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  #16 (permalink)  
Old 02-13-2009, 09:18 AM
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Quote:
Originally Posted by 454C10
rpm's at 70 mph will be 3200 rpm with 28 inch tall tires.

3400 rpms at 75

3600 rpms at 80


the 2nd cam will seem to make the engine rev easier at highway speeds.

The 1st cam will make it seem like the engine is over revving when driving at speeds over 60 mph. The second cam will start to feel that way at 70.

Very few trucks run 28" tires, it appears that he has 33's which through those RPM's out the window.

Valve sizes- smaller is better for milage. Cam- smaller is better for milage. Gears- smaller is better for milage. Tires- Smaller is better for milage. See the trend...

Are you after milage or power? If you never plan on seeing the other side of 4500 RPM then the smallest cam is the best choice, no question about it. You cannot have milage and power- especially in a NA carb'd truck with 33" tires.




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  #17 (permalink)  
Old 02-13-2009, 09:46 AM
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Yeah not sure how folks missed that. What would change with 33" tire. Sounds like you state the smaller cam all the way around. I am thinking about buying a camel hump head today (041 or 186 havent decided). Will this add a little. Would the second cam be all that bad. I am looking for mileage, but a little performance as well. A mild 350.. or RV type cam. Would the first be an RV type grind or the second.

A friend is telling me to put a 270 in it. Is this too much. I want some performance, but I don't want gas mileage to suffer. Just from adding 23 more cubes (327 to 350) just may be enough. Won't I have a bit more torque naturally in the 350.

Last edited by Carlos9; 02-13-2009 at 10:31 AM.
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  #18 (permalink)  
Old 02-13-2009, 01:45 PM
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Quote:
Originally Posted by ap72
Very few trucks run 28" tires, it appears that he has 33's which through those RPM's out the window.

Valve sizes- smaller is better for milage. Cam- smaller is better for milage. Gears- smaller is better for milage. Tires- Smaller is better for milage. See the trend...

Are you after milage or power? If you never plan on seeing the other side of 4500 RPM then the smallest cam is the best choice, no question about it. You cannot have milage and power- especially in a NA carb'd truck with 33" tires.

have you seen stock c10 1969 tires and rims? tiny. 28 inch is about stock height. 33 inches is not stock for a 69. But yes, 33's make a difference. 75 mph would be 3000 rpms which is better, but I still would go with the 2nd cam for a less buzzy engine at 3000 rpms. I would use the smaller cam if you drive more on city streets than the highway.

a 33 inch tire with a 3.73 would turn like a 3.16 gear with a 28 inch tire.

are those 33's fat or skinny???

my 70 c10, when it had a 350, did a best of 17 mpg with 3.08 gears, th350 trans, 28 inch tires (skinny), and a cam about the size of the first cam. weighed 3850 pounds empty. had headers and duals and a holley 3310. with a q-jet, I'm guessing it would have gone up another 1 mpg.
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  #19 (permalink)  
Old 02-13-2009, 05:24 PM
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I think I have to agree with 454C10 about the 2nd cam and use a Q-jet.
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  #20 (permalink)  
Old 02-13-2009, 09:13 PM
 
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no is stating that u should sway out your 3.73 for 3.42s
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  #21 (permalink)  
Old 02-14-2009, 12:14 PM
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Quote:
Originally Posted by 454cutlass86
no is stating that u should sway out your 3.73 for 3.42s

Did you mean to say no one is stating here?
Thanks guys, these are good comments. It will be either between cams 1 or 2. I am after mpg and I still think I can get some performance. I talked to a guy yesterday who ports heads and he stated I wanted to choose a cam where the powere was right there from the start (the first cam). He also went on to state the biggest thing I can add to help both the engine and drivability is overdrive. He said I could go from 10 to 16-17 mpg difference. I feel like that's where I losing gas mileage anyway is up in the 70ish range because the motors workign really hard. He says is increases the longevity of the motor as well.

HEADS
I am looking into vortecs now.. after spending a couple days looking around for ole irons. There aren't any. Plenty of 882 and a lot of newer stuff no one wants. Right now I am looking at a vortec head Summit part no. NAL-12558060. I can get this pair to my door for $590.

I am also looking at a pair of 041 heads at a local machine shop I just stop thinking about. They have 2.02/1.60 stainless steel manley valves, screw-in studs-guideplates, and have been cleaned up just a touch on intake/exh. ports, bronze guides, good springs etc. They have this coating inside as well. The guy is selling me on all the upgrades. Any big deal about stainless valves.

My question is how much better would these vortecs be compared to the 041's with me not doing the recommended upgrades on the springs for the vortecs.. (doing screw in studs/guide plates etc. as well). The vortecs are 1.94/1.5 compared to 2.02/1.6.


Talk to me! I will be buying heads withing the next few days.
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  #22 (permalink)  
Old 02-14-2009, 02:09 PM
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vortec are better heads even with the smaller valves. however, vortec heads require a vortec intake, vortec rocker arms, and vortec valve covers. These extra part things add up cost. Plus the vortecs need some machine work if you plan to run more than 0.450" lift.

What intake and carb are you using now?

how do you have the ignition timing set (initial, max mechanical, and vacuum advance)?

running headers?

what mpg are you getting now?
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  #23 (permalink)  
Old 02-14-2009, 03:20 PM
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I am getting decent mileage now, but not sure what. I am running stock iron intake and quadrajet carb. I have ram horns, but plan on headers down the line. Everyone thinks I have headers now though. As far as intakes go, I still have to buy one for the new engine. What intake would I use to still run my quad. How much are the rockers. I would still need to purchase with the 041 heads, but with them, I can do what I want lift wise because they're set-up with screw ins already.

I thought the max on vortecs was .480. Least that's what advertised. Th only advantage is the combustion chambers on teh vortecs sounds like. I would have to spend money to get them to the point of where the 041 heads are.

What about compression ratio. Where would I be with a 64cc head. The block has not been decked at all. Heads minimal clean-up.

Currently have hei unit with 17 degrees initial. vac. advance. Tires are huge 33" not small. Wide and tall.

Last edited by Carlos9; 02-14-2009 at 05:38 PM.
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  #24 (permalink)  
Old 02-14-2009, 06:54 PM
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My 72 with a rebuilt 350, q-jet, 3.73s. and 350 auto made 14mpg around town believe it or not. Had 31" tall tires and it would roast those all day long. Dont know if it had an aftermarket cam or what but it sure had some power and surprisingly good mileage. I never checked highway mileage but it wasnt too bad either.
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  #25 (permalink)  
Old 02-15-2009, 07:12 AM
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first check your mpg. if you are getting 15 mpg or better on the highway at 70 mph then don't mess with it.

a 350 needs 50 to 55 degrees of ignition timing while diving down the highway (low load, high vacuum). rev your engine up to 3000 rpm and measure how much total advance the engine gets from the mechanical and vacuum advance combined.

install some small tube headers before the cam. That will be the biggest gain in mpg from extra mid range torque. use some dynomax super turbos mufflers and a H or X cross over pipe.
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  #26 (permalink)  
Old 02-15-2009, 03:05 PM
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The deeper gear (3.73 opposed to 3.08) is always going to use more fuel regardless of cam. What the guy told you about overdrive is right, the biggest thing that would help your situation is a 700R or a 4L60. The C4 Corvettes with the TPI motors had a 700R4 w/ 2.73 gears. They were torque monsters but fell on their face at 5000 rpm. I've got an 87 and at 70 mph cruising I'm around 2k rpm's. I never understood why they never put the TPI motor in a truck. I think they were better suited in a light duty truck than the Corvette.
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Old 02-15-2009, 04:19 PM
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use the smallest cam, i think your truck is heavier, anytime mieage is a priority, longer duration cams are out the window...
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  #28 (permalink)  
Old 02-16-2009, 08:50 AM
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Quote:
Originally Posted by roknroy
use the smallest cam, i think your truck is heavier, anytime mieage is a priority, longer duration cams are out the window...

I thought that was easy to see as well... And that having peak power outside your driving range was a little senseless...



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  #29 (permalink)  
Old 02-16-2009, 09:38 AM
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These are all great discussions, but something I want to add that I don't think we mentioned...

Overlap is one of the big determining factors with MPG. You didn't list LSA numbers for those cams, but its possible that a cam with a longer duration, wider LSA (and therefore less overlap) can make better MPG numbers than a smaller cam with more overlap. But its also not usually advisable in a naturally aspirated engine to go with a big duration and a big LSA in search of power and mileage. That usually leads to disappointing dyno numbers.

Otherwise, I second the vortec recommendation. Their chambers are very nice; much more inspired than anything before them. They allow for much more compression on cheap gas, and the fast-burning characteristics mean you only need about 32 degrees total ignition lead. That means 9.5:1 on 87 octane depending on cam.
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Old 02-16-2009, 10:22 AM
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Quote:
Originally Posted by ap72
I thought that was easy to see as well... And that having peak power outside your driving range was a little senseless...

Yeah.. for those who know, but I am still learning. That's why I came on and asked before I bought. I got a guy trying to put a 270 in it.. and I keep telling him that's not what I want. I don't want to build a gas hog. I build my cars to drive them, not let them sit because they're frustrating to drive because of poor gas mileage.

I will be going with the first cam. This is bigger than stock. What are the numbers on a stock cam so I can have some perspective.
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