Technical Aluminum vs steel Pistons s

So do you think that the aluminum piston might like a little more clearance in the bore? Would a cast or forged aluminum piston make a difference? Or would the steel pistons be likely to expand more?

 

Any competent machine shop wants to know; cast, forged, of hyperkinetic piston use as there are different tolerances. This application where there is no engine bore going on it will probably be OK if the weight is close (vibration) and the pin location is the same.

 

Some older cars had different size pistons from the factory. The factory would over bore a cylinder, if it didn’t clean up at standard bore.






Bones

 

Yes, up to at least the '60s the Ford shop manuals stated that it was acceptable to only bore cylinders that needed it since the piston weights were the same for standard and oversize.

Seven steel pistons installed with proper clearances and one aluminum one with the proper clearance for it should be fine... but the 23 gram weight difference probably won't.
And does this engine have the thin steel liners?

By the way... which is heavier, the aluminum or the steel piston?

 

The steel piston is heavier.

 

I've seen odd pistons in a few motors I opened up. It was common to over-bore one hole and put it back in service.

 

I'm for doing a matching set. Why take chances and have to do over? But that's just my opinion. I don't like having to do things over.

 

Mismatched pistons may work, may not. But why take a chance, l could just be lazy but I HATE going back in and redoing it.

 

Back in the fifties, when many people (myself included) didn't have access to much money, computer web sites full of info, and had only rudimentary tools............lots of things were done that anybody would be ashamed to do today. Did they work? Well some did and some didn't.

Aluminum pistons and steel pistons often have different bore to piston clearance..........so your machinist is going to be working to two different specs. Not a good thing when you find that machine shops don't always get things right.

Second, its possible that the ring grooves in the pistons may use different width rings. You didn't say if they are exactly the same. Another consideration is what the piston tops look like and if they have the same compression height......which will affect your compression ratio and possibly any type of squish chamber, further creating a harmonic. When it comes to piston weight, its not just a matter of a few grams, but the exponential effect they have as your rpms increase. I doubt you will have any type of harmonic balancer on the engine, so having matched parts is reasonably worthwile. You should also consider that any additional harmonic produced or amplified by the oddball piston will affect other components wear and longivity.

Now if you lived in Cuba, they do things like that all the time because they have no resources to do things properly.

To build or assemble any engine today is going to require (?) that a reasonable investment must be made for both parts and machining. As long as you have to invest other money into building an engine, most people would consider that a reason to do it correctly.

Myself, when I assemble an engine or anything else I work on, I do it the very best I can because I take pride in what I'm doing.........and doing it wrong is not an option. Now I may do something incorrectly (wrong), but it won't be because I didn't try to do it right. Its an innerself kind of thing.....doing the right thing even when I know no one is watching.

So the answer is that yes you can install the piston in the engine and probably make it work ......maybe even for a long time. But I guarantee you the next guy that tears that engine down is going to question the mechanical aptitude of whoever built it. On the other hand if you go out of your way (spend money) to do it right, you always have a sense of pride in what you did.

 

Just leave that piston out....

Saw a 235 Chevy one time, fellow said it had a miss as long as he owned it. New plug always looked new when it was taken out. Had a shop pull the head, thinking it had a blown head gasket. Got the head off, there was a hickory block drove down in a messed up cylinder. Pulled the pan, Rod was cut off with a torch, rest still bolted to the crank. He had them put it back together and ran it several more years, miss and all.....

 

If it was more important to get your car back up and running, I'd say run the oddball piston and get on with your life. As noted, it's not uncommon for fleet services, etc. to bore/hone single cylinders, replace one piston and send the vehicle back out on the road. BUT, that's because they can't afford to have a garbage truck, bus, fire truck, etc. off the road for more than a day or two in order to rebuild the entire engine when all it needs is a single cylinder repair. Makes more sense to spend a couple hours repairing the single cylinder and getting the vehicle back up and running than having a vehicle down for an extended time. Our world is quite the opposite as we usually have plenty of time up front and don't want to deal with unnecessary repairs once the vehicle is on the road, at least I don't.

If it were me, I would find a matching set of pistons and send everything out to be balanced. You'd be surprised how much a set of the same pistons can differ in weight. A mismatched set? You're just asking for trouble beating up all the parts you really don't want to have to replace (main/rod bearings, pilot bearing, etc.).

 

@ERguitar if you haven't already rebuilt your engine by this time, please give us a call to see how we might help you. If you haven't yet heard of our company, we've been in business 107 years now, we specialize in new oem cast aluminum replacement pistons & other internal parts for vintage engines .
Www.egge.com

 

I learned something new today, steel pistons...

Sounds like Egge Machine has you answer.