500? Caddy

[seaurchin1969]

Hey all, I been a member a while but this is my first post. I have been wanting an airboat for a while, and actually built a mini from a old eldocraft bass boat and a ultralite engine I got in trade. It did the trick for bow fishing solo, but I wanted bigger so I traded it and my bike for an old combee with a dd500 caddy. The engine runs well on trash gas 87 octane no post ignition so I'm guessing I have the larger combustion chamber heads, the engine casting# looks like 49500, and from reading posts, that makes it a 472/500, and I'll have to drop the pan and look at the crank to confirm cid.
As far as I know it's stock
Cast iron intake, 1" carb spacer, holly 4150 vacuume secondary dunno cfm atm, and what looks like a stock hei distributor.
She has a syntech H beam 2 blade prop 70"
At first I had overheat problems, I assumed it just wasn't pulling enough air through the radiator to cool it while idling aroun the lake bow fishing. I removed the theristat, (no I didn't plug the bypass as I have since read about on here) that didn't help so I put an electric fan on the radiator problem solved. I will however be sure to pug that bypass in future. I also ordered a alt bracket from MTS as per you repeated advice got there books and catalog coming too.

Beyond that I have had no real problems, just not the power I would expect, or would like. So I'm considering a rebuild. It Will not run dry empty , it will wind up around 3500 rpm, but some more pitch in the prop will fix that I believe. Gps clocked at 38 mph if memory serves, with two guys and an ice chest in the boat. From what I've read in hear though, I should be able to do alot better.

My real concern I guess is the engine stand, it has verticle mounting bolts front and back, with a rubber grommet between the stand and the motor mount,the rubber is worn out, so engine trim is prolly off. Is the rubber nesicary, or can it be eliminated? I would also would like to rearrange the driver an seating arrangement, and mostly deck it over for shooting fish. I just finished rigging up front steer for it so I can still go fishing solo. Since I can't intrest my kids into coming even to just drive the boat grrrr, the only on who wants to come is the dog lol.

I have rebuilt a couple of sbc over the years, I believe I can handle a caddy rebuild too.
All advice is welcome except using the motor for an anchor.




Block casting #

Engine mounts

[seaurchin1969]

Ok I'm gonna try more pics, an figure out the thumbnail thing rq

[seaurchin1969]

Ok thumbnail fail

[Striker543]

That's a Q blade and you're way over spinning it. Bring it down to 2800 rpm and I bet you see a big performance increase. Also, I would get a new hub to bring your diameter out to 72" or 74".

[SWAMPHUNTER45]

Striker gave you some good advice. If you got the hub and went to 74 inch and pitched just a hair under the 2 mark it should really improve the push. I would not spin that Q past 3000 if it were me.

[seaurchin1969]

This = Q?

[SWAMPHUNTER45]

You cant tell much from that last pic but in the others it appears by blade shape to be a Q which is a common DD Caddy prop.

[Striker543]

What swamp hunter said. The H is a lot narrower than your prop and a 2 blade 70" H would definitely not be enough prop for a cadillac.

[One Eyed Gator]

If you ordered the MTS alt bracket you will need an alt with a 10si case. Also check the alignment I had to shim my pulley's and uses a shorter belt. Works great moves the alt in closer and lower than the factory position.

If I was going to do anything I would verify it had a good timing chain. Take prop and move it see how slack is in the chain.

They are correct it looks like a Q Blade my buddy likes 2750 on the trailer.

[Deano]

. . . If I was going to do anything I would verify it had a good timing chain.
Take prop and move it see how slack is in the chain. . .

For all the research, reading and learning you can do about that Caddy in an airboat application, these are genuine words of wisdom that need to be heeded. Logistically, this should be your starting point before you do anything else if it's your intent to keep and run this engine without having any self inflicted grief.

A worn timing set will allow the timing to float and easily vary over four degrees, which is way to much. You only want to use a Cloyes #91139, which is an adjustable, all steel set. The factory gears had plastic/composite teeth than break off and travel loose through the engine. Upon disassembly, if those gears (and the existing valves seals) are not completely intact, it is imperative that all that crap (to include broken valve seal pieces) be cleaned out of the pan so it doesn't have the opportunity to plug the oil pump pickup.

I'll bet that you will be surprised how much back and forth play there is in your prop without the rotor turning. Usually what happens in addition to the chain stretching is that the keyway in the crank gear gets wallowed out. In a DD application, every time you let off the gas, the chain is acting like a brake for the entire valve train. In this case a bigger engine, more torque, more weight equals more wear at the keyway.

The timing slop that is likely present could be very well be contributing to your heat problem. To much or to little will both do that, and it can't be properly set or curved without that play being eliminated. The second thing to do is address that thermostat/bypass plug scenario so it doesn't run hot without electric fans. It should idle all day without ever getting hot. This thread elaborates on that subject: http://www.southernairboat.com/phpBB3/v ... 5&p=257908

Good luck, you've come to the right place. Lots of Caddy help and knowledge to be had around here.

[One Eyed Gator]

Yes Deano is correct about the key. My key worn a full key width slot in it. Timing would go from 32 to 42 with the chain slop and timing key wear. It is amazing it did not blow up.

I run the same chain he referenced advanced the 3 degrees.

I would also redo the rear motor mount, it is no place to skimp or take a chance with 650lbs of motor. I bent the 1st set I made trying to be light than built the set I have now, I doubt the will bend.

If you have the cast pulley's try to find yourself a set of stamped pulley's but you will need a harmonic balancer for 2 reasons, 1 is the harmonics in the motor with a carbon prop, the other is proper spacing for the belt alignment. you be surprised at the weight difference.

If you do not use the stock Cadillac thermostat you must block the bypass or the motor will never stay cool, it just recirculates the water in the engine.

If you block the bypass drill a small hole whatever you use to block the bypass, so you do not end up with an air-pocket in the motor.

[John C]

You might want to try this option. Caddys are known to have problems with stock timing gears. If you beat on them they will shatter. they are made from hard material. The cloyes gear is made from softer material to prevent this from happening. The problem with the cloyes gear is over time they tend to wallow out the keyway and it throws your timing off. It can cause all kind of problems.
You can pin the gear in place on the crankshaft and it will prevent this from happening. the gear on my caddy is pinned to the crankshaft and it works great. Use a 3/16 solid heat treated pin. Not the rolled type. If you polish the end of the crankshaft and the inside of the gear it will go on easier. Do not use a hammer. Use a 3/16" aircraft drill bit and drill a hole about 1/16" to the right of the hole in the gear. The pin should go through the gear and stick out about a 1/4" on the back side to go into the end of the crankshaft. mark your drill bit so when you drill the crankshaft and insert the pin it sits just below the face of the of the gear. or just below being flush. the pin should be about 1/2" long. The cloyes gear has three keyway settings as where the stock gear has only one. On the cloyes gear there is 2-5 degree retard, 0 degree, and a 2-5degree advance. the 2-5 degree advance is marked with a triangle or arrow head at the top of the keyway. This keyway will give you a little more TQ (power) once everything is installed and pinned in place line the gear up so the triangle or arrowhead that is stamped on the gear points straight up at the camshaft. You should have no more trouble with your timing gear. If you have any questions PM me.


This is from an old post back in 2009. The Caddy motor that I was talking about is still running strong today with Zero problems. The motor was built 10 years ago by Buddy Branch at Cadillac Performance Engineering. He pins all of his cloyes timing gears. It makes them run for a very long time without any problems. one of his little Caddy tricks. Thought I would share it. its been a long time. Wish I still had that boat.

[SWAMPHUNTER45]

You have gotten several real experienced Cadillac airboat users to offer you help.

Don't ignore a single word of it or you will be posting about failures that could have been avoided.

I have sent you a PM and every word I shared has been repeated by these great Southern Airboat members.

ps:

There is a reason those Buddy Branch engines stay together!

They are built right!

[pontoon outlaw]

[seaurchin1969]

Thanks guys, I have been reading a lot of threads you guys have responded to, and there is a wealth of information to be had.

What did you think of the construction of my rear engine mount? Is that typical?

[seaurchin1969]

I put a tarp over it, seems to be getting rain water in the engine. At least that's where I hope it's comming from.

[SWAMPHUNTER45]

Your rear mount is a standard style and works very well. The compressed rubber is also fairly common and should be corrected to both restore engine angle and reduce vibration. Next time try putting stainless fender washers between the block and bushing it seems to make the bushing last a little bit longer, especially if using the conical bushings. Do not over compress and I suggest using poly nuts and washers.

[scottyroll]

... seems to be getting rain water in the engine. At least that's where I hope it's comming from.

How did you notice this? Does it bellow white smoke upon cold start up?

There appears to be possibly green antifreeze around your intake in one of the photos you posted. Might want to check your coolant level to see if it is getting lower after each use.

[Striker543]

I put a tarp over it, seems to be getting rain water in the engine. At least that's where I hope it's comming from.

I have a similar issue. My dipstick condensates bad and I will get some "milk" spots on the dipstick, but the oil from the pan is clean.

Run your engine and check your oil - if all the oil is "milk," you've got bigger problems; if it's just spots on the dipstick and the oil from the pan is clean, I wouldn't worry about it.

[SWAMPHUNTER45]

What I have found Striker is even engines kept under a roof in a high humidity environment will collect some moisture evidence in the valve covers, crank case breather and dip stick tube. This appears to be seasonal in my climate and is timed to cooler temperatures. I have also noted that if engines are started up and run for a few minutes but not kept at a running temperature, they build this moisture evidence faster. We run our engines cool so it is a condition we have frequently encountered. It also seems that ZZPD oil additives enhance the effect.

The great news is it has been our experience that after one or two hours of sustained running at 145 degrees plus it evaporated away and no moisture could be detected. A full engine tear down of a built 509 CID showed no sludge inside the oil pan or block interior. It appears for most cooler running Cadillac's just the humidity collecting from air being drawn through the engine PCV system.

[Striker543]

I've noticed the same. I don't have the problem at all during the summer, but it's constant from roughly November through March. My engine runs cool too and I run Brad Penn oil, which has zinc in it. Now that I know what it is and know that it's not water from the cooling system getting into the oil, I don't worry about it.

[seaurchin1969]

... seems to be getting rain water in the engine. At least that's where I hope it's comming from.

How did you notice this? Does it bellow white smoke upon cold start up?

There appears to be possibly green antifreeze around your intake in one of the photos you posted. Might want to check your coolant level to see if it is getting lower after each use.

I noticed it by checking the oil before I run it.
No it doesn't blow white smoke on start up, from my experience, that would indicate bad valve seals, and the green is, wait for it ........ Mold lol it's outside all the time in the shadow of my house.

[seaurchin1969]

I'm picking up another used for sure 500 short block tomorrow, so I ca get started rebuilding that without taking my boat out of service, and have a spare block. Maby I can track down some smaller cc heads hmmmm

[seaurchin1969]

Fyi I saw a new post. On eBay for a complete running 500 in IL for $650

[scottyroll]

I noticed it by checking the oil before I run it.
No it doesn't blow white smoke on start up, from my experience, that would indicate bad valve seals, and the green is, wait for it ........ Mold lol it's outside all the time in the shadow of my house.

I figure it's better to be dirty on the outside than it is to be dirty on the inside when it comes to a motor!

Glad you were able to get a proper diagnosis from the knowledgeable Caddy folk on here.