Cyclops - jetboatjill needs advice on exhaust manifolds

[jetboatjill]

Cyclops - this is jetboatjill, the one who has the 1971 Sidewinder jet boat. Well, to make a LONG story short, the rebuilt engine (455 Olds) blew up this weekend. When it blew, it had water in the oil. We don't have a clue what happened to make it blow, and to have water in the oil? Could it be that we have the engine too high performance OR the water pump is too forceful? We took the original block, had it cleaned & bored out - ALL new guts - used racing pistons, a radical cam, a high performance carb (Edlebrock) and the top of the line water pump. BUMMER! Just when we got the boat to float and we were starting to have a little bit of fun. The engine blew when we hammered it and got it upon plane - going only 20 mph. Do you have any suggestions? What's your thoughts on this mess???? THANKS again!!!!

[jetboatjill]

Cyclops - I meant NEW racing pistons, NEW radical cam, NEW carb.......ALL NEW parts!!!

[cyclops]

How much do you want to spend on the replacement engine, low to a comfortable high$. Could it be a newer engine? With less speed equipment? A crate engine? Is the size and make important? Is a warrenty needed? Carb and distributor required, or fuel injection and a computer? It will need a exhaust system, wet or dry? What is the rated RPM and horsepower of your jet pump? Do you want whip lash on acceleration or just to be able to do, what mph? -------------------------This is the basis for a replacement engine. ORR.--------------------- Are there boats in your area with excellent running engines in a boat who have to sell theirs first to buy the bigger engine? Take their boat out to verify the engine is good with the best mechanic in the area. Then park the boats side by side and move it in.---------------------- I can't really decide for you. I am a very biased person when it comes between new and used.--------------The 2 of you need some time to be very honest about past and future goals.

[jetboatjill]

Cyclops, Jetboatjill needs advice on exhaust manifolds for a 1971 Sidewinder jet boat. HUM!!! NEW possibility!!!!! How & where can we find a picture of the exhaust manifolds that were factory for the 1971 Sidewinder jet boat? When we bought the boat, we ASSUMED that the exhaust manifolds that came with the boat were the factory exahust manifolds - BUT - we saw a pic of another 1971 Sidewinder AND the exhaust manifolds are totally different from the ones we have!!!! The ones we have are fairly straight line coming off the exterior hull wet exhaust and the ones we saw in the pic are like dramatic in height compared to the ones we have. The pic we saw even has a different design for the "snail" assembly. Soooooo could this be a possibilty as to why we are getting water in the engine which created the engine to blow this past weekend? Do you know where we could find a picture of the factory exahust manifolds that originally came on the 1971 Sidewinder jet boats? Interesting how many 1971 Sidewinder jet boats there are. We've heard from several classic Sidewinder enthusiasts......BUT......few have rebuilt their own engines!!!! THANKS for your help, Cyclops!!!! Have a nice evening!!!! jbj

[cyclops]

You mention that your wet exhaust manifolds are almost straight? And you had a hot rod cam installed? That could be a very possible reason for a blown up engine. Racing cams can cause a exhaust flow problem called "reversion". It means simply that if the cam timing gets too strong the exhaust pulses instead of always being pushed out the pipes can start to reverse their flow on each pulse and really reverse in a split second and head back up the pipe and into the engine cylinders and blow the engine apart.-------------------------------The boats with the long up swept pipes prevent that by mixing the cooling water into the exhaust several feet farther down the exhaust pipe so "reversion" NEVER can occur. So much to learn the hard way.-------------------------------- Or buy a complete marine engine that is warrenteed to run for so many years like a car engine. A bad boat launch off a steeply angled trailer could have put water into the engine causing a very hard slow turning for no apperant reason at the time. That could have very badly stressed the inside parts so badly that they just seemed to let go for no good reason the time you gave it a load to work into. Tough to call this loss of a engine.---------------------------------------There are many good race boat engine builders in the USA. Take your time on buying a replacement engine. Take a pencil a paper with you and find out which builders in your area build great engines or go to outside the area to Cal. Get and read monthly mags about jet boats or drag boats. The engine should be a Dyno tested engine. EVEN if it is a few hundred $ more. It should mean that it can run at full power. A computer controlled engine should have built in a rpm limiter which stops the engine from a over revving condition. If you feel unsure who or what to pick post back.-------------Hop over to your other posting. I have some questions that you 2 need to have answers for. Courage.

[gonzo]

Was there piston damage? What do you mean by blown? I'd like to know the particulars of the damage before offering any advice. Would you consider a 454 GM instead?

[Okie]

You may find some photos and brochures of the original sidewinder on the Fiberglassics web site. It is a great classic boat site to visit. I run a jet boat with a supercharged chev. but I run water jacketed S.S. headers and dump the water into S.S. Super Trapp mufflers that exit over the transom. Never had a problem with water intrusion, heat or noise. If you exit through the transom and the hull has much "V" - the engine will sit low enough in the boat that water intrusion becomes an important consideration. Risers may be in order. As far as a high performance engine goes - It can cost a lot of money to force a hull and pump to run in speed ranges they were never designed to attain.