Man..it seems like everytime i try to fix my stinky old vette-a-roo it wants to tell me 'lick my corvette rear-end, just give up!'... i took the EGR valve off the manifold and blocked it off with a plate Holley sells and plugged the hoses that run from the Exhuast manifold up to the Smog pump which is off my 79 as well....not good when smog time comes :-( anyways, i watch my temperature gauge and at idle when i first start it up it runs fine, but after about 3 minutes i watch the needle moe to about 190...then 220...then about a second later the Thermastat kicks in *btw i didnt have one before the EGR vavle incident* and it goes to about 200 again. when driving though it gets REALLY hot, or so it says...it goes to about 270 or somewhere in the red area. but when i open up the hood after driving for about 20 minutes, i put my hand next to the egine valve cover *which i did while i had the EGR taken off* and its almost Cool! So then i replace my Oil, AND Temp Sender unit *the one on the side of the block the leaks like a Siv (sp) when u replace it. ok to give you the run-down this is what i have modified within the time of the overheating incident:

>upgraded to chrome stamped steel valve covers with a push-in breather w/ no tube to carb
>blocked off EGR valve with EGR block-off plate from Holley
> flushed tranny and put in AMSOIL synthetic tranny fluid and new gasket and filter
> put a Thermastat in the vette which previously didnt have one. 160 degree stat. now.
> car no longer has PCV valve which i plugged off with a vacum cap to bring idle back to normal *no plugged PCV = crap idle*
>used Clean-R-Carb on carbureator to clean gum off it.
> added some cheap off brand P.O.S Octane booster to tank
>Removed Fan shroud

any help would be GREATLY appreciated...Thanks in advance!

 

Your biggest mistake is removing the fan shroud. This will almost guarantee that your engine will overheat. Although, you should be able to clean the radiator nicely while it's off...

 

Get the fan shroud back on there.
Put a 180 temp t-stat in place.
Get a correct PCV valve and breather set up installed.

Did you use a gasket when you blocked off the EGR? If not, your sucking in air under the carb and causing a very lean condition. Even if you did, make sure it's sealed well.
Also I would bet money on those valve covers leaking in 6 months, I have never had good luck with the thin metal chrome plated ones.

 

One thing worth mentioning... it can be difficult to get the right temp sender. Often the units you get at parts stores, while listed as appropriate, doesn't have the right curve and reads way high. (Even Delco senders!) The only one I know of that everyone agrees works is sold by LetricLimited.

Good luck!

 

i would re check the t-stat.a new t-stat can be bad or it could be upside down .also replace fan shroud.

 

um...dont slap me but i uh...cut the fan shroud into about 15 pieces...whoops...with a reinforced metal blade on a drill....i think i made a big mistake. whats wierd is today when i was going to work at about 8 a.m. it was only about 70 degrees outside in Sacramento. the funny thing is i can watch the temp gauge as it rises to about 200 - 220 and then stops and starts to drop slowly, then when i hit traffic *assuming the same temp. outside hasnt risen much* i see it go back to about 220 and stay there. this is what happened this morning which surprised me because it didnt overheat or hit the red. after work though when i was going home i was hitting the middle of the red *about 270* and it felt a bit warm but NOWHERE EVEN CLOSE to what 270 feels like. i know what 270 feels like, my dads 454 which was a high performance block bored out and had aluminum everything hit 220 on a good day and a bad day was about 240 and then i could feel it getting Really warm...anyways.. this wasnt even my dfeinition of warm like on a summer day when its about 95 outside and ur unborn children are screaming "sweat Jeebus! turn on the A/c!" and ur block is Really hitting aboput 240. ok, enough of my retarded talk. do you think that maybe a blocked line in the core or something might be causing this? or should i try taking it to a shop to have the system flushed professionally? or maybe a new Rad? what would you all suggest? today i know for a fact it hit past 220 cuz i have one of those P.O.S. lift type rad. caps that releases the pressure when u lift the lever. think that might be the problem?? OH forgot to ask, what Does the PCV Valve do exactly? and why is my breather on the Passenger side smoking oil enough where its visible after the engine is warmed up? that normal?

 

Sounds like you need to go to the local book or parts store and buy some books on rebuilding engines, they offer much detail advise along with pics and diagrams than can be had here, once you have the basics down come back with questions.

Might even try the site www.howthingswork.com, they have a section dedicated to cars.

 

feel dumb saying this, but I have no idea what a pcv is/does. My money would be on the shroud though. From what I understand, the rad get little air flow without it.

180 thermostat would be good, but I have heard of people using 160. At any rate, checking/replacing the one you have now may not be a bad idea.

Is there a leak anywhere in your coolant system (wouldn't nec be a leak that pours coolant, just one that doesn't allow pressure to build)? After driving around is your upper rad hose firm or soft?

 

Not real sure how you can sense the difference in temp based on your dad's 454, but the shroud is used to funnel air through the radiator. Removing your shroud results in an extremely inefficent cooling system.

Get a new shroud on that car FIRST!!!

 

I did the same thing with my original Vette stereo, then found out they are worth big bucks to restorers...



OK - the PCV valve (positive crankcase ventillation valve) lets the high pressure from the crankcase (the inside of the engine where the crank is) out, otherwise the engine would bust out all of its gaskets and leak badly. The PCV valve is a one-way valve that allows the vapor to go out only. The smoking oil is the oil evaporating from inside the engine, just like water on a stove - especially at the high temps you are running. It's pretty normal to see this oil smoke. Anyway, the PCV usually routes back through the carb so that the oil smoke is mixed with the incoming air and gas, and is burned up in the engine. That helps keep the pollution down. Since the PCV valve lets the vapors out, for the PCV valve to work properly, it needs an inlet. The inlet for fresh air into the crankcase is usually a breather tube on the valve cover on the other side of the engine. It might have a tube from the air cleaner so it gets filtered air, or it might just be a filter on the breather itself.

 

I'm not sure what your goal is here, it sounds like you are trieing to disable all of the smog equipment you can find. If that's what you are doing, a stock motor will not run properly (especially if it's coupled to an automatic trans with a highway gear).

If you are looking for horsepower, you are better off changing the engine with a GM crate motor or rebuilding this one.

This is probably what you don't want to hear, but there is nothing you can do to a stock motor to make it quick without tearing it down or replacing it.

 

71coupe-
"will not run properly" ? please explain further. As far as the converter on the trans I agree, but I think there are a bunch of people with 81's that have disabled the smog equipment (computer included) and have been quite happy with the results.

Evil-
71 is completely right about how ditching the smog equipment will not make your car a rocket. You need some gears, cam, heads, exhaust, intake... etc for that.

 

The engine is built around the smog equipment - heads, intake, carb.
The main issue is the low compression ratio. You really can't do anything until you can bring it up to a performance level 9.5 - 10 to 1,
which would require the engine to be removed & opened up.

One thing if for sure, you will burn up the cat if you leave it on while you disconnect everything else. I've seen them glow red hot with a rich mixture.

I would check out a local machine shop & see what they have. You could pick up a rebuilt shortblock & start building on it instead of messing with a tired smog motor.

As far as the overheating problem - put the fan shroud back on

 

I agree that the compression is way too low for anything performance oriented. But I do not understand how removing the smog equipment would hurt the performance on a stock motor.

Lets say you tune the stock qjet as close to 14:1 as possible, that should keep the cat from overheating right?

 

Oddly enough, it looks like everything you have done so far only caused the engine to overheat and not add anything to horsepower. As Z-man said, the PCV is very important and must be re-installed ASAP to avoid really bad things happening. You need to get a vacuum hose routing diagram. The Haynes manual should contain one for your application if it's stock. If it's not stock, then check with the Bureau of Automotive (BAR) repair. You can also make an appointment with the BAR referee and he will look up a diagram of the system you should have in the car, and will make a copy of it for you...there may be a small charge for their time.

You should also see a huge number of threads in the archives about the fan shroud & air dam (which draws air from under the nose) and how not having one will make your engine overheat due to the radiator angle not being able to draw enough air from the front of the car.

And, unless you have the tools and measuring devices as well as the know-how to tune the carb and engine then blocking the EGR valve will not provide more horsepower...in fact it will reduce it and make your engine run hotter.

Using a carb cleaner around a carburator will dry up all of the existing vacuum hoses, as well as damage the internal diaphrams such as the accelerator pump, and sometimes the fumes will reach to the distributor advance and cause leaks there too.

All things considered, I think you should take the car to a shop and have the pros look at it. Corvette Care is where I take my vette...it's located down Sunrise south of highway 50. I suspect you need a carburator rebuild, a fan shroud and possibly air dam, EGR valve, Air Reactor pump, PCV valve, probably the distributor advance diaphram, and all the vacuum hoses. Then tuned and cleaned up.

My guess is it needs about $100 of parts, and about $400 labor (mostly to rebuild the carb). You can do it yourself of course, but it sounds like you will need to change your tack drastically, and sit down with some books. The Haynes and Chilton's manuals are good and available at AutoZone and/or Kragen. You can also get the Assembly Manual for your year vette at Corvette Care.

Good Luck

 

Please take your Vette to a reputable shop or find someone that knows about engines quick. If I skimmed correctly, I see that you removed your PCV valve, (Positive Crankcase Ventilation) NO GOOD! You're probably losing power from that little mod. PCV valves take the vapors from the crankcase created by the blowby every internal combustion engine creates, and cycle them back through the engine to be ignited. A stuck PCV valve will most likely blow out your oil pan gasket, and no PCV valve will just make your car run like azz. Removing the EGR valve doesn't really help with horsepower at all either. Since it's usually open at cruise speeds, it doesn't really matter. Losing the fan shroud is no good either. The fan shroud, as mentioned earlier, directs air to the radiator. Without it, the air goes wherever it wants, usually not through the radiator. I'm thinking if you try to repair this stuff yourself, you're gonna do some damage. If you have any questions, we're always here to help ya... Good luck!!

 

Not without the smog pump. Honestly, there is really no sense in playing with a stock motor. My advise: Keep the original motor complete with everything attached & functioning (EGR, AIR, etc). When you are ready to build power, build another motor then crate up the original. You will be glad you did considering what smog parts cost if you ever go back to the original setup

 

as far as smog equipment, i can get it somewhat cheap cuz i work for Napa, but i hear what your saying. the fan shroud, i thought about making one of light gauge sheet metal er, did i say that out loud *metal + heat = no no* i have a quick Q. about the cooling system. is it possible to burp the system on a stock vette and if so how? *by burping i mean getting the air from the coolant out of the system* someone said find ur Temp sender light switch and burp it that what but i dont see one? One good thing about me doing my own work is the fact that i see results, but i think whoever said i might do more damage then its worth is probably 60% right....ok 80%...lol um im sorry about the names, but whoever said they have a Corvette place down on Sunrise near Recycle road i think it was? i think they call that one Corvette world unless your talking about another place that im not aware of. Oh, and if you have heard of Motor Machine or if you recommend anyone who can rebuild a stock without the smog can you refer? Is that a wise decision or should i go for a block and build one up, cuz im on a tight budget...when i mean tight i mean $8.50/hour kinda tight now figure that into a corvette kinda lifestyle/upkeep lol

 

wow, i type a lot...i just realized that after being high on oil fumes from my valve covers for the last two days...doh

 

Sorry, I don't mean to be a pirate

71coupe-

Do you mean that the qjet cannot be tuned 14:1, or that the cat will still burn up even if it was?