I purchased a 1968 Baracuda convertible on the internet and it had a rebuilt 340, 904 tranny and i just replaced the 7.25 with a 8.75 posi with a 323 gear. My question is that I'm wanting to know what kind of heads I'm running. I pulled the valve cover and it had stock rocker and under the rocker where these #aawj,2591, & 3488/6 or 3489/5,I'm lost. maybe i'm lost and looking in the wrong place for the #s. the engine has a weland intake with #7507 and a 1406 edelbrock carb. with a duel point destributor sticking behind the intake.I would also like to add that my 340 is sporting a set of factory h.p. headers with 2.5 pipe with cross over and three chamber mufflers.
I would like to know what my option would be to put some more horsepower with min. teardown. I seen where a set of crane rocker would benefit the engine. also the carb. is an economy one but i figured that i could go with some lighter springs on the secondaries and get them to open sooner. the car had some good power from about 50 on.
looking at the prices of the 360 crate motors I don't know about putting alot of money in the 340, but i have been told the the 340 has a better bottom end and that it will hold up better.
I would appreciate some help I'm looking for around 400hp. I have done some more reserch and seen where the heads have a j stamped on them and that the valves are stainless because a magnet will not stick to the stim. I guess I'm correct i don't know.
Next i guess i need to know what size cam i have. I would like to know if putting aluminum roller tip rocker would be worth the effort are would their would be some job to it. would adding petronix ignition modual in place of the duel point are do you have some better solution.
Bennie:The 340 will easily produce 500 HP and actually run on the street. It's all about the right combo of parts. The 340 bottom end is very solid, the heads are good, etcI would NOT recommend the Crane Rockers, especially the aluminum ones. I had a set on my car and I didn't get 6 miles down the road before the rockers came apart and wrecked my motor. Crane had a bad batch of adjuster nuts (probably made in someone's back yard in China or Mexico) that broke when put under minimal stress. The Crane rockers will not give you any additional HP over the factory stamped rockers either (They only help on Chevy's and Fords) (The Chrysler factory rockers are strong, light weight and friction free under oil pressure). Chrysler did there home work when they made the fixed mount shaft rockers. The down side of the factory stamped rockers is no adjustability to them. If you need to use adjustable rockers, go with the Hughes Engines rockers or the Indy rockers They are both bullit proof.
I would recommed looking up 340 motor builds, there are dozens of good articles on this.
I love 340's even though I currently own a 12 second 360. Its all about cost, 360's are cheap and will out power a 340 due to the increased stroke when everything else is equal. As far as your 340 since you have it I would use it. Unless you are going to run a solid lift cam forget about the roller rockers. If you do decide to go with aluminum rockers, Mopar Performance sells a nice set, I upgraded the adjusters to the factory 273 pieces. This is necessary because like the crane units, the adjusters on the Proform rockers kept backing off and needed constant adjustment. Since replacing the adjusters I haven't adjusted the rockers in over a yr. With the gears you are running a mild Hydraulic cam, Max size Mopar .474 with a holley 650 carb, I prefere D.Pumpers, and a set of 1 5/8 headers will liven your ride up. Get rid of the dual points, they will be constantly out of adjustment, upgrade to a mopar electronic ign. kit. This will provide you with a fun reliable combo.