'67 Sportwin powerhead rebuild

[iwombat]

Well I bit the bullet and cracked open the 9.5. Good thing I did too, becase I had an exhaust gasket failing and dribbling water into the lower main bearing. A few more hours and it would have started making noises like an angry dwarf on an anvil.

The assessment:

1) Cylinders look clean and mostly smooth.
2) Piston skirts are badly scored.
3) I had at least one slightly stuck ring.
4) Cylinders are just within tolerance at .002 over.
5) The shift-rod sealing boot is looking real good - bonus!

The rest looks pretty much as you'd expect.

I have a usable set of pistons from my parts motor that look pretty clean, so if I stay at std bore I can use those. I'd really like to go to +.020 pistons, but I'd expect that to be price prohibitive given the vintage of the engine.

Couple of questions though:

The manual doesn't list any end-play specs for checking wrist-pins. What are some tests for assessing wear?

Do the bearing liners ever go bad? I've got some discoloration and maybe pitting (hard to tell) on the center main bearing liner.

 

[F_R]

Re: '67 Sportwin powerhead rebuild

I'm having a problem understanding what you mean by end play in the wrist pin. They are supposed to be a press fit in one side of the piston and a slip fit on the other side. The press fit keeps them from going anywhere once they are installed (hopefully). Yeah, I know, they also have snap rings.

I would say a bit of discoloration on the liners is ok if not too bad. But of course, my experience is in fixing somebody elses motors and if there is ANY doubt, he gets new ones. That's CYA. Besides, they were cheap back then.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

I should of said end-play on the wrist pin bearings (as measured at the end of the connecting rod).

This all became moot anyway, and here's the story:

I went into sea-way and chatted with my friend and fellow piper Ian told him what I was doing and had him chase down pricing for some of the options. I could get a set of +.020 pistons for around $100 which I felt wasn't worth it. So I assembled all the parts I thought I could get by with, which included new rings, a new lower main bearing, bearing seals, gaskets etc. All totalling around $130. Then Ian had this idea that maybe they had some NOS blocks sitting around in back and he'd cut me a deal that would be way cheaper than getting the 20-overs.

Going back to look through the blocks, and there were a lot, I spied what I was looking for and pulled out a sportwin block. Only it was a complete replacement powerhead. Ian asked if I was interested in that (well DJAH!) and what it was worth to me. I figured the value of all those parts + $50 or so, so I offered $200. "Actually I was thinking more like $175", he says. "It's probably been sitting on that shelf for the last 30 years, make it go away"

Done.

So, now my powerhead rebuild only involves applying some hi-temp paint.

Easiest rebuild ever.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

I guess now the question is, how to go about awakening this sleeping RPH.

I'm thinking that putting some penetrating oil in the head to free the rings from the cylinder walls. Then, dumpingsome 2-stroke oil in through the intake and sloshing it around in the lower end should lubricate everything pretty well.

 

[R.Johnson]

Re: '67 Sportwin powerhead rebuild

When you say free the rings, are they rusted to the block?

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

No, it just hasn't been turned over in 30 years and I'm assuming they're really happy where they are. Before I go and turn it I want to make sure there's lube everywhere.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

Let's just say that I've learned the hard way that engines that sit for multiple decades get all comfy and cozy-like in whatever position they've been left.

I've had the bad experience of breaking a ring by trying to turn an engine that had been sitting before a proper lubing.

 

[Paul Moir]

Re: '67 Sportwin powerhead rebuild

If it were me I would just run some good penetrating oil down to the rings. Most good ones contain something to attack rust. I doubt you'll have a problem with the rings stuck to the pistons themselves. The bearings and what not should be protected by the assembly grease.

Good find!

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

Thanks for the validation. Rings with a little oxidation sticking them to the cylinder walls is mostly what I'm concerned about. Good thought about the assembly lube. Probably still plenty slippery as-is.

Now I just have to make a new water tube. The one I took out has been bent and reshaped one too many times by the look of it.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

On to the next question. The factory manual has nothing on installation of the starter - go figure. How many turns does it need before attaching?

 

[Paul Moir]

Re: '67 Sportwin powerhead rebuild

Crank it up 20.5 turns. One of the bolts that hold the starter on go right into a water jacket - you would be wise to put a little gasket sealer on that one.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

Thanks again for the tip.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

It all went together pretty nicely. Thanks for all the help.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

I managed to pop the rings loose with about 2-5 ft lbs of torque after letting everything soak up the penetrating oil. And, as you can sort of see from the picture, I ended up making a shim for the lower front rubber cushion. There was about 1/4 inch gap between the lower two bumpers that didn't exactly seem right. Now everything is nice and snug, but nothing is compressed. Probably came from the factory that way, but this motor always had what seemed like too much forward-to-back play.

 

[iwombat]

Re: '67 Sportwin powerhead rebuild

I finally had a chance to fire it up yesterday in the bucket. Wow what a difference the new powerhead makes. I've got double the compression of the old tired unit and it shows. I'll have to take it out on the boat at some point and break it in properly. That may have to wait until spring, but you never know.

I've got an entire spare powerhead assembly now with nothing to do but sit and oxidize. I thought I'd see if anyone here is willing to offer it a good home (free except shipping) before I put it all up on ebay and get it all out of my shop.