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Questions on my 79

D

desertsled

Guest
Hello folks this is my 1st memo, any help will be app...

1. can I change the rear leaf spring in my garage with a floor jack and 2 stands? I dont want that thing bapping me in the head. How hard will the center bolts be to remove? The shop wants to charge me 2 hours labor 140.00

2. I have the 3 speed auto. Here in Nevada, the speed limit is 75 mph, so everyone goes 80-90. If I take it over 65 mph, my temp gauge edges up to 220. As soon as I take it off the highway, it goes down to 175-180. Is this due to the very high rpms ? (3,500-4,000 @70 mph) I have replaced all of the coolant with 40% dexcool and 60% h2o. Water pump is new with engine. I also have a new fan clutch (how does that thing work anyway?) The themostat is good cause it falls off right at 185. I even tried water wetter (waste of 6 bucks) Do I need overdrive? 2,135.00 dollars, How about changing to a 3:08 rear gear? 750.00 dollars. Im worried about the summer here in Vegas
105-110 degrees is not uncommon. Will that plastic secondary fan come on during hot operation?, or is that only for the AC?

3. I want to fix the A.C. soon. Some mechnics told me to stay away from 134-a. It wont work and it will over pressure the system. Is it even worth it considering problem #2? I Know the compressor is bad. Any tips on replacing the accumulater ? I can barly see it no less remove it.

Thats all for this installment of "the never ending tinker toy in my garage"
 
7

78SilvAnniv

Guest
Running hot and cold

I had the same problem as you with higher speeds resulting in higher temps, and I didn't DARE use the AC! We replaced fan clutches regularly with no results that I could see. Summer was drive slow and winter was now-I-can-finally-drive-faster.
Last summer we removed the fan clutch and installed a flex fan and it has yet to go over 195 at higher speeds in the summer, or with the AC on. I usually only use the AC around town because I like the feel of the humid air at driving speeds. Sooo much nicer than CA's dry oven heat!

I re-did my entire AC system about 4 years ago, upgrading to the 134-a and I have had no problems. You cannot just put 134-a in your original system and expect it to handle it. Certain key elements of the system must be changed out to accept the higher pressures and temps of 134-a. Any reputable AC shop will be able to inform you.
Silver aka:Heidi

btw, welcome to CACC desertsled!
 

1979toy

Well-known member
Joined
Mar 20, 2001
Messages
263
Location
Wichita, KS
Corvette
Red on Red 1979 L-48
The rear spring can be changed with the tools you listed plus a C-clamp and a wood block. Use the clamp and wood on the spring to keep the jack from sliding inward when the spring is jacked. Buy new bolts with rubber or poly bushings for the trailing arm end of the spring.
Do you have the chin spoiler on your car? Is it in good condition? The spoiler directs air to the bottem inlet for the rad. Look in to having your rad. AND BLOCK flushed out. Have your ignition and carb jetting checked to insure that you arn't running lean or too much advance in cruise conditions. A dyno shop should be able to do this for you. 200 degrees is not all that bad if you don't run the A/C.
 

80convertible

Well-known member
Joined
Jan 26, 2001
Messages
416
Location
Asheville, NC
Corvette
1973 converted to 1980 custom convertible
Before you go changing the tranny, you need to inspect and repair the cooling system. I drive at over 3,000 rpm at 70+ mph and never break 180 degrees with a manual tranny. I have repaired/replaced and modified the cooling system for maximum efficiency. Several things to consider: airdam, seals around radiator, professionaly cleaning radiator, fan clutch, hoses and thermostat. As you can see, there are many factors involved in a proper cooling system. My guess is that if you do all the above mentioned first, you will see cooler temps with your existing tranny. One last thing to consider is replacing the fan and fan clutch with an electric fan.

Regards,

Jim
 
S

sac001

Guest
Changing the Rear Spring should be pretty easy. The worst part will be trying to remove the bolts at the outer ends of the spring where they connect to the T-Arms.

When you get to that point, best bet is to cut off the nuts, and replace with new bolts nuts and polyurethane bushings.

The cooling system as suggested really needs to be worked over. There are too many variables, follow the advice above and you should be in good shape.

Welcome to the CAC!

Steve :w
 
D

desertsled

Guest
79 problems

First , thanks to all of you for replying.

Silver... Heidi , so the flex fan is the way to go . Too bad i just spent all that money on the new fan clutch. Today it hit 81 degrees here in Vegas, so I was eger to drive the Vette in town. The gauge read about 190-195 consistantly. What I think Im getting from your note is you dont want the fan to turn at high rpms or highway speeds. Does the clutch work on rpms or temp? or both? On the AC.. retrofit, did they replace the o-rings, acculmulater-drier, and tube? anything else? How bout that secondary fan???? does it come on just for the AC, or also the cooling system?

79toy... Yes I do have a working chin spoiler as well as good duct work. I wonder if it really opens while driving We'll never know. Good point on the timing and jetting. as far as the timing goes It reads 10 degrees btc @ 1800rpm As far as jetting...the air-fuel screws are set for it to pass our smog tests. P.S. the big chevy dealer in town (BILL HEARD) has a vette tech, and he said 230 degrees is normal for here in Vegas.

Jim... What kind of ambient temps do you have in North Carolina?
My temp problems start at around 3000-3500 rpm (60-65 MPH) For me with the 3 speed auto, 70 mph is pushing 4000 rpms. I wish I could do 70 mph and only push 3000 rpm. What about that stock secondary fan? can I wire it to come on if I need it? It just sits there and does nothing .

Steve... The spring end bolts are easy . Ive had them out already. Its the center ones im worried about. I was under there today and I see my strut arm bushings look and feel like beef jerkey. What do you think about thoes adjustable ones for 99.00 pair in mid america? They come with new bushings and you can eliminate the stock adjusters.

Thanks all of you, Mark.
 
R

rpounds

Guest
Mark,

I thought I would chime in here regarding the heating problem. My '75 had the same problems. The fan clutch checked good, I replaced all of the missing rubber seals around the radiator, changed the thermostat, ran different mixes on the anti-freeze, the air dam was in place, tried water wetter (you're right . . . a waste of money), replaced the lower radiator hose thinking that it might be collapsing at high engine RPMs . . . you name it, I did it. Darn thing would still run 220 at 65-70 mph, even on a fairly mild day.

Finally, someone clued me in to the fact that the copper and brass in the radiator, over time, loses it's ability to transfer heat. It very simply becomes less and less efficient. Since it was the original radiator and since I had tried EVERYTHING else, I decided to bite the bullet and buy a new radiator. R&R on the radiator is a pain in the buttocks, but now $290 later, air conditioning on, running even 70-80 on 95 degree days, it runs thermostat temperature . . . if I run a 160 thermostat, it runs 160 . . . 180, it runs 180, etc. If you have tried everything else, R&R the radiator.

I might mention here that the clutch fan really doesn't do much of anything for you at higher speeds. If the car cools well at lower speeds, I would suspect that the clutch fan is working properly. Remember that at lower engine speeds, the engine puts on less heat. As RPMs increase, the frequency of combustion also increases, not to mention the load on the engine . . . therefore, there is more heat to dissapate at higher speeds . . . heat that the radiator can't keep up with. Also, the coolant is moving through the radiator at a higher rate of turn over at higher speeds, so the radiator has less time to act on the coolant as it passes through the core. Anyhow, I hope some of this helps you out from someone who 'been there, done that'.

Sorry, I can't help with the spring question, but as far a third member ratio, I'm running the stock 3.08:1. At 70, I tach up about 2700 RPM or so. As I said before, air on, running hard, hot day . . . it now stays cool.
 
S

sscam69

Guest
Suggestions

Run a search and you will find plenty of previous posts and answers to the questions you have.

Flex fan is not the answer. When you reach higher rpms the fan blades straighten out and reduce the amount of air it pulls in. It sounds like to need more not less. Technically speaking after you begin to cruise your car should be able to push enough air just from the motion to cool the engine hence the front spoiler.
Those are high rpms you are cruising at and I seriously doubt the flex fan is going to help.

230 is to high, I don't think its "normal". There are some engines designed to run "hot" 200 deg or so but not these older engines. Your engine can handle the heat but you are going to run into other problems. When I am cruising at 3000 rpm (@75 mph) my temps go up. when I drop to 2500 rpm it goes back to normal. Thats easily explained, basically you are firing your engine a heck of alot more at 4000 rpm and you need a better cooling system to handle the heat that is being produced. If you start reaching 230 F pull over and cool the car cause you running a risk.

The clutch runs off of temps. It should be able to rotate freely when the engine is off. You do not necessarily need it to be running at its full potential all the time. There are posts that go in depth about why, run a search. When the engine gets hot or overheats it locks to pull more air in.

That flap in the bottom? I had the same problem with my 79 and one of my questions was what was that flap at the bottom for? Its a waste gate. When you are not moving and that fan is moving air in the engine bay will get hot. There is not much room for that air to escape from the cramped space. That flap is suppose to open when the temperatures get high to release the hot air. I don't trust it very much.

This is what I did to relieve the problem. First I had the radiator flushed with new fan clutch and hoseing. I made sure there were not any leaves or stuff stuck in the radiator and cleaned it all out. One thing the previous owner did was somehow went to a smaller diameter fan. Why I don't know. The duma$$ also melted the sides of the shroud. I replaced the shroud and put the right fan in. It should be 18". I also, just in case, put a 16" electric fan against the radiator with a 180 deg switch.

Summer is coming soon and we also see 110 deg days around here. We will see if everything pays off.

sscam69
 
H

hotrodd

Guest
I think the stock temp.for the electric fan is around 230.I changed sending unit and put in a 185.It helped in town.I found out how important the air damn is when I took mine off,run's about 220 when it is 60 degrees outside.
 
S

sscam69

Guest
rpounds posted before i did.

Well as you can tell rpounds and I touched on the same base, so it seems. LOL he posted before I could finish. There is two important points though.

1. Those are really high rpms you are running at, really! Just to cruise at 70 4000 rpm, GEES!

I put in the stock 3.08 gear on mine. It cost me $500. $100 for labor $400 for parts. Go figure. It had a 3.8 before and was doing almost 3000 rpm at 70 mph if i remember correctly.

2. Rpounds mentioned "fouling". Its just a million dollar word for oxidation. If you looked inside your old pump or took a flashlight and peeped through the holes where the pump hooks up you would problably see oxidation forming on the walls. Its white crudy stuff. The passages in the radiator are small and this stuff gets in there and clogs this up and makes it harder for the radiator to cool.

So you could

pull the radiator and have it cleaned out or buy a new one as rpounds mentioned. If you could afford the expense get an aluminum one.

sscam69

Chris (69myway) is selling two. I don't know if he has sold them yet but they are aluminum and cheap. You might want to check it out.
 
S

Stryker_78

Guest
I replaced my spring last year. It was pretty easy once I figured out an easier way to do it. I lowered the car onto the jack and used the weight of the car to compress the sides of the spring to be able to remove them. The centre bolts are nothing to worry about.Once the end bolts are off and the spring is hanging, then remove the centre bolts.It is the reverse to put it back together. I also used poly bushings. Note: Did you buy the 9 or 7 leaf spring? The 7 will give you a much harder and less comfortable ride.

Is your rearend ratio 3.55:1? I just put in that ratio. Up from the original 3.08:1 ratio. My tach at 70 MPH is currently at around 3000 rpm. I too have a 3 speed auto. I am going to a 4 speed auto next summer to bring down my rpms. The price you gave for the new transmission seems quite high. This site sells the tranny you might want to consider. The price seems very good. Installation will not be that much either. :)

http://www.700r4.com/sitemap.html

My temperature never goes over 210 even on the hottest of days. But my hottest of days isn't quite as hot as yours....However I do not have A/C to tax the engine either.

Just my $.02.

Good luck.


Scott :w
 
S

sscam69

Guest
excuse me for being rude!

Welcom to the CAC. You are going to love this place!!!

sscam69
 
7

78SilvAnniv

Guest
Showing my ignorance...

I'm not sure what secondary fan you are talking about. The only fan I know of in my engine bay is the flex fan, formerly the fan clutch.
I have read posts where people do not reccommend the flex fan, but for my particular application, it worked.
As I said, we replaced the fan clutch quite regularly, with little results. New radiator, fan shroud (old one had a 'cut' taken out of the top...probably due to a broken motor mount in its past), hoses, coolant mix and a new GM crate engine.
Still ran hot in the summer heat. Turn on the AC?...engine temp climbed to 240! :eek
For me, the flex fan solved all of my run-hot problems.

I recall purchasing two big-ticket AC items (one was a new compressor) , and the AC shop did everything they were supposed to...but I don't know exactly what they did. The o-rings and accumulater sound familiar...but I think there was something else, too. I recall hoses needed to be a certain kind, too.
Silver
 

chuck

Well-known member
Joined
Feb 7, 2001
Messages
193
Location
Tallmadge,Ohio
Corvette
1977 Dark Red Coupe/Buckskin 04 Spiral Gray/Gray
rpounds said:
Mark,


Finally, someone clued me in to the fact that the copper and brass in the radiator, over time, loses it's ability to transfer heat. It very simply becomes less and less efficient. Since it was the original radiator and since I had tried EVERYTHING else, I decided to bite the bullet and buy a new radiator. R&R on the radiator is a pain in the buttocks, but now $290 later, air conditioning on, running even 70-80 on 95 degree days, it runs thermostat temperature . . . if I run a 160 thermostat, it runs 160 . . . 180, it runs 180, etc. If you have tried everything else, R&R the radiator.

.
This should solve your problem with the overheating
 
S

sac001

Guest
On the rear spring, as stated above, the center bolts going up into the Differential should be easy to remove. As far as the strut rods, you don't need to mess with the Camber adjust bolts to remove the assembly. Before you start, mark them with a crayon, in case you need to loosen the nuts to wiggle the unit free of the differential. (If so, only loosen the nuts, put a wrench on the bolt and keep it still, then it won't mess with the rear wheel alignment.) I think the new setup is probably much better, but if there is nothing wrong with your current strut rods, why replace them now?

When I dropped my spring, I made a compression tool out of some angle iron and 1/2" threaded rod. One piece of angle went over the Differential carrier, and the other end under the spring. Put a "C" Clamp behind the angle so it doesn't slide when compressing the spring. Remove tension from the bolts, unbolt them, unbolt the center, release tension on the spring (loosen the compression tool) and voila! (I actually had to do this two or three times, and by using this tool, life was considerably easier.)

Good luck, and keep us posted.

Steve :w
 
P

page62

Guest
I just spent close to a thousand bucks to fix up the A/C in my '79. I decided to stick with R12 due to the South Texas heat.

There are some jobs I believe should be left to the "pros", and A/C is one of them.

So now I'm broke but satisfied. The first thing the A/C shop discovered was a weak fan clutch (which is part of the high overall price).

They also replaced the compressor with a rebuilt unit, 2 hoses (custom welded -- no hose clamps like previously), accumulator...just about everything except the condenser and evaporator.
Before the fan clutch was replaced, I noticed the engine getting up to 200 once, then cooling off quickly for some reason. So far I haven't had cooling issues, despite 80 degree days and having what I think is a 3:73 (or perhaps 3:55) rear end.
 
S

sscam69

Guest
Man it is humid down there. I was born in McAllen Tx.

Even at night with the windows down cruising you sweat.

Golden rule "stay inside with the air conditioning"

Thats money well spent especially in these things!

sscam69
 
D

desertsled

Guest
Thanks to all of you

O.K. after scouring over ALL these suggestions and comments..........the winner is.... just kidding LOL. Actually I dont even have a Vette.
Its a hot red Yugu. :L

Just kidding again. LOL

I see we have some mech. engineers with us and they brought up some really good points. Rpounds had a very good point about the lower rad hose might be collapsing. can I check that with high Idle? Also the waste gate?
About the rad being old and less efficient,... Ive pulled 35 year old copper and brass out of buildings Ive rehabed, and the only thing Ive seen with age is thinning side walls (due to the scouring effect moving water has on copper) so I would believe the rad should be even more efficient (allthough weeker) as it gets thinner with age. As for heat transfer capability...thin metal conducts heat faster then thick metal, so this would mean older , thinner rad = faster and better heat transfer. (of course untill we pop a hole in it) O.K every one can lower their pant legs down now. :confused

Something else I failed to mention... The origional owners might have changed the coolant once , mabey twice. It was brown and old smelling. I mean the next door neihbors cat didnt even want to drink it!! LOL. when I flushed it. Would it be safe to assume that the small openings within the rad might be part clogged?

sac001... Ill do the strut rods myself , but as far as the spring goes, anything I need to fabricate a holding jig for sounds too scary for me. Last summer I was changing a tire on my boat trailer when the jack slipped and cut off the end of my middle finger (no they couldnt reattach it "not much to work with" doc said) So im a little apprehensive about that

Heidi.. are you sure you dont have a second fan? its thin and sits right up against the inside of the rad. Hotrodd says he thinks it comes on at 230 degrees (a little late?) Are you running hot with the air on even with the flex fan?


Hotrodd. Steve... What does it take to change that temp senser from 230 to 185? how about a switch?

Thanks everyone ..think Ill wash the Yugo err.. I mean Vette!!!
 
7

78SilvAnniv

Guest
Second fan.

Nope.
I just ran outside with the flashlight to check, no fan other than the flex fan. I did not see anywhere where there may have been one that was removed, either. I looked on both sides of the engine radiator and AC radiator.

AC, in town or hwy driving fast or slow...temp stays below 195 with the flex fan.
Heidi
 
S

Stryker_78

Guest
A holding Jig????

I did not require a holding jig when I removed my spring. Just use a jack with a pivoting head. I was however using an hydraulic lift. I lowered the car down onto the the jack with the pivoting head. The weight of the car was more than enough to keep the head planted onto the spring. Trust me it won't budge. I am not a mechanic and it only took me an hour to get this job done once I figured out to use the weight of the car to get the spring compressed to get the tension off of the end bolts so that the could be removed. I wish I had a picture of my setup. My manual said to use a C-clamp, but I did not need it.


Sorry to hear about your finger. :(


Good luck.

Scott
 

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