Buildup opinions

[84cutspreme]

I would like to bump my motor up some. My motor is a sbc 350 and has an eagle rotating assembly with 4.000 bore x 3.480 stroke and 882 heads (76cc combustion, 160cc intake, 1.94/1.5 valves...so stock. I have been planning on a set of aluminum heads, 70cc combustion chamber,180cc intake runner, 2.02/1.6 valve. I am also going to bump up cam and lifters, it will be a full roller setup. I would like to know how big of a cam I can go with before I have to start worrying about vacuum issues. I have power brakes still along with stock a/c and heat, just no cruise control at the moment but I intend to have it eventually. I was originally looking @ comp cams mother thumper. Other info on car, 84 cutlass 2dr, 700r-4(currently 1800 stall speed w/ 30-spline) & 8.5" w/ 3.73. Any and all opinions are appreciated.
Specs: RPM range: 1900-5600
Valve Timing: 0.006
Lobe separation: 107 degrees
Intake Center-Line: 102 degree
Duration: 283 int/303 exh
Duration @ .050" Lift: 227 int/241 exh
Valve Lift: 0.513 int/0.498 exh
Lobe Lift: 0.342 int/0.332 exh
*also I intended to run around a 9.1:1 compression ratio

 

[RITTER]

Typically you don't want to go lower than a 110 lobe seperation to retain vacuum for your power brakes. You can also get a vacuum canister and run a larger camshaft

A good set of GM aluminum heads would be either L98 or LT1 heads :wink:

 

[SScamino]

Yuck... I hate thumpr cams. Just build the motor the right way and sound will come too if that's what you want. Otherwise power will so much better with a different cam. Also why so low on the compression? Especially with Aluminum?

 

[84cutspreme]

I am willing to bump up to 9.5:1 but that's my max because I want it to be very street-able and a little racy. I have already gotten vetoed on the thumper cam, it was a buddies bad suggestion. I want to leave my stock style lower end alone though. Pistons are +7cc flat top with 4-valve reliefs, also only a 2-bolt 010 block. I was looking at the brodix IK 180 heads and just trying to find a nice cam suited for my setup with that. The 70cc will keep compression around 9.1:1 but 64cc heads will bump ump to around 9.6:1 which was higher than I'd like to go.

 

[SScamino]

I am willing to bump up to 9.5:1 but that's my max because I want it to be very street-able and a little racy. I have already gotten vetoed on the thumper cam, it was a buddies bad suggestion. I want to leave my stock style lower end alone though. Pistons are +7cc flat top with 4-valve reliefs, also only a 2-bolt 010 block. I was looking at the brodix IK 180 heads and just trying to find a nice cam suited for my setup with that. The 70cc will keep compression around 9.1:1 but 64cc heads will bump ump to around 9.6:1 which was higher than I'd like to go.

Well. To let you know aluminum dissipate the heat in the combustion chamber and really don't start performing well until 9.5:1. My vortec heads and I are running 9.98 something to 1 and I'm running it on 89 octane PERFECTLY. Just having a huge compression ratio doesn't mean it's not streetable... timing, cams, combustion chamber design etc all play in effect. The IK 180 heads are a great pick and a nice 220 to 235 duration cam on a 110 lSA along with will be perfect. And make awesome power. Providing that the compression is up to par.. Go roller if you can.. if you can't look in the 60103 voodoo cam a lot of people like it..

 

[84cutspreme]

Would you suggest 12-423-8
110 lobe separation
.502/.510 lift w/ factory rocker
224/230 duration @ .050
1900-5600 rpm range

 

[CHRIS.O]

I would suggest you call the manufacturer of your choice and ask them what you should run. They are the pros. Comp cams has a free program called camquest that helps you select cams. It gives you a little dyno sheet with your specs. Its very optimistic in my opinion but still cool to mess with when selecting a cam.

 

[84cutspreme]

yea I've checked it out, but they don't list that many cams, and some of the specs are not specific enough

 

[CHRIS.O]

It list their whole inventory haha. Over 1300 sbc cams. For the correct answer you need to call them. They designed them, they can select the best fit for you. Just do yourself a favor and dont over cam your engine. Goodluck

 

[84cutspreme]

Yup thanks, I know thats where I was headed originally