Mopar 408 cam ??

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1974scamp

1974scamp

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Hi Guys,

I'm planning to build a 408 stroker with stock heads and stock rockers for my 1974 scamp (similar to this one: MRL Stock Rocker/Head 408)
and I'm not sure wich cam to use.

Im planning
1976 360 .030 over
Scat cast steel crank
Scat I-beam rods
Pistons +5cc
Edelbrock Air gap intake
Windage tray
Home ported stock 596 heads 1.88 intake 1.60 exhaust valves
Stock rockers
Compression min. 10.5:1
I have a 650cfm holley dp carb but i think it would ve to small

Built 904 transmission with reverse full manual vb
Stock converter
8 3/4 3.23 sure grip

What do you guys think about this:

https://m.summitracing.com/parts/cca-k20-225-4
 
I'm assuming that this is a non magnum (flat tappet) engine.
Your build is similar to my 408. Mine is a flat tappet hydraulic and what I did was call Bullet Cams and had them grind me one based on the info I supplied to them.
There's 2 good reasons that I can say for doing that. One is when you buy an off the shelf cam many times it's just a Chevy grind on a Mopar core plus most custom ground cams will be made for the Mopar large diameter tappet.
And yes I agree that your 650 carb will be too small.
 
I agree the 650 is to small. BUT! Use what ya got for now.
Your stock converter isn't going to cut it. No way no how. Your going to need a new converter. The gear ratio is low as well. A custom converter will help a bunch with that.

As far as the cam goes, I like it. But with a looser converter and 3.91's
 
Thanks for your help!

Wich converter would you recommend?
What stall speed for a cam like that?

I want to stay with the 3.23 gears it will ne a street car for 99%
 
Rob is absolutely correct about ProTorque. They are awesome!!
So getting back to your cam, with that compression and that gear IMHO you will really need something made just for you.
My 408 has 9.4 compression with 596 heads 3.55 gear with a 28"tire. My converter is rated @ 2400 but we all know thats just a number.
The cam I'm running is a single pattern with 226* @ .050" and a 110 LSA. 503" lift. It idles at 800 rpm and has 14 inches of vacuum. I'm really happy with the results.
You can also try calling Hughes about a camshaft. They have a good selection of cams that are designed just for Mopars.
Ted
 
Thanks again guys but rember the motor is not bulit yet
All i have at the moment is the transmission, the 1976 360 and the carb.
I wanted to order all the other parts from summit next week.

Would this one match better with my setup?

20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

There it says "largest cam for stock converter"

Or maybe this one:

20-224-4 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

Because i think a custom converter will be really expensive.

Ted how much hp and tq is your 408 making?
And wich converter and cam are you running?

Laurin
 
The statement- "largest cam for stock converter" is assuming stock displacement. You're building a 408- different animal. Feed it some camshaft!
 
I have never had my engine on a dyno but I did race it once. It was hard to launch the car due to lots of wheel spin but I was able to coax a 12.88 @ 108 mph pass out of it. This was with a 2.000 sixty foot time. I was shifting the car @ 5500 rpm and it weighed 3520 lbs that day. So with that info some of the h.p. calculators said that I was making 355 h.p. at the wheels to go that slow. That roughly translates to about 405 h.p. at the crank (depending on what % loss you use)
The cam grind that I'm running is from Bullet and it is # CRA 270/270-10HC
This is the converter that I'm running. https://www.summitracing.com/parts/hup-27-25hd/overview/
 
Laurin, I like the second cam better myself, ([email protected]) and would say that it would be pretty good, just mind your tire size. (Converter stall allows higher or lower gears more effectively, hence why I said a custom converter.) Nothing to tall.

What type of speed or 1/4 mile et. are you looking for?

Thanks Ted. My older than normal 904 has a different input spline count making a off the shelf converter basicaly impossible. I gave Pro Torque all the required info except exact HO and TQ lines and levels, since the engine wasn't dyno'd. Told him where I'm going and where I want to end up.

They took my stock converter and opened it up, gave it new internals and a few outer ones.
The converter is rated for 750hp.
 
Oh and one other thing I forgot to say. I did a quick search for one of those cams and it took me to a Chevy pick up truck site.
I keep jumping on this topic because you have a large diameter tappet in that engine and you're giving up some power if you don't utilize it.
Your cam choice is a major part of your build. Take your time,contact some cam companies and get their input.
Ted
 
Indeed so. In the big picture, of it all, the total cost, a few extra bucks for this and that can add up but do not ever let it stop you from getting the max out of your build/combo. In the end, its small potatoes!
Use what you want. But don't let it be a concession.
 
Im not really looking for a 1/4mile time or something like that because Im from Austria and we dont have that much racetracks around.
There is only one 1/8mile race once a year in my area so it is really a street car.

So when i would run the same converter like Ted and the second cam (20-224-4 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts)
it should work very well and i should get about the same numbers like Ted or am i wrong?
 
Well I just ran a few numbers and from what I see you'll wind up with 9.6 to 1 corrected compression and over 200 pounds of cylinder pressure.
Do you have good quality fuel over there?
 
DusTed74 said:
Well I just ran a few numbers and from what I see you'll wind up with 9.6 to 1 corrected compression and over 200 pounds of cylinder pressure.
Do you have good quality fuel over there?
Click to expand...

Yes we have 98 octane at every gas station.
So i was thinking of milling the heads too to 10.5 compression (or maybe 11:1) or wouldnt be that useful?
 
To much compression for that cam. 9.0-1, 9.5-1 max.!!!
 
the iron J heads may limit your cam unless there is some quality work done on them.
the XE268 might be best?
 
Hi mate, glad to hear the 360 build is going strong. I've done something similar but without stroking her to 408, just a .030" overbore with Keith Black hypereutectic flat-top pistons and a Scat cast crank, topped with ported and decked 318 heads that have 2.02" and 1.64" valves fitted. Compression with the 60cc chambers is about 11:1 or so.

I'm using a Crower 31243 grind which is INT/EXH .480/.503 lift and 227/[email protected]" duration. Slow ramp rates by modern standards and rated at 1800~6000rpm by the manufacturer with emphasis in the comments on "9.5:1 compression or more", "headers and 4bbl carburettor", "helped by mild port and larger valves".

Anyway... aside from an outdated Crower 31243 grind... I would recommend the Comp Cams XE275HL - the 'L' is for extra Lift which is provided by faster ramp rates. They are developed for larger diameter Chrysler lifters (.904") and work a treat in modified LA smallblocks. Many magazines have installed this specific camshaft in smaller capacity combinations such as modified 318ci blocks and found them to be excellent performers.

I would definitely look into the XE275HL for a 360+ build as it will let it breath nicely and should be easy to drive with the profile mellowed by your intended 408 cubic inches!

Cheers - boingk
 
most flo tests show stock heads stall at .480 - .490 so going beyond this lift
may get a small gain in power but your past the point of diminishing returns
and efficiency..
 
The build seems slightly odd to me with smaller valves and alot of cubes....... It would make sense in a Tow Application but I would be curious as to how everything turns out....

If penny pinching becomes or is a major consideration make sure to get the right converter as RRR said. This particular build will need someone above my pay grade to fit the combo lol.... It will be a dealbreaker IMO...

JW
 
SLOPAR72 said:
The build seems slightly odd to me with smaller valves and alot of cubes....... It would make sense in a Tow Application but I would be curious as to how everything turns out....

If penny pinching becomes or is a major consideration make sure to get the right converter as RRR said. This particular build will need someone above my pay grade to fit the combo lol.... It will be a dealbreaker IMO...

JW
Click to expand...
i know a few guys with j headed 408's You need a cam with bit of duration to avoid detonation.
They dyno around 350 - 370 hp with .480 - .490 lift cams and are torque monsters!
 
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