I was wondering if someone could give me some help with a cam choice. I am keeping/upgrading the TBI. From what I have read I need to have a LSA from 111-115. What I need to know is what duration should I be looking for to keep it streetable? Here is some info to help you out....LO3 305 so I will be keeping it roller cam and lifters, 10:1 compression with flat tops or "D" port pistons, Vortech heads, probably just have the crank checked and polished if it is ok, unless I can find a good deal on a stroker crank. I dont plan on using nitrous so cast should be ok for the 305. Street driven, maybe see a track once or twice a year for fun. I will beef up the 10 bolt for now with axles and a 3.42 posi and variuos suspension goodies to help. SBF also will be added. SO, if you can help out I would appreciate it. Thanks.

Dave

 

The LT1 cam is a popular upgrade for TBI platforms.

Are the Vortecs being machined for lift?

 

Yes they will be machined for more lift.

 

This is about as much cam duration as you will want to go on a 305:

intake 214(270)
exhaust 220(276)
112 deg LSA

 

Cool, I will take a look and see what I can find around those specs. Thanks!

Dave

 

save your money, the Vortec intake ports stall badly at around .475" lift, and COMP offers about a dozen good HR lobes that are a great match. Also, Vortecs need more exhaust lobe, at least an extra 10 degrees at .050", even with some mild cleanup work in the exhaust ports. It's best to leave the intake ports alone, upgrade to stainless valves with undercut stems and 30 degree back cuts, and have the exhaust seats redone for 1.60" exhaust valves. Including a 75 degree bowl hog. Smooth out that ridge in the exhaust port floor, and taper the exhaust guides, then fully polish the exhaust ports with the finest grit rolls. This will improve the E/I percentage from around .6 to around .75

 

Atilla, do you have a different head option/set up that you would recommend? Thanks.

Dave

 

For a 305, no other head gives as good of results as properly worked vortecs, for the same money. To get results equal to these, you'd have to spend hundreds more on TFS 175cc heads, which are intended for 305s, and are aluminum. Some few years ago, ChevyHighPerformance magazine did an LO3 with milled Vortecs, FelPro steelshims, the GMPP TBI Vortec intake, a custom ground Crane HR cam with 210/214 duration at .050", on a 114 degree lobe separation, with .479/.488 lift, 1.6:1 rocker arms (which they shouldn't've used on the intakes) and a full Edelbrock exhaust with headers and a high flow cat. They found 295 ft-lbs at the rear wheels, through a 700R-4. That's about 378 ft-lbs at the crank. That impressed me.