My block is in shop getting ready for a rebuild.Its going to replace my 307 in my other chevelle. im trying to finalize everything so i have a set plan for the year when building the car. They are boring my block this week and want to know if i want to go .020 or .030 over. Does it really matter? Is .020 better for overheating issues? heres my proposed motor and combo. Feel free to suggest anything that might make it better. Im looking for very good low end with it hitting very hard in the midrange. I do want some upper rpms out of it. My other car is pretty much finished after it hits 3rd gear.

350(basically stock bottom end)
edelbock rpm package(68cc heads)
268 XE comp cam
carberator-3310 holley(any other suggestions?)
HEI with MSD
headers
flowmasters
2200-2400 stall
3:73 gears and posi
turbo 350

That's basically the same setup I had in my 350 + .060". Only I had a pair of cleaned up camel hump heads and 3.36 gears. I assume you're using the rpm manifold in the "package"? The carb is fine for the application too.

I had tons of low end... you'll probably have even more because mine wasn't set up very well.

Make sure your quench and compression is ok and you'll have a blast.

I'd go .020" over for now... that way you can bore it out more on the next rebuild if yuo have to.

graemlins/beers.gif

I will be going with the performer rpm manifold and also 10.7 compression speed pro hyperectectic pistons. That compression is with .030 over and 64cc heads. How much more does it boost compression with .020 over?

FWIW Speed Pro calculates compression using .025 Deck Height and a .041 gaaket(so a not so good .066 quench). I'd have the blocked decked to .010-.015 and use a thin .028 gasket and then find pistons that will give you 9.5-10.0 compression....that thing is gonna ping like crazy with a xe268 cam and 10.7 CR unless you like $6 race gas.

What about just going with the 9.7 compression pistons at .020 over with the xe268? Or maybe the xe272 cam with the 10.7 pistons at .030 over? I guess im trying to find the right balance. I dont mind running a few gallons of high octane fuel in each tankful.

anyone? Im going to orger my pistons today so im trying to figure out what kit i need to order.

What's your rod length?

Im not sure. Its a Target master crate motor

Blaster,
I ran nearly the exact motor you're building except with AFR heads (same volume as yours). I had great performance with classic (cheap) TRW (speed-pro) forged pistons (2256F if i remember correctly). 20 or 30 over won't make any difference, but as suggested, bore only as much as you need.
My block wasn't zero decked, so i ended up using high-quality Felpro "shim" gaskets that are designed to work with aluminum heads. I don't remember the part # but it was easy to find in Jegs/Summit, ~0.028" thickness. AllGoNoShow has it right on - you want ~0.040 quench with this cam.
Your converter is marginal, but it may work OK. I ran a 3000 stall.
I ran 13 sec flat with this motor in a full weight 64 chevelle and 3.73's.
Also, this cam is noisy! It sounded like the lifters were too loose - turns out this cam slams the valves hard! Many people have commented on this - just FYI
Good luck

If those are 5.7" rods, you can get these pistons (http://www.kb-silvolite.com/performance.php?action=details&P_id=156)

If you deck your block to 9.000" these pistons will stick .001" out of the hole. Add a .039" head gasket and you'll have a tight .038" quench area. With the 68cc heads of yours, you will have a compression ratio of 9.7:1 and a DCR of 8.0:1 with the 60 degree intake valve closing of the xe268 cam, which is perfect for the street.

Summit racing part number UEM-KB106020-8... they go for $173.39.

They do use 1/16, 1/16, 3/16 rings though. I've heard mixed remarks about this ring size on the street.

I have the xe262 cam in my other chevelle and like it. Should i go with the xe268 or go up some or go with another cam?

I liked the 268 for the street. It idled pretty smooth... with a VERY slight lope. And I could fry the tires at will. It had a strong low end and midrange. Top end wasn't very strong, but it was for the stret so that wasn't what I was looking for anyway.

I like the XE series a lot. Where you want your power is a personal preference.

If you want something with a a little more power, get the XE274.

Why not see what Harold recommends? :confused: I'll be ordering one of his cams as soon as I get some extra cash flow.

The car will be mostly weekend driver on the street. Im looking for good low end with tons of mid range torque. My other car has a 262 cam in it with the aluminum 58cc corvette heads with high compression. All torque but no top end.