Quality rebuilds??

Ah yes....Me too!

Jeff

CaboJohn said:

You can tell from the carbon pattern on the pistons that the upside down trick was not allowed to run for long. Must of made some kind of funny sound.

As for your picture, it's been too long since I have seen the inside of one so shiny and new. Brings back memories.

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John, yes..... and the shine last for such a short time!


Like I said, I simply stumbled on to the photo when doing a search.

Here's this guy's engine prior to running it. He ran this in 1969 Chevy Nova.
And BTW, he ran Nitrous Oxide on this engine!



He's calling these dished pistons, but these are actually a Low Compression Quench piston, best suited for use with the Vortec swirl type quench area cylinder heads..... and they work much better when installed correctly!

Quite honestly..... this is the style piston that should be used in all "quality" SBC Marine engines...... and in particular, the Vortec version.


He built this engine in 2003, and posted on this Corvette forum back in March, 2008.
It's actually a SBC 6.6L (aka 400 cu in)
One member brought the piston issue to his attention, and here's what he had to say:

"Wow, I am both ashamed and stunned. That pictures was taken when I first assembled the engine back in 2003. I put quite a few miles, many dragstrip passes, and many bottles of nitrous through an engine with the pistons upside down.

I remember checking the piston-valve clearance, and since I have dished pistons I guess it had sufficient clearance. Here is a picture when I was disassembling it.

I wonder how that affected the flame front and quench area. What really bites is that I was almost finished re-assembly. I guess the only right thing to do is flip the pistons over on the rods. Got to love messing with those spiral locks.

Thanks for the good catch Gary. Your easy approach softened the blow too. Man I feel like such a rookie."

Not only were the pistons installed upside down, this would have caused the wrist pin offset to be reversed.
Apparently it was not making any odd sounds, but I'd imagine that the piston skirts were scuffed up.





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Well, seems I learn something new every day. And I just got though putting one back together (but did not have the pistons out). Makes you wonder how many mistakes you make that are never discovered.
CaboJohn

CaboJohn said:

Makes you wonder how many mistakes you make that are never discovered.

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Well, those reversed pistons was a rather large mistake to have made.

In Jeff Smith's article, he sums it up nicely by saying something like; "if you've ever wondered why some engines perform better than others, it's most likely the attention given to the smaller details".... (or sump'n like that).

While the piston selection may not seem like a big deal, the Quench Effect certainly can be!


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Ricardo has said it all. I don't post much here, but I would add these points:

The engine you have is usually a pretty good choice to rebuild, unless you have specific damage to a major part.

A good engine builder is someone who not only knows choice of pistons, ignition and fuel delivery improvements etc, but one who can FIT PARTS TOGETHER PROPERLY. Most of you have heard of blueprinting. All engines are 'blueprinted' to some degree, since the parts do have to mate together. How well they fit is one of the differences between a factory style rebuilding house, and a quality based small performance shop. Making sure that all surfaces are flat, matching ports, measuring bearing tolerances, are all part of the rebuilding process. I have to admit I deal mostly with older engines, 60's and back, so I also ALWAYS have the internal rotating assemblies balanced by someone with up to date balancing equipment. It makes a world of difference in how the engine runs, and how much vibration you feel.

Doing your own research on parts and pieces is important too, just like this thread, where experienced people like Ricardo can alert you to commonly made mistakes. Finding an engine builder who knows the differences between types and applications of engines is important too.

My due diligence on engine rebuilding includes balancing, guides, seats, valve springs, lifters, bearings, pistons, gaskets, fuel pumps, alternator and starter refresh, carburetor rebuilds, blueprinted HV oil pumps, billet oil pump shafts, high quality engine enamel coatings and powdercoatings, manifold cleaning and sandblasting, substituting stamped rockers for rollers, ARP fasteners, line hones, block decking, port matching, polishing, wiring, senders, gauge calibration.... you get the drift.

I don't have a performance boat, I have a cruiser. I do these things because I don't want to do them again soon, and I am a powerboater.... I can't sail back into shore if I have engine issues. I don't want engine issues, and I will spend a little more time, and a little more money to help make my time on the water safer and easier.


Personally, I like to get the feedback of an engine building shop I can communicate with, and an engine builder I trust. He is going to tell me the truth, and isn't afraid to tell me about small problems. The factory style shops have a budget, and a certain level of quality, and that's it. Engines are precision instruments. The more precision? The better the instrument. Find an engine builder who does high performance engines, and has racing experience at a higher level. That doesn't mean your engine has to be a race engine. It means the shop will understand the fundamentals of what makes a engine run properly, they will have more significant investment in up to date quality rebuilding equipment, and processes that are used to achieve the final 10% of build quality will be everyday routine.


Finally for all you greaseballs out there.... A marinized 1958 MEL 430 super marauder tripower setup. Built by Joe Bunetic, polished intake, for my hotrodded 1964 Chris Craft supersport. Just one part of a looooong exxxxxpensive hobby resto process:rolleyes:

Peter, thank you for the compliment.

peter_jardine said:

Finding an engine builder who knows the differences between types and applications of engines is important too.

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I could not agree more!
And this is where you'll often get that "Deer in the Headlights" stare when you mention some of these things that you want to incorporate into your build.
I've personally witnessed the "Stare" when I've mentioned a SBC quench before.

I have a phylisophy.
As a general rule only...... your best machinist person for a Marine build, is one who has owned and operated cruiser style power boats, either presently, or in the past.
The automotive machinist (not to discount their knowledge) typically lacks this experience and knowledge, unless they've been specifically trained.


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