2.8 pistion swap

[brand x]

I saw in tech section that you can put 2.8 pistions in your 2.9 to bump up the compression. I was thinking about pickin up another 2.9 to do the build just wondering if anyone has done it and how it work out and any info on it would be cool thanks

 

[IMenriched]

Havn't done this but heres what I recall.

yes some have done it. 97-89 octane gas is not going to cut it if it is done, prolly will run, just not happily. just something to concider.

obviously you'll have to bore the 2.9 block to fit the 2.8 flat tops pistons. with the raised compression ...it'd be best to get the heavier World Products heads.

and there is clearance concerns on the bottom side of the pistons with rods may not clear in certain areas of rotating mass.

custom cam grind is most likely in order too. if done right it should be hard runner.

in short, lots of machine work...& those whom have done it are kinda tight lipped about it.

 

[brand x]

its just a wheelin truck so if i have to run 93 or a 100 octane thats cool

i would switch over to mas air to help with the tuning

thanks for a the info

 

[Psychopete]

http://www.therangerstation.com/forums/showthread.php?p=155896#post155896

From the tech library:
There has been talk about using 2.8L flat top pistons in the 2.9L engines to increase compression and hopefully increase horsepower. Supposedly, if you would need to get .030 oversize 2.8L pistons and bore the 2.9 block accordingly. It should raise the compression ratio to 10-10.5:1 and would require at least premium gasoline. The increase in power mathematically would be roughly 2-4% per point in compression increased so that being said with the 2.9L at 8.5:1 increasing the compression with those pistons to 10.5:1 you would yield a maximum of 8% increase in power.

Thought this was interesting when I was searching around - ARP Rod Bolts for 2.9L:
http://cgi.ebay.com/ebaymotors/New-...-2.8-2.9L_W0QQitemZ120269221285QQcmdZViewItem

2.9L Piston
http://store.summitracing.com/partdetail.asp?part=STL-520P&autoview=sku

2.8 Piston:
http://store.summitracing.com/partdetail.asp?part=STL-433NP&autoview=sku

IMO, As for which over bore to get, take your engine apart and consult with a machine shop to help guide you through this. I would also consider getting the rods shot peened. Engine management also makes me wonder... You might have to go with a mass air setup, I would definitely go with a hotter cam with that much compression (holy crap! ).

Pete