What camshaft spec for 425 hp

-
PG Duster

PG Duster

Well-Known Member
Joined
Oct 23, 2021
Messages
326
Reaction score
266
Location
California
I have a 1974 plymouth Duster with me in the car it weighs 3500 lbs, with a .30 over 360 magnum 9.1 cr. Edelbrock airgap intake manifold, Holley 750 carburetor, Headers, MSD ignition system, engine quest cylinder heads with 2.02” intake valves, stock bottom end, the transmission is a 727 automatic, with a 3500 stall dice converter, 8 3/4 sure grip rear end with 3:91 gears, Calvert Caltrac bars, springs, and 9 way adjustable rear shocks, 275/60 15 drag radials. What camshaft will I need to make about 425 hp and 12 seconds et in 1/4 mile with my combination ? Your suggestions would help me a lot. This will be a street strip car.
 
Last edited:
I have a 1974 plymouth Duster with me in the car it weighs 3500 lbs, with a .30 over 360 magnum 9.1 cr. Edelbrock airgap intake manifold, Holley 750 carburetor, Headers, MSD ignition system, engine quest cylinder heads with 2.02” intake valves, stock bottom end, the transmission is a 727 automatic, with a 3500 stall dice converter, 8 3/4 sure grip rear end with 3:91 gears, 275/60 15 drag radials. What camshaft will I need to make about 425 hp and 12 seconds et in 1/4 mile with my combination ? Your suggestions would help me a lot.
 
I'm sure the more informed will chime in, but my initial thought is you stall and gears would support a stout street/strip cam, but the CR might be a little low?
 
With your tire and gear your trap RPM will be around 5500 unless the converter is very inefficient. You don’t have much gear for that tire size. And that’s figuring you will be at 110 MPH, which is 12 oh’s if the chassis is very well sorted out. How do you know the converter will stall at 3500 when you haven’t chosen a cam? Cam timing (and how much torque it makes under stall speed) affects stall.
 
Rat Bastid said:
With your tire and gear your trap RPM will be around 5500 unless the converter is very inefficient. You don’t have much gear for that tire size. And that’s figuring you will be at 110 MPH, which is 12 oh’s if the chassis is very well sorted out. How do you know the converter will stall at 3500 when you haven’t chosen a cam? Cam timing (and how much torque it makes under stall speed) affects stall.
Click to expand...
As far as the converter it was built by Dice Performance torque converter’s in Southern California used by a lot of stock and super stock drag car on the west Coast. The estimated stall is 3000 to 3500. And I’m thinking about changing the tire size to 255/60/ 15 drag radials. I’m looking for a cam that would hopefully work with my combination for mid to low 12’s et.
 
Last edited:
Believe it or not, a 500 rpm stall speed change is a big deal. If you are using hydraulic lifters something in the 280-284 range will get you there. With solids 286-288. You can easily over cam what you have and kill it so bad in 60 feet you’ll never get it back. Also, if you dont have enough gear you’ll make the converter much less efficient. Your trap rpm will be high for your mph. And the converter will get blamed, when in fact your gear ratio and tire diameter are making the converter inefficient. Also keep in mind you can have two cams that are 280 on the seat and one can be 238 at .050 and the other one can be 252 at .050 and they won’t perform the same in the same engine. Your best bet is to get on the phone with someone and tell them all that you have and let them pick your cam. Once I decide how much power I need (or want) and I determine how much rpm I need, the first thing I pick is the compression ratio because that sets up everything else. I do all that before I even think about head geometry. Then I figure header size and then I pick a cam and then the converter. I’m sure there are other ways to do it, but that’s how I decide what the end product should look like.
 
What cam did you have in it currently? Have you had it to the track since you put the 3500 converter in it??
 
Not yet still working on it, I bought the car with
12many said:
What cam did you have in it currently? Have you had it to the track since you put the 3500 converter in it??
Click to expand...
A stock rebuilt engine in it. I don’t know what cam is in it. The seller did not have the cam spec, but said it is a aftermarket racer brown cam. It pulls strong to about 5600 and the idle not stock.
 
Last edited:
PG Duster said:
I have a 1974 plymouth Duster with me in the car it weighs 3500 lbs, with a .30 over 360 magnum 9.1 cr. Edelbrock airgap intake manifold, Holley 750 carburetor, Headers, MSD ignition system, engine quest cylinder heads with 2.02” intake valves, stock bottom end, the transmission is a 727 automatic, with a 3500 stall dice converter, 8 3/4 sure grip rear end with 3:91 gears, Calvert Caltrac bars, springs, and 9 way adjustable rear shocks, 275/60 15 drag radials. What camshaft will I need to make about 425 hp and 12 seconds et in 1/4 mile with my combination ? Your suggestions would help me a lot. This will be a street strip car.
Click to expand...

I've seen a lot less run those numbers and quicker. Where your converter stalls is a function of how much torque your engine is making.

Have you run this engine at the track already? IF so what was its ET and MPH. What is the current camshaft?
 
Hysteric said:
I've seen a lot less run those numbers and quicker. Where your converter stalls is a function of how much torque your engine is making.

Have you run this engine at the track already? IF so what was its ET and MPH. What is the current camshaft?
Click to expand...
Not yet still working on it, I bought the car with A stock rebuilt bottom end engine in it. I don’t know what cam is in it. The seller did not have the cam spec, but said it is a aftermarket racer brown cam. It pulls strong to about 5600 and the idle not stock.
 
Last edited:
PG Duster said:
Not yet, I bought the car wi

I bought the car with the rebuilt engine in it. I don’t know what cam is in it. The seller did not have the cam spec, but said it is a aftermarket racer brown cam.
Click to expand...
Being a magnum I assume it’s got the factory 1.6 ratio rocker arms? or does it have aftermarket roller rockers and do you know what ratio they are? You say it has a Racer Brown cam, doubtful it’s a reground hyd roller, Not sure they do hyd roller regrinds or offer their own. Is it hyd flat or a solid?
Those EQ heads have excellent exhaust/intake ratios where a single pattern would likely be used. I’d say determine what you actually have, run it a few test n tunes to suss things out.
 
My current camshaft is a 222/234 hydro from Crower 31242. This will make you laugh as I had a 3200 stall converter that you guessed it stalled @ 3200 so spoke to my machinist and he said the reason for my poor 60 foots was not enough stall so I bought a 3800 stall from Turbo Action that was around a 1K and when I ran it where did it stall? 3200........Expensive lesson. Spend your time tuning what you currently have not spending your money on new parts you think you need.
 
PG Duster said:
True, It could be.
Click to expand...

Run it and get back to us. Understanding what you have is important for you to make an "educated guess" on what direction to take if you need to make changes. Sometimes a change you make will work other times it will leave you scratching your head. Sometimes an engine wont perform the way you think it should and you have to think about what's going on. Most importantly go out there and have fun and enjoy the journey for what it is.

Also have a look at what 318willrun has managed to do with the little he has. Its the simple principle of 1%, keep finding 1% and it adds up over time.
 
PG Duster said:
I have a 1974 plymouth Duster with me in the car it weighs 3500 lbs, with a .30 over 360 magnum 9.1 cr. Edelbrock airgap intake manifold, Holley 750 carburetor, Headers, MSD ignition system, engine quest cylinder heads with 2.02” intake valves, stock bottom end, the transmission is a 727 automatic, with a 3500 stall dice converter, 8 3/4 sure grip rear end with 3:91 gears, Calvert Caltrac bars, springs, and 9 way adjustable rear shocks, 275/60 15 drag radials. What camshaft will I need to make about 425 hp and 12 seconds et in 1/4 mile with my combination ? Your suggestions would help me a lot. This will be a street strip car.
Click to expand...
The MP crate engine can & did run those times but at a lighter weight & more gear. Not a fan of the cam they used.
 
12many said:
Being a magnum I assume it’s got the factory 1.6 ratio rocker arms? or does it have aftermarket roller rockers and do you know what ratio they are? You say it has a Racer Brown cam, doubtful it’s a reground hyd roller, Not sure they do hyd roller regrinds or offer their own. Is it hyd flat or a solid?
Those EQ heads have excellent exhaust/intake ratios where a single pattern would likely be used. I’d say determine what you actually have, run it a few test n tunes to suss things out.
Click to expand...
It’s in the trans shop now getting a 727 trans installed in place of the 904 that let go. When I get it back I have to take the valve covers off and look at the rocker arms. How do you know if it’s a hyd roller with out removing the intake Manifold? The seller could be wrong about who’s camshaft it is. That’s why I was trying to get the cam spec. I lost touch of the the seller, he was supposed to send me the cam spec once he found it.
 
rumblefish360 said:
The MP crate engine can & did run those times but at a lighter weight & more gear. Not a fan of the cam they used.
Click to expand...

In Larry Shepard's book "How to hot rod small block mopar engines" the cam listed for mid 12's is Mopar Performance P4120653AE Mopar Performance Purple Camshaft Kits | Summit Racing
which is mopar's solid 284/284 adv 241/241 @ 50 on a 112 LSA. I used Crowers 31321 which is their solid version of it with 294/298 adv 243/245 @ 50 520/528 lift. It ran 12.6's with that cam and 587 heads.

That said I've seen a 318 run mid 12's with a 218 hydro @ 3500 pounds.
 
Last edited:
Thank you for that info. I had books like those in the 80’s when I had my 71 340 Duster bracket, and my C/stock Road Runner That I used to use religiously. Is there any way to get those now?
 
PG Duster said:
Not yet still working on it, I bought the car with A stock rebuilt bottom end engine in it. I don’t know what cam is in it. The seller did not have the cam spec, but said it is a aftermarket racer brown cam. It pulls strong to about 5600 and the idle not stock.
Click to expand...


If that’s the case, you don’t need a cam. Run what you have, get better shocks and tune the chassis.
 
@Hysteric , It’s been a while since I’ve been in that book. A long way back I followed the MP tips section which never disappointed. Though I could not find the cash for a 6 pack set up back then, the RPM came out and was found very suitable to substitute the 6 pack set up for running the 11’s. In the OP’s case, I’m not to sure his converter is enough for the Hyd. 292/.508 cam to run a low 12 coupled with the 3.91’s in a slightly heavy car. At least as per the speed tips. IIRC, the Hyd 292 is called on. I’d take a guess and say the mechanical 284 would do the trick for the OP. Or your Crower.

When you ran that Crower cam, how heavy was your car?

As noted on the 318 cam, an old member Mike Beck ran a Duster with a 218@050 cam into the low 12’s. I myself started a thread with a split Crane version
(I don’t remember if Mike had the same cam or not but my Crane cam specs were 216/228-.454/.480-112)
just to fool around with and build apon but could not complete the task & goal. The car was sold.

I followed the MP tips on the 12 second section on my 360 w/zero deck KB-107’s, J heads well prepped by a well known shop in the LI,NY area back then, 292/.508, LD-340 w/a big TQ & headers. Behind it was a 4spd manual and 4.10’s. It was really good.
 
PG Duster said:
Thank you for that info. I had books like those in the 80’s when I had my 71 340 Duster bracket, and my C/stock Road Runner That I used to use religiously. Is there any way to get those now?
Click to expand...
The books are still available with the exception *I Think* of the MP books, BUT! You should be able to find them used. Find the small block engines book for it contains the “Speed Tips.”

And now I’m a bit motivated to take a helpful picture or two for you…. Enjoy… some parts will have to be substituted due to MP discontinuing parts.


A1C25360-3F97-4605-B96B-079916457734.jpeg
86645240-5CC3-4B4E-A836-36C67D79A35A.jpeg
A311017C-46C7-44B5-8657-03EB7B22F5E0.jpeg
 
I’d put a solid in it, if for no other reason than to know I won’t have control issues resulting from underperforming hyd lifters.
 
You must log in or register to reply here.
-

Back
Top