Anybody got any ideas what sort of HP my Blown DeSoto 291 should put out? This engine is NOT a Drag Monster. 3> valve job, 140/350 valve springs...7.5:1 SCR , new pistons .030 over, cast rings. Crank .010/.010...Pertronic ignition, roller cam .375 valve lift, .050 duration =236/236. 6-71 GMC 4#'s Boost, 2 Carter Compe***ion 500 CFM's. Sanderson shorties. The Stock engine was raten at 197 HP. Need to get SOME idea what it might put out. HOPEfully at least 250 HP...I'd at least like to be able to break the tires loose. All guesstimates welcome...Thanks guys...
Should make over 250, and you should be able to up the boost to 6-8 psi for 300 ponies THis is all wild guesswork
If it won't make 250 HP I'd take it back apart and start over.... But then again who cares about how much HP it makes just have fun with it.
I would be willing to bet it will make a lot more than 250,,,and easily be able to turn the tires. These engines had a ton of torque to start with. I will guess about 350 or so,,with a monster torque curve. It really depends on how it is setup and tuned,,,could go either way,(up or down). The low boost number is not too bad,,,it should be fine. With 7.5 to 1,you could go higher boost?,,but I don't know how good the heads seal. Remember,,this is a Hemi engine,,they love to have pressure blown into them,,,,it might just scare the hell out of you. Tommy
Are you sure about the .375 lift? The 50 thou duration sounds right, but the lift seems low. Also, keep an eye on your timing and you can run 6lbs no problem. 300 horse should be easy, but with out a real dyno, who knows. Honestly, I wouldn't worry about a horse power number. Power numbers get tosses around all the time and rarely mean anything. This little motor is going to run reeeeally strong. If anyone asks, just say 485 horse and 450 foot pounds of torque.. How will they know if you are full of ****????? Good luck and hurry up. I'm dying to see this thing on the road. -Abone.
ABONE - .375 is it. The duration, compared to the Stock cam is really long. There's not a hell of a lot more room for lift, between the valve and the piston, but the longer duration and 112 lobe center should be good for a Street blower/roller cam. I.O. 6 BTDC/I.C. 50 ABDC, E.O. 50 BBDC/E.C. 6 ATDC. Will be picking up the engine/parts (un***embled) this week, and soon after, there should be fire in the boiler...
I got my 291 started yesterday (although not blown)and I'd be real curious about mine as well.. But Does it really make a difference?? The coolness factor of having an old Desoto Hemi running is good enough for me..
I guess I'm just curious, too. Since I've added the Roller and the Blower, I'd be interested to know how much over 195HP it will add...
I have to ask about the lift too. That sounds like lobe lift to me. It's a roller cam. Stock net lift was about that. Any naturally aspirated early hemi will make well over 1hp/cid with a decent CR, reground cam and headers. Your engine should make over 500hp. If your cam really has .375" valve lift you need to get another one. Are you using stock pistons? For what it's worth forged customs with the pockets machined in for lift will cost you about $525 if they're flat tops. Get some if that's what's holding you back on lift.
Hey 345, get her on the Dyno and tell us what she makes. Im with Johnny5. Your valves lift has gotta be higher than .375" at the valve, or am I nuts? The cam I'm getting ground right now will have a lot more lift than that, decent dur @.050" and it'll be ground on 110 centers.....with around high 7s in CR, ported heads, all the tricks (MSD, decent headers etc) a fresh 6-71 lung and around 8 psi. Although most V8s like 112-114 LC with a blower, apparently Hemis like around 110 b/c of the exh port layout/efficiency and helps prevernt the exh valve getting too hot. I'm shooting for over 500HP/450TQ so I want to ROAST the cheater slicks haha !! BTW, the blower will tame the cam somewhat. Rat
I agree with you totally. Back in the early 70s I had a cam ground for my 341. It was a 302 X .505". Knew nothing then about these engines. The idle was cool but the valves started floating below 5000 RPMs. Live and learn. Bill
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