Street 340 heads/cam recommendation?

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b5cuda

b5cuda

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I’m starting to build a 340 and wondering what heads and cam to select for a street engine. Looking for 350 horsepower with factory manifolds. Block is stock ’69 compression (.030 over), like to use the performer intake, 750 cfm thermoquad carb, and electronic ignition I already have. Car is a ’69 cuda, 3.55 rear-end with an 833OD 4-speed. Goal is to be a fun, reliable year-round driver. My thoughts are either EQ magnum heads (for higher compression, good stock flow, less oil leaks) or #308 swirl port heads? At this point I have only the short block, no heads. Would appreciate advice from anyone who’s done similar 340 builds – thanks!
 
Any heads will do for your power level. I think the EQs are a good choice with the closed chamber and the LA intake pattern. Another good one would be the LA-X heads with the LA rocker gear and LA intake. But either would work. Use flat tops at zero deck, a head gasket .039 tick (felpro performance), and a cam around 220°@.050 and you'll be pretty close.
 
any head, indeed. i would personally stick with a head that has shaft mounted rockers. Just my opinion. also the 300 series casting numbers are prone to crack. they are thin. the thermoquad was never offered in a 750. they are 800 and 850. there were some rare ones that were rated at 1000. run the 850 if you can find one. because of their design the engine will handle it just fine. a mild camshaft a stepor two above the 340 camshaft will get the job done and be very reliable.
 
Look at the comp cams 268 and 280 grinds.
 
@ Moper and others.... what kind of torque numbers/ curve can be expected from the above combo?
 
aquapimp said:
@ Moper and others.... what kind of torque numbers/ curve can be expected from the above combo?
Click to expand...

does it really matter? you'll be makin more power than the stock 340 and they would scream. numbers are for bench racin. build the thing stick it in and drive it.
 
Actually, it does matter to me, as I'm by no means a mechanic, or rich, lol!

I don't want to do too much trial and error; it wastes time and money, especially as a novice!

I would hate to have my build completed, and not be "enough".

@ Strokerscamp: love your avatar. I used to have a 340 Wedge '71 Duster. Car was incredible! I bought it when I was 14 ('88-89) and unfortunately, never was able to complete it as Funds were always tight. Very regrettably, sold it a year and a half later.

Now, it's time to do it right!
 
Thanks guys for the feedback - great input! I'm sure you're right on carb size, it came off a mid-70's 440 a few years back so is most likely the 850.
 
You choke the 340 with 302 heads. A close chamber head will limit your piston choices, the kb hypers which are $250 sit .018 out of the hole.

A good cheap build would be the kb pistons and late 70's early 80's 360 heads. The earlier 68-75 heads would be a little better. Heads you can spend lots of $ on.
 
Just FYI
I built a 340 .30 over with stock 2.02 heads, 268 comp cams, eagle I rods, kb pistons, Mopar electronic ignition, 750 vac sec holley with RPM airgap intake and it dynoed at 344 hp 367 tq.

Should be driving for the first time this weekend with 833 4 speed and 3.55 suregrip so i can update more after the weekend
 
D freak, I think he mentioned 308 heads.

OE poster, I'd follow what Moper said. 350+ hp is an easy grab with what he was saying.
 
As I'm looking at prices ($600 and up for a good rebuild on a set of 308 or J heads), I'm starting to think it makes more sense to buy a new pair of EQ Magnum or RHS. Probably more than I need for a street 340 without headers, but they should give impressive and reliable performance for years to come, and there's plenty of potential for more power if I ever wanted it.
 
I just traded a set of AWESOME J heads to a guy up around Atlanta. He was a great guy to work with so I imagine he would do you right on um. If you're close, I'll send you his contact info. these heads were literally ready to bolt on.
 
rumblefish360 said:
D freak, I think he mentioned 308 heads.

OE poster, I'd follow what Moper said. 350+ hp is an easy grab with what he was saying.
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OH, well the print is so tiny when I seen "swill port" I thought 302's, lol

Yeah the 340's with kb pistons aren't bad, I have the same build with a Crane 220 @ .050 cam and a 10 inch T.C. and 3.91 gears.

Takes on those new factory "400 hp" cars and hangs on or better---and I think my cam is holding it back! Come springtime a new bump stick might be going in.

340's like to rev but with the tci streefighter t.c. it pulls very well after each shift, low rpm is 4,000 plus shifting at 6,500
 
dodge freak said:
OH, well the print is so tiny when I seen "swill port" I thought 302's, lol
Click to expand...


LOL, I do the same thing from time to time.

b5cuda, it's a catch 22 at this point. While the 308 heads rebuild price will end you with a bolt on head and go deal, the switch to a Magnum style head will require hollow pushrods and oil through lifters to start. Next up is if the springs can handle the new lift with the 1.6 ratio over the OE's 1.5 ratio. If not, enter new springs into the price. Will the EQ head except ol LA intakes? I forget these things sometimes.

Getting expensive for a switch huh.
 
For sure. I figure it will run at least $800 to convert to EQ Magnum heads (one version of the EQ comes drilled for LA), less to do factory Magnums but then I have to buy a Magnum intake (or drill the LA intake) and there's also the risk of cracked heads. No perfect solution but I'm not complaining - nice to have so many options, isn't it?!
 
peanut gallery hear. if you have stock dome pistons sticking up out of the block you will have to use open chameber heads like js or thickhead gaskets. you have to do the math before you buy stuff.
 
Still running one(had 2). 70 340, factory piston out of the hole .17.
X or J heads, 2.02, purple stripe cam. 650 or 750, vac carb, didn't make a difference. Very good chebby camero 350, chebby chevelle 396 375hp, 383 cuda killer, with 3.23 gear.
But I think you have to go aftermarket pistons, as according to Dodge, I snagged the last factory 70 340 piston from a dealership in Penn.
 
quench can be adjusted by means of thicker head gaskets, so closed chamber heads on kb 243's is no problem at all.FIW

get 'well ported' J's or RHS from brian at IMM-jmo
 
Here is the setup I got in my 340:
Ross Racings Pistons (Forged Alum .030 Over)
Eagle Crank and H-Beam Rods (Both Forged with ESP Armor)
Total Seal Gapless Piston Rings
X-Heads with Ferrea Valves (Stainless Steel)
Roller Cam, Roller lifters (Hughes version), COMP Roller Rocker Arms
High Volume Water pump & High Volume Oil pump
7qt Oil pan with extended pick up
Windage Tray and Stud gridle
Edelbrock Airgap intake
MSD Distirbuter E-Curve
SFI dampener, SFI Flexplate
All Bolted together using the Strongest ARP Bolts that will bolt to the engine
 
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