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Engine upgrade/ exhaust question


wayland

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Hello All,

I am new to the forum but have been with my beloved skier for about 8 years now. Ill start from the begining and hope to acquire some help I havent been able to find.

Last year my older Skier was starting to have some transmission problems. When in gear and starting to pull a skier out of the water the engine would rev high but the boat would lag and slowly catch back up after I backed off the throttle. (similar to a manual car with a bad clutch)

To the now. The tranny is at the trans shop. I pulled the motor out last weekend and am currently disassembling when time permits. The motor has never been gone through as I am the second owner. I am going to open the motor up while it is out and go through to give it a fresh updating (new gaskets,bearings,seals etc). As I go through the motor I am putting some horsepower into it for the bottom end. Nothing drastic. I have found a clean set of Vortec heads with a new intake and plan to do a mild cam. The piece of info I havent been able to find is will the original exhaust bolt to the newer Vortec heads without any problems or do the vortec heads need updated exhaust manifolds?

Any help would be appreciated.

Thanks

Ryan

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Hello Ryan,

Welcome to the crew. I would update the exhaust manafolds and risers as part of any upgrades you do. Your Bu' is 24 years old there is a chance of the rust though on these parts and then you will be going through the engine again after you get hydrolock.

Here is a good thread on the topic.

http://www.themalibucrew.com/forums/index.php?/topic/31373-exhaust-project-with-flyby-vids/page__hl__ exhaust upgrade

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i don't know the answer but wonder if the addition of vortec heads is why these exhaust manifolds differ.

IIRC someone sent the wrong parts with the boat. I think the dealer stood up and got him the correct ones. You do however bring up a good point to make sure you get the right parts and use a reputable dealer.

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The answer is yes, the original manifolds will fit but you will need to grind the top section of the manifold as the port dimension is different. Not difficult, I did that myself until I upgraded to a set of Stainless Marine units. I gound it worthwhile to go with the upgraded manifolds, I then coupled it to a 4" exhaust system.

You will need to make sure your Vortec heads are the real thing, the true Vortec head came along in 1996. They have a significant flow increase and were the key in bumping the horsepower from ~265 hp to over 300 hp. You have chosen the key upgrade componenet for your mill. The intake manifold should be at least comparable to the GM Marine intake or similar to the Edelbrock Performer RPM. You can tell quickly by checking the height. As for cam, the engine will have the marine cam, so already more than a basse engine, the ZZ4 is a nice upgrade. A good alternative is a set of 1.6 rockers. If you are interested, dig through some of my old posts, I detailed my engine mods previously, I am running a 400 hp setup with a great idle. Have fun, it is a great and rewarding project. With the engine out, I would consider a 383 crank.

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The answer is yes, the original manifolds will fit but you will need to grind the top section of the manifold as the port dimension is different. Not difficult, I did that myself until I upgraded to a set of Stainless Marine units. I gound it worthwhile to go with the upgraded manifolds, I then coupled it to a 4" exhaust system.

You will need to make sure your Vortec heads are the real thing, the true Vortec head came along in 1996. They have a significant flow increase and were the key in bumping the horsepower from ~265 hp to over 300 hp. You have chosen the key upgrade componenet for your mill. The intake manifold should be at least comparable to the GM Marine intake or similar to the Edelbrock Performer RPM. You can tell quickly by checking the height. As for cam, the engine will have the marine cam, so already more than a basse engine, the ZZ4 is a nice upgrade. A good alternative is a set of 1.6 rockers. If you are interested, dig through some of my old posts, I detailed my engine mods previously, I am running a 400 hp setup with a great idle. Have fun, it is a great and rewarding project. With the engine out, I would consider a 383 crank.

Great info - thanks!

Do you mean the exhaust port shape/dimension of the Vortec head is different than stock? In other words, the manifold inlet needs to be ground to port match the head port?

What were the stainless manifolds that you installed? Those already had the right port shape/dimension so no grinding was necessary to port match to the Vortec heads?

Thank you in advance.

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The port shape is different, but the bolt pattern is the same. A simple grind at the top of the manifold will solve the issue if you stay with what I presume are pre 95 manifolds. Newer ones will be okay as they had to match the ports. The vortec heads flow a lot more air, that is the difference.

The manifolds are aluminum, made by a company called Stainless Marine out of Florida (near Miami I think) and yes they were correctly matched.

I actually installed a set of Fast Burn 385 manifolds, which are aluminum. One of my gaols was to reduce weight, which over the course of my build I stripped off 250# so it was very successful along with getting a noticible power boost which was my initial objective.

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Woodski,

I'm sorry, I'm a bit confused. When you say "manifolds" I was assuming you mean the exhaust manifolds....is that right? In other words, a marine-style riser exhaust manifold. The Fast Burn 385s are marine style riser exhaust manifolds in aluminum?

Or do you mean the inlet manifold?

Thanks!

ps. way to go on the weight reduction - 250lbs is a really meaningful amount. I'd like to do the same thing.

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