westcoast head

[blackstrat]

local shop guy trying to sell me a westcoast head for my ski. he says they dont make the head anymore and their like impossible to get. he says i will get good power increase but i dont really believe him. is it worth the $139 bucks he wants for it (w/ 2 sets of domes)? Its only a 580cc seadoo single carb so im wondering if it will do anything at all. anyone have good results with this? ski is stock
thanx

[blackstrat]

......also would i need to rejet?

[Bill O'Neal]

What year is your 580 ? Early 580 carbs cannot be adjusted for high speed adjustments, only low speed adjustments. Use a 110 main jet (sold at Sea Doo dealerships) if you have a 1988-1990 model with a "round body" Mikuni BN carb.

Later models have Mikuni SBN 38 carbs, and can be adjusted.

The Westcoast head will give you some punch out of the hole, no extra top speed unless you use an aftermarket filter too on the carb with rejetting.
If you put a single 44 Mikuni kit on it, with that head and filter, and an OEM or aftermarket high performance pipe, you will be surprized how good it will run. Top speed will go from 38mph to 44 mph, with great accelleration. Use a Solas C impellor with all of those mods, or a Solas B without all of those mods.

[blackstrat]

thanks bill! its a 1994 SPI w/ sbn carberator. i also have an ocean pro filter for it laying around. do you carry those 44mm carbs? i think this model already comes with the seadoo "tuned" pipe and not the crappy one that came on the SP, but i have thought about putting a coffman pipe on it. if i decide not to go with the pipe or carb i should look into the solas B impeller? thanks for your reply!

[Bill O'Neal]

Most all of the Coffman pipes work real good, except the one they made for the 580. I actually think (know) that it makes less power than the oem pipe.

I would steer clear of an OP flame arresstor, because of the chance of cracking the intake manifold. You can remove the screen in your oem flame arresstor and put a K&N onto the air box, thus keeping the oem carb brace.

A 44 kit requires a complete intake manifold change, not just a carb. About $400.00 Carb manifold and filter adapter and filter.

[blackstrat]

thanks for the warning about the coffman pipes. the only other one ive seen around for this motor is the factory pipe but thats a little to expensive (the numbers on the FP site say 20 hp increase!?) i think ill just bolt this head on for now, and decide where to go from there. do you normally have access to that 44mm kit if im interested? thanks a lot

[Bill O'Neal]

I could probably put together a 44 kit for you.

[blackstrat]

okay, i got the head and he threw in three sets of domes. Should i use 34cc, 35cc, or 36 cc domes? i will be using 93 octane gas. also....is there anything i should know before bolting this head on? any knowledge from experiences? thanks a lot guys

[Bill O'Neal]

Start out with the 36's and make darn sure you have .038 squish clearance or more. The head will work best at .038 to .042 squish.

[blackstrat]

what exactly is the "squish" and how do i set it for proper clearance?
After starting with the 36's should i work my way down to the smaller ones?
Sorry for all the ?'s just wanna get this done right. thank you Bill you have been very helpful

[blackstrat]

okay found an old post on how to measure the squish. can it be changed with thicker (or thinner) gaskets?

[ May 26, 2003, 11:35 PM: Message edited by: blackstrat ]

[Bill O'Neal]

Stay with the 36cc domes unless you plan on running racing fuel.

The squish band gap between the piston top and the head is all important. A certain gap must be maintained to keep the mixture moving properly over the top of the piston and not let it get trapped between the head and the piston at the outer edges of the piston, where it will start pre-igniting itself and causing the motor to detonate.
The best way to measure the squish at home is to remove the head and place a piece of .065 soft core solder on top of the piston, right above and parrallel to the wrist pin (north and south). Bolt the head back onto the motor and torque it down. Rotate the motor 360 degrees, or until you feel the solder getting smashed completely and it gets easy to turn the crankshaft further. Remove the head and measure the thickness of the solder at the outer edges. This is your minimum squish clearance reference points (each end of the solder). You will see a flat spot on the solder for about 1/2 inch. It should be a little thicker towards the center, as you measure the flat "squished" piece of solder. This would indicate that the squish band is angled correctly with a positive angle towards the center of the bore.

To set the squish to the correct gap, you adjust it by removing the clyinders and placing the proper thickness base gasket under the clyinders, or re-machining the squish bands on the head, or milling the gasket surface of the head to get within the proper range to use gaskets to shim the clyinders up or down as necessary.

More modified motors are ruined by improper squish than just about any other reason, other than improper mixture or too much timing. That is why we always check squish clearances when we change heads or re-machine clyinders or cases for deck hieghts.

With a crowned piston top like Rotax uses, you need a gap that angles wider as it goes towards the center of the bore away from the clyinder walls. On a 580 motor, it needs to be a minimum of .038 at the junction of the piston and the clyinder wall, getting slightly wider (more gap) as you measure towards the center of the piston. This sets up a wedge-like push of the mixture as the piston nears the top of the bore, and pushes the mixture towards the center of the piston, away from the clyinder wall and the top ring of the piston. Typically a squish band will have about 1.5 degrees of positive angle between the piston top and the head as you move towards the center of the bore.

Also, typically, the larger the bore, the more gap is necessary. That is why we run as little as .038 to .042 on a 580, but more like .065 or more on an 88mm 951 motor.

There is a formula for getting the proper squish. It is measured as "mean squish velocity" which can be mathmatically calculated. Don't ask. Look it up in the SAE papers if you are really curious about it........

[ May 27, 2003, 10:09 AM: Message edited by: Bill O'Neal ]

[Technical Support]

Yes, the thickness of the base gasket is changed to fine tune the squish.

[blackstrat]

hmm...sounds like a lot of work for a mod that was supposed to be "bolt on". will my squish definatly be off if i bolt the head on, or does this just occasionally happen?
should i replace the o rings around the cylinders and water jackets?

[Bill O'Neal]

Ok, now that I explained the correct way to measure squish, I am now going to tell you the easy way.
Remove the sparkplug. Unwind about 6 inches of solder from the solder roll and bend a 90 degree bend in it at about 1.75 inches from the end. Place it through the sparkplug hole with the end pointed either north or south (mag or pto end of the motor) until you feel it stop against the clyinder wall. Hit the start button (plug wires off) and squish the solder. Remove the solder from the sparkplug hole. Measure the solder like I described in my last post.

If it is over .038, run it.

[ May 27, 2003, 08:21 PM: Message edited by: Bill O'Neal ]