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First old car, lots of questions.

  
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First old car, lots of questions.

 
special special
New User | Posts: 21 | Joined: 07/11
Posted: 04/03/13
07:05 AM

Hey guys, I just bought a 1978 Oldsmobile omega. I've have a bunch of questions for you experts here. The car has an early 80's olds 307 V8 w/ a TH350 swapped into it. So far I've rebuilt the carter afb, replaced thermostat and radiator cap, new coolant overflow tank, fuel filter, new front springs, front shocks, and front sway bar mounts. Still need new tires.

I've rebuilt the carb, and it sounds great at warm idle. Sounds like crap when it's cold. Changing the fuel mixture screws just upsets it, and messes with the warm idle too much. I've got black smoke in the exhaust when it's cold. Is there a way to lean out the carb just when the choke is on?

I've got a huge exhaust manifold leak on the passenger side. I've got new gaskets, but I was wondering if I could find some headers for this engine/car combo. Does anyone know what would fit a 78 X-body with an olds 307 and TH350? Something cheap would be nice.

Should the vacuum modulator on the th350 hold a steady vacuum? I put my handheld vacuum pump on it and it hardly pulls anything when I pump on it.

I noticed I have no vacuum advance on the distributor. It's an HEI distributor, so it should have some kind of vacuum canister on it, right?

If you guys can answer any of these questions, I would greatly appreciate it.  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 04/03/13
02:52 PM

the carter afb I've rebuilt the carb, and it sounds great at warm idle. Sounds like crap when it's cold. Changing the fuel mixture screws just upsets it, and messes with the warm idle too much. I've got black smoke in the exhaust when it's cold. Is there a way to lean out the carb just when the choke is on?

the Choke is only supposed to be closed during first cold start.. once the engine starts.. enrichens the mixture for cold start.. there is a fast idle cam that is supposed to engage to hold the idle speed up while the choke is partially closed...  when the choke opens fully. the fast idle cam should drop . as soon as the choke is fully open and the throttle is operated once..

what kind of choke heater do you have??? an electric choke coil..  or do you have a manual choke???

can you post the carb number... 1234s.. and which type of choke you have i can probably find you the  proper info on the basic choke setting..  they made several different choke setups on the afbs..


a huge exhaust manifold leak  i would want to check the exhaust flange donuts first.. make sure that they are sealing...  


these are from a 429CJ that i worked on a few months back... it had serious exhaust leaks..

Exhaustflangebefore Zpsfba5c149

this i did freehand with a die grinder and a carbide cutter... curved sided tree shape..

Exhaustflangeafter Zps5e3c7504


it has the wrong gaskets in it... they were too short for the taller CJ passaged..

Exhaustmanifoldbefore Zps71bfc6eb

it took 3 of us to hold the manifold level while we stroked it back and forth down the belt sander strip that i glued to some plywood.. i should have mounted the plywood to some straight 2x4 first and leveled it..

Exhaustmanifoldafter Zps2270e7d6


you may want to pick up some rubber bands.. i knew i was in trouble with the 429CJ in a 70 torino cobra..  not much clearance.. this is with one side of the engine supported with my lifting bar for transmission work...

429Cjexhaustrubberbands


Should the vacuum modulator on the th350 hold a steady vacuum? I put my handheld vacuum pump on it and it hardly pulls anything when I pump on it.

YES.... it should hold a perfect vacuum.. when applied from the intake manifold vacuum end of the tube...

there are specific elbow hoses available from many transmission parts suppliers for about 2 bucks...   you could have a bad vacuum hose on the modulator end of the tube..  you could have a leaking transmission modulator..  if you find transmission fluid inside the vacuum hose.. the modulator is bad..  easily changed...  the vacuum modulator has to be hooked up with as little vacuum hose as possible so the changes in the vacuum go directly to the modulator... instead of expanding and contracting the long length of hose..



I noticed I have no vacuum advance on the distributor. It's an HEI distributor, so it should have some kind of vacuum canister on it

thats strange...  it should have a vacuum advance on it... i but olds motors from the 80s did have electronic spark control....    with a 7 pin module.. .  these do have some programmed in advance curve in the module..   so you might want to measure it with adjustable timing light..  to see if you can chart its curve .. how much .. how soon..

there are a LOT of options in vacuum advance Olds V8 distributers..   if you ever wanted to put a GM TBI unit off a 305 chevy on your motor.. that would save a lot of time...  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 04/03/13
03:03 PM

as for headers.. i only saw 2... a 500 buck version and an 800 buck version from hooker...

there could be more.. thats what i found on a quick search of a popular performance parts site.
that would fit your nova style oldsmobile..  

special special
New User | Posts: 21 | Joined: 07/11
Posted: 04/03/13
03:49 PM

Alright, I looked under the car and found the hard line for the vacuum modulator. There's a 4" piece of rubber hose that has split at the end. Simple fix.

I pulled the cap off the HEI and it does have a 7 pin module. That's all that's in there though. No mechanical or vacuum advance. There aren't even provisions for them. Three of the pins to the module are disconnected, the wires for them were cut out. Does the 7 pin module just figure out the advance curve on it's own?

EDIT: I have a carter 9635 w/ electric choke.  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 04/03/13
07:30 PM

the bottom of page 12... page 13 and 14 cover the choke and fast idle settings..

carter afb   tuning.pdf   40 pages



do you have an adjustable advance timing light??? with the knob on the back...

or just bring the RPMs up and see if the timing mark advances...

there is some advance designed into the programming in the module..

the 3 wires actually 4.. were for the feed back carb computer system...

with computer operated electronic timing control... EST.. as gm calls it..

below 400 RPMs.. or if the bypass circuit is NOT closed by the computer.. the timing is controlled by the module...  so there is advance built in..

when the system is working ... and EST is operating. there is a knock sensor in the side of the block.. an EST module on the firewall to listen to the knock sensor.. and the ECM...

the ECM looks at the wave form from the PICK up coil..  as the tips of the reluctor approach the tips of the pick up coil. the voltage starts to increase to the positive side...  as the tips all line up the voltage drops to zero and then goes below zero as the tips separate..

the systems looks at this and instead of triggering the module to fire the coil as the voltage drops to zero... that starts a count down timer... so it will trigger the module so many milliseconds later.. this gives the EST system the ability to advance the timing.. as its triggering the pulse on the next cylinder... since the rotor is what directs the spark to the terminals in the cap.. one is just as good as another..  with the V6 versions.. if you looked at the timing in park.. it would have 15 to 20 degrees of timing advance.. step on the brake and drop it in drive.. without touching the gas.. the timing advances to 45 to 55 degrees..  this is all done by the ECM and the EST module..  as its listening for knocks.. if it hears one.. it retards the timing and selects a different cell to choose from out of probably 255 different programmed cells.
when you step on the gas.. the timing will drop back to 20 degrees or so..  but this is all just words... as you don't have EST or an ECM hooked up properly...

there are a LOT of options in HEIs with vacuum advance..  OEM remans..  that might have just a generic curve.. or some performance new HEIs that will have a performance curve.. or a custom curve from some manufacturers... depending on your application..

but... its worth checking to see how much the advance you have from the 7 pin module..

probably enough to be driven without pinging..  

68scott385 68scott385
Enthusiast | Posts: 669 | Joined: 05/09
Posted: 04/04/13
08:28 AM

http://www.jegs.com/i/Flowtech/387/11150/10002/-1?parentProductId=

These headers fit a small block Olds in an F-body application. They may fit the X-body also. The Omega didn't get as much love from the public and aftermarket as the Nova did. Many would say go the easy route and swap in a Chevy motor. IMO, being different from the crowd is more fun.  
68scott385 68scott385 68scott385

special special
New User | Posts: 21 | Joined: 07/11
Posted: 04/08/13
09:33 AM

Well, I've installed a new HEI distributor with mechanical and vacuum advance. I also replaced the intake manifold with an edelbrock performer RPM. I also installed a new set of autometer gauges. Now I have an oil pressure problem.

When you first start the engine it has ~50 psi of oil pressure. It goes down to ~5 psi at hot idle. This is according to the new gauges. The old gauges gave me 60 pounds at first start and ~20 psi at hot idle. I don't see any blue smoke out the back and the dipstick says full (maybe a bit over even). I have 20W-50 in it, I've got to have more pressure than this. I'm afraid to drive this now, what can I do? Confused