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Cam selection

5K views 27 replies 4 participants last post by  Choctaw Bob 
#1 ·
Ok so if you were following my last thread i was building a 350 for nitrous. Ive since abandoned that and am building a 383 all motor.

Im planning on these heads:
Assault Racing Complete SBC Small Block Chevy Aluminum Cylinder Heads Angle Plug 350 383 400 - KMJ Performance
I already ordered this Rotating Assembly at .040:
Assault Pro Series 383 Balanced Rotating Assembly - KMJ Performance

Now that setup should give me around 10.5:1 according to the chart on the Rotating assembly page. With that said i THINK im looking for a cam in the 233 Degree @ .050'' on the intake side. Does that sound right? If i run something better then pump gas is it beneficial to increase this? This is a track only car so no worries on gas mileage etc. Just looking for power.

Heres the cam i was looking at:
SBC 234/.533 242/.548 112+4 OE Hydraulic Roller Camshafts - KMJ Performance

Any help is much appreciated.

-Kenny
 
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#3 · (Edited)
Thats what i feared the info i found was leading me to do. I want the most power possible. Surely there is a cam TOO big for my setup. so what cam might be better suited for making power? STRICTLY for making usuable power in a straight line. If the carb decides what cam i use then what ever the best carb is to throw the best cam in is fine since i have no carb purchased yet. Bassically what cam on the best carb with 110 fuel should i run?

Also if this changes anything im considering building this car specific for 1/8 mile drag as it is a more accessable track around here. there are a few. Also they host sand drags 4 miles from my house a few times a year. If the cars built for 1/8 mile then the 300ft sand drags will be a little better aswell.
 
#4 ·
If you are drag racing:
find a track/car

determine how quick you want to go,with the car you have determine how much power you need IE, a 3300 pound nova will run into the 12s with a 425 hp engine and 4.11 gears/3 speed auto and a fat guy driving.
every hundred pounds will save/cost a tenth or more. If its really a race car then use racing gear ratios.

The heads will tell you how much power you could make,the cam will tell you what RPM that it happens and or if you will meet t he potential of the heads. the CR needs to be factored in. The cubic inches will also determine when the power occurs

and all the stuff you learned last thread
 
#5 ·
The heads will tell you how much power you could make,the cam will tell you what RPM that it happens and or if you will meet t he potential of the heads. the CR needs to be factored in. The cubic inches will also determine when the power occurs.
Ive given all of the above. So what cam fits in the designated slot? lets assume i want to run 5's in the 1/2 mile. Now that theres no such thing as a goal time to avoid surpassing accidently by making too much power... How quick do i want to go? As fast as my motor will push me.

With the data i provided what cam makes the best power? Its a simple goal. "The most power possible" I cant make it any simpler then this.

Heads: 200cc Intake port, 2.02/1.60 valves
Cubic inches: 383
CR: 10.5:1
Camshaft: ?

This question is open to anyone who would like to provide an opinion for the answer.
 
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#10 · (Edited)
I use big cams in my cars,
for you maybe something like this

110173-10S NA 273 279 241 247 .570 .570 110 106 .022 .022 1,2,5
2800-7000 Small Base Circle, Fair idle, High performance Street/Mild Bracket. 10.0:1 CR, 2800+.

Ok now the heads im running says its for flat tappet. Wont work no?

This cam is flat tappet and although this cam dosent have a recommended compression the one next size up says 11:1 or more so perhaps this one being one level less will work on 10.5:1 ? Im liking the RPM range.

Sbc Solid Tappet Chevy 350 383 Camshaft Kit 290/300 Gm - KMJ Performance

EDIT: Now im not seeing that they are for a flat tappet lifter so the heads work either way?
 
#19 ·
If you are building a racetrack only engine why is the compression so low. The 383 rotating assembly I see is for a 1986-up Chevy street engine. They don't give you the flow rate of the heads you have listed. If I was building a cheap 383 engine I would at least buy big enough heads for it to breath. Like these SBC Chevy Aluminum Heads Assembled 210cc 2.02 Angle - KMJ Performance. Since you have a cast crank I wouldn't spin it any more than 6000 rpm. The wimpy hyd. flat tappet cam is about correct for it. You might be in the 400 hp range. Bump the compression up to 11.0-11.5 and get a Comp Cams XR300HR 12-444-8[10]. .562/.580 lift and 248/254 duration. 110 LSA and 106 ICL. Super Victor Intake and a 850 cfm carburetor. This will at least get you up to 450-480 hp and 482 lbs. of torque Then you will need a 3000 lb car with a 3500-4000 stall and some gears.
 
#20 ·
I like that head 50 more bucks aint bad. The rotating assembly i went with is going to have to be the limiting factor. I decided to go low budget. Im just going to have to build the motor to what that setup can handle. Ill get it all put together, Get a car together and run it and see how it is. If its dog slow then i can let everyone i know run it with confidence atleast.
 
#22 ·
It says the springs must be modified. The assault heads dual springs are good to go for that right? It also says the heads must be machined. The assault heads are good to .650" lift so theyll work as is correct?[/QUOTE] You will need to purchase valve springs that the cam manufacturer recommend for the camshaft. The springs that come installed on the heads are for hyd. flat tappet camshafts.
K12-444-8 XR300HR uses 987-16 valve springs, best roller rockers 19001-16, and push rods 7809-16.
 
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#25 ·
It looks to me like the eassult heads are procomps and the assult rotating assembly is scat. And its exteranlly balanced. So its really not great for 7k+ rpm redline. h beam rods and forged crank/pistons would be better. It will still work but might not be as good if your going for max power na. But this will easily take 500hp. I would focus on that level of performance.

With those heads and rotating assembly. I would stay with the 12-225-4 magnum. I got a feeling those heads arent going to flow real well.

Pro built powerglide like vinnie said is what you want for straight race car. Th350 is heavier and has more power loss. Its popular because it can be built cheaply and is really much better on the street than a 2 speed power glide.

Is this your first race car. If so i would focus on the rotating assemblies 500hp range. Its going to come apart at 800 hp. Also 500hp will take you down the track very fast. You will have your hands full getting it in a car and going down the track straight. Also at 500 the weak stuff will start breaking and you will start apending your racing budget on saftey equipment.

Sorry not trying to confuse you just want to help you get something together that will last a few race seasons and provide the punch needed to move you down the track. 1/8 and 1/4 mile cars usally are set up a little different. Might want to make a choice on what ypur going to run. Gears are usally different for 1/8 mile.

Did i hear a "mud racing" in there.... Mud drag racing usally requires a pro to build the engine cause you will be bouncing around and engine will hit the rev limiter and fall on its face. So they build the motors to "cam out" and not over rev or invest thousands in electronics.

Ya if i can make 500hp NA im stoked. I will go with the 12-225-4 magnum as recommended. Im pretty much set at gearing this car for 1/8 mile. And no mud racing the other thing i said was sand drags. Its a 300ft race on something similar to beach sand. Its not very bumpy as top fuel cars often slap paddle tires on and run as is. Beleive it or not they hook better in the sand then they do on asphault. 100ft tall rooster is pretty cool too.
 
#24 ·
A quick reply about the valve springs before you decide what head you are going to use. Here is a cheaper alterate to spending $1000 on Hyd Roller kit. This is the 306S K12-225-4 solid flat tappet complete with cam, lifters, valve springs, locks, retainers and timing chain for $434.95 or $409.88 from Amazon.com + free s&h. Pushrods part# is 7372-16 or 7972-16. Roller Rockers part# 19001-16 recommended for high lift cams. Here is another 210cc set of heads for you to checkout, same brand as KMJ is selling but with upgraded stainless steel valves. White Performance Detail Description. Sounds like a better head than what KMJ was selling. Call them with your cam info.
 
#26 ·
A quick reply about the valve springs before you decide what head you are going to use. Here is a cheaper alterate to spending $1000 on Hyd Roller kit. This is the 306S K12-225-4 solid flat tappet complete with cam, lifters, valve springs, locks, retainers and timing chain for $434.95 or $409.88 from Amazon.com + free s&h. Pushrods part# is 7372-16 or 7972-16. Roller Rockers part# 19001-16 recommended for high lift cams. Here is another 210cc set of heads for you to checkout, same brand as KMJ is selling but with upgraded stainless steel valves. White Performance Detail Description. Sounds like a better head than what KMJ was selling. Call them with your cam info.
Thanks i will deffinatly look into these.
 
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