SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: BIG JOHNSON on May 09, 2012, 08:55:59 PM
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Planning on pulling heads end of season for valve job. Can any efficiency be gained from porting or having them flowed? I've never had to have a motor apart on anything, guess I've had good luck with most things before sold...
Am I better off having work done on the current heads or get some loaded aluminums and r&r?
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Going for the performance huh? Wish I knew more about chevy so i could help.
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Going for the performance huh? Wish I knew more about chevy so i could help.
Not per se, just thinkin since its comin apart, may as well. Us fellas with the tanks need all the help we can get.
The motor has close to 600 hrs, though well-maintained, my old man says might as well freshen and purdy it all up... Don't think I wanna go all out on it.. shit runs great for what it is.. Old man says, "either run it till its dust or do the whole she-bang and stop talking about it"
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that will depend on how much you want to spend. and how much real power your engine will put out with heads you fix or buy. if its a stock motor just have a little work done to your heads. like 3 angle valve grind, matching the combustion chambers. and maybe match porting. spending a ton of money on bad ass heads for a stock motor wont help. youll never notice all the money you spend.
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During my last build I increased compression and did some port work on the heads, I didn't get much of a performance increase until I went to a bigger cam and installed the headers.
It's all about the combination of parts and machine work that will make good power and make it last.
Good luck.
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save your money.
buy a blower.
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I wouldn't waste my money id just freshen up the engine but if your after some more shitnget im personally would go this route http://www.jegs.com/p/Edelbrock/Edelbrock-Marine-Top-End-Kits/762825/10002/-1
Fat fingered from the phone - Corey
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just do a nice valve job, you wont notice any thing under a 50hp gain in a jet boat.. now if you are going to upgrade the cam and such then go for it
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Big J,
This is my unabashed humble opinion... :sly:
I used to hang out at my dads machine shop as a kid...Guess you could say i grew up with a silver wrench in my mouth... :-\
The guys at Gromm Racing Cylinder Heads said something decades ago that I will never forget.
"You can kick performance right in the face with a good port job, if everything does not match to a tee, you may have been better off leaving it stock".
Meaning to me, just because you have $400 running shoes on does not make you a faster runner..... ;)
Let me tell you my odd analysis on porting and polishing.
1). If you will be running RPM's and a camshaft to support it that exceeds the capability of factory condition cylinder heads, you should consider porting.
2). If you have matched every component as far as carburetor, intake, exhaust, camshaft, compression ratio and are looking for that ever so elusive extra 10 HP, then porting may be desirable.
3). If you have a "guru" that can guarantee or money back that you will see a performance gain in RPM and dyno proven HP, I say go for it (but I will need his digits.. ;D)
4). If you are going to build a lake boat that is making 400-500 HP and does everything you want it to do and have no delusions of going 100 MPH...Use the money to fill the cooler and the gas tank. :thumbup:
A camshaft and a carburetor, sometimes exhaust, some compression are your biggest "bang for the buck"...Anything after that the dollar per horsepower gets stupid....
Again, these are just my thoughts shared on an Internet forum and in no way are meant to insult or pursued you in any direction or the other....
GT
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GT, I was waiting for a response from ya.
Good points you bring to the table. I have a good runnin motor as of now, with 2 cyl @ 125 and the other 6 @ 140 to 60 mph..
I AM going to do a valve job on both sides after this season, because I know there's somethin that happened with the leaky riser above the two cylinders that I have lower compression on.
Buying a 15 yr old 21' cruiser, I am beating the odds at 60mph..
I'm that kinda guy, in my 2002 chevy truck, I always lift the door handle when I shut my driver door so I don't wear out the pins, and I remove my wallet full of credit cards before entry so I don't stretch the leather in the 2011 chevy.
Think I've damn near come to the conclusion to just do the valve job and keep the leaks held until I'm ready to do the whole shot years from now.
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I appreciate the responses from everyone.
One more question for the night; is there any damage I will do to my motor by running it another 15-20 hrs this season? The water leak at the riser has been corrected. Aside from burning a slight amount of oil, if any, is there any further damage that may occur? I never noticed oil consumption, maybe due to the old carb problem that was filling the case with fuel improperly regulated...
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I appreciate the responses from everyone.
One more question for the night; is there any damage I will do to my motor by running it another 15-20 hrs this season? The water leak at the riser has been corrected. Aside from burning a slight amount of oil, if any, is there any further damage that may occur? I never noticed oil consumption, maybe due to the old carb problem that was filling the case with fuel improperly regulated...
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I don't think I would have any problems running for the season, or more..The only potential issue I may caution you on would be if you really do have a valve problem in a valve or two, there is a potential of burning a valve, which if a pie shaped piece drops out, it could make some nice desk art out of a piston (aka paperweight)...
I would be willing to bet your compression loss is a rusted cylinder, not a valve...Have you done a leak down test?
GT
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Have not done a leakdown.. I have the motion-pro kit for doing leakdown check on the quadzilla, but don't know if it applies to a big block... Whom would a guy go to for a leakdown test?
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Have not done a leakdown.. I have the motion-pro kit for doing leakdown check on the quadzilla, but don't know if it applies to a big block... Whom would a guy go to for a leakdown test?
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If the Motion Pro is what I think it is, the two stroke version differs from the four......But stabbing in the dark...
I bought my tester from Snap On tool years ago, but the cheapo I picked up from Harbor Freight works just as well and it's on sale! :thumbup: :thumbup:
http://www.harborfreight.com/cylinder-leak-down-tester-94190.html (http://www.harborfreight.com/cylinder-leak-down-tester-94190.html)