Engine: 259 vs R1 pistons

[jwitt]

Is there any difference in 259 flat top pistons and R1 pistons?

[StudeRich]

Yes a Critical Difference; to prevent the Piston going THROUGH the Cyl. head with the longer stroke, the Wrist Pin HAD to be Raised on a 289 Piston.

Do remember though, that a Flat Top Avanti R1/R2 Piston has 10.25 to 1 Compression with 259/289 '63/'64 Lark/Hawk/Avanti R1, 1557570 casting # Heads.

This is why we sell the Shallow Dish Avanti Pistons with about 9.0 Comp. which is a bit better option than the R2, "Thin top deck" Lower Comp./Higher cc, Truck Heads for about the same Comp.

vs a Standard 289 Deep Dish Piston with 8.25 to 8.50 Comp. with the SAME Heads.

[JoeHall]

If I were to rebuild another standard 289, I'd use shallow dish pistons. Pretty sure the 289 would tolerate them, year round, even with AC, as long as a good radiator is used. The result should be a bump in power and MPG.

[Mike Van Veghten]

Remember too that much of any combustion chamber cleanup will drop the cc's so a 289 with a flat top piston with a reworked head is a good thing.

Mike

[PackardV8]

Remember too that much of any combustion chamber cleanup will drop the cc's so a 289 with a flat top piston with a reworked head is a good thing. Mike

For true, Joe and Mike have good advice; when beginning to build a 289”, the choice between flat top, shallow or full dish pistons is a complex multi-variable regression analysis. Has the block been overbored? If so, how much? Has the block been square decked? Have the heads been surfaced? Steel or sandwich head gaskets? What cam is being used? Are you a CASO who’s going to try using regular gas?

the pistons all cost the same, so get a recommendation from someone who’s BTDT.

jack vines

[JoeHall]

I experimented with 289/259 piston changes, by happenstance, back in the late 80s / early 90s. First, I rebuilt the 289 in a 63 Cruiser, and ordered all parts from an elderly gentleman in Colorado named Mr. Snearly. He sent what I now know to be R1 pistons; I could see they were different, but installed them anyway. The car had lots of zip, and got good MPG, but tended to run a bit on the warm side. Next, I rebuilt a 259, and Mr. Snearly sent more R1 pistons. As with the 289, I installed them anyway, but was reluctant when I noticed they sat deeper in the holes. I shaved the heads .030" and called it a wrap. That car ran on the cool side, lost 2-3 MPG, and was a bit more sluggish, but I ran it for 100,000 miles in the 62GT. That 259 is sitting out in the garage, since I replaced it with a 289, about 5-6 years and 45,000 miles ago.

[PackardV8]

Joe, only you could have lived with that for 100,000 miles. No surprise it was a bit soft; your R1/259” combination probably was no more than 6:1 compression. You could have run it on kerosene.

I got sold a 289” core that was even worse. A Puget Sound CASO had gone through his scrap pile and combined a 289” P full flow block, 259” crank and dished 289” pistons. That would have been 5:1 compression.

Jack Vines

[GrumpyOne]

Awright... All interesting answers so what would happen if...

I were to substitue mid fifties xxxxxx555 heads on a '63 base Cruiser 289 engine? Would it explode? Be whimpy?? Or not much change at all.

As an aside, I want to put that engine into a '55 Prez sedan and retain the ability of use a four bolt valvecover to retain the "original" look...