Retard the timing to help with overheating?

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GeeLeDouche
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Retard the timing to help with overheating?

Post by GeeLeDouche » Thu Jun 23, 2011 2:00 am

So.. as some of you may know I've been fighting a never ending battle with my 0-470 overheating like a banshee. Well, I took it in to the mechanic to have him help me diagnose why the Cylinders are getting so hot and he suggested retarding the timing down from 25 degrees down to 20 and that should help. He also did a compression test on all the cylinders and found that all of my cylinders are right around 70, except for the one he just barely put a new piston and rings in. (It was down to 20 :shock: ) He said that the new piston rings had probably not seated yet adn thats why the 1 cylinder had low compression... anywho. I dont think I've ever heard of setting the timing back a few degrees being a "fix" for the engine getting to hot. Anyone ever done this with any success? thanks guys!


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Ps- Also,, does 70 sound about right for the compression?
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Re: Retard the timing to help with overheating?

Post by Screamin Seaman » Thu Jun 23, 2011 2:52 am

timing thats too retarded will burn an exhaust valve.
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Re: Retard the timing to help with overheating?

Post by billybob » Thu Jun 23, 2011 5:23 am

24 or 23 is all I would back it down to. It will make a difference. 20 pounds in a new cylinder seems alot low.
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Re: Retard the timing to help with overheating?

Post by Whitebear » Thu Jun 23, 2011 6:05 am

If its timed correctly and set to factory spec and it overheats, the problem is elsewhere.
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Des Moines Boater
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Re: Retard the timing to help with overheating?

Post by Des Moines Boater » Thu Jun 23, 2011 7:52 am

Pull that cylinder and find out what went wrong. 20 pounds is way too low. Do you know how hot your cylinders were getting? Setting the timing wrong isn't going to help anything. Can you find another mechanic to help you out? Let us know what you find.

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Re: Retard the timing to help with overheating?

Post by twister69z » Thu Jun 23, 2011 7:55 am

Des Moines Boater wrote:Pull that cylinder and find out what went wrong. 20 pounds is way too low. Do you know how hot your cylinders were getting? Setting the timing wrong isn't going to help anything. Can you find another mechanic to help you out? Let us know what you find.
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Re: Retard the timing to help with overheating?

Post by MJD291 » Thu Jun 23, 2011 9:10 am

What is overheating?? Oil Temp?? Cylinder Temp??? What are the temps??? Sorry I haven't followed your previous threads and was curious.
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Re: Retard the timing to help with overheating?

Post by Dixiedog60 » Thu Jun 23, 2011 9:22 am

Bad bearings make great oil heaters as I recently experienced. Hope thats not your problem.
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Re: Retard the timing to help with overheating?

Post by Terry Bailey » Thu Jun 23, 2011 9:27 am

put new rings in my gpu all had over 90psi before seating rings.eng smoked alittle for about 10 hrs now no smoke and and still have good comp.

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Re: Retard the timing to help with overheating?

Post by GeeLeDouche » Thu Jun 23, 2011 9:53 am

I have both high oil temps (270+) and high cylinder temps. I monitored them pretty close last time I took my boat out and a few of them got right around 475, but most of them didnt break 425. My mechanic told me that the reason that cylinder was probably so low is because the rings hadnt seated yet, but I;m not sure if thats the problem or not.. This is the same cylinder that I burned a hole through the piston in a month or two ago.
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Re: Retard the timing to help with overheating?

Post by JT540 » Thu Jun 23, 2011 10:52 am

GeeLeDouche wrote:I have both high oil temps (270+) and high cylinder temps. I monitored them pretty close last time I took my boat out and a few of them got right around 475, but most of them didnt break 425. My mechanic told me that the reason that cylinder was probably so low is because the rings hadnt seated yet, but I;m not sure if thats the problem or not.. This is the same cylinder that I burned a hole through the piston in a month or two ago.
sounds like a lean condition to me. check your carb again. and check for intake leaks.
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Re: Retard the timing to help with overheating?

Post by MJD291 » Thu Jun 23, 2011 11:00 am

JT540 wrote:
GeeLeDouche wrote:I have both high oil temps (270+) and high cylinder temps. I monitored them pretty close last time I took my boat out and a few of them got right around 475, but most of them didnt break 425. My mechanic told me that the reason that cylinder was probably so low is because the rings hadnt seated yet, but I;m not sure if thats the problem or not.. This is the same cylinder that I burned a hole through the piston in a month or two ago.
sounds like a lean condition to me. check your carb again. and check for intake leaks.

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Re: Retard the timing to help with overheating?

Post by mudholian » Thu Jun 23, 2011 12:45 pm

0-470 GPU? Can you post a pic?

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Re: Retard the timing to help with overheating?

Post by Deep Diver » Thu Jun 23, 2011 12:50 pm

if its an auto carb install 4 numbers larger. possibly low fuel pressure?

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Re: Retard the timing to help with overheating?

Post by mudholian » Thu Jun 23, 2011 12:57 pm

Nevermind, I remember your last post, seen the pic. Dude, your oil is bybassing in your engine... I must not be explaining it right or something. Call this number 407-927-9701 and talk to JC Stanley, he might be ablt to explain it to you better. ask him about oil bypassing internal. I had the same exact issue and wish I had a pic to show you what I done.

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Re: Retard the timing to help with overheating?

Post by GMAC 76 » Thu Jun 23, 2011 2:37 pm

Gee, i have not been following your heating problem so what i am going to tell ya has probably already been addressed BUT, this spring a buddy bought a 470 with no carb he later picked up an MA-4-5 which bolted right up the engine started right up idled fine good throttle response but would get terrible hot when crusing he tried everything like i assume you have come to find out the MA-4-5 carb was for a 4 cyl lycoming and running way to lean put the right internal parts (discharge nozzle, idle tube,etc) and set it up to 0470 specs and that took care of the heating problem just another idea good luck

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Re: Retard the timing to help with overheating?

Post by littlejoe » Thu Jun 23, 2011 4:12 pm

your compression is way to low your pistons dissapate heat through the rings to the barrel if they are to loose,the wrong size or worn out your engine will run much higher temps.I just honed my jugs and installed new rings I'm running 115 to 120 psi and my rings have not seated yet.anything under about 65 psi is a dead hole :shock:

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Re: Retard the timing to help with overheating?

Post by GeeLeDouche » Thu Jun 23, 2011 7:30 pm

Yeah, as far as I know I'm still running the stock carb. Its just what came with the motor.

These are about the best pics I have of my carb..

Image
Image
Image

(Just FYI the yellow tube going into my carb is to help with Carb Icing. We call it a hot air exchange)
Last edited by GeeLeDouche on Thu Jun 23, 2011 7:50 pm, edited 1 time in total.
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GeeLeDouche
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Re: Retard the timing to help with overheating?

Post by GeeLeDouche » Thu Jun 23, 2011 7:34 pm

I plan on checking the intake for leaks. If that doesnt work, I dont know WTF to do with it..
16x8 Utah style hull With a Waterthunder motor W/ 2.3 CH3 reduction swinging a 3 blade 78" R.
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Re: Retard the timing to help with overheating?

Post by mudholian » Thu Jun 23, 2011 8:44 pm

Aircraft 470, thought it was a ground power, disreguard what I said about the oil bypass, If I were you I would still call JC, very nice and helpful guy over the phone.

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Re: Retard the timing to help with overheating?

Post by hmgm123 » Thu Jun 23, 2011 10:10 pm

Are you sure your oil cooler isn't clogged. What oil pressure are you running after it is warmed up at idle and cruise?

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Re: Retard the timing to help with overheating?

Post by GeeLeDouche » Fri Jun 24, 2011 3:21 am

No, I'm not sure my cooler isnt plugged, but I dont think that would explain the cylinder temp getting so hot would it? My oil pressure is pretty low.. right around 20-25ish. I called JC and he told me to find the numbers on my carb and get back to him to make sure I have the correct carb on there. And yes, he is a very nice and very helpful guy!
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Re: Retard the timing to help with overheating?

Post by Des Moines Boater » Fri Jun 24, 2011 7:56 am

With the cylinder and oil pressure both in the 20's, it sounds like you need to pull that engine off and have it overhauled.

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Re: Retard the timing to help with overheating?

Post by Daddy Dave » Fri Jun 24, 2011 8:13 am

On the 0-470s I have had, idle oil pressure in the 20s is normal. Run oil pressure is something else altogether - it should be at least high 40s - on up. Several have advised to check the oil flow circuit through the oil cooler -- nothing is more important. It COULD have been routed improperly years ago -- No flow - restricted oil flow will create the conditions you describe. If that is happening, then the center cyls will get very hot, quickly. No cyl. should show 20 lbs of compression -- but, that's another issue altogether.
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Re: Retard the timing to help with overheating?

Post by jinotown » Fri Jun 24, 2011 10:04 am

I have not read your previous posts and I'm not sure how many hours are on those rings so I will give some basics. It takes at least 30 to 50 hours for those rings to break in to the point you will see a noticeable CHT drop and temps stabilize. Hopefully the cylinders were honed when the rings were installed or they will not break in properly. If the CHT got over 500 degrees at all when the rings were first installed, the cylinders can glaze and they will never break in. Only another hone will cure that. 70 PSI on a warm engine with good rings is not very good. I like to see 15 to 19 PSI per point of compression(105+). If you are quoting your oil pressure at idle, it seems OK. A general rule of thumb on oil pressure is 10 PSI per 1K rpm is good. Verify your oil temp gauge is accurate. I have had more than one cause me to chase a non-existent problem. The temp problems may be indirectly related but I would track the oil and CHT temp issues separately and cure one at a time.
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