https://www.compcams.com/magnum-250-250-solid-flat-cam-for-chrysler-383-440.html

Hey all, like most of us I am on a budget and I am trying to make the most with what I have. I am building a B based 512 for 72 Duster with the goals of being somewhere in the 600-650Hp range. I am doing some parts trading to help a friend out more than myself and in the trade I an going to end up with a Comp cams Magnum 250/ solid cam and lifters. Is there any opinion on this cam that could be shared and how it might perform in the theoretic 512 B based combo with a heads the flow 300 cfm. How well would this cam perform in the 512 packed noted below?


Currently I have a set of fully ported Bruce Toth heads (same casting as the Marsh performance heads), Set of Crane Gold 1.6 rockers I bought new many years ago, 2 intakes to choose from Eddy RPM and a M1 single plane, both intakes being fully ported and gasket matched. With a Quick Fuel 850 dp to top it off until I go EFI.
As per a previous post I am still waiting to purchase my bottom end but I except to do so in the next 2 months. Also on the shelf is a Comp Cams XE284 that I feel is a bit small for the goal I trying to reach.

Thanks

cam is to small in my opinion. add some lift & about 10 to 15 deg of duration , that 250 cam will be in the 550 hp range at best with 300 cfm in my opinion, call & talk to Dwayne Porter, Porter Racing Heads

What is a Magnum 250? Do you mean the Magnum 294S which has a duration of 250 @ 050? If that is the cam you are talking about then it should be fine for a 512 inch street engine. It might not be big enough to make 650 hp but it will pull hard in a pump gas 512, especially with the 1.60 rocker arms. You can go larger with the cam but you'll start to give up street manners so then it just depends on how much you're willing to live with on the street.

Here are the specs AndyF

That cam will work really nice in a street driven 512 when you combine it with the Performer RPM and the 1.60 rocker arms. I doubt that it will make 600 hp but it might make an honest 550 hp at 6000 rpm. It will be plenty of power for a Duster unless you're trying to run 9's.

No specific cam recomendation hear, just an opinion on cam choice. Write down the charactotistics you want in a cam. Things like maintenance intervals, where you want it to smooth out so it can work well with your trans, quality of parts you are willing to buy. Add anything else you think is important. The LAST thing you want on your list is a horsepower goal. That often forces the builder into a compromise they may not like for a mostly street car.

If you're looking for 650 hp on your 512, I think you need more cam. My 400/512 according to a mobile chassis dyno produces 645 rwhp. My 512 has Stage 6 heads that flow 350@650 a solid roller that's 272@50 with 650 lift. I run a Super Victor intake with 950 QF carb on pumpgas with 10.5 cr. Makes my e body run 10.5s @125mph.

LOL, that's the opposite of how I do it. I start w/ the power I want, then compromise everywhere else!

In all seriousness, Greg gives good advice here. I'm just willing to deal w/ more than most on the street to get the performance I'm after.

Realistically the car will probably only see the track 3-4 times a year and be a weekend street bruiser at the local cruises. I tend to be that guy who compromises street manners for performance but I am trying to find a little middle ground here this time around.
I enjoy rowdy car on the street but I need something I can drive 200 miles in a day if I want to. The car is being mini tubbed so I can 325/50/15s with my 3.91 gears. I still need to get my trans/converter set up but I'm leaning for an A518 for the OD. Bruce sent me a few pics of the head work being done last night...

If you are mostly driving on the street then that 294S with the 1.60 rockers and the Performer RPM should be a good combo. Especially if you want to cruise down the freeway to a car show. I'd put it together with that combo and drive it for a year and see how it works for you. Once you get some miles on it you can change your mind.

The more I think about it, the more I agree with you Andy. The 16 year old racer in me wants a 700 hp monster but in reality, I don't think I would enjoy driving a race car as much as I want to drive this. I have been following your Duster build very closely and love the work you do and your articles. I am at the point where I have everything I need to build this engine minus the rotating assembly. I hope to have that purchased in the next 2-3 weeks or I'll blow the cash on something else I dont need lol. I just want to make sure it's done right the first time so it only needs done once.

Thanks for the input

This is what I'm running in my low deck 512. With 1.6 RAS rockers B3 Geometry set up 10.3 comp Trick Flow 240s M1 single plane both ported by Larry Smith with a 850 Thumper carb. Been to busy with work to dyno. But will be on the pump in about a week or so. I will post results. Hoping for any where between 590-610 hp. Will see though. Not chasing a number. It will make what it makes. But should be a real nice pump gas street engine.

Sounds like you will drive a lot on the street, so that cam is fine.
But IMO, it is small for 512 CID.
I run the MP 0.557" solid cam (~255 at 0.050") in my 446 CID street Cuda with 10.7 CR, 4000 rpm stall, 3.91 gears. Great.
Your 512 CID will eat duration for breakfast and have tons of torque, so I would run 260-265 degrees at 0.050"

I agree that cam is really small and it has really conservative ramps. I wouldn’t spend 1k on Head porting and then install a cam that won’t take advantage of it anyways. After lash you’re only gonna be lifting the valve .500ish. And the duration is 10 degrees too small.
That stroker is going to need air to breathe.

I agree the cam is small for the build. The build was set up on purpose to the Way conservative side on the lobes lift and duration. With 1.6 rockers after lash should be around the .540 lift area. With Larrys porting the low lift numbers are very good. But starting there for now knowing this cam was small. We know we have the option of stepping it up later and maybe going EFI. We started here because the car will be driven to shows 5-6 hrs away. But again I totally agree with you guys on this cam. Will see what it pulls on the dyno.

This engine will certainly hit the dyno. I am not opposed to going larger with the cam, I can afford to spend an extra $300-500 to make it perform more to it's potential. Though I still need some sensibility as it will be driven on the street on the weekends going to and from various events. That being said... it was your money what cam would you install?

I seem to recall talk of an overdrive trans, conservative gearing, and a fairly heavy vehicle being part of the mix as well.

One size def doesn’t fit all.

What I installed or what you already have. This car will be used with the same intended use as yours. Im thinking the next cam. If I even do another cam it will still be conservative also. But more like 560-570 lift with 1.6 rockers and roughly 250-260 range @50. But thats just me. I like my pure street stuff more conservative than others.

Thats exactly right Mr Porter. And I think you nailed it with the cam for this build and it's intended use. Matt Hensley thought it was a very good cam for this engines application. During the build.

I agree as I run a Dwayne Porter solid flat tappet cam in my pump gas 493 street car and I love it. He knows his stuff so I would give him a call. Good luck , Ron