78 turbo lesabre

[Dirtexpo]

I just had the engine rebuilt in my car, but when we started putting everything back together, the vac lines where all crossed up. I put a new stock turbo on, cam etc. But the two vac lines from the turbo were not on the vac diagram. Can anyone tell me or show me where those lines go.

 

[b4black]

The two ports are on the wastegate actuator. One pushes the rod out, opening the wastegate. This is the port furthest away from the wastegate. Connect it to the turbo compressor's foot (outlet). The pressure/boost forces the diaphragm out. There is another port on the compressor foot that goes to the boost light switches.

The other (closest to the WG) port is a mystery. From the factory it is connected to plenum, just before the compressor. I think vacuum assists the spring inside the actuator that holds the WG closed. I find this port usually leaks inside the actuator. The spring is under a lot of tension and doesn't need extra help. I always disconnect this line and cap the plenum port. This is what the turbo rebuilders I have spoken with recommend also.

 

[Dirtexpo]

78 turbo vac lines

I am seaching for answers. On my 78 Lesabre the wastegate has one vac port on it. I'm trying to install my turbo I'm getting no boost. The turbo has two vac ports on it which is said to go to the wastegate, but the wastegate already has a hose on it running from the pcv valve. So if the line from the turbo goes to the waste gate where does it go.

 

[Ttype83]

Re: 78 turbo vac lines

Originally posted by Dirtexpo
:On my 78 Lesabre the wastegate has one vac port on it.

Good, you only need one for now

I'm trying to install my turbo I'm getting no boost. The turbo has two vac ports on it which is said to go to the wastegate, but the wastegate already has a hose on it running from the pcv valve. [/QUOTE]

The vac line is wrong, the pvc should be connected the the back of the carb. The wastegate actuator needs to be connected to the compresser foot like B4Black said. This is way you are not getting boost, no pressure to open it.
HtH
Jim

 

[Dirtexpo]

Is there anyone who can send me or a link to a diagram of the vac hoses for the 78 lesabre engine. I don't know if the rest of the lines are in properly.

 

[Dirtexpo]

Is there anyone who can send me or a link to a diagram of the vac hoses for the 78 lesabre engine. I don't know if the rest of the lines are in properly.

 

[Dirtexpo]

low boost

I just dont know what to do. My lesabre has been in and out the shop , their trying to figure out the problem, but they are stuck. I was driving on the freeway and the car started backfiring. When I took it in the mech. said that it might be a elec. problem, and that I was never getting any boost from the begining. I never noticed because I never drove the car hard. They went through the wiring and said thats OK. The problem I was having is low boost from the turbo. He told me that the 2 in pipes should be larger 2.5 or 3. My thing is with the motor being bored over 30, new cam,rods and pisons I should be getting more out of my car. Where am I going wrong.

 

[b4black]

Originally posted by Dirtexpo
Is there anyone who can send me or a link to a diagram of the vac hoses for the 78 lesabre engine. I don't know if the rest of the lines are in properly.

Sorry I missed this before. Assuming you have a 4-barrel:
'78 A&B vacuum diagram - 4 barrel

If there are any electrical problems, I would start with the ESC (Turbo Control Center) first. Read this page Knock, Knock and Peter's wesbite as well (my link is dead; Peter, where did your site go?). Temporaily bypassing the ESC could help diagnosis.

You must get a boost gauge. The stock set up should not have any problem getting to 9 psi. If not, the first thing to look for is a restriction (plugged cat?).


With all the work going into the motor, I would go with '79 and later heads. They have larger intake and exhaust ports. Then you would need a '79 intake and exhaust manifolds, but that can be done later. CHANGE THE HEADS while they're off. Junkyard heads are dirt cheap.


We can help you with this car. But it gonna take some homework on your part. Read everything you can, because there are a few things different about a Turbo Buick than the average engine. Maybe print this stuff out and see if your mechanic while do some homework as well. A Buick shop manual (check ebay) will help a lot tool.

Keep us informed, so we can help!

 

[Dirtexpo]

low boost

I talked to my mech. today and no answers. The problem is still low boost. I dont know what the problem is. The vac. line diagram is the one we used so that part should be right. We thought that the 2 in. pipes were to small thats not it . We thought that it was the turbo box, thats not it. What the differance between the 78 and the 79 intake and exhust manifolds, heads etc. AND WHAT TO DO ABOUT THIS LOW BOOST

 

[Silver 6]

Just a thought...

Do you still have the original pellet bed convertor? These were very restrictive and it could be clogged. Exhaust back pressure would cause much of what you are reporting. You could have them do a pressure check.

 

[b4black]

Since the '79 heads have larger ports, the intake and exhaust manifolds need to match them to take full advantage. The '79 head is much better than the '78. If you drill and tap a hole for the knock sensor on the back of the block you can use a 1980 aluminum intake (after moving the sensor to the new hole). Something to consider if you ever have major engine work done again.



How do you know you have low boost and how low is it? Check and see if you secondaries are opening. Try clamping the wastegate shut and slowly get into the boost to rule out the actuator (you'll really need to boost gauge for this.) Can you unhook the exhaust before the converter?

 

[Dirtexpo]

low boost

The mech said that the boost light was showing boost. And I remove the cat when I replaced the exhuast.

 

[Dirtexpo]

slow take off

I got boost. the turbos kicking in , and am getting good power. The problem now is a slow take off. I still have work to do to the rear end and pipes. I want to know what differance will I feel with the bigger rear end (373), will it solve my problems on take off or is that the way the turbo cars feel. Another thing was the pipes the Mech. said that I had 2 in pipes and I needed 2.5, could that be the problem on take off. I put the 2 in pipes on, but I didn't know that 2.5 in pipes was the size that was on the car when I removed the Cat.

 

[b4black]

The turbo will always have some lag, but it can be made worse by a number of things. It's hard to describe what is normal. A common problem is too cold incoming air. (The carb is metered for warmed air). If the THERMAC air cleaner box (and the tube to the exhaust manifold) has been messed with, or the coolant to heat the plenum has been turned off, it will cause sluggish take-offs.

Exhaust restrictions come into play by limiting max boost. They aren't a problem for takeoff. I wouldn't worry about the 2" pipe. -the downpipe is only 2" from the factory. The converter was likely the biggest restriction.

What rear ratio do you have now? 3.73 is pretty steep for a non-OD trans. I would stick to about a 3.08.

Your mechanic sounds like hes making good suggestions for performance modifications, but your still in the "get it running right" phase. You'll get much further with a good running Turbo V6, than you will by compensating for probelms.



My '83 had both lights turning on and I thought I had good boost. When I added a boost gauge I saw I was only at 6psi. I fixed a minor problem on the carb and went to 9 psi. 6's was nice, 9's better.

 

[Dirtexpo]

slow take off

The hose coming from the air cleaner tank to the lower driver side of the motor is not connected. Could that be the problem and what does it do?

 

[b4black]

THERMOSTATIC AIR CLEANER (THERMAC) - The air cleaner is design to provide an incoming air temperature of about 115 degrees (F). A temperature sensor is in the carburetor elbow and is used to control a vacuum actuated damper door in the snorkel of the air box. This door on the snorkel blends incoming air with air heated by the right side exhaust manifold, via a very narrow duct. This improves winter weather driveability. Warmer climate and summer only driven vehicles can do without thus system. During WOT acceleration, the (carburetor) vacuum drops to zero and the door will slowly open to allow unblended air through the snorkel alone. There is an inline delay valve which could be remove for quicker opening of the damper door.

Without the tubing, the THERMAC has no source of heated air. Make sure the damper door is working. Make sure there is a place on the manifold to connect the hose. There should be a heat shield (stove) over the manifold. The tubing is available at most auto parts stores (you may need to use two short ones).

 

[Dirtexpo]

shut down

I was driving yesterday, and the car just shut down. It was like whenever it whated to. At first it was fine then a hesitation and the cars would shut down. Sometimes it started but the last time it did not. I had to have it towed home I haven't talked to the mech. yet, because he is about to install the rear end. I don't know what the problem is. If the thermac has no source of hot air could that make the car shut down like that.

 

[b4black]

No, it just causes a stumble or bog when you start to accelerate. It can cuase it to stall when decelerating or idling, but it would always restart.


Suddenly dying and then not restarting sounds either like a fuel or electrical problem.

 

[Dirtexpo]

starting line

How do I get a fast start in this car. I read that the 78 motor is capable of doing 13s or even 12s in the quarter mile. I don't think that my car will do that ( being a big body car, Lesabre Sports Coupe) . If so tell me what to do.

 

[b4black]

I guess it depends on someone definition of "capable".

The only magazine test I could find on a '78 LeSabre SC was 18.2 @ 79 mph. I doubt this was power launched, and 93 octane wasn't common back then, so you should be able to get 17's without problems. Tuning and minor mods will get you the 16's. 15's and 14's lower will take some work. Beyond that will be tough without some major changes.

To power lauch - one foot on the brake and one on the gas. Press the gas to raise the boost (lower the vacuum). If you have a vacuum/boost gauge it helps a lot. At ~0 psi, let off the brake and mash the gas. You could try leaving on the yellow light (~3 psi), but this is probaly too much. This heats up the tranmission, so don't stand on it too long and let it cool off between lauches.