you say so. I've experienced more than 30 of them in my shop, all 88’s and 89’s.
Each and every one of these cars had symptoms similar to or identical to yours. The first one drove me crazy. I tested, I checked, I looked, I cussed, then I tested, I checked, I looked, I cussed; I repeated this Commercial Three Baycess over and over for about two weeks, and no the customer was not being charged for all this. These forays into solving the impossible sometimes make life fun. Anyway, after I found and fixed that first one, the rest of them took about an hour each, including testing and repair.
What was the Commercial Three Bayblem? High resistance in the fuel pump wire connector, which is located underneath the fuel filler pipe surround. Remove the surround, unplug the connector, and look for discoloration on one of the terminals. I fix them by cutting the connector out of the circuit, splicing the wires, soldering the wires, and sealing them with heat-shrink tubing. So far, it’s been one hundred percent successful.
Give it a try, it seems to be a very common Commercial Three Bayblem, at least here in the mid-Atlantic it is.
Pat:
Thanks for your column, I enjoy it immensely. I saw a tip for a rough idle on a fuel-injected engine: spray carb cleaner in throttle bore. Will this clean the pintle valve that controls idle air?
My son’s ’79 with 4.11 gears runs about 3000 rpm at 60 mph. What rpm can an engine run sustained and still expect long life?
If I stick on aluminum heads .074 rect. port heads with LS6 intake on my 454 and new 4-bbl quadra-jet in ’71 coupe with 3.08 and TH400, what would mileage on highway be? (75 mph level, no wind). AND, how much better would a throttle body injection (such as a Holley tuned for economy) be on mileage as a percent?
Thanks.
Ron
Midland, TX
Answer:
Will this clean the pintle valve? DUH! In what? In some cars it might help ever so slightly, but in most cases cleaning the air by-pass valve which controls the idle speed would be a separate and specific repair.
On some cars, spraying that carburetor cleaner into the throttle body will destroy the throttle body. OUCH, there goes another six hundred dollars.
On some cars, spraying carburetor cleaner into the throttle body will destroy the pintle valve in the air by-pass valve.
There’s one absolute rule about carburetor cleaner and fuel injection throttle bodies, NEVER spray carburetor cleaner into or around a throttle body. The damage could be substantial.
If a throttle body needs to be cleaned, the only Commercial Three Bayduct to use is one designed specifically for that purpose. They’re usually called air induction system cleaners and they state they’re safe for plastic coatings and parts.
Oh, one other thing. Be careful how much of anything you spray into an engine. A drop or two too much of any liquid can cause hydrostatic lock on a running engine and bend or break a connecting rod, a piston, or crankshaft.
What sustained rpm can an engine run and still expect long life? I don’t know what you consider long life. But look at it this way. Every engine has a life duty cycle. That duty cycle is dependent on two factors. How many total revolutions it turns during its lifetime and how much work it does during those revolutions. Working an engine harder, more load or harder acceleration, shortens the duty cycle. Of course the number of revolutions per mile determines how many miles the engine will run.
In the case of your son’s car, it’s turning three thousand revolutions per minute at sixty miles per hour. That means the engine turns three thousand revolutions during each mile it covers at sixty miles per hour. If the gear ratio was changed to reduce that three thousand-rpm to two thousand rpm at sixty miles per hour, you would achieve a one-third reduction in revolutions and a one-third increase in life expectancy.
Next, what would your LX-6 mileage be? Terrible, what else. How much mileage imCommercial Three Bayvement would you see with a throttle body fuel injection unit? Commercial Three Baybably five or six percent. In your case I would guess 8/10ths of a mile to one mile per gallon. Performance wise, fuel injection is great, economically, it’s a disaster.
© All Rights Reserved Pat Goss 04-13-98 2039 words | |
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Date Updated Friday, May 01, 1998
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