Chaparral2f Posted November 2, 2008 Share Posted November 2, 2008 Does anyone have Desktop Dyno? If so would you run my engine? I am looking at two different cams and would like to have some input on their performance. I couldn’t care less about how it is going to idle, all I’m interested in is raising the horsepower, between about 3000 and 7000 rpm. Here are the specs on my engine. Block: 355 cid Bore 4.030†/ Stroke 3.480Deck height 0.0†Rotating assembly: Forged steel crank / 3.48†stroke Polished shot peened Chevy 5.7†rods Keith Black flat top Hyperutectic pistons Sealed power rings Heads: HO Corvette aluminium Fully ported: Intake Volume 180cc / exhaust volume 73cc Combustion volume 58cc Compression ratio 11.40 Valves: Intake 1.940†/ Exhaust 1.5†Rocker ratio 1.5 Stock length push rods Lifters Hydraulic Flat tappet Induction: Weiand Stealth duel plane 750 Carter Carburator. Exhaust: 1 3/4†block hugger headers 2 ½†stainless pipes Flow Master mufflers Ignition: Vertex Magneto These are specs of the cam I am looking at. Lift : int .555†exh .555†Duration at. .050†int 260 exh 260 OR Lift int.525†exh .525 Duration at .050†Int 253 exh 253 Any suggestions will be greatly appreciated Thanx Joe Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted November 2, 2008 Share Posted November 2, 2008 "Does anyone have Desktop Dyno? If so would you run my engine? I am looking at two different cams and would like to have some input on their performance. I couldn’t care less about how it is going to idle, all I’m interested in is raising the horsepower, between about 3000 and 7000 rpm. Here are the specs on my engine.Block: 355 cid Bore 4.030” / Stroke 3.480Deck height 0.0” Rotating assembly: Forged steel crank / 3.48” stroke Polished shot peened Chevy 5.7” rods Keith Black flat top Hyperutectic pistons Sealed power rings Heads: HO Corvette aluminium Fully ported: Intake Volume 180cc / exhaust volume 73cc Combustion volume 58cc Compression ratio 11.40 Valves: Intake 1.940” / Exhaust 1.5” Rocker ratio 1.5 Stock length push rods Lifters Hydraulic Flat tappet Induction: Weiand Stealth duel plane 750 Carter Carburator. Exhaust: 1 3/4” block hugger headers 2 ½” stainless pipes Flow Master mufflers Ignition: Vertex Magneto These are specs of the cam I am looking at. Lift : int .555” exh .555” Duration at. .050” int 260 exh 260 OR Lift int.525” exh .525 Duration at .050” Int 253 exh 253 Any suggestions will be greatly appreciated Thanx Joe without even running the numbers I can tell you even the milder cams too large, even ported those corvette heads become a restriction to air flow rates at about 6000rpm with that intake, youll want a cam thats in the 240 durration range, going much larger with the cam durration in that combo will only kill low & mid rpm power, especially if you stick with a flat tappet hydraulic cam thats probably going into valve control issues at about 6300rpm something like this crower roller cam with 1.6:1 ratio roller rockers will maximize the combo http://users.erols.com/srweiss/tablehdc.htm http://crower.com/misc/cam_spec/cam_finder.php?part_num=00423&x=40&y=11 http://www.compcams.com/Camquest/default.asp comp cams is now offering a free cam selection software,THIS IS A USEFUL TOOL, this is useful in seeing the lift/duration/LCA they suggest for your application, in most cases they get fairly close so its a tool thats useful, now you don,t necessarily need to buy a COMP CAM but a cam with a similar lift/duration/LCA from your favorite manufacturer probably should be fairly close to whats recommended willing to spend a few bucks ,want far more detailed results and a program requireing FAR more detailed input?? http://www.auto-ware.com/software/eap/eap.htm but Ill tell your with almost zero chance of being proven wrong that the combo you listed will give up more low and upper rpm power than it can gain with a larger cam like you listed than the crower cam I listed, or something similar, if its matched to the listed components, and youll need too check your springs and clearances ,if you want to spin it up and make significantly more hp? you need much better heads like AFR 210cc and better headers and a single plane intake, like a weiand /Holley 300-110 and even then the gains over the crower cam listed will be minor at best, because the better heads and intake will boost that cams efficiency[/b] Quote Link to comment Share on other sites More sharing options...
jt1 Posted November 3, 2008 Share Posted November 3, 2008 Have you checked piston to valve clearance to see how much lift you can run? I bet that's getting tight with the KB's and zero deck. Retainer/guide and coil bind must be checked also. jt Quote Link to comment Share on other sites More sharing options...
310z Posted November 4, 2008 Share Posted November 4, 2008 My thoughts are simular to Grumpyvette. The cam is not the only issue. To run either of those cams and the RPM you mention, you need heads with an intake volume of 220 to 240cc. Then either of those cams will come to life. Quote Link to comment Share on other sites More sharing options...
Pyro Posted November 5, 2008 Share Posted November 5, 2008 too much cam. plus we also need the lsa spec. may work with 106 or 108 lsa. a ran a 11:1 362 cid, zero deck, 64cc dart heads with 200cc intake ports with full length headers, rpm intake, 750 holley, and a compcam 292H. trans was a t5 and diff was r200 3.90. it ran strong from 3000 to valve float (7200 prms). I would normally shift at 7K since it seemed to still be making power at that rpm. However, my best et's were achieved with 6500 rpm shifts. Most dyno sheets I have seen with that cam show max hp at 6900. I don't like your carb or those heads, and I think you are running too much cr. A compcam 294S (solid flat tappet) might be a better setup for you. Plus a set of 64cc heads with 200cc ports would help. Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted November 7, 2008 Author Share Posted November 7, 2008 Thanks for all the input, I agree that bigger heads would be the way to go, and I may do that in the near future. However right now I'm buried in getting the chassis finished and the body to fit on it. I will probably go with the Comp 292. When I pull the heads, I can gain some help by going to a thicker head gasket and a little selective work on the chambers. Luckily I have a set of heavier valve springs and 1.6 rockers. That should solve my problems (I think.) Quote Link to comment Share on other sites More sharing options...
jt1 Posted November 7, 2008 Share Posted November 7, 2008 You need to think about your goals and priorities. With the rest of your combo, your best performance is going to be with a smaller cam, say 230-235@50 w 110 or 112 LSA. A solid will let it rev a little better than a hydraulic, at the cost of being noisier and requiring occasional adjustment. A big hyd will have weak bottom end because of the duration and overlap, and you can't turn a hyd much over 6K or so, depending on the combo, with out pump/float/stability issues. About the only thing a big hyd cam does well is sound good cruising around town, which is fine, but don't fool yourself into thinking it's the best performer. John Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.