Stock heads/rotating assembly, hot cam/vlave springs- how far can you go?
Holy chit that’s a lotta questions. I’m going to break it up.
.....so I'm looking for a stopgap measure to still be able to have some fun this summer. Perhaps a cam/valve spring upgrade could do the trick for now.
This shouldn’t be to hard, but you may be disappointed.
Based on the Magnum 380 crate engine, it seems like there's at least 80hp to be had from a cam/valve spring/intake upgrade over a stock 5.9L which is pretty amazing. Unless I'm mistaken the difference between the Magnum 300 (which I have) or a junk yard 5.9 are relatively minimal.
True! The difference is a cam, intake and I also think the suggested header and carb sizes.
My question is about whether or not this is the best we can do on the stock heads/rotating assembly or if people have done better with a custom grind? If you've gone this route, how did your motor come out? Is it possible to get some good lope/overlap sounds?
Better? What is better? If more HP is better, then it will happen at a higher RPM than the cam issued by MP. There will be a lack of torque to go with it down low.
The Rhythm of the over lap sound can be enhanced. But the question is, will the new timing events work well?
Would the use of a dual plane intake be a detriment? I have to figure that Mopar Performance went with the single plane for a reason...
IMO, the MP dual plane would not be good on the 360/380 engine. MP used there own single plane intake because it suites the intended purpose better than the dual plane does. The RPM, IMO, would be the intake to use on the 360/380 engine. But that is not a MP intake and that’s the reason they didn’t use it.
So the question was asked in general so that it might benefit other forum members....but before anyone asks, here's my application: '73 Sport, nearly full weight (fiberglass hood and a few weight reductions here and there. The drivetrain consists of a somewhat built 904 (TF2 shift kit, ~5800 rpm governor weight, stronger bands/clutches, deep pan), a TCI Streetfighter 2600 rpm stall, aluminum driveshaft, Moser 8.75" with Eaton helical limited slip, 4.10 final drive.
This reads like a street car that’s able to lay down a decent strip number for what it is. But if you use that MP 380 cam, I think that stall is a bit on the “Way Low” side.
Almost all of my work so far ha s been suspension/steering/brakes, all focused around handling. I prefer to use my car for general backroad hooligan driving so I really want a motor that breathes and feels relatively happy revving out upper 5ks at least. Can that be accomplished with stock heads? Is it worth the trouble?
There ability to rev is controlled by the valve spring.
There ability to make power is limited by the amount of air they can flow.
Actual RPM really has nothing to do with it. Though the small stock window and what the head can flow is a limiting factor, I do t think I could put a RPM point on the head and say, that’s all there good for. Though a larger cam would make more power, with a limited flowing head, the power band window becomes smaller.
Once again, any experiences or opinions are extremely welcome.
If you want to make that “For now” change until your other engine is done, I suggest a copy of the 360/380 engine. But! You probably can not get that cam anymore. Which I think is a good thing. Comp Cams has a very similar mechanical cam that will have more lift with the 1/6 rocker since there listed lift is based on a 1.5 rocker.
You can also search for a similar spec roller cam.
In addition to the better cam, I would most certainly use a Edelbrock RPM for the Magnum engine.
Hughes engines has a Trick retainer and spring package for the Magnum head. IIRC, they said it was good until a .540 lift.
I don’t see a need for a custom grind cam for this temporary engine.
You can always talk to the cam grinder and ask to move the centerline to a 108 if you wanted to. That would also lend to “That Sound” you mentioned about.
