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Old 09-16-2007, 01:46 PM
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A hot small block 350...

So I'm building a small block 350 to put in a '76 Chevy short stepside, and I'm starting to realize that bigger parts is not always better. This thing doesn't need to do 9 second times, but I have a little money and am willing to sink it here to make the rig fast

My goals are to have something tending more quick than a high top speed, though at the same time I plan to have everything balanced and put together for high RPM's.

Above all I LOVE the rough idle of a high overlap cam, but don't want one at the expense of to much performance.

So here's the question. I have a new Edelbrock 650 carb, headers on straight through duel exahust, and am looking for recomendations for cam, valve train components, intake manifold, and whatever else you think would make this thing quick.

Oh, I have a 400 Turbo W/Shift kit and a 700R4, whichever. Don't know rearend, but can pretty easily get whatever.

What do you all think?

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Old 09-16-2007, 03:22 PM
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In my experience, there are 3 ways to make a vehicle QUICKER.

1. Pass more air through the motor by using a bigger motor or extending the rpm range of the one you have.

2. Using a shorter gear to apply more work to the tire.

3. Bolt a blower on it.

For a mostly street-driven motor, passing more air through the one you have by extending the rpm range (naturally aspirated) doesn't make much sense. It results in a soggy bottom due to the longer cam you must run to support the extended rpm's which must then be crutched up with a looser converter to get "up on the cam" and move the truck from a standstill. You then have the problem of the converter slipping at cruise rpm's, wasting fuel and building heat which must be addressed. And of course with the longer cam, you must build the motor with a higher static compression ratio to support the cam and that gets you into trouble with using pump gas. Given what I just said, using a bigger motor looks to be the better solution to the problem. If you're hung up on a small block, then either go with a stroker kit or start with a 400 block. If you're open to options on the motor, start with a big block. It's a bolt-in in your truck.

Using a blower will make the motor think it's half-again bigger than it actually is and it will still be street-friendly. Build with somewhere in the range of 8.0:1 static compression ratio with good parts in the short block.

As far as the transmission, the 700R4 would be a far better choice so long as you realize that a stock box won't take a lot of abuse. It will give you a 3.06 first gear compared to a 2.48 first gear on the TH400, so getting the truck moving from a standstill will be done easier with the shorter gear. Then, you have the added benefit of an overdrive gear (0.70) in the 700R4 to reduce rpm's whan cruising and save a little fuel and wear and tear on the motor. Using a 3.50 to 3.70 rear gear would give you the best of both worlds, acceleration and reduced rpm's for cruising. (2.59 final drive with a 3.70 rear gear).

If you do go with the 700R4, do some research on strengthening it so it will stand up to the abuse you will dish out to it.

Read this article I wrote for the wiki to understand more about why a shorter gear will accelerate the vehicle quicker......
http://www.crankshaftcoalition.com/w...he_car_quicker

Last edited by techinspector1; 09-16-2007 at 03:32 PM.
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Old 09-16-2007, 03:29 PM
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You're very smart for spending money on the right things instead of the bigger things.

Big payoffs can be found in heads. Cams are pretty much standard. Some companies use different ramp speeds but overall output for a given cam card will be the same regardless of manufacturer. Heads on the other hand can be wildly different. Keep the intake port volume as low as possible while still getting as much flow as possible. An excellent example of this is a Vortec head which flows an impressive 239 cfms with a small 170cc intake port. Most of the aftermarket heads from Dart, World, and Brodix can't match that with 180cc ports.

Flow makes horsepower. Small ports make high velocity which makes torque and drivability. Don't go overboard on 200cc heads since that will sacrifice drivability and torque.

Spending money on heads will almost always pay off. Vortecs will do really well up to 400 hp as-cast, more with porting.

Once you select heads you'll find that you can achieve your power goals with less cam. A good comparison is an old-school muscle car engine vs. an LS1. The old school small block used to make 350 hp, but it needed 11:1 compression and a seriously lumpy cam to compensate for pathetic heads. An LS1 does it with 10.5:1 and an incredibly mild cam. Not to mention, an LS1 is just a whiff away from 450-500 hp with very minor work. That's a good example of how the LS1's excellent heads can make the same horsepower with a silky smooth idle and tons of torque.

I personally would go for a vortec-headed small block in the 9:1 range. Choose a cam to fit your horsepower needs up to the limits of the heads. A cam that would make about 350-400 hp with vortec heads might look something like 212/218 duration on a 112 LSA. You'll get a little lope out of it.

Can't stress it enough: Big power with streetability and torque means most of your money should be spent in the heads.

As far as the tranny is concerned, crunch the numbers. I personally cannot stand the 700r4 tranny. The 3.06 first jumping to a 1.63 second is the largest ratio jump of any automatic tranny ever. GM did it to compensate for the super high cruising gears they put in their cars. What it means is; unless you have a crazy fat torque curve, it will cause your acceleration to suffer by dropping your RPMs too far in the 1-2 shift.

The Th400 is an excellent and darn near bullet proof tranny, but has neither an OD or a lockup TC. You might find it to be a non-issue depending on your torque peak and how much time you actually spend on the highway. You might be able to find a rear axle ratio that satisfies all situations with only 3 gears in the tranny.

For a 4-speed I might suggest a 200-4r... but like the 700r4 it has some weaknesses. It has one of the nicest gear ratio spreads 1-3, plus it has a .67 OD. That means you can run deeper rear gears, have the same 1st gear launch as the 700r4, and still get your highway revs down with the tall OD. Plus you get a debatably stronger tranny with a much more reasonable 1-2 shift.

Last edited by curtis73; 09-16-2007 at 03:38 PM.
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Old 09-16-2007, 03:50 PM
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Curtis is correct. Using the correct heads will pass more air in the same rpm range originally planned.
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Old 09-16-2007, 05:49 PM
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Here is a pretty basic Hi performance 350sbc recipe that will make well over 400hp and a ton of torque (420++ftlbs). It's all bolt on stuff. And it will have the required rough idle without getting carried away.
rebuild your 350 using hypereutectic flat top pistons. Nice if you can get the block "0 decked" to ensure the proper compression ratio and quench clearance using a .040" felpro head gasket.
you can use the stock cast crank, get a new balancer.
assembled Edelbrock E-TEC 170 cylinder heads. Edelbrock Performer RPM air gap manifold ( vortec/etec)
You can use your Edelbrock 650 carb
Isky 280H Mega-Cam #201280
1.5:1 rockers (narrow body for etec heads)
long tube headers and 2.5" dual exhaust.
Use a high performance HEI vacuum advance distributor. It will need minor advance curve tuning to dial it in. ( this isky cam will want a increased initial advance at idle (18 to 24degBTDC) and around 31 to 36deg total mechanical timing. This will involve limiting the mechanical advance travel and swapping advance springs to dial in the advance curve. I like the MSD "ready to run" billet distributor with vac/advance, needing only a 12v power source and a MSD Blaster 2 coil.
It has a fully adjustable advance curve and instructions and all the spark power you'll ever need. Its reliable and goof proof.
It is critical to match the rear gear ratio and trans torque converter stall speed the your application. I would suggest selling the TH700r4 to someone you don't like and work with the TH-400 trans. I would use a 11" "3000 stall" torque converter and a 4.11:1 rear gear ratio and a 28" tall rear tire. If you want a taller or shorter tire use a corrisponding higher or lower gear ratio to get the same effective overall gearing. Your cruising rpm with a be a just right 3000rpm at 60MPH. eg: For a 30" or 31" tall tire use a 4.30 or 4.56 gear. For a 26" tall tire use a 3.73 gear. This is the right gearing for this combination in your truck for best performance/economy mix. Fuel economy will be reasonable for this type of motor. Overdrive will not help. You'll have the get up and go, power and throttle response you're looking for.
And a good power/drivability compromise with the cool idle sound you're after.
There are many ways to skin a cat but this recipe is pretty well goof proof and will get your the results you're after the first time without having to take out a second morgage.

For "track days" match the 4.11's with a short diameter but sticky Street/strip "DOT tire" (8.5"x26"x15") for maximum performance.
A entry level 150-180HP nitrous system will take care of 98% of the street competition.

Last edited by F-BIRD'88; 09-16-2007 at 06:15 PM.
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Old 09-16-2007, 07:33 PM
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So this is pretty cool. It has finally given me a direction from all the mass of information I found. Thanks very much!

Tech, I thought about putting a blower in, but I'm not sure it's worth the $$. Besides, I don't really think the motor is built enough to justify/withstand a blower. Though I adore the sound, especially with a blow off valve

F-Bird answered a lot of the questions, thanks! If I go with your recipe, which sounds pretty good to me, I'm going to be replacing a lot of the moving parts. Great! Is there any reason I would not want to have everything balanced at the same time? That makes a huge amount of sense to me. Wouldn't that also vastly help my top RPM? What's the thoughts on that?

Curtis, it sounds like those Vortec heads are bowtie brand, but what motors do they come off? I have quite a selection of mills to pull parts from...

Regarding the gearing, I was leaning towards the TH400 already. The rearend under it now (whatever that may be) is pretty dang low so that when you get up to 60mph the RPM's are climbing, at least to my untrained ear and lack of tach. But if you punch it at that point, dang... it moves!! :-D

I definantly like the small block because of the higher RPM and lighter weight. If I tear into this 350 though and find that the cylindars/compression is bad, is there any reason not to make it a 383? I also have a 400 small block, but didn't like the lack of water jackets... even though I have a four core radiator to put in this thing

Would the recipe change dramaticly if I did that? Is there a genuine reason to do that? I've heard awesome things about the 350 and it is currently big enough to fit my ego, at least for a first rod And 400hp is what I was shooting for to begin with. The whole thing sounds like poetry to me, but just thought I would check out other options while I'm here.

Thanks again for all the help! Lots of good ideas. I'll try and get a project journal and pics as soon as I get back. Grrrr... I'm a firefighter (I work communications out on the big wildfires) and got tapped for this fire just when things were getting interesting. While this is funding my project, words can not express my eagerness to get back to that beautiful blue pile of scrap metal...
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Old 09-16-2007, 08:30 PM
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Quote:
Originally Posted by playswithfire
Curtis, it sounds like those Vortec heads are bowtie brand, but what motors do they come off? I have quite a selection of mills to pull parts from...
Any chevy pickup or van with an SBC 350 from 96 and later will have vortec heads. You're looking for casting numbers that end with 906 or 062. Despite what you hear, they are the same exact head, but as originally delivered from GM the 906s have a different exhaust valve seat which gives up a little flow. If they're getting a valve job, its a non-issue. I have an 062 and a 906 on the same engine, no big deal.

Quote:
Regarding the gearing, I was leaning towards the TH400 already. The rearend under it now (whatever that may be) is pretty dang low so that when you get up to 60mph the RPM's are climbing, at least to my untrained ear and lack of tach. But if you punch it at that point, dang... it moves!! :-D
When we get to that point (like once you've chosen a cam and have some other things ironed out) post these questions over in the transmission/rear end forum. We can show you how to crunch the numbers and find a rear/tranny combo that will be just right.

Quote:
is there any reason not to make it a 383? I also have a 400 small block, but didn't like the lack of water jackets... Would the recipe change dramaticly if I did that? Is there a genuine reason to do that? I've heard awesome things about the 350 and it is currently big enough to fit my ego, at least for a first rod And 400hp is what I was shooting for to begin with.
No reason at all not to. If you compared three small blocks, all three with identical heads, cam, compression, etc, but the only difference is that one is a 350, one is a 383, and one is a 400, you would see that the peak HP is very similar, it will just occur at a slightly lower RPM. The torque peak will be improved a bit and also come at a lower RPM. The main difference will be that the 400 with 400 hp will be more "streetable" (lower smoother idle, more torque, lower redline) compared to the other two. It would also therefore affect which rear gears and torque converter stall you would choose since the torque peaks in different places.
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Old 09-17-2007, 12:12 AM
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Ahhh... I'm just begining to understand torque vs. horsepower. So cubic inches are going to dictate torque rather than HP, essentially? Or rather, size has more of an effect on torque? Which granted, is going to get me off the line faster, but with the light back end of this stepside I suspect I'm going to have all the torque I know what to do with coming off the line
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Old 09-17-2007, 01:30 AM
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Well, its complicated but you have the basic idea. Torque is created by peak cylinder pressures; that is to say, when you assemble and engine with certain parts it will run with certain parameters. An engine is a fixed mechanical piece, so the combination of parts performs "best" at one RPM. The combination of parts works together in such a way that the valves opening and closing combined with head flow, carb size, etc, in such a way that at a certain RPM it traps the greatest amount of air/gas in the cylinder for combustion. It is at this point that the combustion pressure is greatest and has the greatest effect on the crank. That is to say, that is where the torque peak is. Horsepower is a way of expressing how the engine makes torque over time. If an engine makes 100 lb-ft of torque at 2000 rpms, it makes less horsepower than an engine with 100 lb-ft at 3000 rpms because the second engine is applying that same torque 50% more often. That's extremely simplified and possibly a bit confusing, but suffice it to say that the "larger" the part (bigger cam, more flow in the heads, bigger exhaust, etc) the higher RPM the engine will need to spin to make its power and torque. All the parts need to be matched so they work together.

On the street, you want your torque and power to come at a lower RPM, so you shouldn't go too nuts with parts.

Torque is the force that overcomes inertia, so torque will launch you and put you back in the seat. Horsepower is still a very effective means of acceleration, but what actually gets you moving from a stop is torque.
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Old 09-17-2007, 01:39 PM
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So, having done a little more reserch, I think I'm leaning towards using Vortec heads rather than Edelbrock heads. $1000 for heads is a little more than I want to sink into any one part at this point, though they sound good. But the Vortec heads also sound pretty solid for this build, and with the Edelbrock Performer Air-Gap intake should be a pretty good.

I'm assuming that the stock valves, springs, etc in the Vortec heads are going to want replacing... right? Or are they good as is, and will match up with that Isky 280 cam?

I'm still pretty hazy on how to know what the valve size and lift should be with any given set up. I now understand that you can have oversized head ports and runners causing you to loose air flow. But can that be an issue with valves? Is anything short of the piston running into the valve a bad thing?

Thanks again for all the help!
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Old 09-17-2007, 04:40 PM
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Quote:
Originally Posted by playswithfire
I'm assuming that the stock valves, springs, etc in the Vortec heads are going to want replacing... right? Or are they good as is, and will match up with that Isky 280 cam?
They need to change. Factory vortec heads and springs are limited to .470" lift. Comp and several other companies sell spring/retainer kits that allow .550" lift. Any more than that and you'll have to do some machine work to the heads; specifically having the valve guides turned down a bit. You'll need better springs with that cam anyway, so just get ones that are good for the higher lift and you should be OK

Quote:
I'm still pretty hazy on how to know what the valve size and lift should be with any given set up. I now understand that you can have oversized head ports and runners causing you to loose air flow. But can that be an issue with valves? Is anything short of the piston running into the valve a bad thing?
You basically need as much valve size as is required. Cop-out answer I know. The larger valves will flow more to a certain extent. Going too far puts the valves too close to the cylinder walls and will start to hurt flow. You'll hear that referred to as valve shrouding. The stock valves in your vortec heads should be plenty. if you want more, you can step up to 2.02 intake valves and 1.6 exhaust valves, but only if you need more flow. I prefer getting flow with pocket porting before valves for the shrouding reason.

how much lift you need is more a fuction of how much the heads flow. On a flowbench, heads will flow their most at a certain valve lift. In the case of the vortecs its at about .500" lift on the intake side, then it starts falling off at .600" lift. If you choose your valve lift for .550" you spend the maximum amount of time at or near the peak flow which means horsepower. Any more lift and wasting time at lifts that are too high and you'll lose power.
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Old 09-17-2007, 05:35 PM
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Great dialog here. Curtis, I think you and a few others are really helping this youngster on his (assumption on my part) way. I just happened to note that "plays. . . " mentioned an Edelbrock Performer air gap. I'd just like to chime in that the Edelbrock Performer RPM Air Gap would likely be a better choice in any kind of performance 350, unless Corvette-like hood clearance was an issue. In a truck, I doubt it would be.
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Old 09-18-2007, 04:59 AM
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Yes indeed, thank you all so much! I have ten times the grasp on the subject that I did before, and a very definite direction. Thanks!

Check out

Crazy street rod

for my next project As soon as this Chevy is up and running I have an '82 Dodge half ton with a 225 slant six that is a perfect candidate for this.

Should be fun!
-David
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Old 09-18-2007, 05:02 PM
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Sweet...keep us posted
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