10.5:1 383
scat crank and rods, probe forged pistons (-8.5cc rev dome)
Assault aluminum heads, 200cc runner, 64cc chambers
(ported heads, should flow about 290 cfm @ .600, exhaust should flow over 200 cfm at .600)
Edelbrock Performer RPM intake
850 Holley
1 3/4 long tube headers, 3 in dual exhaust, likely open headers at track

paired with a Coan built turbo 350 trans, transbrake, full reverse valve body, 36 element drum, hd sprag, etc etc


i am looking for a hydraulic roller cam. really leaning towards Howards brand, just unsure of which grind will suit my build best, and which will make most power. little street use, but will see a lot of time at the strip. i am hoping to make well over 500 hp/500 ft lbs. shouldnt be too much of a stretch, based on some dyno proven combos ive seen online.

heres a few that have caught my eye.. also will likely be running 1.6 rocker on the intake, 1.5 on the exhaust

Howards 183365-10 245/245 .560/.560 110 lsa

Howards 110275-10 241/247 .545/.565 110 lsa

Howards 111655-10 243/249 .600/.600 110 lsa

Howards 180335-10 247/251 .550/.540 110 lsa

When is it a good idea to go with a single pattern cam such as the 245/245 vs a split pattern such as the 241/247?

 

Howards 180335-10 247/251 .550/.540 110 lsa

 

Regardless of the cam you decide on, I think you'll you want more intake than the Edlebrock will give you...doesn't sound to me like you're just building a quick daily driver here...

 

I agree with 8Mike9 on the intake. All of the cams you have listed are at least at the top edge of the Performer RPM's operating range. I would lean more towards a single plane and just go a little higher stall. You want at least 3,500 with this motor anyway.

The single pattern cam is geared towards an engine combination that wants a little more intake duration to optimize cylinder filling. I would say if you were going with a dual plane intake, you might want a single pattern cam. For instance, the ZZX cam is a 240/240 grind and was originally designed to maximize power from the long runner TPI, which needs more time to fill the cylinder.

Any one of those cams will work well for you. Milder will be more forgiving, putting around on the street, and will provide more lower RPM torque. Definitely, if you stick with the dual plane manifold, go with one of the top two. The second one down is for engines with lower exhaust flow. With large tube headers and free flowing exhaust, you shouldn't need that. If you want to maximize power, with a wider flatter torque curve, ditch the dual plane for a single plane and go with the bottom of the list. I assume that Howards lists gross lift based on 1.5 rocker ratio, which means that with 1.6 rockers, the bottom cam is going to put you real close to .600 lift. Check lobe lift on these cams to be sure and decide on rocker ratio based on that to get as close to the rated max flow lift of the intake and exhaust ports. Since the heads are ported, it's not a bad idea to get them flowed so you know where they actually are. You may end up with more than .600 lift for max flow.

 

I wanted to stop back by and tell you guys thanks for the excellent replies, and I took all of your advice into consideration when picking my cam. I ended up going with the 243/249 @ .050 cam. Adv duration 296/302, duration at .200 168/174. Hoping its gonna be a performer. I was a little worried the 247/251 cam was too big for my compression ratio, and I like the thought of cramming as much as .630 lift in the intake with a 1.6 rocker swap with the 243/249 cam.

I am also strongly considering the single plane idea.. I read this carcraft article [http://www.carcraft.com/techarticles..._intakes_test/ [/URL] .. interesting read. Had no idea an intake swap could seriously be worth nearly 60 hp on a 500 hp small block.. Would be interested to know how the Performer rpm stacks up against the top of the list. An intake is something I can experiment with once I get the truck on the track.

 

Cam selection really comes down to a matter of compromise. More duration will produce more top end power(within the limits of the cylinder heads), while less duration will produce more low to mid range torque, again depending on the cylinder heads. Your 200cc, plus porting, intake ports flowing 290cfm will support around 580HP. To move that much air through 383cid, you will need to turn 6,500-7,000rpm. The large ports will be less freindly to low rpm torque. Again, the choice of heads dictates what sort of motor this will be and therefore what sort of cam choice you should make. 10.5:1 is pretty good squeeze and would support the higher duration you were considering. It would have less compression down low and would want a higher converter stall, but again it's a question of compromise. As with the intake, the cam isn't that hard to swap if you decide to play with something different later on.

 

I like your choice but you will really need to get good springs and lifters to match, and i'd recommend a 3/8" pushrod. That will keep things stable at high rpm. Vic jr single plane or equal for sure! Shift 7k easily

 

Good write up by Car Craft. You'll notice that for the 406, at their build level, they only tested single plane manifolds. As was said earlier, the single plane, with more closely matched runner length, and larger plenum is really the only choice for the power level you're looking at. The Performer RPM is a dual plane that is modified by cutting down the wall that separates the two planes, thus making it a sort of hybrid dual/single plane piece. This certainly extends it usable RPM range, but it really is pretty much capped at around 470HP and the torque curve would be more peaky, rather than broad and flat like that of a true single plane. Your heads and range of cam choices definitely points towards a broad flat torque curve.

 

Thanks again guys.

I feel pretty good about the cam choice. I am not expecting to make 580 hp or even 550. If i could see a real deal 510- 520 hp out of this combo (with a good single plane) id be ecstatic. I am afraid 520 may even be a little optimistic, but we shall see. I dont believe many of the numbers or even dynos i see online. Had a guy yesterday tell me his "dyno proven" 383 10.13 compression, dart 215 heads, 236 @.050 roller and he says it makes 633 hp 580 something ft lbs. right.......

I was under the impression the Performer RPM was about the best choice idle-6500 on the market. I am certainly not opposed to going with a good single plane I dont know for sure if my cam will still be making power at 7000. I was thinking my shift points would be somewhere around 6400-6600 rpm, but again, we shall see when the rubber meets the road.

I have the Comp Cams part no 853-16 lifters. I am going with Howards #98445 for the valve springs. They are dual springs, 125 lbs on the seat at 1.875, but will shim it a little maybe 1.850? They will have about 370 lbs open pressure at .600 lift, 380+ at .630 if i run a 1.6 rocker. This should be enough to control the valve train, right? Pushrods will be the last thing I purchase, I can go with 3/8. Glad you told me, I was just about to order 5/16 guideplates.

Can anyone explain how to calculate valve spring seat pressure when changing the installed height? For example, 125 lbs at 1.875 would be what at 1.850 installed height?

 

From your stated seat pressure and open (.600") pressure, those look to be about 400 lb/in springs.
So, (1.875-1.850)in x 400 lb/in = 10 lbs difference.

Honestly, I think 135 lbs on the seat is marginal to control the valves with that cam at 6600 rpm. To be safe, I'd be looking for a little more spring.
The hydraulic intensity on that cam looks about like what I have on the cam in my LT1; I'm running 160 on the seat with a 228/234 .617" lift cam (280/286 advertised) spinning to 7000, hydraulic rollers.

 

I concur lol i would run a spring closer to 160 lbs and 400 open

I have a 246 deg .640" cam and run 180/450 but i have a heavier valve and boost to deal with but it goes to 7200

 

So an installed height of 1.800 would give me approximately 155 lbs on the seat.
.600 lift x 399 spring rate + 155 = ~395 open pressure
.630 lift x 399 spring rate + 155 = ~406 lbs open pressure

The springs are good for .735 lift, coil bind at 1.080. I should be able to install at 1.800 and still have plenty of room, even with a 1.6 rocker.

Sound a little better?

 

Does sound alot better to me. Whats the diameter of the spring tho?

 

I'm no expert on hydraulic cam selection. And I know you like Howards. But the guys at comp are really helpful and really smart. You give them a call and tell them what what you have and where you want to be. If they don't already have a grind that fits your needs. They will custom grind one. I think it cost me $25.00 extra for them to grind my blower cam. Just a little FYI.

 

Its a 1.460 dual valve spring.

I would like a rocker arm recommendation too.. I am buying a full set, so should I go with 1.5s intake and exhaust or 1.6 intake and exhaust? Any problems running a 1.6 rocker on the exhaust?

My first thought was go 1.5s to establish a baseline, buy half a set of 1.6 later to swap on the intake. But now, I am thinking i could benefit from the extra lift off the bat. My heads flow well to about .650 lift. 1.6 would have me at .630 intake/exhaust.

 

More on intake is better for few more ponies, generally, but it may not. Hard to say for certain. Its got the duration and lift as is to make good numbers. 1.6/1.5 intake/exhaust is what i'd run if you could get half and half

 

Personally, I like the idea of 1.6 rockers on both sides. More is better right? For valve spring ideas, take a look at Crane Cams website. They have what is probably the best valve spring listing that I have found in my searching. They list single and dual spring sets, along with the individual springs in each dual set so that you can mix and match for desired pressures. They also have a brief explanation of spring types and recommendations based on cam profile.

I agree that the springs you have listed are light for what you are building. In fact, those springs are about exactly what I have now in my Trick Flow G2s that cap at about 6,500. These are 420lb/in dual 1.46 springs 125 seat @1.875 and 376 open @ 1.275, .600 max lift. I have looked at Crane's dual springs to use in my 377 or 406 build that will run to 7,000rpm. They have a set that is 448lb/in, 135 on the seat and 420 open.

Definitely a good idea to talk with someone at Comp cams tech line. Crane has a tech line as well where you could get good information. I have looked around on the net at the different valve spring listings. Comp and Crane both have good lists and offer technical advice. Remember too, valve spring choice, like the rest of engine design is a compromise. Lighter springs will allow valve float at lower rpms, heavier springs will cause accelerated valve and seat wear. I decided that 135/420 was probably the best compromise for me in the -7,000 rpm range with a hyd roller. Before I ordered anything though, I would talk to my machinist.

As far as the Performer RPM goes, it is a great intake, just not for an engine build like what you're talking about. It is intended for street engines making up to about 450HP at 6,500rpm. Sure you could probably push it past that, but it will cost you power at the upper end of your torque curve. As I said, for your build, according to your stated head flow and cam selection, you are really looking at single plane.

You are at the place now where you may want to think about this. You may want to run a Performer rpm if you intend to run this motor extensively on the street. But if that is where you decide to go, consider milder cam choices. The cool thing about intakes and cams is they aren't that hard to change if you decide later that you want more, or less of either.

You have had your heads ported. Were they CNC ported or hand ported? You may want to look at having them flowed to determine actual flow after the port work. You are putting alot of thought into this build and knowing actual flow after the port work will help you make informed choices.