Author Topic: '73 350 Setup  (Read 8094 times)

Offline mbvanhorn

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Re: '73 350 Setup
« Reply #15 on: August 29, 2013, 12:09:38 AM »
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.

Offline rich weyand

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Re: '73 350 Setup
« Reply #16 on: August 29, 2013, 01:17:44 AM »
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!
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline nlauffer

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Re: '73 350 Setup
« Reply #17 on: September 09, 2013, 03:11:13 PM »
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.

Offline rich weyand

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Re: '73 350 Setup
« Reply #18 on: September 09, 2013, 03:36:59 PM »
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline nlauffer

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'73 350 Setup
« Reply #19 on: September 09, 2013, 07:24:10 PM »
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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Offline nlauffer

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'73 350 Setup
« Reply #20 on: September 09, 2013, 07:28:44 PM »
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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Offline nlauffer

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'73 350 Setup
« Reply #21 on: September 09, 2013, 07:34:20 PM »
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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Offline rich weyand

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Re: '73 350 Setup
« Reply #22 on: September 09, 2013, 11:07:49 PM »
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.
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline nlauffer

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Re: '73 350 Setup
« Reply #23 on: September 10, 2013, 02:07:58 PM »
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.