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Cam for a Vortec 355

12K views 35 replies 10 participants last post by  ap72 
#1 ·
Hello! This is my first post here.


I'm just woundering what cam will be the best for my engine. Car is Camaro 69 with a th350 with 3000 stall and 3,55 gears. Vortec heads 10:5.1 cr Air gap intake quickfuel 750 e85 headers
Xe274 or 12-672-4 cs nostalgia 30-30h+ or Isky 278 mega cam

thanks alot for the help!
Cheers from Sweden!
 
#4 ·
Then you need to step up to a roller cam if you want that much lift. You only need about 225/230 duration (on a hydraulic cam), and maybe 5 degrees or so less.

If you can't afford a roller cam you can run an aggressive solid flat tappet cam with higher ratio rockers, good springs, and grooved lifter bores and face oiling lifters and it MAY last.

For something like that try the Lunati 60140 and only run 1.6 rockers on the intake.

Running a roller cam will get you better performance and durability, but the costs are higher as I'm sure you know.
 
#7 ·
I wouldn't worry about this link too much as it doesn't account for displacement, heads, intake, exhaust, application, carb, fuel, etc. Without considering those aspects its as useful as any advertisement or summit catalog (not much), I still can't figure out why it hasn't been deleted as its VERY misguiding.

Truth be told with E85 as your fuel you can run as small of a cam as you want, and your heads will go into choke right under 6,000rpm or so so there's no sense in camming for more than that unless you want your efficiency to go to hell. Assuming a good dual plane intake, headers, and exhaust, you'll want about 220-225 duration on the intake, and 225-230 duration on the exhaust for a hydraulic cam @.050".

As Cobalt mentioned stock heads peak out at a hair over .500" lift, going past that on stock ports and valve job won't gain you much (though it will pick up a little).

For a good street 350 stick with 1.94/1.5 valves but get a good valve job, open the throat to about 89-90% and open your runners up (finished volume around 190cc's with good even runner taper is a good target for Vortec heads). Those mods can pick up another 25+hp on a well built 350.
 
#11 ·
Here are a few cams I would use if I had a Chevy 355. Howards Cams CL112591-08 - Howards Cams Hydraulic Flat Tappet Camshaft and Lifter Kits - Overview - SummitRacing.com Lunati 10120410LK - Lunati Bracket Master II Cam and Lifter Kits - Overview - SummitRacing.com Crane Cams 100072 - Crane Energizer Cam and Lifter Kits - Overview - SummitRacing.com A good friend of mine bought a 1969 Camaro with a 6 cyl back in the late 70's. Then he bought a 350 rebuildable core. He rebuilt the motor using all GM parts from our local Chevrolet dealer. When he finished he had a strong running 69 Camaro, 4 speed trans, 4.11:1 rear. The exterior color was Hugger Orange with a standard black interior.
 
#13 ·
I would like a hyd roller but The prize is too high in Sweden, about twice as much. So i like to keep it a hyd flat tappet for now. Car Will be a weekend warrior no daily driver.about 80% street and 20 strip. So i cant decide between those cam i listed.

Thanks alot all help I'm really grateful for the help!
 
#19 ·
ap72 I don't agree. Although it would be better to fully port the heads along with the bigger valves, they'll still flow better even at lowlift with pocket porting and bigger valves. I would agree that 2.05's may be overkill for the application they won't hurt anything and at least here in the states 2.05's don't cost any more than 2.02's. If I stayed with 1.94's I'd be very careful who I let touch the seats.
 
#22 ·
I have read that adding larger valves to Vortecs is bad because it decreases intake charge velocity. Also the casting is pretty thin and close to the water jacket and cutting for larger valves increases chances of a crack developing — which is also a factor that needs consideration when porting Vortecs. The intake flow numbers for Vortecs are pretty awesome. They are lackluster in exhaust flow, so if you port, do the exhaust side.
 
#27 ·
They aren't related directly BUT what F'bird is getting at is that with a 26-28" tire size and a 1:1 final trans ratio those rear gears and stall would help put the operating band of the engine closer to where the cam causes it to make most of its power. If you move your power band up then you need steeper gears to make your car run at that RPM.

Changing gears is not totally necessary but in most cases it enables the driver to make the best use of the new found power at the higher RPM ranges.
 
#28 ·
AP72,you are correct"They aren't related directly"

most cars and trucks have multi gear transmissions,to say a car with a flat tappet hydraulic cam "needs" 4.30 or 4.56 gears?
Im trying not to correct or call out anyone,but,,,,,,,?lets think about gear choices and applications.I use 3.5 gears and my cam is 256/264@50 with valve lift over 600,is my gear choice wrong?
 
#30 ·
It's not wrong, just a different approach. Some people will run a 700R4 or simmilar style OD trans with a steep gear (like 4.10s) so they can have great acceleration and decent cruising RPM. You're doing the same thing but with a 3 speed instead of a 4- using the first two gears for acceleration and your final gear for cruising.

Its not the best thing for a strip only car but it works fine for a car that sees street time- especially freeway time.
 
#31 ·
addressed directly to f bird,Ill help you out here.using my car as an example,engine peak power on dyno was 6470 rpm,so call it 6500,,,3.50 gears,2.78 1st gear= 55mph,2nd gear 1.89 = 81 mph,3rd gear 1.28= 120 mph,4th gear 1= 153 mph. I used 27.7 for tire height.
This would make my car shift into 4th at the end of a 1/4 mile drag strip,if I raced 1/4 miles.
NOTE: not everyone races 1/4 mile,Im more interested in road racing. A straight offers more than a 1/4 mile and you enter off a corner,plus you need to slow down for the next corner.If I had 4.56 gears the 1st gear would be useless even coming out of a hair pin.
I guarantee my car accelerate very quickly.It weighs about 3300 pounds.There is noway my car could use 4.56 gears with any street tire except drag radials and believe me,I havent found too many cars that accelerate faster from 10 mph that are driven on street tires.
also,theres noway I want to drive on the freeway with my tach sitting at 3200 rpm.I can drive very nice at 2200 rpm and thats 63 mph,which is a common speed limit here
 
#33 ·
fbird,you are missing the point.The gears in the diff really have nothing to do with the engine.You cannot just say this cam needs this gear.What you can say is this cam works best at this RPM or RPM range.The rear gear ratio is tuned for application.If someone drives a lot at highway speeds,that application needs to incorporate a final drive ratio that is efficient,and that can vary alot.If someone wants to use a long duration cam(for w/e reason)then point out that the final drive and tire size will put the engine at a disadvantage because,,,then talk about cams and engine rpms and all the variables that contribute to w/e adverse effects that may be present.

NOTE:If I make peak torque at 3500 rpm,it doesnt mean I have to drive at peak anything,,,,lots of math rather than random numbers that have to match.

If I had a 283 in my corvette,I would still use 3.5 gears.Its the gearing I want/need for what it does.It just wouldnt do it as quickly. The car came with 2.73 gears and a whopping 160 horses.
A 195 horse 283 with 3.50 gears would match the 350 and 2.73 gears
 
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