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CuttyGMachine 03-20-2008 07:24 PM

Cam Selection help
 
I finally got the information on how the motor in my Cutlass was built, and I'd like to run a cam selection by the collective. Here is what I've got:

SBC, .030 over
14014416 305 heads opened up with 1.94 intake valves
1.5 ratio roller rockers
Speedpro flat top pistons (TRW-L2256F30)
MSD 6AL ignition, coil, distributor
Edelbrock AirGap intake
Edelbrock 1611 Performer 750 carb
Turbo 350 trans with shift kit and 2800 stall converter
1 5/8 headers and free flow exhaust, but with cats

I'm looking for solid street performance with very occassional trips to the strip. I want enough vacuum for power brakes. It's all going in an 83 Olds Cutlass, about 3500 lbs in current trim.

I'm looking at something along the lines of the Summit K1105 or Comp Cams 12-243-3. Both are in the neighborhood of 226/243, with less than .500 lift. The lobe separation is significantly different between these 2 cams.

Any thoughts? Am I smoking crack with these cams? Or can I go hotter safely? Am I missing important details? This will be my first American iron build, so I am looking at it as a learning experience. But I don't want to totally F it up in the learning process. :)


thanks

stu...

techinspector1 03-21-2008 12:30 AM

You didn't give two of the important details. Piston deck height and compressed head gasket thickness. These determine the squish. Guesstimating the gasket at 8 cc's (0.040") and the piston deck height volume at 5 cc's (0.025"), your static c.r. will be 10.56 and the cams you're looking at would work. Problem is, adding the gasket and deck gives a squish of 0.065". This may be too thick to allow operation on pump gas without detonation (ideal 0.035" to 0.045").

If whomever built the motor took squish into consideration and set it with, for instance, 0.025" deck and used a 0.015" steel shim gasket, then the squish would be at 0.040" but the static c.r. would be 11.23:1, so it wouldn't run on pump gas anyway, even with a tight squish (IN MY OPINION).

Now, you could go with a longer cam and try to squeak by with leaking off some of the compression, but you're already limiting yourself because the heads are gonna sign off about 5,000 rpm's and the cam you're lookin' at will operate from 2200 to 5700. If you went longer on the cam, you might operate from, for instance 2800 to 6200. Then the heads would be a mis-match and the converter would be a mis-match.

Who chose the parts for this motor anyway? What's the piston deck height? What's the gasket thickness?

F-BIRD'88 03-21-2008 07:04 PM

You're building a near identical motor as I just did.
Isky Cams #201027 Z-27 fits the bill. It's a snotty lil "high perf street" mechanical cam.
282-282 247-247 @.050" .507" gross lift .016" lash 108LSA goes in on a 104 intake C/L try it... :thumbup:
get some 4.10's and some sticky tires.

As long as you did a healthy port job on the heads, you should be happy with the result.

www.iskycams.com


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