Thinking of temporarily running 403 olds while work is done to 455...........

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lladnaR

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« on: November 05, 2013, 07:36:03 PM »
Hello,

 My name's Randall. I'm new on here & have never been on a forum before, so please excuse if I post stuff in the wrong place, etc. I've been in & around jet boats all my life sans  the last 15 years or  so............  A couple of weeks ago I found a decent deal (cheap) on a '75 Tahiti 18" jet, so I bought it & viola! I'm back into jet boats again. So this thing has a 455 olds in it. The guy advertised it as "ready for the water". When I looked at it I noticed that a head bolt "head" is broken off. Ready for the water my a**. I have a considerable amount of oldsmobile parts @ home including a ready to run 403 olds. While I have the 455 out to go through it, I was thinking of running the 403. What I'm concerned about is exhaust width @ the transom Vs @ the snail outlets. The 455 is considerably wider than the 403, is it too much for the exhaust hoses to compensate for?


mash on it

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« Reply #1 on: November 06, 2013, 08:02:19 AM »
How much narrower? I went from BBF to BBC and there was very little 'bend' in the hose, height was about the same too.
Is the 403 fresh? I'm not an Olds guy, but have pulled one or too. Will the logs and snails bolt up? Water pump plate bolt up too?
If so do it.  :thumbup: there's still Nov. and Dec. left for the river

Dan'l
CJ/RR 212...under construction  "Pistol Annie"

lladnaR

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« Reply #2 on: November 06, 2013, 10:29:15 AM »
 455's about 3 inches wider. Maybe they didn't cut the exhaust holes for a particular engine, but just in a standardized location?
 Everything else is the same, all of the accessories will match except ski tow rack thing. Heck, even an olds 350 diesel would bolt in there, that would be interesting wouldn't it? I wonder how a diesel would act in a jet with an A-impeller?
 As for the 403, I rebuilt it back in '97. 350 #7 heads & a mild cam. I'd figure 325 hp  375-400 tq. It probably has 25-30k on it but its all late teens to early 20's "hard" miles. It ran fine when I pulled it, just been sittin on a stand since about 2001-2002.

SoCalPSD

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« Reply #3 on: November 06, 2013, 11:06:02 AM »
Those hard miles means its been worn into jet boat motor specs lol. So those three inches is that over all or three inches either side? If it's over all your good to go if its three inches each side well it will be fun manhandling the hose but it will work either way


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lladnaR

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« Reply #4 on: November 06, 2013, 11:22:52 AM »
Its overall, so 1.5" per side. Ill update when its in there.

HardLuck Baker

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« Reply #5 on: November 06, 2013, 07:10:02 PM »
We need to see some pictures!!


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lladnaR

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« Reply #6 on: November 24, 2013, 08:10:17 PM »
So I'm close to done with the swap.  It turns out the exhaust does cause some issues, but the issues I thought I'd have were ok.
So deck height is a big factor, the water feed to the back of the snail hits the stringers before the mounts line up.

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lladnaR

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« Reply #7 on: November 24, 2013, 08:16:41 PM »
I was thinking of feeding the snails from another location,  but some friends offered their snails instead.  I got one installed eithout much hassle.  The other side was damaged during disassembly & must be repaired. 

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lladnaR

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« Reply #8 on: November 24, 2013, 08:23:23 PM »
The other issue was the oil filter relocating adapter,  can't run a ph25 filter, have to run a skinny one. The change in deck height makes the snail interfere with the bigger filter. Whatever the factory number is for the 403 works fine.
There is 1 corner of the adapter that just barely makes contact with the log. A file fixed that. Ill attach pics of that when I get the log repaired.

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