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73-87 Chevy _ GMC Trucks => Performance => Topic started by: mbvanhorn on August 25, 2013, 11:52:42 PM
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HEy there, building my first C10 and would like some input/thoughts on my chioices.
I have looked around and am starting to plan my setup. Here's what I have so far..
Truck will be for cruising, meet-ups, and hopefully still be able to impress over a stock truck.
I am just going to include the links to make it easier.
Already bored .030 over, dished pistons, 3spd, Holley 600
Voodoo Cam 262/268 http://www.summitracing.com/parts/lun-10120702lk/overview/
Summit Vortec Heads http://www.summitracing.com/parts/sum-151124
Air Gap Intake http://www.summitracing.com/parts/edl-7516/overview/
Headers--Open to suggestions for vortec heads/fitment
Gears-- I know nothing about them
Also, do I need to upgrade springs? or are the ones that come with those heads ok?
Thanks,
Matt
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The air-gap intake manifold is great as long as you use a thermostatic air cleaner. If you plan on an open-element air cleaner (the two chrome pie plates setup), then don't use the air-gap intake manifold. Here's why:
http://forum.73-87chevytrucks.com/smforum/index.php/topic,26459.msg220588.html#msg220588
http://forum.73-87chevytrucks.com/smforum/index.php/topic,26161.msg217465.html#msg217465
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I see, I guess I'll go with the Air Gap, NOT the RPM version, and copy your riser mod. What do you think of my cam/head choice?
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Actually will the (NON - RPM) Air Gap Intake even fit the Vortec heads?
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I haven't used the Voodoo cams or the Vortec heads, so I can't give a good opinion there. That particular cam, though, has too much lift for stock Vortec heads. Were you planning on modifying the heads to increase the retainer to seals clearance?
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Here's a sample discussion from another forum on Vortec heads and high-lift cams: http://www.hotrodders.com/forum/vortec-heads-max-lift-32857.html
Just google: Vortec maximum lift.
The 7516 Edelbrock manifold will fit the Vortec heads. The 2601 is for the stock heads.
About the cam, I don't know about Voodoo cams as opposed to other company's, but I can speak to the cam specs. Lunati says that's a great "4x4 and marine" cam, but lists the power range on that cam from 1400 to 5800 rpm. And the lobe separation is 112*. That sounds like a winder, not a lugger, to me. You are putting this engine in a 5000 pound truck. You want torque, not horsepower. A torquer cam should have a lobe separation much tighter, like 108*, and shorter valve durations. A 262/268 cam is going to have a much later intake valve closure and much earlier exhaust valve opening than you want for torque. That indicates that cam is designed for high-rpm horsepower, where those numbers will help the engine breathe and give higher horsepower. Great if you are circle racing. But for street use, you spend almost all your time in the bottom half of the rpm range.
Look for a cam with 108 LSA, shorter duration, and a lower recommended rpm range if you want better street performance. Don't fall for an old-tech grind, though. Subtract the duration at .050 from the end-to-end duration. You want a difference of 40-50 degrees. Larger difference are characteristic of older grinds, while the newer computer-designed grinds get the valves off the seats much quicker, which makes it easier to maximize performance parameters. On that score alone, you can see that the Lunati cam is a modern grind.
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The Summit Vortec heads can handle .520 lift right out of the box.
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The Summit Vortec heads can handle .520 lift right out of the box.
Ah. So the Summit versions come with the bosses cut down already?
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Thats what they claim in the details of the description.
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The 7516 Edelbrock manifold will fit the Vortec heads. The 2601 is for the stock heads.
OK, I thought you said staty away from "RPM" (7516) in another post.
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Rich, Does this Cam seem more appropriate then? http://www.summitracing.com/parts/isk-cl201264/overview/make/chevrolet
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The 7516 Edelbrock manifold will fit the Vortec heads. The 2601 is for the stock heads.
OK, I thought you said staty away from "RPM" (7516) in another post.
Given a choice, yes. High-rise manifolds increase horsepower a bit, while reducing torque a bit. But Edelbrock has no standard-rise air-gap manifold for Vortec heads.
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Rich, Does this Cam seem more appropriate then? http://www.summitracing.com/parts/isk-cl201264/overview/make/chevrolet
No, that's worse. Look at the operating range. 2000 rpm on up. If you want a two-lane terror, you'll have great 50-90 passing times, but it will a stone brick off the line. A stock truck will blow your doors off until it gets its breath at about 3000 rpm. You can put a tall torque converter on it, then you just need to work out a bulk deal on replacement transmissions.
Somewhere along the line you seem to have been convinced that a high duration camshaft is better, a "bigger" cam. For high-rpm horsepower, yes. For a street machine, no. Many of the hot rod boys (you know, '32 Deuces and triple-5 Chevys) use marine cams to get the fat torque curves that make a car fun to drive on the street.
Look at Comp 12-235-2, 12-231-2, 12-300-4, and 12-304-4, for example. 12-300-4 was my choice. Sean Murphy at SMI recommended the 12-235-2 as being sort of like a ZZ4 without going to rollers.
Google my last name and 12-300-4, and you should see some threads here and elsewhere with long discussions about this.
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Check the Edlebrock 2116 Performer.....its what I am using.......from idle to 5500 rpm
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The advantage of the air-gap manifolds is that the carburetor is always operating in its most desired temperature range. Carburetion, as opposed to fuel injection, is a collection of compromises. Various circuits, springs, air bleeds, and venturis in carburetors give you almost the right mixture under most conditions. Fuelies have a computer monitoring the actual mixture constantly and continuously adjusting it to be a perfect mixture in all conditions. Carburetors are open-loop systems, and fuelies are closed-loop systems. With an air-gap manifold and thermostatic air cleaner, the carburetor is always running in a narrow temperature range: the carburetor is isolated from engine heat, and then heated by the induction air system to proper temperature. This allows closer approximation to the correct mixture, because you can tune the carb to that narrow temperature range. Not a big deal in moderate climates -- in Hawaii or Southern California, why bother? -- but in places where you have seasonal weather, it makes a huge difference.
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Great info, I live in south Texas so we have two seasons..10 month summer and a two month cool front. I take it the air gap isn't necessary? Just go with the performer? I like the idea of a zz4 style cam.
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Use the air-gap manifold without the thermostatic air cleaner. You don't need carb heat there. What the air-gap manifold does for you is keep the carb from getting over-heated by the engine oil splashed against the underside of the intake manifold. Problem is, when it's cold, the carb takes forever to heat up to operating temp, so you need the thermostatic air cleaner. You live in a part of the country where 1) the air-gap manifold will really help keep carb temps down to proper levels and 2) you don't need to worry about heating the carb when it is cold, because you never get cold!
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Rich, you made this comment earlier:
About the cam, I don't know about Voodoo cams as opposed to other company's, but I can speak to the cam specs. Lunati says that's a great "4x4 and marine" cam, but lists the power range on that cam from 1400 to 5800 rpm. And the lobe separation is 112*. That sounds like a winder, not a lugger, to me. You are putting this engine in a 5000 pound truck. You want torque, not horsepower. A torquer cam should have a lobe separation much tighter, like 108*, and shorter valve durations. A 262/268 cam is going to have a much later intake valve closure and much earlier exhaust valve opening than you want for torque. That indicates that cam is designed for high-rpm horsepower, where those numbers will help the engine breathe and give higher horsepower. Great if you are circle racing. But for street use, you spend almost all your time in the bottom half of the rpm range.
Look for a cam with 108 LSA, shorter duration, and a lower recommended rpm range if you want better street performance. Don't fall for an old-tech grind, though. Subtract the duration at .050 from the end-to-end duration. You want a difference of 40-50 degrees. Larger difference are characteristic of older grinds, while the newer computer-designed grinds get the valves off the seats much quicker, which makes it easier to maximize performance parameters. On that score alone, you can see that the Lunati cam is a modern grind.
I thought it was the other way, that 108 was a high horsepower LSA vs 112 being for torque. I know there is more to it than that, but just wondering.
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Narrower LSA is for torque. See this article, for instance.
http://www.chevyhiperformance.com/tech/engines_drivetrain/cams_heads_valvetrain/0705ch_camshaft_profiling/viewall.html
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I read your post again and finally figured out what you were talking about when you said the difference in full and .050 duration. Can you explain any more about that. I have seen it referred to in old vs new grinds and the fact that computer software lets them design more complex love designs. But I'm still not completely sure.
Quicker off the seat and open fuller quicker allowing for more open time while keeping the overall duration down. Kind of like the difference between egg shaped hydraulic flat with pointed top vs hydraulic roller with the flatter top.
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LSA??? Smaller means what? Smaller means quicker response more low end torque and lopey idle.
Larger is more high rpm power and smoother idle
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LSA of 108, duration 262 or less with .050 at 220ish and lift of .460 - .470. Where do you find this camshaft or am I thinking about this wrong?
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No, I think you're on track. I would just go to Comp cams and start surfing the cams and looking at numbers over there.
As for the advertised versus .050 durations: the advertised (or seat-to-seat) determines things like gas mileage and static compression, because the cylinder pressure will start to drop as soon as the exhaust valve opens and the compression won't start until the intake valve is all the way shut. What the .050 durations tell you is how fast the valve is coming off the seat (like 268-222 = 46*, which is fast, where an old grind will be 268-193 = 75*, which is slow). That will tell you about flow, because you will get the bulk of your flow when the valve is open .050 or more.
See my post on the other thread for another dyno chart, this time on what I think is an equivalent for that Lunati cam.
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This is starting to make more sense.
I apologize for posting so much on this topic but it so similar to mine I thought it would be good information.
And my post above that should have been love not "love". I hate auto correct.