[1965gp]

Wife was driving her 79 TA with a 403 this morning and it got really hot then spewed water. When I saw it there were no broken hoses so I took it to my friends shop. Turns out it corroded or popped out a freeze plug.

The motor has been great since we bought the car in 2003. The kid we bought it from said he rebuilt it but who knows? It’s been crazy reliable is all can say.

The shop which I have trusted for a long time suggested pulling the 403 and going through it which is probably the best / most expensive route.

I can swap in a solid running Pontiac 350 and probably have as much or more power. Will need to buy an intake and headers.

Or just replace the freeze plug and any others that show any corrosion and move on.

Thoughts??

[Baron Von Zeppelin]

Freeze plugs , then tell her to quit being so ruff on it .

[DaleO]

I would replace the freeze plug and look at the others or see if there was anything else needing attention. That's all I would do.

[1965gp]

Hell she wasn’t 15 min from the house!

[242177P]

Freeze plugs. Might not need to pull the motor
if you use those rubber expansion plugs. Yeah,
it's totally a band-aid move, but it buys you time.
In which you can formulate a plan.

P350 loses some cubes, but the 403 has a short
stroke. Like small block Chevy short (Chevy guys
LOVE the 3.75 stroke 383). IIRC, the Olds shaker
base has a different offset?

[4dblnkldude]

I like to do things the hard way. Perfect excuse to get the olds outta there.

[4dblnkldude]

Shoot where you at? I just put a perfect running 77 400 on FBMP. $1,200 and ran a 15.1 in my 81!

[1965gp]

Located in Houston. We’ve never had an issue with this car getting hot. My instinct is that the thermostat got stuck and the increased pressure blew through the corroded freeze plug.

It’s been so hot here in TX that it has really tested the limits of our cooling systems.

What rubber plug are you talking about? Is there a reason I can’t use a brass plug?

[PAUL K]

If the plug "blew out" there could be more to it. If a plug corrodes it usually starts dripping. It's very common for Olds 403 blocks to crack on the deck surface. This can cause all kinds of issues including pressurizing the coolant system.... At some point pressure test the cooling system and run a compression test. If any cylinders seem low perform a leakdown test. Hopefully it's just an unhappy aged freeze plug and nothing more.

[Baron Von Zeppelin]

Originally Posted by 1965gp

,,,, What rubber plug are you talking about? Is there a reason I can’t use a brass plug?

Its a metal/rubber expansion plug that bolts in and expands as you tighten it up.
Real handy when you don't have access to hammer in a new one.

[Joe's Garage]

Originally Posted by 1965gp

What rubber plug are you talking about?

One like this. Dorman makes them in various sizes.

Great for a 'quickie fix'. They don't normally require you to take out anything else to get clearance.

Just get the rest of the old plug out and install one of these and tighten the nut until it's tight and seals up.

[Schurkey]

If one core plug corroded...all the other core plugs have been bathing in the same acidic coolant.

Replace ALL of them. Every one.

And, sure--check around the core plug holes for cracks. Pressure-test the cooling system, verify cranking compression and perhaps a cylinder leakdown test. All of those are recommended.

[1965gp]

All great suggestions. I figure I will pull the headers to make it easier. Is the easiest way to remove them still to dislodge them with a screwdriver and hammer?

[mgarblik]

It's not easy to replace ALL the freeze plugs with the engine in the car. A few will possibly require transmission removal if in the back of the block. I do not have all the Oldsmobile locations memorized, but you need to look them up if replacing them all. If the Olds heads have plugs in the ends like a Pontiac, you need to remove the engine or the heads to get to the rear ones. We are talking about allot of work here in the car. When I worked at the Pontiac dealer, we had a service bulletin on the Pontiac Firebirds, freeze plugs. It instructed the technicians to pull the carpet and insulation back. Cut a hole through the firewall with a hole saw. Then remove the freeze plug from inside the car. Then patch the hole. Yikes!! That's the way cars were repaired on the cheap at the dealers.
My suggestion: Replace the one plug that came out. Then pressure test the cooling system. Do the pressure test with all the spark plugs removed and bump the engine over to inspect for coolant in the cylinders. If all dry, inspect the rest of the plugs as best you can for rust or weeping. If others look bad, I would remove the engine before trying to replace all of them in the car. Hope you get lucky with just one.

[Mr Anonymous]

If you pull it out to do the freeze plugs, a quick swap of an early 330-350 olds head (up to the to 7a) will take you from 7.9:1 to roughly 9.5:1 and the response will be fantastic. Adding a 2.07 valve would help too, but just the swap by itself really wakes it up. If you were closer, I'd hook you up with the heads. I've done some, and its remarkable.

4.351 x 3.385, they are very snappy until the main webs explode. There is an aftermarket 4.00 crank available that takes it over 475 cubic inches. all in the small block olds package. The bore and stroke is delightful, even stock, and has a factory 6.00 forged rod.

[HWYSTR455]

Yeah, the O350 head swap is great, the windowed 403 block, not so much.

They do make halos for it tho, not how much better it makes them but would have to help some.

If you can find a 400P that would be the way to go, but it depends on what you want to do with the car. You can use all late model 400 OE parts and make it look factory if you wanted to.

.

[Schurkey]

Originally Posted by mgarblik

It's not easy to replace ALL the freeze plugs with the engine in the car.

Of course the engine comes out.

Originally Posted by mgarblik

My suggestion: Replace the one plug that came out. Then pressure test the cooling system. Do the pressure test with all the spark plugs removed and bump the engine over to inspect for coolant in the cylinders. If all dry, inspect the rest of the plugs as best you can for rust or weeping.

Not a "bad" plan, but the downside is that all the corrosion on a core plug happens on the water-jacket side, not the visible side.

Core plugs can be almost completely rotted away, and you wouldn't see it from the outside of the block.

Originally Posted by HWYSTR455

the windowed 403 block, not so much.

They do make halos for it tho, not how much better it makes them but would have to help some.

"Halo" girdles get a fair amount of attention, but they have remarkably little strength in the direction that needs reinforcement the most. The best use of a halo girdle is to pick up all the main caps from the roadway/racetrack with one hand.

REAL girdles can make a major block-strength improvement. Halos...no.

[1965gp]

So it looks like the motor is coming out……

What should I look for on the heads?

[HWYSTR455]

Originally Posted by Schurkey

.....


"Halo" girdles get a fair amount of attention, but they have remarkably little strength in the direction that needs reinforcement the most. The best use of a halo girdle is to pick up all the main caps from the roadway/racetrack with one hand.

REAL girdles can make a major block-strength improvement. Halos...no.

Yup, kind of what I was alluding to, and to my knowledge, no one makes a true girdle for the Olds blocks.

OP - If or when you pull and tear down the O engine, and you start adding it up to do the things that really 'should' be done, you might as well do a Pontiac engine. Even though there is support for the Olds 455 that isn't 'bad', the Pontiac engine is a much better foundation. And, of course, the car is a Pontiac.



.

[Baron Von Zeppelin]

Tap on the plugs with a pick hammer and see if they are solid - or puncture.
They will cave if they are weakening very much.

If its just one bad plug , fix it and be done.