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Discussion Starter #1
Looking for help in a few things for a first build. Hoping for 350 hp and a flat torque curve of 350 or more if possible with a static cr of 9.0-9.5 on cali 91 pump gas working below 6k rpm (5500 is possible). I have a free set of vortec heads that need a good cleanup and valve job that ill be using.
Parts i have on my list to use.
Pistons: https://www.jegs.com/i/Sealed-Power/844/H345DCP/10002/-1
Stock 5.7 rods
stock ~64cc vortec heads
stock crank
carb: 600cfm edelbrock performer mechanical secondary i already have
intake: jegs vortec intake
cam: 12-205-2 - High Energy™
going in a 74 swb c10 with a th350 and 3.08 gears going to be 90% street driven and taken to the strip a few times a year

does this sound like a solid reliable build on 91 octane pump gas with that cam?
i was hoping to keep the stock converter if possible, trying to scrounge as much as i can budget wise but remain reliable
 

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Discussion Starter #3
any real suggestions on the cam? vortecs being limited on the lift i want to try to avoid getting them machined for a higher lift but if i gotta do it, i gotta do it.
 

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You won't like the 1.548" compression height of those pistons. They will put the piston down in the bore by 0.012" more than the stock pistons, making engineering a good squish/quench into the motor impossible, without severely cutting the block decks. Not recommended. It's too late to begin a build for you this evening, but if nobody steps up to the plate, I will try to help you tomorrow.
 

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Discussion Starter #7
thanks a ton. ive seen you on this forum giving out some extremely educated help when i just lurked the forum. that makes alot of sense about the pistons. it seemed a bit low of an advertised cr for flat tops on a 64cc head (9.3) right? would love to have your input if you have the time tomorrow
 

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Also if more info helps I am picking up the core monday and do not know if the pistons would be any good to reuse (maybe). It is a cheapo 100 dollar 350 long block that has been in storage for years so who knows. pictures looked like it was a bit oily from regular use so its not a dry rusted stored block
 

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lets get your core and pull it apart. Measure everything and let Richard look for the parts. He sometimes even supplies part numbers. Draw up the plan and get er dun,,,
Now is a good time to tell us what the application and driving style will be?
If you tune for 5500 rpm you could make 375 hp and 350 torque with out troubles. Also state your budget?
L
 

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Discussion Starter #11
like the original post said almost 100% street driven taken maybe 25 miles at most on the freeway to the strip and back. going to be in a 74 c10 swb with 308 gears and a th350 with a stock converter. 375hp sounds awesome. im looking for the kick in the back feeling that carries when taking off from a stop and from a downshift from a nice torque curve more than chasing high revving horsepower if that makes a difference. budget wise im trying to save wherever i can but if somethings got to be done so be it. the free heads and 100 dollar core might be an indication of my budget. thanks in advance for the help.
 

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For neck snapping power you need to get the RPM up faster. Search the junkyards for a donor truck with 3.73 or 4.10 gears, and swap the entire axle. Make sure you get an open differential for the swap, not a G80 Gov-Lok, since there are several brands of limited slips you can swap into the stock open differential. The 4.10's are very common in the 3/4 ton trucks, often with a very strong 14 bolt axle, but then you would have 8 bolt wheels. 3.73's were an option in the 1/2 tons.

You can also run smaller tires, but I think they look silly with the large truck wheel wells. 4.10's and 31" tires aren't too bad for freeway driving, and they look right on a normal height truck.

Make sure you use a torque converter that is a good match to your cam. Usually something around 2500 rpm is a good compromise, but I would ask the cam manufacturer. If you want to keep your stock converter, you may want to limit cam duration, which might keep HP down to 325-330 due to the milder cam. A cam that is set up to max out at 5500 RPM is unlikely to have the torque you want at 1500 rpm coming off a stoplight.

Bruce
 

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Discussion Starter #13
Good points, I think I can manage the 100-200 bucks for a 2500 converter but not really looking to change the rear gears right now. With 275 60 15s on it it's already at 3000rpm at 75-80mph. Plus ths added cost.
 

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Discussion Starter #14
Also 5500rpm isn't set in stone. Lower rpm is fine with me. Might keep the engine together longer as well right?
 

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5500 rpm is very mild. Most LS engines rev that high from the factory. Stick with Richard for a matched parts build.
Many options for a 363 (cheapo stroker) or other internals to add inches.
well tuned 375 hp engine doesn't need much of a convertor. Lots of parts that help low end torque, IE: dual plane intake/high velocity carb or spread bore, Vortec heads with short intake duration with minor exhaust split and long tube small diameter headers,,,
 

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You don't need to worry about your max RPM. You need to plan for what RPM that flat torque curve starts, and use it effectively.

As Vinniekq2 explained, there are several things you can do to help build your low end torque (dual plane, headers, etc.). However, you still have a heavy vehicle and 3.08 gears. Swapping out to 3.73's would really wake this combination up if you plan to keep your stock TH350 converter and stock height tires, but want to be able to try it out for weekend drag races.

Swapping your entire rear end for a lower ratio one from the junkyard is signifiant physical labor, but not challenging or expensive compared to the work you are doing on the engine. AFAIK, the only thing you need to check is how the driveshaft attaches to the axle.
If you scroll down on this web page to the listing for axle ratios, you can see what was offered in different years. 1973 - 1987 Chevy Truck Specs, Engines, transmissions, transfer cases, and rear ends, gear ratios - Chuck's Chevy Truck Pages

Bruce
 

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OK, to start with that's a crappy piston it's one of those rebuilder pistons that sits low in the bore (shorter than factory 1.56 compression height, pin center to crown) these are for maintaining stock compression an a decked block that the mass rebuilders use.

Two, for a big truck you need either more displacement which generates more torque or with a smaller engine more rear gearing to push it further up the rpm range to generate more horespower that you then trade out as torque. That's the rocket science, there ain't no way around short of boost. For a heavy street driven vehicle it's easier to live with a larger motor turning slower. These last longer and are way easier on your butt and hearing than a smaller motor all twisted up to find some power. To that end for a few dollars more building a 383 out of the 350 is the smart choice.

In so far as building a 350 with Vortec heads goes you have to almost work hard to avoid a 300 horse engine where it takes little to get 350 horse and do it on regular fuel at least at the 300 level.

Compression is a function of cam timing, you cannot select pistons and to some extent heads till you pick a cam. For a spectrum with the L31 heads at timing of about 200 degrees at .050 lift easily builds a 300 horse 9.0 engine. Pump that to 220 degrees and 9.5 and with stock valve train and mild headers you,ve got 380 give or take 5. Getting serious with valve train parts, big headers, carb, and intake and with L 31 heads you can easily pull over 400 horses from a 350 with these heads so 'yes' they rock.

Keep in mind that any power improvement installed ahead of an old automatic quickly puts you in line for a new automatic. Especially anything that isn't a TH 400.

Bogie
 

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I like Vinnie's idea of waiting to see what you have before even thinking of parts or procedures. The block could have been already bored 0.060" over and is toast.

And Bogie knocks it out of the park in post #17....

75GMCK25 (Bruce) said it best as far as gears.....if you are looking for neck-snapping performance, you are going to have to change gears and converter. And trust me, 100 to 200 dollars will not get you a converter that will do what you want it to, much less last for any period of time. You get what you pay for.

I have always said that hot rodders begin on the wrong end of the vehicle, that they should build the correct rear differential FIRST, then move toward the front to make improvements there. Often, the vehicle will be so much more fun to drive with the correct gears, that mods to the motor/converter might be unnecessary. You are in the correct neighborhood with the cam to support a 4-speed auto trans, so that may be an option for you as far as engine rpm's and fuel mileage. A freshly bored and honed 350 with a fresh set of the correct pistons (the ones you found have the correct compression distance, but don't have enough dish to them. They would create a 10.15:1 static compression ratio when used with the L31 heads and that could create a problem on pump gas) along with the set of L31 heads with a fresh 5-angle valve job, Alex's springs and the studs pinned with a Mr. Gasket kit would support even more lift while maintaining about the same duration that you have chosen. The L31 heads will support lift to 0.500", but pretty much quit flowing more after that.

I would use a high-rise, dual-plane intake manifold such as the Edelbrock Performer RPM 7101 or the Weiand 8150 Speed Warrior. I ADVISE AGAINST USING AN AIR GAP MANIFOLD ON THE STREET.
A good set of 1 5/8" headers with minimum 3/8" header flanges would be my choice for exhaust, along with an X pipe or H pipe immediately after the collectors.

With a short cam, a 2000/2500 rpm stall converter that has the lock-up feature for runnin' the freeway might be the hot tip. An OD trans, using a 3.73 rear gear, is a killer combo.

I will direct your attention to another Hotrodders thread from a few years ago to explain the diff swap.....
http://www.hotrodders.com/forum/easiest-best-option-rear-end-swap-1982-chevy-silverado-c10-364018.html

You said this.....
"With 275 60 15s on it it's already at 3000rpm at 75-80mph. Plus ths added cost."

Gomezbzzt, let's get serious here for a moment. I don't think you are going to get what you want for what you want to spend. You're going to either have to come up with more money or cut back on what you want the truck to do. One or the other. That's my opinion. What I have laid out above will do what you want, but it will cost more than you want to spend, I think. There used to be a sign in the speed shop I used to go into all the time. It said....."Speed costs money, how fast do you want to go"?

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Discussion Starter #19
I'll definitely be opening up the core before trying to order parts. Just wanted an idea. I keep hearing this "neck snapping speed" that I'm not really looking for. To give some perspective on what the truck is now it runs a 15.8 with 3.08 gears that to be honest I'm pretty happy with, a th350 with an unknown shift kit harsh enough to bark an open differential on the street, tail wind, on a cold night, after sacrificing a goat... Can I safely guess it makes most likely around 250hp? less?
Sorry if I gave the wrong idea of what I was looking for. 350hp was ideal but I'd be alright with something I'd get on a budget. As for the "200 bucks for a torque converter" I just did a quick search on prices and I was actually expecting in the 2-500 dollar range. Where should I start? This is an exercise and learning experience to build my first engine as much it is about picking up power so as far as budget goes I want to learn to do things right so I don't have to do them again. I am budget conscious but I plan on doing this build over a span of months slowly getting research and advice, and making a list. I would like to keep the heads I have now and keep it a 350 in the end.
 

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"I keep hearing this "neck snapping speed" that I'm not really looking for."

Really? Well, what I was going on was the statement that you made in post #11......

"I'm looking for the kick in the back feeling that carries when taking off from a stop and from a downshift"

If that isn't really what you want, then let's talk after you disassemble your motor and have a better idea of what you're working with.......:thumbup:

I would strongly suggest that you do all your homework about the L31 heads and find out everything you can about them. For instance, you might learn that the excellent flow characteristics of the heads can be attributed to the valve job that the factory did on them. I would very strongly advise you to emulate that valve job using a machinist who knows what he is doing. Here's a good starter tutorial for you....
http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head

And here is some of the best reading you could do to understand the use of a flat tappet hydraulic cam and tappets in a world that has eliminated extreme pressure lubricants from off-the-shelf motor oils.......
http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks

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