How do you make 350+hp in a 350??

[chevyc1068]

I'm looking at pulling a 350 out of a 69 c10 that supposedly has about 60-70k miles on it since a rebuild and I'm not for sure how many before that. I don't know because the previous owner put in this engine after the old one wore out, and this one was just a rebuilt one. Though it is still supposed to be a 69 350. Ok, enough with the life history. I want to make this engine produce 350+hp and if possible 400+ torque. So what parts do I need to put on this to do that. I'm looking at rebuilding the stock heads, new cam, intake, carb, headers with dual exhaust, all that good stuff. I will also be rebuilding it, pistons, rings, gaskets, timing etc. But no nitrous or blower systems. I would like to keep the fuel economy fairly high since this will be a daily driver, though I want some power to set me back in my seat when a really romp on it. I need good low end torque but would also like to be cruisin at 60mph and romp on it to pass someone and be able to tear right past them. So first of all do you think I can achieve that much power with an old motor or will I find all the weak spots. So if you made it this far without giving up, any suggestions???

I could really use your input on this.

[redhead69]

hmm sounds like somebody wants a zz4 crate motor..Or build your own for half the price. http://store.summitracing.com/partde...9&autoview=sku

[bigblockorange]

I built a 1970 R/S Camaro a few years ago I used a 70 350 with 2.02 proflows in a set of double hump heads and the Elderbock performer package cam, intake and carb. It was .030 w/ flat tops. I had a 3:55 rear and a 5 speed. It ran on pump gas true HP unknown but a kick in the pants for a close to stock SBC. No regrets other than I sold the car 10 years was long enough. The key is match the cam,intake,carb,compression and valve size. BBO

[Jtrux]

I'm really surprised you didn't get a zillion responses on this one. I think the most limiting part of your buildup according to what you said is the heads. Personally i'd put aftermarket heads on it. There's a lot of technology out there, why not take advantage of it. 2.02 valves would be the right choice and I would suggest 180cc intake runners because they'll build better lowend torque. On the shortblock end of things, you don't need a whole lot because 350 hp isn't anything crazy. You can run stock cast pistons although it never hurts to have forged. You said you want to make torque so i'd try to go with 9:1 compression. I'm partial to Edelbrock intakes so i'd pick their RPM Air-Gap intake with a 650 Holley double pumper (I like Holleys, I think they are realy easy to fine tune) on top. Roller rockers are definitely worth the expense too. Go with a an Comp Cams Extreme Energy cam like a 268 grind or maybe a 274 grind.

...or buy a crate motor and let them do the thinking for you

[Billla]

1HP/CID at the flywheel, right? And I'll assume you want the least expensive route to get there

• .030 overbore, hyperutectic pistons
• 9.5 - 10:1 CR **NO HIGHER**
• Ported stock heads with larger valves -or- new Vortecs
• CompCams 12-231-2 4x4 cam
• Edelbrock Performer intake
• Edelbrock Performer or Holley Street Avenger 600 CFM carb
• Summit or other HEI distributor

Will deliver somewhere close to 350 FWHP @ 5000 RPM, and > 400 FWTQ 2000-4500 RPM. Basically this is a straight shortblock overhaul upping the CR a bit and then investing in heads and cam. Should be able to get this built for ~$2500 depending on parts condition, what you reuse, etc.

[brak]

Quick way to gain some ponies... Stroke it

Provided the rods are of an acceptable length (depends on the crank), you could swap to a "stroker" crank (383 maybe?) without rebuilding the engine completely. heard of people using a 400 crank with good success...

Just flip that puppy over and swap it.

[The Hard Way]

Originally Posted by brak

Quick way to gain some ponies... Stroke it

Provided the rods are of an acceptable length (depends on the crank), you could swap to a "stroker" crank (383 maybe?) without rebuilding the engine completely. heard of people using a 400 crank with good success...

Just flip that puppy over and swap it.

You have to either have different pistons or shorter rods with a stroker crank, otherwise the piston will smash into the head.

I think Jtrux and Billa have offered good advice. You can always check the newsstand for Hot Rod, Car Craft, Chevy High Performance, or Super Chevy, they typically have engine builds pretty frequently. 1hp per cubic inch is very doable, especially if you copy a dyno-proven engine exactly, that way you know the parts are matched to work together.

[Jtrux]

Originally Posted by brak

Quick way to gain some ponies... Stroke it

Provided the rods are of an acceptable length (depends on the crank), you could swap to a "stroker" crank (383 maybe?) without rebuilding the engine completely. heard of people using a 400 crank with good success...

Just flip that puppy over and swap it.

The main journals on a 400 are smaller than a 350 so you need a special spacer. Not only that but you can get a NEW 383 crank that'll drop right in for under 300 bucks or maybe less.

[Billla]

Originally Posted by brak

Quick way to gain some ponies... Stroke it

Most common "stroker" for a 350 is the 3.75 stroke for 383 CID. I can't see any way to do this without a rebuild, IMHO. At this build level, 28 CID (383-355) nets ~28 HP and ~28 TQ, and you should figure that a stroker adds about $500-$700 to the price of the build.

If you need to junk the crank, then a stroker gets way more attractive as you have to buy a crank anyway

I'm not saying you can't build an el Cheapo stroker - you can; it's done all the time - but they're typically not a very durable engine.

[chevyc1068]

Yah, I was really hoping for more posts than this to, but I'll take what I can get. I'll be running 3.73 gears so that should help a little bit. Do you guys really think that 600cfm would be enough uumph to get me up and going at WOT? Will it keep me out of the secondaries at 65mph?

So If i were to go with the vortec heads which ones should I use, and what else do you need to complete the valvetrain? Otherwise I figure on porting the heads, and redoing them that way.

Also any suggestions to get more power would be very welcomed. And I assume that you think that this old engine will be able to handle that much power??

Thanks. Keep it coming.

[49studebaker]

Originally Posted by chevyc1068

Yah, I was really hoping for more posts than this to, but I'll take what I can get. I'll be running 3.73 gears so that should help a little bit. Do you guys really think that 600cfm would be enough uumph to get me up and going at WOT? Will it keep me out of the secondaries at 65mph?

So If i were to go with the vortec heads which ones should I use, and what else do you need to complete the valvetrain? Otherwise I figure on porting the heads, and redoing them that way.

Also any suggestions to get more power would be very welcomed. And I assume that you think that this old engine will be able to handle that much power??

Thanks. Keep it coming.

600 cfm is big enough. A lot of people make the mistake of over carburating.

[Idaho Outlaw]

Originally Posted by chevyc1068

Yah, I was really hoping for more posts than this to, but I'll take what I can get. I'll be running 3.73 gears so that should help a little bit. Do you guys really think that 600cfm would be enough uumph to get me up and going at WOT? Will it keep me out of the secondaries at 65mph?
So If i were to go with the vortec heads which ones should I use, and what else do you need to complete the valvetrain? Otherwise I figure on porting the heads, and redoing them that way.

Also any suggestions to get more power would be very welcomed. And I assume that you think that this old engine will be able to handle that much power??

Thanks. Keep it coming.

Are you looking for 350HP at the flywheel or at the rear axle? If it is at the flywheel, than your 3.73's don't matter.

This is an area of debate. I had read an article (it's been so long, I don't remember who or when), that explained that many people put too large of a CFM carb on their motor's. And I can see the though process of "more fuel, more power". Yes the motor burns fuel, but it is a big ol' air pump. So long story short, IMO 600CFM is fine.

[cameeks]

This is a good formula you can use to get an idea of what carb to use.
CFM = Engine Size × RPM @ Peak Power ÷ 3456

[chevyc1068]

Well I would like to make 350 at drive wheels, but probably will only make it to 350 at flywheel, unless anybody has some good suggestions on how to make 350 at wheels. Yah, I've heard that statement before to, but I read a book by David Vizard, and he used a 750 holley on everyone of his builds. But if you guys think that 600 is enough I guess I trust you.

[Billla]

Originally Posted by chevyc1068

unless anybody has some good suggestions on how to make 350 at wheels.

Sure: spend more money Seriously, the HP wanted sets the price, and the price sets the HP...you can work it either way

You don't need to take our word on carb sizing - it's physics The only time you really need to look hard at carb sizing is when you're turning the engine past 5500 - 6000 RPM.

It is physically impossible for a normally aspirated 355 to take in more than 600 CFM until you pass 5850 RPM.

CFM = ((CI x RPM)/3456) x VE

[Boog]

Excuse me Murdock. [I would like to keep the fuel economy fairly high since this will be a daily driver, though I want some power to set me back in my seat when a really romp on it]

These two things do not go together well. You can build some good mileage OR good power to set you back in the seat. Which will it be?

[Billla]

Originally Posted by Boog

These two things do not go together well. You can build some good mileage OR good power to set you back in the seat. Which will it be?

I think you can get both, especially in our trucks. The back in the seat thing comes from low-end torque...which is what we build truck engines for generally. A reasonably powerful engine doesn't have to be a gas pig...and shouldn't be - being more efficient.

[chevyc1068]

Well I'm talking above 14 or 15 mpg. I don't want to make less than that. I'm not going to stroke it unless for some reason i would have to buy a new crank, then I might consider it.

Does anybody know of a book or site or something that shows different engine builds and their dynos?

[Billla]

Originally Posted by chevyc1068

Does anybody know of a book or site or something that shows different engine builds and their dynos?

David Vizard's books are generally pretty good for these. You do need to discount the HP he makes with stock heads because he is a wiz of a porter and will put 20+ hours into a set of heads.

Otherwise, head down to the library and spend some time with CarCraft and Chevy High Performance back-issues. CC is doing some really nice work over the last year or so with a new editor that's really a car guy. CHP does OK...but they do a lot of sitting around watching other people do the work.

Popular Hot Rodding Engine Masters is another good one.

The problem with some of these is that they're mondo max HP builds :/

[PanelDeland]

Look at Edelbrock.They have package deals on heads,intake,cam and carbs.With a stout shortblock(use the stroker if you have to buy a crank) and the hei and good tuning 350 ought to be easy.I think 14-15 mpg is gonna be tough with 3:73's but maybe....An overdrive would probably get you there though.

[cooters]

vortec 5.7 heads are definently the best fuel milage/power head for the money. Large valves are not required for low end torque. Strokers cannot be built really cheap because you need to factor in more expensive pistons and never build a 383 without balancing the crank and rods. As for the theory of a 350 not being able to swallow 600 cfm, then why is a qjet 680 to 750 cfm? Volumetric efficency determines the cfm required. To make a true 350hp a 262 comp cam, edelbrock performer rpm intake, vortec heads, and about 650 cfm carb.

[Billla]

Originally Posted by cooters

vortec 5.7 heads are definently the best fuel milage/power head for the money. Large valves are not required for low end torque. Strokers cannot be built really cheap because you need to factor in more expensive pistons and never build a 383 without balancing the crank and rods. As for the theory of a 350 not being able to swallow 600 cfm, then why is a qjet 680 to 750 cfm? Volumetric efficency determines the cfm required. To make a true 350hp a 262 comp cam, edelbrock performer rpm intake, vortec heads, and about 650 cfm carb.

383 stroker pistons generally aren't more expensive - they have a shorter compression height (1.425 vs. 1.560) so actually use less material.

Completely agree that VE determines CFM, which is why it's included in the sizing formula. It's not possible to exceed 100% VE with a normally aspirated engine except with very high overlap camshafts and then only at very high RPM..and most street engines see possibly 75-80% VE.

So doing the math:

CFM = ((CI x RPM)/3456) x VE

CFM = ((350 CID x 6000 RPM / 3456) x 100% VE

CFM = 607

Q-Jets were built so large because GM wanted *one* carb for every 4bbl application. This is why the primaries are so small and the secondaries so large...it was an "autosizing" carb

[cooters]

I will agree with the math billla. I will clarify myself. A carbs rating according to the flow benches i have tested on are not acurate. Therefore a 600cfm carb does not flow the number. On the dyno i have found a 600 edelbrock is to small for a TRUE 350hp motor unless you start playing with the carb. They tend to fall down a little when wot is called for. This being said, they are good for daily drivers as long as you dont drive it hard. I am just going back to the question WHAT DOES IT TAKE TO PRODUCE 350hp. Also keep in mind that on a dyno hp is corrected to sea level, which means alot if you live in Columus Ohio

[Dough88]

If you're looking for engine parts or even fully built engines, you might want to check racejunk.com. I havent bought from anybody there yet but they've got performance parts out the wazoo (used and new).

[blacktruck]

it can be done, quite easily if you have the right parts and knowlegdge on hand. i'd say find a set of L31 vortecs. with an edelbrock performer or rpm intake. scoggin dickey has a pretty good deal on modified vortec heads. i think for like $1k you get fully machined vortec heads, and matching intake. those heads with the right cam should be able to make some decent horsepower. speed is relative to money, how fast do you wanna spend?