Posted By: watermans340
340 smallblock screamer - 10/02/13 08:47 PM
hey guys i finally got back into building my 340 in my 71 demon. i wanted to to see if i can get some responces on my plan to see what you all think. stock stroke 340 factory forged crank and rods with forged pistons 0.040 over and about 10 out of the hole plan on running cnc ported (runners and bowls) eddy performer rpm heads, 2.02 intake and 1.60 exhaust valves with a comp cams hydrolic flat tappet (.564 lift on intake and exhaust and 251 257 duration) i will have to use 1.6 rockers bringing the lift to just over .600 topped off with performer rpm air gap (home ported) manifold and either my 770 street avenger with vacume secondaries or 750 double pumper and dougs 1 5/8 headesr. i know i should use a 850 or 950 carb and large tube headers but money is always the issue. what do you guys think of my set up and what do you think it will make in hp? thanks for any input!!!
Posted By: Hot 340
Re: 340 smallblock screamer - 10/02/13 09:13 PM
Too many issues running hydraulic lifters today, quality aint there in the lifter mechanisms imo. Go solid. And put some money inside the bellhousing esp with stock stroke.
Posted By: Hot 340
Re: 340 smallblock screamer - 10/02/13 09:30 PM
And .010 out of the hole will need a thicker head gasket than a standard felpro with a closed chamber head.
Posted By: justinp61
Re: 340 smallblock screamer - 10/02/13 09:52 PM
Measure the piston to valve clearance with that much lift and the pistons .040" out of the hole. I'd use good rod and main bolts and a single plane intake, something like a Weiand X-Cellerator would work great. Oh yeah, a good balance job is a must if you are going to spin it up. Not real big on a hydraulic cam this big either.
Posted By: Guitar Jones
Re: 340 smallblock screamer - 10/02/13 09:53 PM
I ran my 360 with pistons .011 out of the hole with the standard .039 FelPro and small chamber W5's without issues for 15 years buzzing it to 7500. I'm not saying you should do that, it was just the way mine ended up with the parts I had and the very limited 4 day time schedule to put it together while still holding down a 12 hour a day job. Piston to valve clearance was very tight too at .076/.083, you can believe I was puckering the first time I winged it in the water box.
Posted By: Cab_Burge
Re: 340 smallblock screamer - 10/02/13 10:24 PM
Are the Eddy heads a open chamber like the stock X and J heads are? If so make sure your piston to head clearances are sufficent for the RPM you want to run
I like and shoot for a mininum of .035
Posted By: 340B5
Re: 340 smallblock screamer - 10/02/13 10:33 PM
That cam is more suited to a stroker. I tried one in my 340 installed per factory specs and ended up replacing it w/a Racer Brown that netted almost .4 in ET. Thinking back, if I would have advanced it 3 deg, it would have been close to the Racer Brown open/closing specs.
Posted By: watermans340
Re: 340 smallblock screamer - 10/03/13 04:47 AM
heads are closed chamber 64cc. 10.5 to one compression. .035 quench. is there any bad ideas or flaws in my components??
i would not buy the cam until you flow the heads.
put the cam where the heads want to be
Posted By: watermans340
Re: 340 smallblock screamer - 10/04/13 02:56 AM
Cheap street duster I believe they flow around 265/200 @ .500 lift doo you think .600 lift & 250ish duration is too much cam for a 340 0.040 over 10.5 compression? Begining to consider the roller cam again...
Posted By: watermans340
Re: 340 smallblock screamer - 10/04/13 03:14 AM
According to cam quest this set up will make around 573 hp and 503 ft lbs. Generous #s I'm sure
peak numbers are only a portion of it..
i would graph the flow and have a cam built the leverages your flow based on what you want to do with the car..
if the port is dead after .500" or goes turbulent then it would be unnecessary to go to .600"
thats an over simplification..but you get the idea
ill also say...lets say hypothetically .522" valve lift is a sweet spot in the port...than i would go just a lil past that valve lift so the port sees the sweet spot twice.once on the valves way up then again on the valves way down..
again this is over simplification ..but gives you some cause to do a little more home work.
some known combos have already sorted these things out.
but the/your hardware becomes the fixed items in the equation..the correct cam will put them to your advantage..fwiw
Posted By: watermans340
Re: 340 smallblock screamer - 10/04/13 10:41 PM
ok final head specs; 190 intake runner, 2.02 intak 1.60 exhaust valves, flowing 272 and 230 at .600 lift and they can flow beyond that but i dont want to run more than .600 lift.64 cc closed chamber. engine is 340, .040 over, .010 outa the hole, .035-.040 quench,10.5 to 1 compression. i think 550hp is doable, and with the 3600-3800 stall converter and 430 gears spinning littlt 27 inch tall rear rubbers im hoping to dip into the 10s in the quarter.
Posted By: thedriver
Re: 340 smallblock screamer - 10/05/13 05:25 AM
That motor will make 320 to the tire.
Posted By: watermans340
Re: 340 smallblock screamer - 10/08/13 05:24 AM
Well it seems everyone has an opinion and ill admit I don't agree with many of them. Apparently someone has already built my exact motor and knows what power it will make lol.I don't think a hi 10 second 2800 to 2900 pound a body is out of the possibility. And with the head flow #s I think 500 plus hp is very doable.as far as streetability goes I never said I'd be crusing the highway but you can believe it will be a 100 percent street strip car.insured.registered exc.o yea and the whole plan is th whip on every ford n chevy that pulls up next to me at a red light! Its not a drag car its a overall total package car!
Posted By: Bad340fish
Re: 340 smallblock screamer - 10/08/13 05:39 AM
I hope it runs 10s for you. The weight will make that easier.
I have something similar. 68 Barracuda 3500lbs, 360, 11:1, shady dell stage 2 port edelbrocks, solid roller, victor intake, 830 Holley, tti headers and a full exhaust system, 4500 8" ta converter, 727, 3.91 gears, 275/50 drag radials. Still ironing some things out but it's been a best of 11.37 and a best mph of 117.5. I let off before the mph traps on its best et run so the mph was way low. I haven't had it back out since drag week where it ran those numbers.
I wanted this combo to be in the tens and it likely won't get there. If it does make it there it will have to have more converter(5000-5500) and a low gear 904. The small tti headers likely don't help it any either.
Posted By: Guitar Jones
Re: 340 smallblock screamer - 10/08/13 12:25 PM
Well having ran a 340 for many years I can tell you this, you really do have to wing it to make the horsepower. I was turning mine to 8000 rpm's. It requires a lot of gear (I was using a 5.13 with a 30" tall tire) and a low gear 904 really helps it. It would be SO much easier to do with a stroker though.
Posted By: 76318dart
Re: 340 smallblock screamer - 10/08/13 08:31 PM
I run a stroker and love it. My dad runs a 340 in his dart. Weighs 3500 w/him. He runs 12.20s with his and its best 60ft was 1.69 that's with 3800 stall and 430s. But now day's stroker is where its at.
The pistons will rock at TDC, hence only the outside edges of the pistons touching, it was not noticeable when turning the motor over with the spark plugs out when degreeing the cam and again when I checked the net valve lift at each retainer with the actual valve springs and valve lash set cold 
Evidently with the motor warmed up at WOT the pistons and rods grew enough to allow the piston edges to touch, no noise, no loss or gain of power once I switched the head gaskests to a thicker set of MLS 
I strongly suggest checking every piston to head clearances by putting the pistons at TDC with the heads on and torque down and then remove the rod caps and put a dial indicator on the rod and push the rod up into the head and see how much actual clearances to the heads you have cold on every piston 
why do all that for a 400hp build?