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How do I know if I have 472 or 500 Caddy? I have a coolant l

dgc

Active member
Hey guys, just trying to figure out if I have a 472 or 500ci caddy V8.

I have a Water dripping issue??

I replaced the headers with SS headers. Overnight the right side header bolts dripped some coolant out??? It continues to drip and its a slow drip but the front 3 bolts are dripping? Can it be interior corrosion? Or did someone install bolts too long and damage the water jacket area?

The boat runs great. I was just installing an almuminum radiator, intake and new headers..

No coolant in oil and no water in my exhaust..

I can probably install the headers and RTV the bolt hole to seal the coolant. It did leak prior to removing the old headers...

worse case scenario:
If my heads are shot, where can I get headers for this motor possbile in aluminum?? If not I will need to repair or buy the right side head.

I appreciate your input.



12 x 8 3/4 deck aluminum hull with Caddy Direct drive
 

SWAMPHUNTER45

Well-known member
Two options:
1) drop pan check crank casting ID
2) measure piston stroke via plug hole

How long of a bolt did you put into the head?
 

dgc

Active member
I did not put in new bolts.

It had headers before with standard header bolts.

I just noticed coolant drip on front 3 header bolt hold when I went to install new headers today. I stopped and waited to see why it's dripping before installing new headers.



I think I will measure stroke depth while I replace spark plugs.

Anyone know best plugs and part number and gap for these Caddy engines.????

Thks!
 

Deano

Well-known member
I guess you have already confirmed the casting number on the block is xxx5200? If so, just measure the stroke through a plug hole. A 472 will measure less than 4 1/8 and a 500 will measure more than 4 1/4.

It isn't likely that it is leaking as you suspect from the three forward header bolts. The middle of those bolts goes through to dead air space, there is no way for anything to leak there. Are you sure it hasn't run down from the front of the engine to drip from that neighborhood?

In any case, if it is leaking where described, the head gasket on that side almost has to be bad. Two of the three bolts you reference do dead end at a head bolt, but given a good head gasket, those should still be dry holes. The other lesser likelihood is that the head is cracked. Now if it was severely overheated that likelihood would be increased dramatically. In either case, RTV is not the answer if you're going further than the end of the driveway.
 

SWAMPHUNTER45

Well-known member
I called MTS a few months ago and they had been out of stock on the direct replacment version for some time. They had the D port version but they dont bolt up to standard style headers. Before you start buying anything you need to see which heads and what pistons are installed. Did you take this engine out of the car yourself of buy a used engine from another airboater?
 

Deano

Well-known member
SWAMPHUNTER45 said:
. . . Before you start buying anything you need to see which heads and what pistons are installed. Did you take this engine out of the car yourself of buy a used engine from another airboater?
These are words of wisdom that are worthy of being expanded on. The early, small chamber heads and the later, open chamber heads require different pistons. If somebody before you slapped some small chamber heads on a later model long block, the compression is well over twelve to one and nothing you do will allow that to work with regular pump gas except correcting that mismatch. Not to say this is what happened, but however remote; it is a possibility that should be confirmed or denied, before you redo things to arrive at the same result.

There are casting numbers on the heads. After you pull that head, post the casting number and a good picture of the piston(s) that are in it, we can positively identify exactly what you have. Measuring the stroke is also more straight forward with the head removed.

You should add your location to your profile, as there may be an experienced Caddy guy near you.
 

LoxStroker383

Well-known member
Also you can get the liquid blue dye that checks for exhaust gases in the coolant. I have a test kit myself. Where are you located im in Palm Beach County I would be happy to let you borrow it.
 

LoxStroker383

Well-known member
Also you can get the liquid blue dye that checks for exhaust gases in the coolant. I have a test kit myself. Where are you located im in Palm Beach County I would be happy to let you borrow it.
 

dgc

Active member
Ok so today I will verify its a 500

I will get casting son heads and block


I bought the airboat recently and it runs well even direct drive.

Maybe it's high compression but I hope not.


I will post pictures soon to verify..


Now how do I know what Pistons are in it without pulling heads I assume that's not possible.


I'm thinking its a head bolt leaking very little water.

I can probably rtv it snd install new headers but now that I know I think I rather resolve and bullet proof before hunting season.


I was just upgrading the headers and a new Eldebrok alumninum intake manifold. That's it!


I will get back on soon with more info so I can make a good move as to keeping it reliable...

THks!
 

SWAMPHUNTER45

Well-known member
In a direct drive application the factory manifold works better than the high rise. That said if you are still gonna put the Edelbrock on it then read up on welding the center. If not your leaving torque on the table.

The heads a have casting numbers that tells you if open or closed chamber.

Pistons you need to see so without pulling a head the only other way is a fiber opton inspection camera.

Hope this helps
 

dgc

Active member
SWAMPHUNTER45 said:
In a direct drive application the factory manifold works better than the high rise. That said if you are still gonna put the Edelbrock on it then read up on welding the center. If not your leaving torque on the table.

The heads a have casting numbers that tells you if open or closed chamber.

Pistons you need to see so without pulling a head the only other way is a fiber opton inspection camera.

Hope this helps



That sure is helpful information.

I will be checking casting numbers soon and posting pictures..

Thks!
 

One Eyed Gator

Well-known member
If it is a 500ci motor then to be high comp it has to a 70' all others were lower compression, with that said there are several different pistons the went in those motor. I believe up to 72 the 472 and 500 had the 76cc after that they were 120cc heads.

With the edelbrock my engine ran better with no spacer and the exhaust crossover welded. I also had to make a thin SS block off plate to sit between the head and intake gasket to keep it from burning through. Sure does cut 30lbs off the motor though. As for a carb many with run ok out of the box but dial what you have in and you will see a little performance gain.

If I had the take off the heads I would invest in new valves properly cut for a good seal and valve springs properly shimmed. In a DD the better it seals the more torque you create.

FYI Oil pump bypass should be polished so it does not stick and if you run mechanical fuel pump check the stock filter ofter.

I have seen a lot of caddy blocks and very few have true round cylinders from the factory.
 

Deano

Well-known member
nebraskaairboater said:
If you match or research the head casting numbers and replace with the same style head the type of pistons isn't going to make a difference. As stated earlier in the thread hopefully you don't have a crack between the water jacket and head bolt boss in the block. I assume you want to run it until you find another set of heads so I wanted to throw it out there that the pistons in the block won't matter if you find the casting numbers off the heads and replace with like for like heads.
Dan, with all due respect . . . you have completely missed the point and are giving bad advice.

The point was that if someone else had already switched the heads to the wrong ones, this mismatch could and likely would have created the problem in the beginning. If that happened, you are recommending that he go get more of wrong heads and reinstall them. :scratch:

The pistons have to match the CORRECT heads, not match the heads (that may have been wrong) that were on the engine when he bought it 40 years after the factory assembled it.

This is why said:
Not to say this is what happened, but however remote; it is a possibility that should be confirmed or denied, before you redo things to arrive at the same result.
 

One Eyed Gator

Well-known member
Had a friend that pull a caddy from a car put on the boat and ran like crap We found out it had pistons for the 76cc heads but had 1 76cc and 1 120cc head. corect compression on 1 side and and very little compression on the 120 side.

I would take the time to verify all the parts.
 

sidejobs

Well-known member
I don't get on here as often as I'd like. So here's my advice. Listen to deano !!! He will not tell you anything that isn't true. And he will not assume to know anything he doesn't. If there is something he is unsure of he has the resources to find out. So again. Listen to his advice !
 

sidejobs

Well-known member
One Eyed Gator said:
Had a friend that pull a caddy from a car put on the boat and ran like crap We found out it had pistons for the 76cc heads but had 1 76cc and 1 120cc head. corect compression on 1 side and and very little compression on the 120 side.

I would take the time to verify all the parts.
I pulled a 500 from a 73 eldorado that appeared to have never been touched. Looked like original paint still on it ! And it had a 76cc on one side and a 425 !!! Head on the other lol. So you never know
 

nebraskaairboater

Well-known member
sorry if I gave bad advice... I was basing it on the statement that it ran great just dripped coolant at the bolts. I know assuming is wrong but if it had a mismatch of pistons to heads it wouldn't run great. I have deleted my previous post as to not give bad advice to anyone.
 
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