409 Camshaft Selection Question

[jm32409]

Guys,

I need some help making some decsions on what cam I am going to use. I went through the old threads and there were a few ideas but here goes. My motor is a 340hp car motor .30 Ross 10.5:1 forged pistons, I will be using the 817 heads however we are doing some work to the heads. Bowl blend and so forth and adding larger valves. I have been on the phone with Comp Cams several times and they have been most helpful but it has been my experience in the past that the cam grinders offer a little more conservative profile than you would like. What they reccommend is 236@50 with a 561 lift 108 lobe center and then advancing cam 4 degrees. Not knowing these engines that well will this have a rough lopey idle? I am going for that nasty drag car idle but still able to run. I am putting this in a 34 Ford, 700 R4 4:11 gears 32" rear tires. They reccommend a 2500 stall converter. My other question is that the valve springs they reccommend 911-16 have an installed height that will be hard to get. Is it common to use longer valves in these engines to attain the desires spring pressures? Any problems to look out for? Do the push rods need to changed as well, guide plates needed......

Any help would be greatly appreciated.

Thank You,

JM

[Bungy]

That 236@50 will definitely give you a lopey idle. I would say that's a pretty good cam for your combo. Since you are adding larger valves, you can go with BBC valves which are longer then the original 409s and my help get the installed height you are looking for. You will need new pushrods when changing the length of the valves and adding a higher lift cam. For some additional cam options, go to the home page, click on links and then click on "A Bruneau Performance"

[jim_ss409]

I think 236deg. @ .050 with a 108deg. LSA sounds about right for what you want. I know those cam company reps are usually pretty conservative and the duration isn't all that big but with that 108deg LSA you'll have alot of overlap and that's what gives you the lopey idle. :beerbang It might be wortwhile giving Aubrey a call, he really knows cams.

[jm32409]

236@50 is around 282 advertised that is not very much duration for a big block, what profiles are some of you guys running?

[jim_ss409]

I'm running a hydraulic roller with 238-248 @.050 with a 110 deg. LSA in a 476ci stroker. It will idle down to about 800rpm but it's pretty lopey, not too bad but you never forget you're driving a muscle car. As a rule of thumb you usually add about 8deg. of .050 duration for every 50ci. of displacement, so a 236deg. cam in a 454 would idle about the same as a 220deg. cam in a 350. So this cam would be a bit rougher in a 409. jm32409, as you pointed out your car is light, has low gears, plenty of compression and a good valve job so you would be able to go with more duration than normal. I'd stick with the 108LSA so that you'd have plenty of overlap (that'll make a big cam sound huge) you could bump up the duration a bit to about the 240, 244 range, or go with a split profile with something like 236 intake and 244 exhaust. I think if you go much bigger than that you'll start to give up low end torque. If you went with 240 deg. and a 108LSA you'd have 24deg of overlap at .050 so it would idle rougher than a cam with 250 deg. and a 113.5 LSA (I think that's the numbers for a Z-11 cam) and of course modern cams open the valves quicker and higher so you don't really need quite as much duration as you used to. A tight LSA like 108 really boosts the midrange power and makes the engine feel really snappy and fast reving. Just right for a streetrod if you ask me. :D By the way, free flowing exhaust is more important on an engine with lots of overlap. A while back when I talked to Curt Harvey (he's built hundreds, maybe thousands of these engines) he recomended the Isky Z-45 cam for a stock stroke 409 with high perf. heads. Here's the specs. on it... Isky CHZ45 Solid, power range 2500-6500; .530 lift; 278° duration; 240° @ .050; 110 lobe center. Lopey idle This is a solid lifter cam so you would take away about 6 to 8deg. of duration when comparing it to a hydraulic to alow for valve lash. So, assuming that Comp. was talking hydraulics, this would be roughly equivelent to a 232 or 234 deg. cam. I'm no expert but if I were picking a cam for your car and I wanted it to sound really edgy without sacrificing too much drivabillity I'd probably go for something like this one I found on Aubreys site. http://www.bruneauperformance.ca/intro.html It doesn't give the LSA specs but I'd guess that it would be 110 if you wanted 108 you might have to get a custom grind. I think this would be about as big as you could go and still be able to comfortably drive it. If you were intending to use power brakes I think you'd have to take about 8 deg. off this spec. H-240592D
10 - 11:1
6300
R
284/296
240/246
.592/.595

[Ragtop]

This is great! I'm presently building the exact same combination and I've been wondering about what cam to use. My '34 is a long ways from completion, but this is interesting.

[jm32409]

JimsSS409 thanks for all the info that is good to know. Right now I am looking at a comp grind which is 236@50 with 560 lift and also and isky grind which is 250@50 with 560 lift both have a 108 lobe center. From what you say the first cam might be a better choice. One other question did you have to use longer valves to get the installed height on the reccommended spring? By using a +.50 lock I am getting up to 1.830 installed height with the stock height valves. I found an isky spring that has a good seat pressure at that height. Anyone know where to get the 2.07 valves with an 11/32 stem?

Thanks for the help.

Jeff

[Bungy]

Jeff, Are these valves for the 817 heads? If so you will need 3/8" stems unless you put in smaller guides. Show Cars sells valves or I'm sure someone in the "links" section could set you up with a set. Don't know if you will find 2.07s in 11/32" stems.

[jim_ss409]

I got all my valvetrain parts from C.H. Enterprizes. http://www.mr409.com/ Then I brought all the parts to the guy that was doing the heads. I never thought to write down any part numbers. :takethat