SBC Piston pin - Spirolock or pressed ?

[68maliblue]

I'm trying to put together a budget SBC build for an old pickup truck. The Silvolite pistons are 35-37 grams heavier than the pistons that were originally in the engine. The piston pin in the Silvolite pistons weighs 144 grams. These are basic cast pistons designed for a pressed pin. I found a Manley piston pin p/n 42213 that is the same length and diameter (.927 dia x 2.95 long) and only 117 grams which would get me to within 10 grams of the original piston. However the data on this pin says it is for spirolock applications only. Is this going to affect anything if I use it on a pressed pin piston? Does this it really matter if this pin is used in a pressed or bushed application?

[superpursuit]

Piston pins for use with locks are usually shorter to allow for the pin to fit between the grooves for the locks. If your Silvolite pins are the same length then you could use them.

Allan.

[68maliblue]

The silvolite pins measure 2.990” so they are .040” longer. Doesn’t look like it will make much difference as the end on the pin hangs outside the piston pin bosses about .030” on either side when installed in the pin bore.

[PackardV8]

For an internally balanced beater build, just equalize the pistons, pins, rod small ends, big ends and don't worry about the extra grams, you'll most likely never notice any difference.

[Dave Koehler]

I like your new pin idea.

[PackardV8]

I like your new pin idea.

Agree, Dave, nothing wrong with that idea, but for not much more than the cost of lighter pins, couldn't he have the crank spun up bobweighted for the new pins he already paid for?

The OP did say it was a budget build, but we don't put anything together without a new balance.

[Baprace]

I'm trying to put together a budget SBC build for an old pickup truck. The Silvolite pistons are 35-37 grams heavier than the pistons that were originally in the engine. The piston pin in the Silvolite pistons weighs 144 grams. These are basic cast pistons designed for a pressed pin. I found a Manley piston pin p/n 42213 that is the same length and diameter (.927 dia x 2.95 long) and only 117 grams which would get me to within 10 grams of the original piston. However the data on this pin says it is for spirolock applications only. Is this going to affect anything if I use it on a pressed pin piston? Does this it really matter if this pin is used in a pressed or bushed application?

68maliblue, check the pin press in the con rod before you get too involved, stock replacement press pins are usually bigger OD than floater pins.

[BillK]

However the data on this pin says it is for spirolock applications only.

Blue,
I would call Manley to make sure but if I had to guess I would bet that is says that to make sure the pins were not used with the newer round wire type of locks which require a chamfered pin end.

I have used a press fit setup on plenty of pistons that came with grooves and spiral locks. A perfect example is a 502 Mercruiser engine I just did some work on for a customer. It had JE pistons and the 2 replacements I got came with spiral locks BUT the original ones were press fit into a Manley H Beam rod that is made only for Mercruiser.

As long as you have the proper press fit in the rod you should not have any problems.

[68maliblue]

Current pins measure .927 so no oversize. New pins are for spirolock and squared off on the end so they should be ok as long as they measure the same.

[Dan Timberlake]

I assume you'll be heating the rod eyes to assemble.

If you are actually pressing the R&P together I'd prep at least one end of the pin with a polished radius.

What is the wall thickness on the light pins?

[68maliblue]

I don’t have the pins yet. I’ll have to call Manley to find out

[BillK]

New pins are for spirolock and squared off on the end so they should be ok as long as they measure the same.

That part does not matter because if you are press fitting them you are not using the pin locks anyway.

Do yourself a favor and do not try to press the pins in unless you have a fixture that supports the connecting rod, not the piston. Even then I wouldnt do it. Heat the rods in a proper rod heater and slide them in.

[Mark O'Neal]

I'm trying to put together a budget SBC build for an old pickup truck. The Silvolite pistons are 35-37 grams heavier than the pistons that were originally in the engine. The piston pin in the Silvolite pistons weighs 144 grams. These are basic cast pistons designed for a pressed pin. I found a Manley piston pin p/n 42213 that is the same length and diameter (.927 dia x 2.95 long) and only 117 grams which would get me to within 10 grams of the original piston. However the data on this pin says it is for spirolock applications only. Is this going to affect anything if I use it on a pressed pin piston? Does this it really matter if this pin is used in a pressed or bushed application?

That means you can't use it with wire locks.

No, it doesn't matter.