LawrenceF

I'm putting together an LQ4 based motor to go in my '55 F100 that's getting twin turbos. I found a set of new stock sized forged pistons on ebay, then realised the wrist pin is the wrong size after I'd bought them. Is it worth getting the stock ones re-bushed or should I go for forged ones? I intend keeping the stock crank and I'm not aiming that high HP wise (like 600 or so). Any recommendations for stock length rods? I can find plenty of 6.1 but hardly any 6.098 forged ones.

TurboGibbs

iTrader: (6)

The older SBC rods have .927" wrist pin and the gen3 LSx engines have a .945" wrist pin. Not sure how you got some 4.000" bore pistons with the correct pin height yet wrong diameter pin unless they were an oddball custom made piston for a SBC with a different stroke or connecting rod length of course. I'd double check the pin height on your pistons (the distance from the center of the wrist pin to the top of the piston). It should be 1.331 with a 6.098" rod give or take a few .001's depending on how far it is in or out of the bore. There is no aftermarket 6.098 rods that i'm aware of. All the aftermarket rods for the gen3 are sbc aftermarket rods that were already into production (they share the same bearing journal dimensions and same bearing). I know Manley has made the 6.100 sbc rod for years and they have bushed the wrist pin hole larger to the .945" so you can use them with stock pin height pistons in a gen3 with a 3.622 stroke. The .002" difference in length between the 6.098 and 6.100 rods is negligable and would effect compression just slightly. With your power goals i'd go ahead and get some aftermarket rods rather than re-bush.
Hope this helps.

LawrenceF

Thanks for the info TurboGibbs!. They are Wiseco K392AS pistons, which are listed for an LQ4 and have .927 wrist pins. On wiseco's spec it shows them being stock deck height with a 6.098 rod and slightly too high with a 6.125 rod (but I guess thats for the LSx style blocks as the deck is a different height according to the same spec page). I've found a couple of 6.098 forged rods, these are the cheapest

http://cgi.ebay.com/ebaymotors/ws/eB...m=140098174990

I guess these look like my best bet?

TurboGibbs

iTrader: (6)

Those pistons have a 1.304" pin height which would make them for a 6.125 rod. The gen3's have a 9.240" deck height if you want to check my math.

http://store.summitracing.com/partde...S&autoview=sku

LawrenceF

Have a look at http://www.wiseco.com/PDFs/Catalogs/AB05_chevy.pdf

On page 9 they list them as 6.0 truck reverse dome, 9.213 deck with 6.098 rod?

TurboGibbs

iTrader: (6)

Yeah, and it also shows that the piston height will be 9.240 with the 6.125 rod. You can use with either one to get whatever compression you want. Your std old sbc's had the piston .025" down in the hole. The gen3's usually are .006 or so out of the hole. This gives for a much tighter quinch area which helps supress detonation and gives a cleaner burn. The 6.125 you'd be "zero deck" so to say, none in or out of the hole which would be best.

LawrenceF

Sorry if this is a dumb question, but on that page they show zero deck as 9.230 for the trucks, which would put me .010 above deck or have I got that all wrong?

TurboGibbs

iTrader: (6)

Here is something I found in a search.
It says it is 234.7mm /25.4=9.240"
I dunno. 9.240 is all I ever heard of.
http://www.cadillac.com/cadillacjsp/.../car/specs.jsp

LawrenceF

I was just looking through the 2001 factory manual I have and found the spec. It's listed as 9.235-9.245, so I guess 9.240 is smack in the middle for that. So I guess that puts me at .005 at worst with 6.125 rods?

hotrod04

iTrader: (1)

I bought the Manley .945 wrist pin and 6.100 with diamond forged pistons for my LQ4 and work great.