new jet boat with 455 olds some questions plz
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new jet boat with 455 olds some questions plz

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    Member weezy950's Avatar
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    Default new jet boat with 455 olds some questions plz

    hey everybody im new to this scene and may sound a little lost but i appreciate any feedback or help i can get to learn as much as i can. i have looked and read on forums as much as possible and learned a lil bit about the oil return issue with olds motors but couldnt find too many answers to other questions i had. i just recently purchased a 1971 jet boat the previous owner said it was a 455 olds motor. he wasnt much help in describing it too much plus i was excited for the purchase so i didnt remember all the questions i had. it runs great lots of fun i just got back from havasu this past weekend and had no problems with it. not sure how fast i was going but didnt seem too fast lol and i would like to go faster.. i have a couple of questions as to 1.why it would backfire or popp when i would hit 4200-4500 rpm then i would let off the gas, 2.what should my water temp be at? 3.what should my oil pressure be at? 4.how can i get a bigger rooster tail? 5.where can i find the headers that come up out by the motor? i like it loud and looks cooler. and how do i cover up the old exhaust pipe holes? again sorry for any dumb questions im a noob and would like to learn as much as i can here...thanks again!!
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    Senior Member pilot940's Avatar
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    Quote Originally Posted by weezy950 View Post
    hey everybody im new to this scene and may sound a little lost but i appreciate any feedback or help i can get to learn as much as i can. i have looked and read on forums as much as possible and learned a lil bit about the oil return issue with olds motors but couldnt find too many answers to other questions i had. i just recently purchased a 1971 jet boat the previous owner said it was a 455 olds motor. he wasnt much help in describing it too much plus i was excited for the purchase so i didnt remember all the questions i had. it runs great lots of fun i just got back from havasu this past weekend and had no problems with it. not sure how fast i was going but didnt seem too fast lol and i would like to go faster.. i have a couple of questions as to 1.why it would backfire or popp when i would hit 4200-4500 rpm then i would let off the gas, 2.what should my water temp be at? 3.what should my oil pressure be at? 4.how can i get a bigger rooster tail? 5.where can i find the headers that come up out by the motor? i like it loud and looks cooler. and how do i cover up the old exhaust pipe holes? again sorry for any dumb questions im a noob and would like to learn as much as i can here...thanks again!!
    Nice looking boat, glad to see another Olds! My guess on the back fire might be your timing, I can't tell by the pics if you have vac advance or just mechanical. when you set the timing you should have a max of 34 degrees and all in by 3k rpm. your timing could be fine in the low rpm range, but when you accelerate, it may be bringing it past 34degrees causing backfire. My oil psi with 10-30 wt semi synthetic is 75psi at 3k 40psi idle after start up, once warmed it is about 40psi at 3k and 18psi at idle. Thats about usual for and olds, you can tweak it by changing oil weights, but stay with oils that have zinc in them. As for the parts, there are some good vendors on here that can help you, I got my headers and diverter through JBP, great company. Good luck and have fun!

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    Member weezy950's Avatar
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    Quote Originally Posted by pilot940 View Post
    Nice looking boat, glad to see another Olds! My guess on the back fire might be your timing, I can't tell by the pics if you have vac advance or just mechanical. when you set the timing you should have a max of 34 degrees and all in by 3k rpm. your timing could be fine in the low rpm range, but when you accelerate, it may be bringing it past 34degrees causing backfire.

    thanks! where can i find to adjust the timing?

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    Senior Member pilot940's Avatar
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    Quote Originally Posted by weezy950 View Post
    thanks! where can i find to adjust the timing?
    You will have to get a timing light and loosen the bolt on the distributor hold down and slightly turn it. If you have never done it before, get somebody who has, to help you!!!


    Another thing: You have a torker intake manifold on there. Those are typically only good for heads that have been ported to flow very well. Typically when guys put those on without any head mods or other engine mods they will lose power. I would suggest you go with the performer intake manifold if you want to liven it up a bit. (I'm guessing your heads aren't ported) However it all depends how involved you wanna get with it.

    What size carb do you have?

    What large letter is printed on your heads? K? J? C? .....

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    The Good mrjoshua's Avatar
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    Google the pdf "The Practical Olds" Written by Timminator. very informative about what you can do with and expect from a 455 olds. As for the exhaust holes thru your transom. They make aluminum block off plates that have a threaded bolt. just sandwich the transom in between and silicone around the edge. pretty simple. Great looking boat. Be safe ,good luck and have fun.

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    About the backfire issue...

    You could be leaning out on fuel at WOT... either because of carb jetting, secondary opening rate, or inadequate fuel delivery to the carb
    - are you running a stock mechanical fuel pump? how do your spark plugs look after a good run... white, tan, brown, black?
    - does your carb have mechanical or vacuum secondaries?

    Water temp... I like to run 180* idle and 150* cruise... I control it with a tap on the water inlet line... if you run the engine too cold all the time, moisture will build up in the engine and create rust and gray slime

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    Member apollo18's Avatar
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    Quote Originally Posted by mrjoshua View Post
    Google the pdf "The Practical Olds" Written by Timminator. very informative about what you can do with and expect from a 455 olds. As for the exhaust holes thru your transom. They make aluminum block off plates that have a threaded bolt. just sandwich the transom in between and silicone around the edge. pretty simple. Great looking boat. Be safe ,good luck and have fun.

    is this the article your talking about?
    http://classiccustomboats.com/pages/practical_olds.pdf

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