CUTLASS Project "In between"

Oct 14, 2008
7,447
113
Melville,Saskatchewan
Flat top pistons so yeah probably 8.5 to 1 or somewhere in there, about the best i was going to get without some domed pistons and i just wasnt going to do that for a play engine.
Who makes flat top pistons for a 260? I thought the stock pistons were a small dish. If those flat top pistons sit .025" in the hole, you actually should be around 9.5 to 1, if they are a true flat top. That SP2P intake should work perfectly with the 500 cfm carb. An 800 cfm Qjet would overwhelm the intake at full throttle, part throttle was amazing. The 450ish GM TBI worked well with it, I could do a one wheel peel with it and pulled fine to the 4200 rpm shift points, idle to 4000 rpm is its rating. Good luck and Thornton Jr manifolds are a nice upgrade for a 260.
 

scoti

G-Body Guru
Supporting Member
Sep 5, 2019
804
93
Texas
Looks like a stock dished piston to me. I'm no pro though....
 

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Oct 14, 2008
7,447
113
Melville,Saskatchewan
I think they are around 10cc but could not find that info again. If that is right, it will a touch below 8.5 to 1.
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
3,328
113
Upstate NY
Too much cam is a great place for the compression equalizer :

1624499234390.png



Looks great though, really glad to see you and your son having fun with this!!!! Keep his hands dirty!
 
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84dragcutlass

Royal Smart Person
Supporting Member
Thread starter
Aug 20, 2009
1,065
113
North Vernon IN
Who makes flat top pistons for a 260? I thought the stock pistons were a small dish. If those flat top pistons sit .025" in the hole, you actually should be around 9.5 to 1, if they are a true flat top. That SP2P intake should work perfectly with the 500 cfm carb. An 800 cfm Qjet would overwhelm the intake at full throttle, part throttle was amazing. The 450ish GM TBI worked well with it, I could do a one wheel peel with it and pulled fine to the 4200 rpm shift points, idle to 4000 rpm is its rating. Good luck and Thornton Jr manifolds are a nice upgrade for a 260.
Yep you are correct they are a small dish, idk if i was thinking of another engine or just having a brain fart first thing in the morning but my mistake. Either way though will be better than it was before by some degree. I didnt want to go big on the carb after seeing the tiny ports on that SP2P intake, and with such a small displacement it wouldn't need a lot of carb anyway. The Thornton manifolds are something that i am more personally excited about because back in the day i cant tell you how many 307 powered cars i had that i would block off the crossover port on the passenger manifold so i could run dual exhaust without having to run the crossover and they never seemed to be real good and always were a pain. So having a bolt on manifold that i dont have to do that is really cool, i just told my son the other day he's lucky because i sure didn't have all this fancy stuff on any of my earlier cars.
 
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84dragcutlass

Royal Smart Person
Supporting Member
Thread starter
Aug 20, 2009
1,065
113
North Vernon IN
Too much cam is a great place for the compression equalizer :

View attachment 178462


Looks great though, really glad to see you and your son having fun with this!!!! Keep his hands dirty!

No kidding there! We had talked about upgrading it in the future when he's older just to see what it will take. I have to admit the small little engine on some boost would be fun.
 
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Oct 14, 2008
7,447
113
Melville,Saskatchewan
Yeah, between Thornton, Mark Remmel, Rocket Racing and BTR to a lesser extent there is a ton of Olds parts available that weren't a few years ago.
 
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