Whats a good Street/Strip Compression ?

[cudacarl]

I'm in the process of rebuilding my 340. The parts i'm using are Speed Pro Forged Pistons(1.840) P/N 2316f (60over), Sealed Power Moly Rings, Clevite 77 bearings all around,and Comps Cams 268 Xtreme Energy Hydraulic cam 268/280 .477/.480. It has a Steel Internally balanced crank, Rebuilt x-heads port matched to an edelbrock rpm performer intake w/edelbrock 750 cfm carb. I have crane gold roller rockers but i had some problems with them so i'm going to get it running and tuned with the stock valve train before trying the gold rollers again. (Crane sent me new adjusters that were snapping due to a manufacturing defect). The machine shop doing the work had just done a 340 for a guy and he used a hughes timing chain. I bought that same chain but while i was on there i saw a 340 that they sell with 10.2:1 compression that runs on 92/93 octane. I was going to go 9.5:1 but i wouldn't mind more compression. I only use the car on weekends but do take it on long distance drives from time to time. Should i stick with 9.5:1 or go for more? The car is a '73 cuda with a 4-speed and 3.54 8 3/4 posi rear. Originally this was to be on a tight budget but when in rome...

[PRO]

Hughes has some great proven combos with higher compression on pump gas,what enables them to get away with these combo are their quench chambers,remember quench chambers are a combination of the top of the piston and the head chamber,so youll have to run their recommended piston and head and corresponding head gasket,if not youll surely have detonation.They usually use KB pistons with a step in the dome.Usually 9.5-9.8:1 is the max with iron heads.Your combo sounds like a great daily driver setup to me.......PRO....

[rumblefish360]

I used the KB zero deck pistons with "J" heads. (72cc chambers) It is advertised at 9.8 to 1 compresion. The engine pinged on less than 93 octane. Although the cam was only a 288 dur. purple unit. It definately could have used more cam to help bleed of compression.
If you plan on running in the street, a larger cam can help. It can be hard to balance the trade off. You run the risk of "to large of a cam" for the rear gears and cruiseing rpm range.
I would say stick to your plan. Unless you don't already have alot invested already. No need to waste money.
Your current combo sounds great. Run what your doing. A higher compression isn't needed for the your writin combo.

[Darn Dart]

Hey cudacarl, I run the TRW 2316f piston in my 73 Dart Sport with a 70 340. I had my J head milled to 63cc bringing the compression up to 10.5. Been running Amoco 93 octane pump gas for the past 2 years at the track. My cam is a little more agressive than yours(Hughes 3844). I have run 12.06 @ 110 mph. Your combo should make awsome street power. I would cc your heads to get the volume of the chambers. Mine were 72cc to start with and a .050 cut brought them down to 63ccc. TRW/ Speed Pro advertises 9.5 compression with 72cc heads for 10.5 wtih 63cc heads with the 2316f piston.

[cudacarl]

Hey Darn Dart what compression with my setup not to put you on the spot!!!! You think 9.8:1 is good. I got to give the shop an answer on monday!10.5:1 sounds too strong but if it will work i'll do it!..

[Darn Dart]

cudacarl, for a street car and the 268 xtreme cam I would go with the 9.8 compression. The difference going to a 10.5 would not even be noticable on the street. I use the 268 comp xtreme cam in my wifes car with 9.3 compression and it works great(8.30 in the 1/8 mile, that is about a 12.90? in the quarter). The 268 xtreme is a awsome street cam it makes power from 1500rpm all the way to 6000, you won't be disappointed!

[MoparMuscl]

With that small of a cam I would stick to 9.5:1 because not much of that compression will get bled off. I have a 10:1 360 and it definatly pings on anything less that 93. If I can't find 93 the timing gets cut.

Good Luck

[6pakman]

sounds like a great combo to me. my 340 6pak is running 10.5.1 with a comp cam that is bumped up just a hair over stock specs. i can run with the big blocks all day long.( iv'e even dusted a few). i wouldnt change that combo at all. if you do, dont go over 10.5.1. it sounds very streetable, but to get a nice idle, try to get it down to about 700 rpms. the low idle will have a nice rythem to the rumble of the exhaust. youll see. have fun.

[ohioDemon]

cudacarl. i run 10.2 cr in a 360 motor . i also use a comp cams xtremeenergy 284/296 .510 hyd. I run sunoco ultra 94 octane gas and have no pinging problems. my car is a 1972 dodge demon 366 auto 3000 stall 4.11 gears. it just ran a 12.73 @107 at kil-kare dragway in xenia.ohio all this on street tires !!!