Custom vs Factory Quality of Motors?
 

Hello Folks - been a while as I have been saving up to get my motors replaced in the old Harley.

Had an interesting conversation with a gent recently who basically said that a new motor from the factory will outlast a rebuild because:

-Robots are doing the the measuring
-Robots are doing the machining
-Robots are doing the assembly
-Repetition has removed inaccuracies

....And the quality is much higher over-all since there is no human error or "wiggle" factor in the over-all build.

This might be a stupid question but is he right? For someone looking for 500 HP out of a big block marine engine - am I better off just buying factory new?

Factory new Vs. rebuilt will almost always last longer. BUT, that is also considering you are going to have to punch the old block out at least .030 over. As the block ages, and you bore it out, it's not going to be as strong. Plus, you'll have an array of parts from different vendors etc that you piece together. The factory spends a lot of R&D time getting their engines to the best setup.

Now, dollar for dollar the rebuild is simply more economical. If you get the right builder, it's going to last anyway, etc.

It depends on who is doing the work. A top builder is going to be able to hold to closer tolerances than any automated process, if he knows his stuff. His experience will allow him to identify issues he sees- something a robot is incapable of.

As far as the block aging, 20 years ago, we used to dig for the GM tall deck 427 truck blocks. They had been thermally cycled so many times they were more stable.

The only place that can sell you a new, never used motor is GM. Last time I looked, their highly automated production processes still aren't capable of turning out a flawless, issue-free product. That's not to say they don't build a good, solid, reliable product. There's just no guarantee it's always going to be 100% perfect. Ultimately it will be assembled by a human. With a custom motor, you get to pick that exact person based on record & reputation.

good comments guys - keep them coming

I like going with a quality builder and having something a little different than most. That being said, you have to be sure that they know what they are doing and will stand behind their product.

Wrong. GM's engine factorys aren't populated with robots. Engines are still built by people. Sure there's a lot of automated processes and fancy tools, but there's still people on the line putting things together. I'm sure no robot would draw a smilie on the rear cam cover :D

The "perception" that a rebuild or custom motor doesn't last as long as "factory new" is because most custom motors have the sh!t run out of 'em...of course they're gonna wear out sooner. As for rebuilds, you get what you pay for. Buy a Jasper, don't expect someone with 20yrs of experience to have put it together. Use someone that's been building all sorts of engines for 20yrs, use it the same as a "factory original" engine, and I bet it will last just as long if not longer.

I was thinking the same. I can't imagine a engine being assembled by a robot..Does anyone know who assembles engines on a production line with machinery? I am curious to see the process..any video?

The quality comes with the details! Anybody, machine or robot can build a motor. It's not who built it!, its how its built!
I think that the factories have gotten much better at building high quality high performance engines than they did in the past due mostly to better machining practices, higher and better materials technology and the greater demands of extended warranties in the vehicle applications.
Believe me when I say I see a lot of factory performance engines that would never pass our inspection process let alone leave the shipping dock!
However that said, even GM, Ford , Chrysler and the Imports have special engine assembly operations to manufacture and assemble their best perfromance engine offerings. In these operations a great deal of personal individual care and training goes into "Getting it Right" . ie; Hand Built!
I know there are years of engine offerings from the great marine engine endurance builders, that when compared to standard engine production are light years ahead in building a long lasting engine package when you compare the moderate horsepower 425 to 550HPHP engines to the factory produced packages!
You will spend more for privatly built quality marine engines but from the "Good Guys" than you will for most factory engines but that's because it's small limited hand built pieces and some much better aftermarket specialty parts coupled with the personal attention each motor receives.

My bised two cents from an engine builder!

Regards,
Ray @ Raylar

If money wasn't an object, I'd take the new one everytime. At least you get a warranty with it. If it's a Merc, there are a ton of places that will recognize the warranty, where if you get a custom built engine from across country, they may very well honor it, but you might have to ship it to them to decide whether it's a build issue or not.

Jmho

Without speaking directly as to how any particular client(s)assemble an engine, basically all of the manufacturers utilize a combination of robotic processes, automation-both dedicated & flexible, as well as people.