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Old 07-13-2016, 12:41 AM   #1
Farmtruck 2
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1970 Custom Camper C/20 tuning questions

Currently my truck is equipped with the factory 402 that has various mods. An Edelbrock performer intake, a custom built and tuned quadratoilet (That came on the truck stock), a custom ground RV cam, the heads that have been reubuilt and gone through that are hooked to port matched manifolds and 2 1/2 exhaust pipes with dual turbo thrush mufflers. I've been thinking that having a built carb, aluminum intake and heads that have been built hooked up to cast iron manifolds seems like it makes the mentioned work somewhat redundant. At some point I'm going to get longtube headers, 3 inch exhaust pipes, some type of x-pipe and dual Black Widow exhaust (Or maybe some type of straight through exhaust if I can't afford the Black Widow's) and I was wondering, what kind of tuning would I have to do to make the most out of the new exhaust system? I'd assume some type of jetting change, but I'd like someone's expertise. Any and all help is deeply appreciated
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Old 03-19-2021, 06:07 PM   #2
unclesalty
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Re: 1970 Custom Camper C/20 tuning questions

Build it for how you drive it.
You must spend a lot of time at the racetrack.
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Old 03-19-2021, 06:20 PM   #3
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Re: 1970 Custom Camper C/20 tuning questions

I think the original design of a quadra-jet carb compliments an RV ground camshaft very nicely. So does the iron manifolds and 2 1/2” dual exhaust. I can see sourcing maybe a manifold with tight runners that’ll keep your intake port velocity high, to sit well with the throttle response and torque curve. Iron out your timing curve and your golden. Wouldn’t the latter items you referred to seem to be counter productive to your build?
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Old 03-19-2021, 08:06 PM   #4
Farmtruck 2
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Re: 1970 Custom Camper C/20 tuning questions

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Originally Posted by unclesalty View Post
I think the original design of a quadra-jet carb compliments an RV ground camshaft very nicely. So does the iron manifolds and 2 1/2” dual exhaust. I can see sourcing maybe a manifold with tight runners that’ll keep your intake port velocity high, to sit well with the throttle response and torque curve. Iron out your timing curve and your golden. Wouldn’t the latter items you referred to seem to be counter productive to your build?
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I had completely forgotten about this website until I got the notifications for someone replying to this in my email lol. In the time since I made this thread, I've done several things to the trucks. Chronologically, I ****canned the stock advance springs and replaced them with 2 "light" springs so all my advance comes in right as I hit the throttle. That made a huge difference, a lot more than I was expecting. After that I installed a set of Hedmen longtubes, 2.5 inch pipes and straight through magnaflow exhaust. I ended up having a change of heart about how much I enjoy the sound of chambered mufflers lol. The truck also came with 2 inch pipes stock, but for some reason I thought they were 2.5 inch back then. After that I ditched the Quadrajet after tinkering with it and having it rebuilt by the guy who originally built it in the mid 90's. With both the body and top plate being warped pretty bad, there was only so much I could do and I was tired of dealing with it. I replaced it with an Edelbrock 650cfm AVS2. It being vacuum secondaries, spread bore and having annular boosters on the primaries attracted me to it. That was also a huge upgrade, although I definetly should've done some more research. I wasn't sure if the primaries were the same size between the 650 and 800, so I went with the 650 to prioritize low end responsiveness, but it definetly limits this carb for future use. After that I messed around with timing some more and gave it a while bunch more initial timing, but idk how much because the marks on the balancer are all weird. Then, when you get the distributor dropped in properly and all the marks line up, the vacuum advance canister hits the intake and you can't get the timing you need lol. Overall I'm happy with the upgrades I've made. I have a while box of ignition based goodies sitting in my room, so I'm just waiting for the weather to not be ****, and then it'll be time for even more upgrades!
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