Mythbuster needed Big CID= less duration sensitive

[LowBuckX]

Need MythBuster.. Big CID = less Duration sensitive.
Trying to pick a cam today and was made a little confused by the salesman so Im holding off.
I told him all my specs for my 406. Told him the RPM range Id like to make my power in. He quoted me a cam with 236* 242* at .050. I Questioned the duration being a bit high for the rpm range I wanted to stay in and he told me larger CID engines arent as sensitive to duration and the higher duration would be a better choice..
Does this sound right.

Motor is
406 CID
TFS 23* unported heads
.030 over bore
5.56 rods
trw forged pistons (they claim 10.5;1 with 64 cc heads)

Car has 3;55 gears with 2800 stall converter
will be running Doug thorley tri-Y and X pipe with mufflers to be determined later.

Id like the motor to make its power under 5500rpm With lots of low-mid range TQ
He suggested

Brand: COMP Cams
Product Line: COMP Cams Xtreme Energy Retro-Fit Camshafts
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,500-6,000 RPM
Intake Duration at 050 inch Lift: 236
Exhaust Duration at 050 inch Lift: 242
Duration at 050 inch Lift: 236 int./242 exh.
Advertised Intake Duration: 288
Advertised Exhaust Duration: 294

Intake Valve Lift with Factory Rocker Arm Ratio: 0.520 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.540 in.
Valve Lift with Factory Rocker Arm Ratio: 0.520 int./0.540 exh. lift
Lobe Separation (degrees): 110

Computer Controlled Compatible: No
Grind Number: CS XR288HR-10

I was thinking
COMP Cams
Product Line: COMP Cams Xtreme Energy Retro-Fit Camshafts
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,200-5,800 RPM
Intake Duration at 050 inch Lift: 230
Exhaust Duration at 050 inch Lift: 236
Duration at 050 inch Lift: 230 int./236 exh.
Advertised Intake Duration: 282
Advertised Exhaust Duration: 288
Advertised Duration: 282 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.520 in.
Valve Lift with Factory Rocker Arm Ratio: 0.510 int./0.520 exh. lift
Lobe Separation (degrees): 110

Grind Number: CS XR282HR-10

[68sixspeed]

I don't know if this helps, but both of my motors have about the same duration on a mech. roller, 260/268 at .050; the 358 has .634 lift; the 427 has .698/.650 lift (higher ratio rockers, but not much difference at the cam); the 358 made peak hp right at 7000rpm; the 427 with a very similar cam made peak hp at 6600. I wouldn't be worried about being over-cammed with the hyd. roller you are looking at. (come on-- big mechanical roller- it's more fun!!) -Dan

[ponchopwr70]

My 388 I have a lunati cam with 235 duration @50 507 lift and 108ls. My cr is 10.8:1. I have a 2400 stall 3.55 gears 26" tire. I think the first cam would be a better choice.

[tumper93]

I have that same cam xr294hr in my 385. Another guy around here is running that cam in his 383 and loves it. I did alot of checking before I made the desision to get it. I never called comp but rather went and tried to find out all that ran it and whether they liked it, was it too much for the street etc. The guy who did my machine work runs a shop that builds alot of dragsters with custom cams and when he talked to his source at comp they told him it would be the best choice for his street 383 also. I have not gotten mine going so I cannot say but am in dire need to hear and feel it. The cam is not going to be over the top for a 406 and you will without a doubt love it. Big cube small blocks can benifit from a cam like this, it isn't like putting it in a 327 or 350 which it would probably be harsh on around town. Hope this helps

[Madspeed]

I have been running comp cams for years
they have some pretty sophisticated computer software and Lots of money in testing to be able to punch your info into a computer and have it spit out the proper cam.

I would trust the comp cam guru its actually a computer program.

Just my .02c

[rocketman]

236/242 in a 406 would be a good cam,I would go one bigger myself

[WS6]

Isn't there a general rule of +3 degrees duration for every 10 cu inches increase over a 350 SBC would act basically the same?

Anywho the 236/242 in a 406 won't be too much. You're choice would make good power, but would leave you wanting more.

A 230/230 on a 110 in a 355 is nothing for an old school car running on the street. You're 51 cu inches more.

[LowBuckX]

I got this email today from Comp... An even bigger recommendation.. But I may go for it..

I would look at our part number 12-443-8 for your motor.

Comp Cams wrote:

> <http://www.CompCams.com (http://www.CompCams.com)>
>
> CAMSHAFT RECOMMENDATION REQUEST CONFIRMATION: 9/22/2006 / 1:42:07 AM
>

Here are the specs of this cam

Brand:COMP Cams (http://store.summitracing.com/egnsearch.asp?N=400114+115)Product Line:COMP Cams Xtreme Energy Retro-Fit Camshafts (http://store.summitracing.com/egnsearch.asp?N=400114+307990+115&autoview=sku)Cam Style:Hydraulic roller tappetBasic Operating RPM Range:2,800-6,100 RPM

Intake Duration at 050 inch Lift:242

Exhaust Duration at 050 inch Lift:248

Duration at 050 inch Lift:242 int./248 exh.

Advertised Intake Duration:294

Advertised Exhaust Duration:300

Advertised Duration:294 int./300 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.540 in.


Exhaust Valve Lift with Factory Rocker Arm Ratio:0.562 in.

Valve Lift with Factory Rocker Arm Ratio:0.540 int./0.562
exh. lift

Lobe Separation (degrees):110Intake Valve Lash:0.000 in.Exhaust Valve Lash:0.000 in.Computer Controlled Compatible:NoGrind Number:CS XR294HR-10Quantity:Sold individually.

[rocketman]

I would put 1.6 rockers on it,to get more lift out of it.what would be a nice thumper street cam,I run a 260/268 in my 396.

[LowBuckX]

Im have the 1.5 that came off the original build so that is what Im running. LowBuck

[WS6]

I'd stay with their first recommendation since you desire low end power. The 242/248 will still have low end by the simple fact that it's a 406 cu in engine. However, since you seem to emphasising low to mid range power I would stay with the lower powerband cam the 236/242. I must also warn you that I prefer to stay on the conservative side for cams. I like my drivability to be as intact as possible.

[c4racer]

You need to also match the cam to the head flow as well as target RPM to make the most area under the curve power. For those heads I would stick with the smaller 236 cam. The 242 might be a better choice if you were running heads that flowed up in the 280+ cfm range (intake). I think you will be very happy with the 236.

[c4racer]

btw - one point of clarification. Technically big CID motors are not less sensitive to duration. I think it is more acurate, or at least more clear, to say that you need to scale the duration of the cam with engine size to obtain similar RPM power / torque curves and RPM at peak power.

For example, take that 236 cam in a 406 with your heads and you may end up with peak power in the 5800rpm range and the cam will make power from 2500-6000. But drop it in a 302 and peak power will be closer to 7000rpm and it will make power from 4000-7500. Just as an illustration, I'm not trying to be real acurate with the absolute numbers here.

The RPM ranges listed for most SBC cams are based on a 350 inch engine. So you need to scale up accordingly for a larger engine. Probably 1-2 cam sizes from a 350 to 406 to get the same RPM range as a general rule.

[LowBuckX]

I understand what you are saying ...


Now I got another cam recomendation from Lazer cams but it died hard on my Desktop dyno. But made huge tq but lost over 60Hp and 1000 rpm from any of the other cams recommended.

FRom Lazer

Hi, Shawn. Thanks for writing. Here's a great piece to run hard from 1800-6000:

Camshaft: CS-HR281A-287B-08 $288.76
@.050: 228 234
Lift: 529 522
Lobe separation: 108, with 104 intake centerline

[c4racer]

Ya - that cam seems a tad on the small side for a 406 with decent heads.

[Rick Dorion]

I supplied Mike Lewis (Wolfplace at chevelles.com) with flow info for my 410 , 3.55 gearing, street use, wtc. and he discussed with comp cams. They ground me a custom HR similiar to yours but with .580 lift on the intake. I think your recommendation from them is sound.