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mild building a small blcck

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mwood1985

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im looking to juice up my 350 a littel bit power wise. currently ive got a stock 70s cam 97 vortec heads and a 650 edelbrock with headers. if i have the heads switched to 2.02 1.60 valves and a intake matched to the cam what kinda power increase can i guess on having. tryign to decide if going into a great running motor is worth it
 
couldn't hurt, but are you doing the work or at least have someone that can cut a deal with you? That would help sway your decision.
 
im a mechanic so ill be doing it myself. just wondering from everyone elses experience what kinda increases they got numbers wise from stock
 
what intake are you running now? Stock with a carb adapter or something?

Guessing what numbers you would make is just...guessing. Setting up parts to complement other parts is always best as you know. Seems nobody sells heads with the smaller valves anymore and if you can support the larger valves than the benefits will be great. Include the intake matching (which I'm not too familiar with) and there you go.

BTW, how would you describe the cam or where you are trying to find more power?
 
yeah the previous owner had a pre 87 intake drilled for a vortec bolt pattern. im not a big fan of it being rigged like that
 
the motor is in a mud truck on 38s with 4.56 gears a a 4 speed manual. id like to get a little more torque and hp from idle up to about 5500rpms
.
 
If it's a 70's "smog" cam, opening the valves up isn't likely to help anything. The valves/heads probably already outflow the cam, and the intake isn't likely a restriction either.

I've seen at least a couple of builds/comments from builders that opening the valves up on the Vortecs doesn't help like it does on the earlier heads. Yes, it DOES help support more power, but you need to be capable of making that power first.

As things go, opening the valves up would probably be one of the last places I'd look for power (barring an all out race motor), after proper axle gearing, higher compression via non-dished pistons, better cam, proper quench, timing dialed in, fueling correct, etc.

Edit: was typing when you sent your response. Race car my dad is partners on is running 2.02's at 65-7000RPM on the Vortecs. Cam and compression are what you need at the higher RPM's, if you don't already have good compression.
 
There are a lot better places to spend money than by putting bigger valves in a Vortec head.

Martin
 
It's been close to a decade since I did the research and put Vortec heads on my motor (regular SBC Vortec heads), but what I remember is that they didn't flow more with bigger valves (sometimes less!). Seems like the intake runners and valves were sized together to be optimized from the factory and bigger valves didn't really help.
 
The cam is your problem, leave the valves be, put a cam in it, and maybe a intake if you'd like, and run it. Compression is your friend, but that requires pulling the motor and added expense.
 
10:1, the infamous comp 268 grind, stock vortecs, and a dual plane should get you damn near 380hp and 400ft/lbs of torque... Thats like the basic done a thousand times small block budget build.
 
It all depends on what you want to do. I roughly copied the 406 Impersonator article from chevy high performance, for my 79 pickup. 406 sbc 525 tq. 420hp. I had a 383 with off the shelf edelbrock performer heads, egr intake, cam, and 9.5:1 or so compression. I now have a 400 bored .030 over with scat 9000 series crank and rods and flat top hypers at 10:1+. The heads and intake had extensive work done by a porting guy that does a lot of race work and has done some engineering for nascar type engines. The cam is a comp 270 magnum. Vortec heads would have been similar if also modified by the same guy. He said you trade better spark plug placement with the vortec for the aluminum and higher compression capability of the edelbrock. The edelbrock parts didn't flow worth a crap in stock form. He matched flow capabilities of a non-smog well known manifold, with the edelbrock smog legal part.

It wasn't cheap to do a great sb 400, but the torque over the 383 is amazing. It also blew cleaner than the average 79 sb 350 on the smog papers. I also am only running a 600 elelbrock afb carb and that engine should have at least a 700 cfm carb. At 5500 rpm WOT it is still pulling 5 inches of vacuum with at most 1.5psi of exhaust pressure on a single 3" system.

I put a new gm 5.7 crate engine in my 88 K5. It runs good, but really could use more power. My budget was small and being tbi, it would have been more work to get more power. Go with as much power as you can afford. Like others said, and my uncle told me long ago-when my engine was stock, you have to upgrade all of it to match and work together. I probably have an easy $8k into my engine. It has tons of upgrades and great parts. The oil pan, timing cover, and air cleaner housing are stock. That is about it though. The rest has been upgraded to match the capabilities of the other parts.

I picked up a used VW based dune buggy (tubing frame attached to original rear axle assembly and front beam). The guy I bought it from claimed to spend around $5k on a 1915 engine and $2k on the non-bus transmission. Others confirm that it is easy to spend that kind of money to get good performance levels. Engines (especially older designs) are not cheap when it comes to performance.

There are some parts that are less expensive and ways to do things more economically compared to what I did, but power will still require a total package to work together and some decent money.
 
Engine

I just rebuilt mine in my 77 k5 its a 71 vette short block with the pink rods and cast crank, I put hyperutectic 2 valve releif pistons 9.76 to 1 compression. My heads are 62 to 65 327 fuelie heads with 194 150 valves mild port job. Weiand stealth intale edelbrock 650 and a summit racing cam n lifter set with 272/282 duration with about 460 468 lift (i dont have the cam card with me). The heads have stainless valves too. I asked the guy at the machine shop who pressed my wristpins how much power id be making (he has a dyno but I cant afford it) he said about 350 give or take. He also said 194 valves are better in a truck cause trucks need torque and 202 valves are for high rpm power. My motor can handle 5500 6000 no problem. Just a comparison for you id leave the valves alone if I were but a mild port job will do your motor good.
 
Intakes and valve size...

When selecting an intake, keep in mind that the Vortec head has a taller, raised port location that does not match up well to non-Vortec intakes. If the intake was ported to match the height of the Vortec runner, then it would be so wide that the flow numbers would drastically be reduced. If the Vortec head was 'ported' to match the intake, the mouth would be so wide that you would lose torque in gobs due to the CC increase. You should find at least 10+ hp in the 3500 to 5000 rpm range with just a standard Vortec -based intake that has the correct runner location, not to mention a realistic 15+ ft/lb of torque to be had up to about 4000 rpm.

Vortec combustion chambers do not lend well (from the factory) to larger 2.02 valves due to shrouding of the intake valve at over .200 lift. When we did my Vortec engine, we did a flowbench test between my 1.94 heads and a customer's 2.02 heads and found that they flow similar numbers to about .200, then my heads actually were better to .400...and his started to outflow mine after .550. However, the cam I selected was tapped out at .515 lift (even with the 1.6 rockers) so the 1.94 was beneficial. Once we cleared out some space in the combustion chamber for the 2.02 valve, he picked up approx 15-20 cfm of flow from .300 to .600 lift, so you would want to look into a larger valve only if you budgeted to have the combustion chamber clearance to help unshroud the intake valve and if the engine was to see higher RPM than stock on a regular basis. If this clearance is not done to correctly keep the intended shape of the chamber, quench and flame travel will suffer, negating the benefits of the Vortec head to begin with. Overall, I say it it would not be any advantage in a Blazer/Jimmy engine so I am sticking with the 1.94 Vortecs.

Dos centavos,

MLRTYME
 
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