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Old 01-23-2019, 12:09 PM
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Ideas for possible 350 mods

I'll ask my question first then add back story. I came across this article and thought it sounded like a good build for my weekend cruiser s10.
Chevy Small Block Build - Mildly Amusing - Super Chevy Magazine
I am using vortec heads with dished pistons and .041 s/q while they used some 882s ported to about the same flow. Also my intake is a non air gap. I would assume the results would be similar. Even if you call it 350 hp this looks like a nice streetable reliable engine. I would go with the next size up and call it good but that one is on a 114 lsa and I don't know how that would compare. Any opinions or other suggestions?
Back story
My project has been on hold for a while until I get the time to trace a wiring issue. I have a buddy that's going to help me with that but it hasn't been fired up since changing the heads and intake. I have an unknown cam that is a bit big if it's what the previous owner says. I did a bunch of tuning thanks to some good advice from members on here and swapped out the 76cc heads. I don't know how much that will help but I would like to change the cam eventually if for no other reason than so I know what it is. How long till I do depends on drivability when I get it back running. Just trying to get a game plan together for now.

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Old 01-23-2019, 01:04 PM
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Speaking just to the camshaft, borrow or purchase a degree wheel then map out what you actually have sitting in there. You might find that it will work fine but maybe needs to be degree'd correctly or possibly advanced if you feel like the bottom-end is soft.
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Old 01-23-2019, 03:41 PM
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He said it was a howards with .480 lift. Looks like that one would have 231 at .050 duration. Idle is pretty aggressive and vacuum is 6-10 depending on idle speed. One of the big problems was that the rpms would drop a lot when I put it in gear. I'm hoping the added compression helps as I would rather not change the cam if I can make it work. Definitely plan to pull the timing cover and get it degreed right if I feel like there's a chance it will work for me.

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Old 01-23-2019, 09:28 PM
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Quote:
Originally Posted by Jojo'sdaddy View Post
He said it was a howards with .480 lift. Looks like that one would have 231 at .050 duration. Idle is pretty aggressive and vacuum is 6-10 depending on idle speed. One of the big problems was that the rpms would drop a lot when I put it in gear. I'm hoping the added compression helps as I would rather not change the cam if I can make it work. Definitely plan to pull the timing cover and get it degreed right if I feel like there's a chance it will work for me.

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Initial timing setting, timing curve, and how the vacuum advance is connected and the amount it adds can also effect idle like this, especially with that much cam duration. Cam like this will typically need a recurve and shortening of the amount of mechanical advance added by the distributor weights and springs, and want an 14-18° initial timing setting, 34-38° Total mechanical, and 10-14° added by the vacuum advance.
Some info help here, pay attention to the carb transition slot setting info included in the distributor section too.
https://www.crankshaftcoalition.com/...EI_distributor

Too low of stall rpm on the torque converter will do this also too....this size cam would want a 2800 stall as about the minimum. 2400 stall really won't be enough.
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Old 01-23-2019, 10:08 PM
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Thanks Eric I think you sent me that link when I asked about the rpm drop before. Initial timing ended up best at 18. I decided to change the heads before going any further with distributor tuning in case I got everything right then had to readjust for the higher compression.
I have thought about a converter but am hesitant since I don't know what cam it is for sure. I checked lift at the rockers and the lifters. I got high 300s intake and low 400s exhaust. Someone said the lifters could be affecting the measurements and it pulls pretty good when the revs get up so I don't know. My thought process is that I know everything else I have and it would make sense to get the correct cam for my combo if the heads and timing adjustments don't do the trick.

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Old 01-23-2019, 10:26 PM
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You can get reliable cam lobe lift measurements off the pushrod tip with a pair of rockers removed...a dial indicator spring isn't strong enough to alter the reading any by moving the lifter plunger.

Can't do a good reading with the rockers in place and adjusted though, valvesprings will move plunger and alter readings.
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Old 01-24-2019, 09:58 AM
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Would that be better than the reading off the lifter? The dial indicator was a little bit angled so it's probably slightly higher. I think the readings were .250 & .275. I didn't write it down but remember doing the math and they backed up my measurements at the rocker

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Old 01-24-2019, 02:51 PM
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Quote:
Originally Posted by Jojo'sdaddy View Post
Would that be better than the reading off the lifter? The dial indicator was a little bit angled so it's probably slightly higher. I think the readings were .250 & .275. I didn't write it down but remember doing the math and they backed up my measurements at the rocker

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Edge of the lifter body, or tip of pushrod should measure out the same as you won't be depressing the lifter plunger if there isn't a valvespring involved. If you got repeatable measurements then likely they are right.

The .250" and .275" for lobe lifts seem awful low though, multiplied by the 1.5 rocker ratio that's just .375" and .412" valve lift.
Need .320" lobe to get .480" valve lift w/1.5 rocker.
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Old 01-24-2019, 06:16 PM
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Yeah I wish I had noted the measurements at the time. Hopefully I can get out and measure at the pushrod pretty soon.

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Old 01-24-2019, 08:21 PM
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Not having the DI parallel to the PR introduces some geometric errors however a careful eyeball would still be close enough for double checking things.
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Old 01-26-2019, 04:31 PM
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Yeah I don't think the small angle the di was at would have made that big of a difference. Kind of thinking doing a bunch of work beyond a measurement to verify and tuning the carb and distributor wouldn't be a good idea. The one piece of advice nobody seems to argue about is pick a cam for your combo instead of building your car around the cam. That brings me back to getting the right cam for the rest of the build if the one in there isn't livable when I get it back on the road.

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Old 01-26-2019, 04:36 PM
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One thing I noticed is although I didn't measure accurately both attempts show a split between intake and exhaust lift.

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Old 01-26-2019, 08:30 PM
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Pretty typical. Cams designed for stock heads often need a bit more for restrictive powers and mufflers.
Something to keep in mind too. In a new cam, the parkerizing can change things a bit. The lift can also be nominal. As intended after break in wear on FT stuff. A few thou isn’t a need to worry. If you check all 16 loves some surprising things show up.
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