BuffaloBillPatri Posted January 5, 2013 Share Posted January 5, 2013 Hello, I haven't been here for quite some time. Here is what I have: 1972 Monte Carlo 4.56 posi, TH400 with GV OD (3.56 in OD) 3000 RPM convertor 355 with forged flat tops .025" in hole with .015 steel shim head gasket, 4 valve reliefs stock rods & crank, balanced Edelbrock ProFlo 3500 EFI MSD ignition 1-5/8" headers & 2.5" dual exhaust, H-pipe Summit aluminum heads (rebranded Brodix IK180) 2.02/1.60 64cc 180cc flow is suppose to be 244/175 cfm @ 28" H2O Good PAC beehive valve springs & Smith pushrods Lunati 50156 retro roller cam & lifters 232/242* @ .050" .510/.525 lift (stock rockers), rated to 6500 RPM + Comp full roller rockers 1.6, lift = .544/.560 SCR = 10.25, DCR @ sea level 8.66, at Denver 5280' about 7.6 I live in Colorado & drive from 5280' to 8500' altitude It SUCKS gas! I'm thinking of putting in about 15* smaller cam for street torque & MPG I have my eye on Howards Cams 113215-08 217/225* @ .050" .495/.500 lift (stock rockers) 108* LSA With my 10.25 CR, this cam would have a very high DCR of 8.95 at sea level, but about 7.9 @ 5280 Comments? Quote Link to comment Share on other sites More sharing options...
gprimm Posted January 5, 2013 Share Posted January 5, 2013 If you already haven't, I'd call Howard's tech line. I sympathize with the altitude thing. My son graduated from the Air Force Academy in 2011 and bought his 1978 Malibu Classic wagon from a fella, now a friend, in Canyon City in 2007 the day before he in-processed. I completely rebuilt this clean car for performance. Including a custom built 355 (10:1) with a Howard Cam. The cam is milder than what you are considering, but it is excellent. The engine builder really believes in Howard. Ran great here in IL, but at altitude at the Academy, I bet he lost 25+% of his power. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted January 5, 2013 Share Posted January 5, 2013 What about just changing rear gears to 3.73 or 4.11 even? 4.56 are DEEP! Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted January 5, 2013 Share Posted January 5, 2013 I agree with Scott, I would drop some gear. With the cam change it might really feel gear bound. I have run Howards cams and the guys seem very knowledgeable. They should be get you where you want to be. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted January 5, 2013 Share Posted January 5, 2013 a cam change isn't going to help your economy much, I agree with a different gear Quote Link to comment Share on other sites More sharing options...
MGD72Monte Posted January 5, 2013 Share Posted January 5, 2013 4.56 !!!! I think others have nailed it, that should be your first stop. Then depending on the results, I would start looking at the engine. Quote Link to comment Share on other sites More sharing options...
502ci Posted January 5, 2013 Share Posted January 5, 2013 Gotta agree with the others on the rear gear change, even with the overdrive and a 3.56 final drive ratio it is not too highway friendly. Quote Link to comment Share on other sites More sharing options...
BuffaloBillPatri Posted January 5, 2013 Author Share Posted January 5, 2013 Thanks guys, The Howards cam that I'm looking at would gain low & mid-range torque and MPG. .3 higher DCR & 12* less overlap. I plan to use my 1.6 rockers for .528/.534 lift I will loose some HP above 5400 RPM. The Edelbrock 3500 has only a small control panel that stays attached. It lets me control timing & mixture as cells every 1000 RPM & 3 vacuum ranges. No PC port. Has storage for 3 data sets, I use 1 for power settings, & 1 for lean mixture. Unit shows about 4" of vacuum with key on & motor off, due to altitude. I have an O2 sensor in each side. Passenger is used by 3500 & it displays red/green LED real-time. Drivers side has a seperate gauge that I monitor. They generally agree with each other. Dizzy is special for & controlled by 3500 As I have low vacuum, I put on a hydroboost brake unit rebuilt from Astro van. I spent lots of TLC setting up the 12 bolt gears & it's dead quiet. I would hate to tear it down. Next rear tires will be taller so as to turn less RPM on highway. In OD my gear ratio is 3.56 I usually leave it in Auto mode & it acts like a 4 speed auto. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted January 7, 2013 Share Posted January 7, 2013 With those gears, and on the street you won't be able to tell any difference from a cam change. It doesn't matter if you had a six cylinder in there, your mileage will likely suck with a final drive ratio of 3.5X. I have 3.55s and they are too deep for any real highway useage. You also won't tell any difference in torque from a cam change because your rear gears can probably break the tires loose at will anyway. Quote Link to comment Share on other sites More sharing options...
BuffaloBillPatri Posted January 8, 2013 Author Share Posted January 8, 2013 Thanks for input. My mixture runs about 14.7 +- in both sides at cruze. I have 10.25 CR with .040" squish, flat tops & alum. heads. My convertor is B&M Hole-shot 3000 & my synthetic ATF does get hot 230* or so if I let it slip a bunch. I have oversized alum. radiator with ATF preheater/cooler built in + a seperate cooler in front. So I need to keep above 3000 RPM as much as possible. I'm thinking of getting 214/224* regrind on my cam from Lunati, must stay with 110* LSA & 106* ICL they can keep all or most all of my .510/.525 lift (1.5 rockers) no hardening necessary as it's already been done. Probably couldn't drive it below 4000' altitude in summer as it would have DCR = 8.92 @ sea level. I need more compression than the aprox. 7 DCR that I have at 8500' altitude now. I can barely get rear tires to chirp. Everything up here needs about 50% more air, including me. 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.