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Caddy Timing quetion..

Smuggler

Well-known member
My cousin has a direct drive 500 caddy and I noticed that his vacuum advance is hooked up.. Waterthunder helped me out on my SBC timing. He told me what to set it at, what springs to use in the distributor and to plug off the vacuum advance.

Now I have the same questions for the 500 caddy.. I am thinking that if the advance is hooked up then we should just start fresh..

What should the timing be set at and and what RPM should it be at when setting it?

Should I buy another advance kit and use the same springs as I did on my SBC?

Should I plug off the advance on his also?

I would appreciate any info I can get.
Thanks!!
 
Thanks for the reply Bondsman but I briefly look at that site and did a search also and it seams everything I looked at was hot rod related. His boat has a wood prop and only turns 2700 max so I don't know if that info would apply. Or does it? How did you do yours before you added the gear box?
 
Smuggler--we need to know WHAT Cadillac engine he has i.e. early 76cc heads or later 120cc heads, what carb, what propeller, what boat (weight) and any mods to the engine. THEN we can talk about timing. Regards, Charles "Maddog" Morehead
 
when it was stock with a cam mod .i locked the vacume.ran 14degrees of initial timing and 36deg. total timing with the light springs.i ran cheap crap gas with no ping.i set initial timing at 750 rpm.then i idled it down to 600 so when i stopped after running it wouldn't diesel or backspin.
 
Alright, I am confused. No, I stay confused, I am more confused. I called Potter about this very thing. I didn't talk to Potter I talked to some young man that works there. I assume he knew what he was talking about BUT. I ask about initial timing and setting it at 14 degs.. I have a modified distributor and it is suppose to be a custom-made unit from PSD. He said that initial floats and to set the total at 36 deg.. I went to NAPA and bought a descent timing light. I checked and I have 14 deg at idle. I tried to check total at somewhere around 2500 to 3000 rpm and it was beyond my timing marks. I have not touched anything sense a true mechanic set it. I was just seeing if I could see how he got there so if and when I needed to set it I could. I run a 500 Caddy, Pistons are forged by Arias and are .040" oversize with a 9.7:1 compression ratio, with Potters roller rockers & heavy duty springs, and a Holly 850 dp. I have a 3 blade Sensenich wide blade set to max rpm of 4500 and a 2.38:1 Stinger soft gear drive. Runs great here. I do get some dieseling when I run it hard and don't let it idle for a minute or two. How do you set initial timing and lock it down?

Kim
 
Kim

I personally would suggest trying to get all your timing in by say 2500 to 3000 RPM.
You can check your timing above this RPM range to see if your timing is all in.

If your harmonic balancer does not have a timing tape that reads to 36 degrees BTDC then you cannot set your total timing with a standard light.
Also, if you did not mark your harmonic balancer @ 36 degrees BTDC when degreeing your cam you still cannot use a standard timing light to set the total timing on your engine @ 36 degrees BTDC.

Start thinking total timing and forget the initial. Buy or borrow a timing light that has a dial on the back or at least one you can set your total timing to what you want. Then, with the vacuum advance uhooked, set your timing to where TDC#1 on your harmnonic balancer and zero on your timing tab line up. This will give you the total degrees timing BTDC that you desire. I suggest you do not ever hook up your vacuum advance hose again. Keep it simple.
If you learn to use an adjustable timing light you can set your total timing and then learn how much advance is built in to your very own distrubitor.


36 degrees total in your scenario is possibly tooooo much total timing. I would suggest 28-32 degrees total for your engine. Seems that @ 4500 governed you must be building lots of cylinder pressure down low due to very little valve overlap.
You are building static therefore taking care of the dynamic so no need to manipulate with timing.
 
DO YOUR TOTAL , DONT WORRY ABOUT THE BOTTOM ! I DO THE 34 ON TOP ! I GOT THE SAME SET UP AS YOU , BUT I GOT KB PISTONS AND GOT A MSD TIMING BOX WITH A FIXED DISTRIBUTOR ! IT RETAFDS UNDER 1000 AND ALL IN BY 3000 ! THIS GAS QUALITY SUCKS RITE NOW ANYWAY ! LIKE FISH SAID ! :D
 
The size of the boat and the reduction mostly dictate what timing you should run. I have a 18ft barge with a 1.7 belt reduction so I cant run as much timing as a 14ft boat. I removed the vacuum advance and run a total timing of 26 degrees. It runs perfect I can let it sit for a month turn the key without touching the gas and she fires right up and idles perfectly.
 
Waterthunder":3sgklnkm said:
The size of the boat and the reduction mostly dictate what timing you should run. I have a 18ft barge with a 1.7 belt reduction so I cant run as much timing as a 14ft boat. I removed the vacuum advance and run a total timing of 26 degrees. It runs perfect I can let it sit for a month turn the key without touching the gas and she fires right up and idles perfectly.

Interesting, I would have thought that piston dome volume, shape and size of combustion chamber, how much valve overlap, idle circuitry, and quality of fuel would mostly dictate what timing you should run.
 
My experience has taught me to run 34-36 total timing with the big Cadillac. 14 initial is perfect. But the top is what matters. I bring mine all in by 2000. All computer driven, no vacuum. Thunder----I would have to see a Cadillac start right up with no pump of the accelerator after a month. Are you running HEI? Carb?

Maddog
 
i don't run more than 34deg. total now with a gearbox all in by 2300rpm . i ran 36 but i blew a head gasket and now i am just hinky about it.
 
Flying Fish it all matters and the hull size and weight maters just as much as the dome or compression! To state what timing to run without knowing ALL the specs is ignorant! I'm sorry I just assumed everybody knew all of motor specs were involved and that was automatically considered and they just left out the boat and gearbox.
 
Bondsman I tell people you can't tell the difference between 34 degrees and 32 accept when you burn a piston. I did a dyno pull on one of my 500HP motors I went from 36 to 35 to 34 to 33 to 32 to 30 to 29 degrees and the horsepower I lost was VERY little and you couldn't tell on a boat I promise you. So I just got more aggressive on my timing curve but with less timing!
 
Waterthunder":2c930rwl said:
To state what timing to run without knowing ALL the specs is ignorant! I'm sorry I just assumed everybody knew all of motor specs were involved and that was automatically considered and they just left out the boat and gearbox.
we still don't know the total setup and ruagatr asked for it no info was given on the setup still.then he just asked how mine was setup we are not trying to be ignorant just answering the mans simple question.
 
Waterthunder":2lz8p592 said:
Bondsman I tell people you can't tell the difference between 34 degrees and 32 accept when you burn a piston. I did a dyno pull on one of my 500HP motors I went from 36 to 35 to 34 to 33 to 32 to 30 to 29 degrees and the horsepower I lost was VERY little and you couldn't tell on a boat I promise you. So I just got more aggressive on my timing curve but with less timing!
i agree some engines there is little power loss.i did not have a dino to test n tune my motor i cannot tell any change in performance from 34-36deg total but less then 32deg. i loose rpm.i dont run the 36 anymore cause alot of the caddy venders say that my bore beeing .060 over and running felpro's is a big no-no.some have no problems.i lost a head gasket running hard with 36 total.at 34 total ran it harder than before and she is running good.so that is why i have been hinky about 36deg.
 
Waterthunder":nlbbde4a said:
Flying Fish it all matters and the hull size and weight maters just as much as the dome or compression! To state what timing to run without knowing ALL the specs is ignorant! I'm sorry I just assumed everybody knew all of motor specs were involved and that was automatically considered and they just left out the boat and gearbox.

Thunder-
On a 9.7 to 1 static compression airboat engine topped with a 850 cfm carb coupled to a 2.38 to 1 reduction and assuming carb is jetted proper. 28-32 degrees total timing is a conservative suggestion.
Trust me, I guarantee it.
 
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