09-04-2017, 04:45 PM | #1 |
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Cam vs mpg
I have a 69 c10 with a 350
65 cc iron heads with 2.02 and 1.60 valves. 165 cc runners Performer dual plane intake 600 cfm carb Headers and 2.5in dual exhaust Th400 tranny with stock converter 12 bolt rear end with 3.08 gear and 30in tire. My current cam is 204-214 @.5 and 420-440 lift with 112 lsa. My question is... what would be the best cam for performance and milage? In getting 18 mpg now if I keep my foot out of it. Wouldn't mind going a touch bigger if it won't kill me. Thanks |
09-04-2017, 06:13 PM | #2 |
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Re: Cam vs mpg
18 mpg in these old bricks is great. How much mpg are you willing to lose?
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09-04-2017, 06:32 PM | #3 |
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Re: Cam vs mpg
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09-04-2017, 09:46 PM | #4 |
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Re: Cam vs mpg
I would leave it alone and brag about the gas mileage if it was mine. If you change the cam you are going to lose gas mileage and take the chance of creating a problem where there is no problem.
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09-04-2017, 10:48 PM | #5 |
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Re: Cam vs mpg
Crower used to sell a system in the early '80s with really high static compression ratio pistons and special custom cam with late intake valve closure to manage the peak pressure without knock. I forget what he called it. I think Hot Rod tested it and they would up making 25mpg in a street rod.
It was a neat idea to market it, but he wasn't the first to invent it. Sometimes called the Miller cycle.
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09-04-2017, 11:00 PM | #6 |
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Re: Cam vs mpg
I agree with leaving it alone.
But if you must change the cam, I would go with a more modern grind and stay with a 112 LSA. Call a few cam companies' tech dept and get their input.
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09-05-2017, 08:47 AM | #7 |
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Re: Cam vs mpg
The cam/specs you have now IS the best blend of performance and mileage. If you get a big enough cam to actually notice a difference over what you have now (like 218* @ .050" or bigger), you'll need a higher than stock stall in the torque converter to get the most out of the new cam and then your mileage will start to suffer.
In my '65 Bel Air station wagon (daily driver) I have a small cam in it similar to what you're running and I get 17mpg in it with 3.08's & TH350 w/stock converter and 28" tall rear tires. It's a 350 with an Edelbrock performer intake & Holley 650 vac sec 4bbl carb. In my '05 GMC w/5.3, I put a 215* @ .050" cam in it, mileage stayed about the same (18), but then I installed a 2600rpm stall torque converter to take full advantage of the bigger cam and promptly lost 2 mpg. 18mpg in your truck with a strong 350 is great. If you're happy with it now, I'd weld the hood shut and drive it.
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09-05-2017, 09:02 AM | #8 | |
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Re: Cam vs mpg
Quote:
Regarding cam swap. I agree with above posts. If the truck is getting 18 mpg on the highway I wouldn't tweak one thing. As a poster once said "weld the hood shut and leave it alone."
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09-05-2017, 05:15 PM | #9 |
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Re: Cam vs mpg
I'd agree with not touching it. ..18mpg from a smallblock and without a od trans is like finding a unicorn. ..or bigfoot......or bigfoot riding a unicorn
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09-05-2017, 11:36 PM | #10 | |||
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Re: Cam vs mpg
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It's funny because it's true! Gary
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09-06-2017, 01:26 AM | #11 |
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Re: Cam vs mpg
Keep the cam and swap in a 700R4.
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09-06-2017, 01:05 PM | #12 |
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Re: Cam vs mpg
I would have to agree.. leave it alone and drive the wheels off.. that is great mpg..
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09-06-2017, 06:40 PM | #13 |
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Re: Cam vs mpg
Well I was really wanting to put a bigger cam in it so I could get that lopy idle sound I like so much and not lose performance.
Thank you all |
09-06-2017, 06:54 PM | #14 |
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Re: Cam vs mpg
When I eventually get mine going it will have an equivalent to the classic 1970 Corvette LT-1 cam (GM p/n 3972178) in it. I'll post how that goes. Of course I don't have the "before" case, only the "after" case.
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09-06-2017, 08:49 PM | #15 |
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Re: Cam vs mpg
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09-06-2017, 09:04 PM | #16 |
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Re: Cam vs mpg
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09-07-2017, 07:14 AM | #17 |
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Re: Cam vs mpg
I lean out the idle circuit a little bit to roughen the idle a tad to imitate a big cam. It sounds cool idling through the fairgrounds. As soon as I touch the gas it's smooth as silk though. I have about the same cam with 3.08's in my truck and Impala. This is on my hot rod Impala not my work trucks though.
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09-07-2017, 08:52 PM | #18 | |
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Re: Cam vs mpg
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If you want a big lopy cam get a light weight car and build you a drag racer. If you want a good cruising truck with power in the low rpm range where you need it leave your motor alone. |
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09-07-2017, 09:39 PM | #19 | |
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Re: Cam vs mpg
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09-07-2017, 11:25 PM | #20 |
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Re: Cam vs mpg
You just have to ask yourself if having that lopey idle is worth loosing maybe 5 mpg's or more depending on the cam.
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09-08-2017, 02:13 AM | #21 |
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Re: Cam vs mpg
After listening to these guys the 210-218 total lift at .526-.522 sounds like I would be losing out on mileage without gaining much if anything.
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09-08-2017, 02:14 AM | #22 | |
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09-08-2017, 06:21 AM | #23 |
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09-11-2017, 01:25 AM | #24 |
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09-11-2017, 06:38 AM | #25 |
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