Right now I have 9:1 with Keith Black pistons with .133 dome and 119cc or better 781 open chamber oval ports.

My piston have had 3 sets of rings on them even though low miles. Long story. But I'm thinking about replacing them with either KB with a .250 dome or forged with a .270 dome and end up with 10:1.

Will this cause problems for a mostly street engine? The weights on the pistons are different so a rebalance Is probably needed.

Is 10:1 too much for the street with iron heads? I have a Comp Cams 274XE cam and RPM Air Gap with and 870 Holley street avenger. I run a TH400 and 3.50 gears.

Would I gain much by going up a full point?

Or should I run these pistons again?

Thanks. :confused:

I run 10.59 to 1 with no problems...
My pistons have a .100 dome,heads are 101 cc's(215's),piston to deck clearance .008,and a .039 head gasket.16* base,38 total with no detonation problems what so ever.

I run 10:1 comp on my 454 bored .040 over,run 18deg initial timing with 38 total with no detonation on pump gas(94 octane).The pistons are speed pro #H693CP with .230 dome.

Mr. 4 speed didn't say what cam he has so your results could be different. 10.0 will work fine with the 274 cam. DLoad the DCR calculator linked in my sig and run the numbers yourself. Balancing is probably. You can compare the weights and if they are very close you might get by without balancing. I think you'd pick up a very noticable amount by upping the CR.

My cam is the UD 280/288 .525/.550 112 LSA

I built my 454 with 9:1 compression. Now i wish i built it with 10:1 compression so i wouldn't have had such a hard time finding the right cam. I might angle mill the heads (Merlins) to get me into the 10:1 range later.

The Cam i picked with 9:1 is the XE270 4x4 cam, should be good for a street engine, wont know till i fire it up later this month.

-Ryan

IMHO, I consider 10:1 the right number! MINIMUM if you want POWER!

My 460 is approx 10:1 with the TRW L2465F pistons and 781 heads. So far it has run good while breaking in the CAM and for a short test drive. No signs of detonation and Wow what a kick!. Will know more as I get her to the track and get a little more seat time.

Oh BTW - My DCR came out at 7.4 with the Performer RPM CAM. I will probably change to a UD CAM Later but this one was free along with pistons, springs, lifters and Intake so I used it.

Troy.

What grind of UD will you drop in?