[johnreeves]

Hi All,

I'm looking to change the camshaft in my 1969 firebird, Rebuilt 455/30over 9.2 :1 compression ?, I have 100 cc chamber 5C heads , stock rods, ,4 tube headers,350 trans ,2000 stall, HEI, cast intake 750 VS. Camshaft that is currently in the engine is a 217/221 272/278 .454/.454 106. This was my choice with a 2.56 ratio. I had the rear end rebuilt and switched to 3.55 gears. The car runs fine but I guess I was expecting the car to pull harder from 3000-5000 RPM, Is there any suggestions on things to check that would improve the performance? Or would switching to a larger camshaft grind (I was thinking of a 744 clone) improve the performance the most.
Thanks for the advice.

[screamingchief]

That's an odd looking set of cam specs,I dont know of any commonly available grinds that uses that tight an LSA on that size cam.

I dunno,are you sure that 106° is not the installed centerline for the intake lobe?

Obviously a cam change will do what you want,you're gonna need a bit more duration regardless of what LSA is to be used.

If your looking for all around good manners you'll want to keep the LSA in mind when looking for a new grind and try to stay on the "wide" side of that choice.

If you want it "snotty" then a tight LSA can be used,but it will need even more duration than the wide LSA cam choices will.

Then there is that pesky "middle of the road"...

Might wanna look at the crower #60243,that would be a better "baseline" choice than most of the 744 "clone" cams would be.

JMO/HTH.

[Half-Inch Stud]

shoot for 236/246 at .050 and don't sweat the LSA with your combo. 108 LSA might ber ideal, or may not matter if you had 104 or 112 depending on how you launch. Since you got a 2000 stall converter& 3.55gear, &headers error on the side of lower LSA for TQ peak at lower RPM. Other folks here might make a passionate plea for 116 LSA but 112 LSA is the upper LAS you'll find. Run Rhoads lifters with the 108 LSA and be way ahead on variable valve timing.

[stobin]

Make that ADVICE. Spell check!!!! Sorry.
I agree with the Crower #60243 recommendation. With your compression and gear, that would be a great choice for the street. I think the 236/246/108 will be a bit too much unlesss you want a very rough idle. You will also need more converter with that grind. I am sure the 112 LSA on the Crower will keep the idle characteristics more liveable.

[ta man]

I doubt you have as much compression as you think.Lots of cams to choose from.But I would do something with the heads.Have they been milled?New springs?A good spring is a crower 68404 will drop right in.Will allow a higher lift.What do you have for exhaust?

[Half-Inch Stud]

johnreeves, you could follow my 12.0ET signature (Lunati SPC-320 cam in +4ADV) and enjoy off-idle 60foots, and camm-induced EGR improvements in highway MPH that is quite exciting for ability to claim >16MPG, perhaps 20MPG at 65+MPH for 4hour stints. Vacuum was 11-12" with Rhoads. Note the 3.31:1 gearing. HIS

[johnreeves]

Screamingchief, You are correct,(UD cam) the separation angle is 110deg. intake lobe degreed to 106 deg.
Ta man, I'm not sure about the compression ratio . I just plugged the numbers in on a program listed on a web site, it stated 9.18:1. The springs that I have installed on the heads are H.O. Racing VS 11's. Not sure how much lift they will take. I'll try to do some research. If they will handle the lift of the crower 60243 cam (.494 lift), then I'll leave them in place. If not I'll take your advice and purchase the Crower 68484 springs.
Thanks to all.

[Half-Inch Stud]

Only now, do I notice the Low compression from the 100 cc 5C heads.
Thus I agree with stobin now, you'll want to use a cam smaller than my reco.

However, since you got the 3.55 gears, you could still run on the wild side per me post #6 with Rhoads & 1.5:1 rockers. Partcularly if you have a 2800-3200 converter in the future.