[421gto]

we are having a 65 421 rebuilt, but wheres the best place to get a new set pistons from ? Its going to be stock so we dont need anything special, just stock.

I know egge machine have them listed, someone else said wiseco.com - any others ?

cheers from a very wet UK,
si

[PONTIAC LARRY]

Here's some stock replacement that are the hypereutectic type and claimed as stronger than factory cast although forged would be preferred to help resist damage from potential detonation since stock heads yield around 10:1 compression.

http://cgi.ebay.com/ebaymotors/421-P...-/200309977778

They say all bore sizes are available. $398

[Ragtop Man]

2X -- but the incremental lifespan of a detonating engine with forged pistons (v HE cast) is not a whole lot longer.

Stock replacement pistons put you in the 10-2-10.5 range depending on the cyl heads, you need to build for the fuel you have in the area. IIRC, euro pump gas premium is something like 96 octane, so a cast rebuilder piston should be okay.

Only problem: with the cost of gas, a fill up is more than the pistons!

BOB

[lust4speed]

Stock 421 bore is 4.09375 and stock 428 bore is 4.12 so you could bore out to the 428 piston size. They should be more readily available, and it only requires about a .026" cut - or not even a standard .030" 421 overbore size.

[421gto]

thanks guys, think we may have it sorted now, was talking to the engine builder yesterday and it looks like we are going the 428 route.

Bob, filling up with gas does seem to double the value of most cars...........

cheers
si

[coreybrenner]

On another note, I'm thinking of stroking the 389 in the parts car to a 421, but would like to use later model heads because of their superior combustion chambers. Is there a piston which will work with the later-model valve angles (but not be the 8-eyebrow weirdo-cut ones)?

I'm thinking of running propane in the finished product, so high compression isn't a big downer.

[b-man]

Originally Posted by coreybrenner

On another note, I'm thinking of stroking the 389 in the parts car to a 421, but would like to use later model heads because of their superior combustion chambers. Is there a piston which will work with the later-model valve angles (but not be the 8-eyebrow weirdo-cut ones)?

I'm thinking of running propane in the finished product, so high compression isn't a big downer.

Standard bore 428 pistons will be what you want. The valve reliefs will be in the right place for the later model 14-degree valve angle heads, the 389/421 originally used 20-degree heads.

I have been shopping around for affordable 421 pistons myself, the one that catches my eye is the $465 Probe SRS 428 Flat Top piston set which can be had in +.005" oversize (4.125"), you can see it listed here on the PPR site:http://pacificperformanceracing.com/...-bearings.html

This +.005" 428 size will require boring your 389 block +.0625" over the stock 4.0625 bore size. In comparison just about any off the shelf 428 piston you'll find is +.030 (4.150") and is going to require boring your 389 block +.0875 over.

Of course you can order Ross pistons in any bore size and top configuration you like (dome, flat top, dished) for around $700 a set.

[coreybrenner]

Awesome. I didn't catch whether the Probes were forged or not, though. I had thought about 428 standard-bore forgings, but was trying to get away with the minimum necessary overbore. I'd rather not hog out the cylinders, if I don't need to, but if I need to, then I guess that's how it'll be. 'Course, going with later heads begs the question, "why not just go with a 400 block"? And since I've got one, I may just do that. Hmm.

[b-man]

The Probe SRS 428 pistons are forged with a flat top with 2 valve reliefs (total volume of 5.5ccs) , sorry I didn't mention that.

To avoid boring your 389 block excessively you can get Ross forged pistons in pretty much any bore size as long as there is a piston ring set available in the size you want. To do it a bit more affordably you'll have to settle for 428 pistons in either std or +.005", unfortunately std bore 428 pistons are not readily available off the shelf these days.

[PONTIAC LARRY]

I like the sound of the Probe .005" over 428 piston for a nice 4" forged crank 389-400 build. A super HD 59 389 block bored .0625" with a 4" forged stroker and Tomahawk rods.. MMM