340 rebuild in my future...

[elevenssc]

The 340 in my 1970 Cuda is going on 30 plus years since it's last rebuild.  The engine has a nasty vibration above 4000 rpm that I'm suspecting is something very unusual/non standard (posted harmonic balancer questions a while ago...replaced harmonic balancer and vibration got worse). The car budget looks to be in line with an infusion of funds to allow an engine rebuild.  Big ticket items for the rebuild are new heads (cast iron aftermarket), roller cam and lifters, as well as roller rockers.  Headers and exhaust (flow masters and X-pipe) are also on the wish list.

I know enough that airflow makes horse power and components need to be matched as best as possible to maximixe the combination.  I'd like to get a horse power per cube, use pump gas and have a combination that has good street manners.  My question to the group is...
1) cam specs...what should get me to 340 hp?
2) cylinder heads...what kind?...combustion chamber volume?...valve sizes? (I'm going cast iron to keep costs down)
3) I see that there are aftermarket roller lifters that do not require all the block mods to maintain oil pressure...anyone used them yet?
4) someone out there has done what I'm looking to do...what combo's did you use, and how we're the results?

Thanks in advance for your feedback.

[73restomod]

I would go for, ede RPM-airgap, TTi headers, RHS heads, hydraulic roller cam in the low 260-275 duration, .550 lift, if you want more lift go with 1.6 roller rockers. Keeping the duration low will make it more drivable, increase fuel economy, etc. However, this combo would make more like 400hp, if you are only looking to a have horse per cube, rebuild it with headers, 3 angle valve job, and use the big CFM thermoquad. That would put it in the 330-350 hp range easily.
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[Chryco Psycho]

I tend to agree with the parts list except that you can easily get a flat tappet cam withing the range you are looking at & as long as you use good oil it will be reliable

[73restomod]

Talk to your machinist, if you want a good deal on oil. Mine can get me a case (12 qts.) Of Brad Penn high zinc oil for 54 bucks, so I run flat tappets in my motors.

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[GranCuda1970]

I picked up 7 quarts of valvoline race oil supposed to have high zddp zinc and phosphorus on sale 5.99 at shucks o-reilly.

[elevenssc]

 If I can get 400 horses, the more the merrier.  Anything in the 1.0 to 1.2 horses per cube will be just fine.  Anything much over that and things start to get exponentially pricey.

Anyone try the LA-X heads from Indy Cylinder Head?  I saw them at this years Mopars in the Park and thought they looked decent. 

I was looking to go the roller route from an efficiency perspective (more efficient, more power).  I like the stock shaft mounted rockers and want to keep this setup, but in roller trim.

[Chryco Psycho]

the RHS or LA X heads are good .
 You could use the later 88 up LA block , it will have a hyd roller cam & lifters in it & has the deeper lifter bores for the roller lifters . Just something to think about as you could snag one from a wrecker for probably 1- $200 .
 I too far prefer the shaft rocker system over the chevy ball stud , look at PRW stainless steel rockers , affordable & good quality .
For serious power I would look at a Mopar R3 block with 6 Bolt / cyl W8 or 9 heads

[73restomod]

Yeah the RHS/LA-X  heads flow almost as much un-ported as a good set of max ported 915s, or X heads. Other pluses include lighter valves, great chambers, and a meaty deck. They also out- flow the eddy heads.

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[elevenssc]

Chryco...a noobie question...are the Magnum 360's (Dodge Ram) interchangeable with my 340?  So the 88 and newer LA motor you reference would be the 360?  I'm assuning so, but not 100% sure.

[Chryco Psycho]

87-92 are LA engines & will bolt in , they use roller cams , serpentine belt systems , 302 or 308 head castings with shaft rockers  & are available as 318 or 360 cid .
The 93 are magnums & while they will bolt in everything changed , barrel intakes with front mounted throttle bodys & ball stud rockers .

[elevenssc]

Another question...headers vs factory hi-po exhaust manifolds...will the headers perform better enough to justify the cost? (I already have the hi-po exhaust manifolds so I need to ask)

[Chryco Psycho]

I would expect apporx 20 Hp gain with headers