OK i did the compresion test on my 1983 470 170hp

fmalott

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i did the compression test and the results were very surprising #1 145psi, #2 150psi, #3 145, #4 130 so the dreaded #4 cylinder signs are showing but still good reading. so here is were i'm at i will be pulling motor to replace all gaskets they all need it. the head gasket and the cam seals i will be replacing and i will be inspecting cam for wear i will be checking all crank shaft bearings for wear and rebuilding the head and getting machined so total over haul. So should i just hone the cylinders out (i have one of those honing tools you put on your drill) and just replace the rings since there is good compression i will be measuring to see if the cylinders are out of round and they have not bein already rebuilt
P.S. i know the compression is good sorry guys i love tearing things apart it will give me a peace of mind that everything is perfect then i don't have to worry about it later if they are out of round then i get someone professional to hone out and get me fitted up to new bore size, if they are nice and round and not worn out that i don't need to go get it bored out then just replacing rings seems ok what do you think?
 

stonyloam

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Re: OK i did the compresion test on my 1983 470 170hp

Sounds like a plan. I would consider having hardened exhaust seats installed in the head. Have fun;)
 

joewithaboat

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Re: OK i did the compresion test on my 1983 470 170hp

Plan sounds ok Except "Hone with a hand held drill"
It would be very unlikely that you would do anything except possibly ruin it.
A good Dial bore gauge to check your progress would cost 3 to 4 times what a competent machine shop would charge to bore and hone it properly. When you see the tools that the machine shop uses you will understand. I worked in one for a couple years while in college and have done all of this stuff many times.
good luck!
 

fmalott

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Re: OK i did the compresion test on my 1983 470 170hp

i'm actually leaning towards a shop doing it i can do it but there is not enough hours in a day stonyloam i'm not sure what you mean by hardened exhaust seats
 

joewithaboat

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Re: OK i did the compresion test on my 1983 470 170hp

Hard exhaust seats are bored and press fit into the head to prevent valve erosion. The lead in the fuel in the old days prevented this. Some factory heads that don?t have hard seats inserted have heat treated seats "induction hardened" but it doesn?t work that well.
Forward to 1:07 in this video, its a triumph head but you get the picture.
http://www.youtube.com/watch?v=5hvtIo2jDwI
 

fmalott

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Re: OK i did the compresion test on my 1983 470 170hp

so if i went to a local machine shop that does work on motor heads they will know what i'm talking about or is this just a merc thing
 

joewithaboat

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Re: OK i did the compresion test on my 1983 470 170hp

Some but not all shops will have machines to install seats. You should find someone that frequently works on that particular head if possible. You can get into problems with seat sizes and cutting into the water jacket if not careful and or familiar with the casting. I have no specific knowledge of this motor or head by the way but have worked on big block ford (385 series) which I think is where that head comes from.... anyway you might ask stoneyloam above to elaborate on his exp with the need for hard seats in this head he might have some, as he mentioned it.
 

stonyloam

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Re: OK i did the compresion test on my 1983 470 170hp

I had some significant pitting around the valve seat due to coolant leaking into the #4 cylinder. My machinist installed a new hard seat and valve to take care of it and at his suggestion we went ahead and replaced all 4 exhaust seats. It was not very expensive, around $20 each as I recall. He was pretty experienced with 470 heads and he measured the valve stem heights to make sure they were the same after the work, so the pushrods would be the correct length. Since your #4 was a little low it might be something to ask about. Yeah taking it to a machine shop is a good idea. Have fun!
 

dollarten

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Re: OK i did the compresion test on my 1983 470 170hp

Some but not all shops will have machines to install seats. You should find someone that frequently works on that particular head if possible. You can get into problems with seat sizes and cutting into the water jacket if not careful and or familiar with the casting. I have no specific knowledge of this motor or head by the way but have worked on big block ford (385 series) which I think is where that head comes from.... anyway you might ask stoneyloam above to elaborate on his exp with the need for hard seats in this head he might have some, as he mentioned it.
joewithaboat, I have heard of some of the complications of hitting water when cutting for different valve seats , maybe to replace a worn one but I would go slow on replacing all of them Here is a story right from Mercury Marine on valve seat erosion . This goes back away but, forgive me One of the service school instructors in Fon Du Lac , Wi. was telling about a test that was ran on a 302 Ford ,,back when they ran Ford engines and were having high failures on valve guides and seat in this particular engine . Now this was in the time when all gasoline was leaded . They were going take a 302 engine , called the 188 at the time and put it on the dyno and simulate a load on the engine. This load would be the similar to engine being run at wide open throttle in a boat at approximately 4200 RPMs . The test was going to for 100 Hours . The engine starting loosing power at 40-50 hours . At 60 hours the test was ended due to severe power loss . The heads were removed and were beyond serviceable with normal repair procedures . Valve seats , valve guides , beyond repair . This same engine received a new set of stock heads and a new test was started . This time with the same load but , with the throttle bought back to give 5 inches of manifold vacuum and running about 3600 RPMs . The engine concluded the 100 hour test and the engine ran great for the entire duration . Cylinder heads removed again and inspection showed minimal wear and could have been reused as is This is a true story and sorry about the length here but ,draw you own conclusions . Mercruiser uses passenger type car engine in actuality and will give great service when used in moderation and occasional ,short full throttle runs . When they are run at full load , which the owners manual suggests not to do , their life will be shortened
 

dollarten

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Re: OK i did the compresion test on my 1983 470 170hp

I had some significant pitting around the valve seat due to coolant leaking into the #4 cylinder. My machinist installed a new hard seat and valve to take care of it and at his suggestion we went ahead and replaced all 4 exhaust seats. It was not very expensive, around $20 each as I recall. He was pretty experienced with 470 heads and he measured the valve stem heights to make sure they were the same after the work, so the pushrods would be the correct length. Since your #4 was a little low it might be something to ask about. Yeah taking it to a machine shop is a good idea. Have fun!
Sounds like your machinist knew what he was doing , stony and for a good price . Not to throw cold water on your program but I had to share my story also from Mercury Marine . I was typing ( one peck at a time ) when your story was posted 2 minutes prior
 

stonyloam

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Re: OK i did the compresion test on my 1983 470 170hp

Sounds like your machinist knew what he was doing

Yeah he was recommended by my local Merc dealer, he does work for them. Great story! That is why I almost never run WOT for any extended period of time, usually 3500 or so, plenty fast enough for an old guy LOL.
 

natemoore

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Re: OK i did the compresion test on my 1983 470 170hp

I had some significant pitting around the valve seat due to coolant leaking into the #4 cylinder. My machinist installed a new hard seat and valve to take care of it and at his suggestion we went ahead and replaced all 4 exhaust seats. It was not very expensive, around $20 each as I recall. He was pretty experienced with 470 heads and he measured the valve stem heights to make sure they were the same after the work, so the pushrods would be the correct length. Since your #4 was a little low it might be something to ask about. Yeah taking it to a machine shop is a good idea. Have fun!

What is it about #4 that makes it the problem child of the 470?
 

fmalott

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Re: OK i did the compresion test on my 1983 470 170hp

wow! great info guys i don't have the head off yet but when i looked in the oil filler hole it looks very clean the old fellow i bought the boat off took very good care of the boat i'm the second owner i don't go boating every day when at the cottage when i do i don't go WOT i like to cruise and look at the view. the old fellow just got to old to do it anymore when he bought the boat back in 1983 he was around 50 years he said he didn't drive the boat hard he said he was to old for that we had a good laugh at that one i'm 50 now LOL. he did regular oil changes changed plugs etc etc. what surprised me he said i never had to pull the motor to do any work of any sort just your bellows he changed a couple of times. so with the compression as good as it is i think i don't need to do all what your saying but i will be documenting that info some day i might run across that problem at least i will be informed and when i get the head machined i will ask the machinist about it and see what more info he can produce. just by what a couple of you said i can see the problem occuring if you go WOT all the time i will be definitly looking more into this
 

fmalott

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Re: OK i did the compresion test on my 1983 470 170hp

i'm starting a new thread about this hardening thing my main concern with this thread is the rings and pistons i'm pretty set on what i'm doing with that thanks
 
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