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500 caddilac hill burner

Kbrewer

Member
So I recently just put a 500 caddilac off of market place on my 11.8 foot hull it runs dry good idles good sounds great runs fantastic for an un known engine, until about 30 mins of giving her the beans I hear a loud backfire it shut off and will not start back, any ideas on coming issues with these engines?
 

keys2pines

Well-known member
Don't have any experience with those engines. However, on any other engine I would say it sounds like the timing chain broke. Pull the distributor cap and see if the rotor is turning when you crank it. If it's an interference engine, you may have now bent some valves.
 

Deano

Well-known member
My first blind guess, based on likelihood and given the lack of additional information would be that it threw a lifter.
First clarification please, we are talking about a DD on your <12' hull correct? RPMs at mishap, may be more than passively relevant.

In any case, understand that these engines came equipped with soft valve springs, ie. 60-65 lbs soft!
That was just fine in the early '70s pushing a land barge at low RPMs, BUT . . . half a century later, given wear, time, and reality, not so much.

The good news is (or might be) that only the very earliest of those engines with the smaller, 76cc chamber heads had the interference issue eluded to earlier. The later ones (the majority) with the larger 120cc chamber heads do not present that complication.

In any case, I would be hesitant to just start spinning it with the starter until I identified what happened. No need in making a potentially bad situation worse. Pull the plugs and the distributor cap and turn it over by hand with the prop.

If the rotor doesn't turn, the chain is obviously suspect. If that appears OK, pull the valve covers and confirm that all the rockers are where they are supposed to be. I suspect you will find one of them tried to escape his defined space on the pedestal and most likely bent the push rod in the process. Usually that push rod will no longer by visible because it is now laying in the valley under the intake. It is also quite possible that the after that, the lifter escaped it's bore and is now elsewhere. That doesn't always happen, you might be lucky enough to fish it out and find the lifter still where it is supposed to be. I wouldn't hold my breathe for that one, though.

It was always recommended by people here who know, that before putting one of those guys back in service, to replace the chain and preferably the lifters as well. It is possible (hopefully) that the stretched chain just jumped a tooth and replacing that will solve the immediate problem. In any case, I suggest you [Search] here and read a lot as your proceed. There is likely more old Caddy information readily available, here than anywhere else.

Although the current [Search] feature doesn't quite match the old one, that doesn't change how much info is here to be had.
 

John Fenner

Well-known member
Good advice above, pull the rocker covers and observe valve action rotating by hand, "battery disconnected"
If all that looks good, rotate it to top dead center #1 compression stroke observe the rotor position of the distributor, if not aiming at the #1 pot, timing issue, for an abrupt shut down as you described, could be the distributor pickup coil the module or the weights, many varitives to check.
 

One Eyed Gator

Well-known member
When I ran my caddy I was having a timing issue. Found the the timing set crank gear itself was eaten away by the crank key. Slot in the gear was almost twice the size of key. Variable timing lol.

Deano has some good advice if that not the issue check the crank gear.
 

Deano

Well-known member
I'd caution anybody, that you had better know what you are looking at before you make that trip.
 

John Fenner

Well-known member
When I ran my caddy I was having a timing issue. Found the the timing set crank gear itself was eaten away by the crank key. Slot in the gear was almost twice the size of key. Variable timing lol.

Deano has some good advice if that not the issue check the crank gear.
Back in 88/95 we had a fleet of caddy DD engines swinging 80" wood props on tour boats, twin engine 24'x15' the engine builder had custom cam grind to build up the lower end torque, they ran very strong, the weakest link was the crank timing cog as it was an advance type with the 3 different keyways, the harmonics of the setup shattered the gears, changed many of them out over that timeline, they didn't have many high performance parts back then, had to build outside the box so to speak.
 

Deano

Well-known member
Kbrewer, After looking back at this thread again this morning and seeing how the conversation has turned toward Cadillac timing sets, it becomes glaring obvious that I neglected to point out that the timing set you want to use is a Cloyes 91-139 (better confirm that number, as I have CRS). This gear set is not the 'double roller' that the advertisements claim, but it does include a healthy chain and two steel gears. The crank gear has three keyways. The one, will allow you to advance the timing a little, which will help your cause with a direct drive.

I didn't, but maybe should have elaborated on that point previously. The standard, OEM gear set had some kind of glorified plastic teeth that seemed to suit the purpose for the time being. However as the decades passed those guys got beyond brittle and liked to break off. This may well be your problem, in fact, if the rockers are all where they belong (ie. intact), then I would bet this is your issue. A word of caution in that regard... Be sure you drop the pan and thoroughly clean everything, to include the oil pick-up tube. You will likely find that shit everywhere, because the the last guy probably didn't do that and there remnants of more than just the current incident. The way that pick-up is constructed it will suck up and hold all of those little broken teeth pieces. Removing it and running pressurized air or better yet, water through it backwards, is generally the most thorough and time effective means of doing that. On that note, be aware that front gasket set will include two o-rings for the reinstall of that pick-up tube (one is for the 425). Confirm you use the right one, when you reassemble it!

As far as the Double Wide Keyway goes . . . What OEG and John have reported is much more common than most people reading this realize.
At a glance, this all reads like the crank gears are inferior or somehow defective. That is not the case. This is not something you see happen in an old land barge. This occurrence is quite specific to an air boat application (dd especially), and is in fact, quite common where the hours have been amassed like the boat owner would hope for. Consider if you will, that with the mass of the prop bolted directly to the crankshaft, EVERY TIME you let off the throttle . . . you not only have the mass of the prop and the valve train acting as a brake, but you also have centrifugal force of that mass, plus the wind resistance the prop USED to be pushing. While the crank and all its weight and mass are turning Clockwise, when you let off the gas, you have everything just listed attempting to turn Counter-Clockwise! Something has to give (or wear), and that something is the crank gear keyway. I had some pictures of this hacing happened that were quite impressive, but sadly, that computer is no longer with us.

One last thing . . . Be Aware before the fact, that the instructions with that timing set are less clear then black mud. Search here first, or at least be aware that those gear set instructions are left-handed, backwards, inside out, upside down, etc. IIRC, If you install the timing marks in standard fashion with them both being UP, you need to install the chain with #4 at TDC, NOT #1. Then turn the assembly to #1 TDC to stab the distributor. Again, this is from memory, so double check it when you get that far. In any case, don't be bashful about asking questions. These old Caddies have their idiosyncrasies, but there a few of us left willing to help when we can.

Let us know what you find when you tear into into it. A few of us are more than passively curious.
 

JLP3314

Well-known member
I'd caution anybody, that you had better know what you are looking at before you make that trip.
Real close to me but I actually failed to read his post.
He's selling it as parts, (no crank and many other parts needed to build an engine).
Simply trying to help...
 

Deano

Well-known member
JLP, I tried to word that response so as not to sound derogatory, but evidently failed.
I am sure everybody (myself included) read that as if you were meaning to help, and not otherwise.
My point was no reflection on you whatsoever, but rather for the benefit of someone not 'Old Cadillac' familiar . . . which is most people.

There are obviously complications with, and knowledge required to successfully purchase any pile of parts and arrive at having a running engine. All of that reality is compounded in the case of the 'Old Cadillac'.

When there is a pile of parts such as those for sale, the seller always claims it is a '500 Caddy'. Realistically, it could be comprised of unusable parts from 1 500, 3 472s, and 2 more 425s. If you aren't familiar with all the possibilities and know all the different numbers involved for blocks, heads and cranks (and know what works with what), you will be wasting money and setting yourself up for an expensive heartburn.

It is an undeniable, and somewhat sad reality, that these engines are not the cost effective, quick and easy alternative they used to be.
It can still be done for the same reasons and attain the same results, but because of lacking parts availability and the associated expense, it is not cost effective like it once was. This is why I caution against jumping in that hole, unless you are already aware how deep it can be.
 

Deano

Well-known member
"500 caddilac hill burner" - always wanted to see one of these, maybe one day ;)
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