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Discussion Starter · #1 ·
Hi guys I've being of building my cars and pulling my hair out with some of the finishing touches.
This my 79 firebird with 403 Olds engine. The car is my every day driver , so doesn't look much ( half sanded , no carpets or hood lining )
Just front seats and seat belts but I have started at the back and worked my way forward but just mechanical. I've done new fuel tank and lines,diff, suspension front and rear lowing the car 3" I've owned 2nd gen firebirds for 35yrs. I have always had chev engines never had a problem, I knew my way around chev engines and even had a 400 with Siamese bores so when I came across 403 with same problem I thought no sweat. I did some research and found out about the holes in the wedding and the way to fix this problem . I would have normally ditch this engine for a chev or new modem LS engines but this is a numbers matching car and engine was rebuilt but hadn't been started,gear box was good and I put a diff in a had here out of a firebird I put a 9" in before. But it over heats when on the hiway or drive around town at ,80kph for a while it starts to rise. I have gone through everything this not my first rodeo.
First I thought the top rad hose was creating vac lock because it sits high over the alternator. So I changed it to run in front of the alternator and now it sits level with top of rad. Then I put electric fans on from a vy commodore that had twin fans factory with shroud that fitted perfectly and draw 3000cfm.
Still no luck. Rad was new at the beginning. I had to modify my bottom rad outlet because of steering box, it's RHD . and for some reason when I got it back I noticed the inlet and outlet had being reduced in diameter probably 4or5 mm smaller my be more but I could still tighten clamp with spanner couldn't get tight enough with screw driver doesn't leak.im going to get them fixed but I can't imagine this is the problem. I don't want to pull heads,as a last resort. I'm thinking of putting a factory clutch and fan on with shroud don't need max power it's drive car I've got a 77 with turbo LS1 and 79 trans am. Also getting parts for Oldsmobile's engines in Australia is a pain. Timing marker is just for 3 models and cant get it anymore and not only is unable to be found but replacement looks different but apparently mounts the same. Just to make it more fun you can't use the one of any other 403 engine the timing marks are different. And I was considering connecting the heater hoses from manifold to water pump together just In case it helps but technically it should make any difference. I live in a constantly hot city so a heater is not necessarily. It's cold Maybe for 4 days a year.ive done leak down test with no problems. I know this is long but I don't want to read through a heap of stuff I've already looked at, I'm looking for something Ive missed .oh by the way which rocket scientist thought it would be a good idea to run fuel line down the opposite side of the fuel.pump and under a hot engine. That's a great idea. I know Pontiac engines pump is on US drivers side but it chev is on the left.
 

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'93 6-spd Trans Am - '96 C4
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As too lean of an air-fuel ratio and/or incorrect timing are also causes of overheating, you need to get the timing sorted out first; then maybe figure out how the carb is setup before moving much deeper into this. There are Harmonic Balancers available for that engine with Timing marks new from Summit Racing and likely JEGS, Rock Auto, and others as well; but you're probably going to want to sit down and take a long deep breath before looking at them.




Alternatively, a local machine shop should be able to "divide" your balancer and stamp a few marks left and right of 0? Say every 5 degrees each side up to 40?

Just a thought.

Good Luck!
 

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Discussion Starter · #3 ·
Thanks for replying. I got a timing marker today from classic industries I've also bought a new billet dist plugs and leads. I can now set timing properly. I did know that timing can cause over heating with bad vac advance. I'll get onto fitting all the new stuff and
setting the timing and see what happens. I didn't know how old the dist was i.
Thanks for reminding me about the effects of bad tuning. I didn't build the engine so I'm in the dark about what was replaced and what was from old build. It's frustrating..
Thanks again
 

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Discussion Starter · #5 ·
Ok I have new 3 core rad and new water pump. I bought the car and engine was rebuilt and just sat in the car not hooked up. I know the mechanic who built the engine I . I didn't have shroud or fan with this car but I have spares around here. I can use. I've replaced everything. If the problem was consistently the same I might be able to track it down . It's frustrating because I know this is fixable and after 35yrs of doing this I should be able to fix this. I was going to replace water pump with hi volume pump.
The last option is to check head gaskets..
 

· Ramblin' Wreck
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Read everything you can find on rebuilding these motors....then just do it. It's not as hard as it sounds if you are willing to just "DO IT"... $30 an hour mechanics do that every day ;-)
 

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Discussion Starter · #8 ·
Im Harley mech so rebuilding engine isn't a issue but the guy who just built it is a friend who owns his own shop doing every day jap British and Australian so I trust him the only thing I would do is fit the alloy heads I already had here but as I said the engine was just done. I've done about 500 klms and the engine is strong. Just have 2 issues over heating off and on and now I just got new dist plugs and leads and a timing marker I can time it right and check vac advance. Then I'll see what happens.
Thanks for all the advise.
 

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Discussion Starter · #9 ·
I think people might be misunderstanding my harmonic balancer has timing marks I had no marker or pointer might be a better description that bolts to timing cover so timing was a guess enough to Start the engine for the first time. Because I don't have the tools to correctly set up my new 750 Holley so I've just reverted to basic set instructions for Holley. It's being awhile since I have dealt while old school carby. But until I've timed it right and set up carby..
And see where I stand
Thanks again
 

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Discussion Starter · #11 ·
He doesn't remember exactly what was done to the engine as far as spec's go. He built the engine 2 1/2 yr ago. And because it was for himself he didn't have a detailed list. The alloy heads, manifold and forged pistons I already have sitting around here I bought them on the cheap yrs ago ,heads need some work but manifold and pistons are new and if the bores are .030 over I'm set all this owes me $400 and low compression is fixable but as I said this is my every day driver and I'm looking for reliability and strength. And yes this is the nitrous engine I haven't fitted until I've done a few thousand ks and the lower compression won't hurt with the nitrous.
 

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Hi guys I've being of building my cars and pulling my hair out with some of the finishing touches.
This my 79 firebird with 403 Olds engine. The car is my every day driver , so doesn't look much ( half sanded , no carpets or hood lining )
Just front seats and seat belts but I have started at the back and worked my way forward but just mechanical. I've done new fuel tank and lines,diff, suspension front and rear lowing the car 3" I've owned 2nd gen firebirds for 35yrs. I have always had chev engines never had a problem, I knew my way around chev engines and even had a 400 with Siamese bores so when I came across 403 with same problem I thought no sweat. I did some research and found out about the holes in the wedding and the way to fix this problem . I would have normally ditch this engine for a chev or new modem LS engines but this is a numbers matching car and engine was rebuilt but hadn't been started,gear box was good and I put a diff in a had here out of a firebird I put a 9" in before. But it over heats when on the hiway or drive around town at ,80kph for a while it starts to rise. I have gone through everything this not my first rodeo.
First I thought the top rad hose was creating vac lock because it sits high over the alternator. So I changed it to run in front of the alternator and now it sits level with top of rad. Then I put electric fans on from a vy commodore that had twin fans factory with shroud that fitted perfectly and draw 3000cfm.
Still no luck. Rad was new at the beginning. I had to modify my bottom rad outlet because of steering box, it's RHD . and for some reason when I got it back I noticed the inlet and outlet had being reduced in diameter probably 4or5 mm smaller my be more but I could still tighten clamp with spanner couldn't get tight enough with screw driver doesn't leak.im going to get them fixed but I can't imagine this is the problem. I don't want to pull heads,as a last resort. I'm thinking of putting a factory clutch and fan on with shroud don't need max power it's drive car I've got a 77 with turbo LS1 and 79 trans am. Also getting parts for Oldsmobile's engines in Australia is a pain. Timing marker is just for 3 models and cant get it anymore and not only is unable to be found but replacement looks different but apparently mounts the same. Just to make it more fun you can't use the one of any other 403 engine the timing marks are different. And I was considering connecting the heater hoses from manifold to water pump together just In case it helps but technically it should make any difference. I live in a constantly hot city so a heater is not necessarily. It's cold Maybe for 4 days a year.ive done leak down test with no problems. I know this is long but I don't want to read through a heap of stuff I've already looked at, I'm looking for something Ive missed .oh by the way which rocket scientist thought it would be a good idea to run fuel line down the opposite side of the fuel.pump and under a hot engine. That's a great idea. I know Pontiac engines pump is on US drivers side but it chev is on the left.
I had that problem. It would run around 220 after I would take the engine out. My problem was an air bubble. I knew this because I would run 160. I raised the front end up 6 " took the radiator cap off and idle the car for 5 minutes. I knew it burped because my coolant level dropped a bunch. Good luck.
 

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Discussion Starter · #14 ·
Thanks for your help. I've actually changed the top rad hose so it runs level with top of rad, it would be a problem if I decided to put old shroud and clutch fan back on. But I have set of factory twin thermo fans and shroud off a V8 vy commodore (2002 Australian car) this fits like it was made for it and are supposed to draw 4000 CFM So i don't think it's the problem..
But to answer your solution yes I have bled air out of the system everytime I open the cap. That's why I changed my top rad hose It's just been to inconsistent. I haven't fitted my new dist plugs and leads and I final got a timing point that points to timing marks on harmonic balancer I'm going to send it to dyno tuning shop and get them to set timing ,carby and all things to do with tuning. This will eliminate another reason for heating . I know the engine was built properly just not sure on some of the exterior parts he's a mate and a tight ass so did he replace the dist or water pump or fuel pump. The carby was carp but it was good enough to do start up... So I've replaced the dist ,rad,fuel pump,carby, thermostat and housing all hoses, my next thing after tune up, I will charge water pump for hiflow pump. This will just leave head gaskets but I'm not going after them until my alloy heads and manifold are back from the machine shop. I just thought I would put some miles on the new rebuilt engine seemed a shame to waste perfectly new top end.
Thanks for your advice.
 
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