I have an olds 403 fitted with 455 c heads with a full port and polish. My cam is a hydraulic roller form comp. at duration at .50 in is 247 in and 254 exh. lift is in teh mid 500's. lsa 110. Im trying to make big torque and close to 500hp. Is My lift enough or should i switch from my 1:6 ratio rockers to 1:7 to get more lift? If i do switch to the 1:7 rockers how much can i expect my duration to increase?

 

What's the compression ratio? Manifold? Carb?

 

10:1 compression. rmp intake and holley 750 dp

 

ive got olds c heads with full port and polish

 

Yeah you should make 500hp. not sure about the torque though. A cam with that much duration is going to have a higher rpm torque peak.

Just FYI, contrary to popular belief, the Comp Xtreme lobes aren't the best for every application. You need to match the characteristics of the head flow to the profile of the cam. You have a lot duration there, maybe too much for your compression and application. To really make use of that much cam you need to go 11.0:1 and maybe a Victor manifold. You need to see what your heads flow at .500, .550 and .600 lift especially to determine what rocker you need.

I did a 436 BBC with out of the box Edelbrock heads, RPM intake, and an Avenger 770, 10.5:1. Made 515hp/540lbft of torque with only a 234/240 hydraulic roller cam, .639 lift. Why? Cuz the cam matched the combination. He was glad it made more torque than hp, that's what moves your vehicle down the road/track.

 

i was thinking about using the rhoads vmax lifters to bring my duration down at least 10 degrees. I have heard many good things about them. the only downside that i understand is that they are some what loud.

 

and does an lsa of 110 and centerline of 106 help my cam at all?

 

110 doesn't, the 106 does. Actually if the cam was ground on a 112 or 114 it would be better. And you might want to think about about putting it in closer to a 102 centerline than a 106.

Bottom line? Your cam is too big for the rest of your application.

 

what if i use the rhoads v-max lifters and drop the duration to about 238 in. and 244 exh? That would be a 10 degree drop

 

i need the cam's rpm range to start closer to 2500. thats the stall converter i have

 

You can advance the cam to 102 or less but I hate to say it but everything you do will be a band-aid. You need a smaller cam, or a bigger manifold, more compression and more gear and/or converter.

Your cam is too big imo.

 

if i grind my cam and take like 15 degrees off if possible do you think that would be a good cam for my application and is my centerline and lsa ok?

 

How much do they want to grind it? I'd go with about 236/242 or so, maybe on a 112 depending on your gear, vehicle weight, etc. They can change the LSA a little depending on how much they're taking off.

 

its a 79 trans am. i think they weigh about 3600lbs and i have 4:10 gears

 

Then I'd raise the compression to closer to 11.0:1 and use a Victor if possible. Then that cam would be a better match. Otherwise grind it to my earlier spec. JMO.