'79 Caddy 425 with 454 TBI into a J-20

[jaber]

The build thread is here...

http://www.ifsja.org/forums/vb/showthread.php?t=110126

Truck runs, but over heats instantly. Flushed the block out 3 times and it is still boiling over.

Runs a little rich on the program its on, but the tuning hardware is 20 miles away. The stock engine does not have much power. not in the set up I have at the moment. I'll update when I get time to play with it more.

[Daddio]

I have some experience with big caddys. After I rebuilt my 500 I was having over heating issues. It would get hot and then too tight to turn over until it cooled off. Very scary considering it was basically brand new and I had lots of money sunk into it. (425's are basically a small bore 500).

I think there several things happening, but the main problem ended up being the thermostat. The caddy intake has an internal coolant bypass and it needs the correct thermostat to block the bypass directly below the thermostat. Regular thermostats will fit, but they wont block the bypass. Some people put a small freeze plug in the bypass, but if you do that be sure to drill a small hole in it to allow trapped air out. It will take longer to heat up with out the bypass, but it may also run a bit cooler.

[jaber]

Originally Posted by Daddio

I think there several things happening, but the main problem ended up being the thermostat. The caddy intake has an internal coolant bypass and it needs the correct thermostat to block the bypass directly below the thermostat. Regular thermostats will fit, but they wont block the bypass. Some people put a small freeze plug in the bypass, but if you do that be sure to drill a small hole in it to allow trapped air out. It will take longer to heat up with out the bypass, but it may also run a bit cooler.

Not sure I'm understanding this.
When I start it, it builds heat in the front of the intake almost instantly. Once the t-stat opens, you can hear the AF serging into the rad.

Would drilling a hole in the t-stat help at all?
Does this just sound like theres air trapped?
Would really like to get this dialed in, I need to haul a couple of trucks and this truck has the suspension for the job...

[jaber]

After doing some reading on the Caddy forum, I have decided to do the head gaskets and see how this helps. They were saying that a bad HG would pressurize the cooling system and it would explain what is going on here. Just wondering if I should through an RV cam into it while its apart?

Thoughts? It has about 150K on the stock engine now.

[fulsizjeep]

If you are taking the heads off on 150k engine, may as well do the cam, lifters and tc set if it does not break the bank.

[jaber]

I have a Comp Cams 260h grind in the GWs 360, and love it. Does anyone know of a better low end cam grind?

[addicted]

Originally Posted by jaber

I have a Comp Cams 260h grind in the GWs 360, and love it. Does anyone know of a better low end cam grind?

That grind seems to be about the best going for a RV/towing type cam. I'm planning on running one in my 455 build.

[jaber]

If the cam bearings are still good, is it safe to run the originals?
The other install I did was a fresh rebuild, so it had all new bearings. I understand Plasti-guage on crank bearings, is there a way to check the cam bearings?

[Daddio]

Sorry for the late reply.

Here is a picture of the correct thermostat:
http://info.rockauto.com/Stant/Detail.html?13459.jpg

Are the heads original to the engine? Sometime people put on the small chamber older heads to bump up compression, but it was usually too much.

Here are some discussions on big block caddys running hot:

http://www.cadillacpower.com/forum/v...12048&p=127750
http://www.cadillacpower.com/forum/v...ic.php?p=74362

Are your heater hoses routed correctly?

On the cam bearing question. I don't know if they tend to have issues, but caddys were prone to having lobes wipped out. Generally the engine don't have issues with oil pressure, but if you have it out and apart the bearings are fairly cheap.

The stock cams were just plain weird. People have tried to figure out what the engineers were thinking, but the specs on lift and duration don't make much sense. Maybe smooth idle was a goal? The aftermarket cams are all regrinds as far as I know. I have the middle grade one from crane and it really woke up the engine. It now pulls strong to above 5K and has a very slight lope.

[jaber]

Originally Posted by Daddio

Sorry for the late reply.

Here is a picture of the correct thermostat:
http://info.rockauto.com/Stant/Detail.html?13459.jpg

Are the heads original to the engine? Sometime people put on the small chamber older heads to bump up compression, but it was usually too much.

Here are some discussions on big block caddys running hot:

http://www.cadillacpower.com/forum/v...12048&p=127750
http://www.cadillacpower.com/forum/v...ic.php?p=74362

Are your heater hoses routed correctly?

On the cam bearing question. I don't know if they tend to have issues, but caddys were prone to having lobes wipped out. Generally the engine don't have issues with oil pressure, but if you have it out and apart the bearings are fairly cheap.

The stock cams were just plain weird. People have tried to figure out what the engineers were thinking, but the specs on lift and duration don't make much sense. Maybe smooth idle was a goal? The aftermarket cams are all regrinds as far as I know. I have the middle grade one from crane and it really woke up the engine. It now pulls strong to above 5K and has a very slight lope.

Thanks for the info and the links. Just joined that site for future reference.
Plus it looks like some would be interested in my TBI install...

The reason for the cam bearing question, was that I'm trying not to pull the engine out, again, if possible. Just trying to salvage a freebie as cheaply as possible. I know, thats a contradiction in terms...

[crazydog]

There seem to be lots to choose from:

http://www.500cid.com/cams.htm

http://www.compcams.com/catalog/COMP...g_2011_126.pdf

http://www.lunatipower.com/ProductGr...?id=287&cid=53

[jaber]

Thanks for the links...

I thought I found the head gasket "set" for $80 through the Vatozone. Went to order it, and they told me it was discontinued...

The search continues....

[Daddio]

Discontinued? Really? Wow.

I might have 1 felpro gasket for a 472/500 in the garage. If so you can have it for the shipping. I don't know if it is the same gasket for a 425, but they are basically identical so it might be the same. I think the kit included everything except the intake, which is just like the AMC pan.

[jaber]

Got the intake one in yesterday, my parts girl is looking for the gasket set to see if she can find me one. Its nice having connections...
If its the full set, I'll check to see if it will work. thanks.

[jaber]

Found the head set through a local supplier. About $100.
Now I just need to find the time...

[brushawg]

Did you find the time? Had thought about the 500 awhile back but wasn't sure.

[jaber]

I found an RV cam through a guy on the Caddy forums. $115 to my door. I'm now getting ready to order the lifters and figure out how to haul this beast the 23 miles to work where I have a full shop to work in. Its getting VERY close...

The guys at the Caddy forum are telling me I should find the intake and exhaust from a 472 to help this one breathe better. And here I was trying to keep it cheap.

[jaber]

Towed it the 23 miles to the shop yesterday and spent today tearing it apart. Had to use a 3" prybar to get the heads to pop off.
Dont think the oil had ever been changed before I got it, there was sludge everywhere. Should have it back together and broke in by this weekend, I'm hoping.

[jaber]

Well, the sad part is the farther I tore this engine down the farther it told me to go.
Turns out every bearing surface in the engine was pitted. Had to cut about a .020 ridge out of the top of the cyls to get pistons out. Everything is apart now, so I'm gathering parts and plotting my course.

Whats the old fable, free will cost you more....

[jaber]

Update.

I got the engine back together and installed and broke the cam in. I'm still having heat issues, so working through that.
Pics...