I recently replaced my 2.8 v6 last year with a carb 96 vortec 350, specs below. Well recently its just became too tame for me. I want something that will throw me back into my seat and just pull hard and have great torque. Is there anything I can do to this motor to help get what I want out of it? I'm running a 95 lt1 camshaft, Alex springs and the rest is stock.

 

I built a vortec headed 224/230 xr276hr (if I recall) motor for my brother. Car has 3.73 gears and a 2800 stall and moves pretty good.

 

GOOGLE is your friend .A multitude of Vortec hot up articles ; only limited by your budget ( which you don't state? )

http://www.hotrod.com/techarticles/e...k_chevy_build/
http://www.chevyhiperformance.com/te...e_roller_cams/

What gears and stall do you have ?
They go along way to the SOTP effect without changing the Hp

 

I'm running 3.42 open gears and a stock stall. I read up on one article from hotrod magazine where they made around 500hp but couldn't find one. My budget is based on $8.03 an hour and around 60 hours every two weeks. I normally have around $200 out of each check free and clear after my bills are paid. I guess what's spoiled me is if riden in an lt1 third gen and an 04 gto with a 5.7 ls1 with a tune and 6 speed with monster clutch and those cars both hauled pure *** when I was in them. But the gto pulled harder than anything I could imagine and I want like to do that.

 

Get some gears and converter before doing anything to the motor, save up for a decent converter. A simple cam swap with gears and converter should do the trick for you

 

Any recommendations on gears and the converter?

 

Did you do the low buck or free stuff? Like optimizing your ign. timing, rejetting your carb, or making a cold air dual snorkel air filter.

 

Not really cheap or free. Rebuild the whole motor to stock, bought the lt1 can used, new higher lift springs, new rebuilt trans and new converter. Rebuilt the carb. And new distributer, plugs, and wires

 

Did You tune it? That was my question.

 

That's my question too. An engine thats not optimally tuned will always dissappoint. And there's a big difference between 'runs good' and optimally tuned.

 

I had my dad tune it so I'm not really sure. I've never tuned a motor and this is the first I've built. I do know my air bleeds are set to 3 turns out, regulator is set at 5psi and dizzy is running off manifold vacuum on the carb( driver side port)

 

Well the air bleeds are only going to set the fuel mixture at idle. It should idle nicely at a low rpm, like 600-ish. That doesn't mean the rest of the carb is correctly tuned. Those jets may be lean or rich. Is the secondaries opening when they're supposed to? Your regulator being set at 5 psi is good, as long as it has a good supply of fuel to send that pressure to the fuel bowl(ie no restrictions, clean filter etc). As far as vacuum to the distributor, which is best will vary motor to motor. I have the most luck with manifold vacuum though. But more importantly is where the timing is at any given time. Not just base setting but the whole curve. When is the timing "all in"? What is the total timing? All this comes into play and should be tweaked/tested to get it nailed down what the engine likes best. I'd suggest searching the internet to find tuning articles, see how its done first. If you're not mechanically inclined enough, or don't want to screw things up, then see if there are local dyno tuners.

 

Dont worry about gears. 3.42 is plenty. I prefer 3.73 but you wont notice that little of a change. The open rear will really start holding you back once hp does increase, if it aint some already.

Optimizing the tune for whatever combination is a must to get your money's worth. I may have missed it but do you have headers already?

You can also look at going to a larger cam. Combining a cam and a good converter will make a big difference.

The main thing is to remember that you will always find somebody that has a faster car. Unless you have a huge budget, which you dont, there are times you have to stop chasing after them. Save your money, do your research, be realistic about what you want, then plan out the build, once.

 

I have a vortec in my 96 chevy 1500 lifted 9 inchs on 35s engine is stock before i touched anything it was a dog added cold air and headers straight piped exaust has cats but punched them out now truck will smoke tires at 40mph the vortec needs to breath if its restricted it will never move how u want it i kept up with the new ford raptor the wieght difference from truck to car is huge ur car should be a torque monster. Im in the process of swapping my iroc to the vortec not close to done but will post up when done

 

sorry for the late reply guys. I'm not running headers, running stock tpi manifolds into a stock 3" y pipe then back to the original v6 2 1/4" exhaust system. I want and plan on going to a larger cam and stalled converter and switching to a better exhaust system to get me away from the stock setup. I'm not wanting to chased cars but I'm wanting the seat of the pants feeling, I want to feel shoved back into my seat untill I'm off the go peddle. I want to feel gs basicly. Right now I'm re doing my timing and cleaning up my fuel system and fixing a transmission leak on it then I'll start looking at different specs.

 

I hear ya. Do the exhaust first. Then save up for the cam/intake/converter.

 

you might want to keep in mind the narrow part of a standard vortec head port restricts flow above about 4700rpm on a 350 enough that power tends to start dropping off compared to a larger more effective port size, so it makes much more sense to cam the engine to operate in the 1500rpm-5500rpm power band.

http://forum.grumpysperformance.com/...php?f=44&t=529

http://forum.grumpysperformance.com/...php?f=52&t=401

 

what if I were to port the heads?

 

Google it
Not generally recommended to port Vortec heads because it destroys where they work best ; mid range
If you want to pull big revs pick another head better suited

 

One thing leads to another.Engines being a air pump means there isn't a stand alone part that will make a difference like a cam change.Take a serious look at the spec's of what you have to see if it is under cam.That has to take into account the SCR compatibility with a cam as only one part of the consideration.There is little or worst nothing to be gained by a cam that over powers the heads intake runner or the intake it's self or doesn't mate up with the SCR so it forced the exhaust gases back into the incoming intake a/f mixture or a exhaust that bottle neck's the exit.

Maximize your current set-up by bring the into it's power band sooner.Then move on from there.

 

All of the above but first and foremost...headers. Even a set of shorties with a decent y-pipe will make a noticable difference over the manifolds.
If you haven't already, get an good intake manifold.
Those two things combined with your heads and even that cam (which you might want to save for next) will put you back in your seat.
I've been there and done that. I have time slips and specs to show for it. It might not keep up with a new GTO but you'll surprise a few people.

 

Nothing will help until you get rid to the 2 1/4 exhaust.

 

AGREED....My STOCK Express had dual 2.75" pipes back to the muffler and a single 3" pipe out of the muffler. I put a set of cheap pacesetter built summit racing brand shorties on it and stuffed it with a stock GM 96 LT4 cam advanced 4* with 1.6:1 crane full roller rockers WOKE it up even with my 3.42 gears and stock 1,600 stall. The LT1 cam the OP has is very similar. Even my 6,200 lbs Express conversion van would jump pretty good when I got on it. Crappy CSFI intake and all.

 

Exhaust change??. Well yes and no. Exhaust systems tend to work towards high rpm ranges. And when you do a rear end gear change it kind of forces you to do something about the exhaust system because now your into the power band sooner at a higher rpm. The nice thing about the o/d trans is allows you to do those deeper gear changes and you still have a reasonable cruise rpm. The same kind of thing with a looser still lock up t/c. That will cause you to must have a aftermarket trans cooler which you should have in any case. Because either a higher stall or a gear change needs extra cooling. If you where to do a chassis dyno tune to see what you have at the rear wheels,that would convince you the need for all the above.

 

An improvement in the exhaust will help everywhere in the rev range. Upper rpms certainly however the aid to low engine speed torque is undeniable. More torque equals more hp.

 

Skinny,never seen a reliable source dyno comparison curve(not one from the comic books trying to sell headers)that headers does much below 3000 to 3500 and up. It has to work that way because the scavenging effect needs rpms to start working. The pause effect increases at it goes higher in the rpm range.

 

There's plenty of data out there to support the use of headers in even a mild build.
Yes, I agree with the scavenging but there a more factors involved than just the headers for that to happen.
Here's a graph from one of Vizard's books. I don't think he publishes in comic books. I also don't he publishes papers for advertising or parts manufacturers. Although the graph doesn't show any data below 2500 it's easy to see that at that rpm and, by extension, below that, there's a definite benefit to headers and a free flowing exhaust. Don't get me wrong, you won't build a super car just by swapping out manifolds however, it's a basic first step in improving an engine's performance.
In my books anyway.

 

I too have a vortec headed 350. What rocker ratio do you have? I have the 1.5's but am thinking about 1.6 to wake it up even further. What do you think? Mine is an EBL controlled TBI with all the performance goodies. I want the throw you back in the seat feeling too. I don't have it yet. I have a 3.5 posi in my 10 bolt but after this weekend I hope to have installed my 3.73 12 bolt. I do have a 2200 stall converter too.

Let me know what you think

 

I have seen very noticeable gains from headers even at lower rpms. I had a 4.7 Dodge that I put 1 1/2" primary shorty headers on. Towing a load in the 1,500-2,500 rpm range, it was much easier to hold speed on a grade. I found myself accelerating up grades at 2,5000 rpm that would require downshifting and climbing to 4,000+ prior to the headers.

I put tri-Ys on my G20, had 1 3/4" primary pacesetters on my 5.7 Hemi, and have had both shorties and doug thorley tri-ys on my 97 Express. Every last one of them had improved power at even low engine speeds and better fuel mileage.

Scavenging effect doesn't need much RPM to get going. Ever heard of Pulse Air Injection? It was a GM system used on 4 cylinder cars that used the exhaust scavenging pulses to pull air into the exhaust manifold to oxidize hydrocarbons. The system even worked at idle.

 

That would depend on what cam lift you have at present ( u don't say ).
Stock the Vortec heads are valve lift limited so that will affect your decision unless you spend $$ for machine work or valve springs
to get the extra lift of the 1.6's.

 

Skinny-the chart does concur with what I was posting.The real rise doesn't happen much until 3,000 to 3,500.The other thing I didn't think of we can't white wash header use for all builds.There is a whole host of factors that come into play like intake,heads,cam timing, etc,etc.Each combo wants it's own header tune.I remember not so long ago we used to be able to buy adjustable collectors and tune headers based on track side results.Some where pretty dramatic once tuned correctly. I also played with collector lengths when I worked at the Chevy motor plant dyno rm. I saw first hand what was possible. Header companies want you to believe one header is fits all as a marketing tool and that is reliant on the fact you don't know how much of what your leaving on the table. To be blunt it is just a lie in the ad's.

 

I see over 20 ft/lbs at 2,500 on that chart thats a big gain especially in lower gears. If that car had a 2500 stall it would see 40 ft/lbs to the input shaft of the trans.

 

Take a look at my posting to skinny.Header companies do play the mind game of louder is more powerfully. If you take a look at Skinny's posted chart,not much under 3,000 grand.

 

Fast-get collector extensions.Go to the track on test and tune.Set a baseline and start cutting back on the extensions in equal lengths until the car starts to fall on it's face.Some you'll find you have to cut into the collector to get tuned correctly. Them are the facts.

 

The only thing I had that didn't run restrictive cats was my Ram. Its gone but did quite well with open headers and roughly 20" of 3" pipe with turndowns bolted behind the collectors. Even my 60' improved noticeably with open exhaust, so much for backpressure = low end torque theory that everyone has burned in their mind. The Ram was quite weird in that regard. Dumping the exhausg in that matter actuall over scavenged the chamber and caused the 02 sensor to see the extra air and caused the ecm to add fuel. The ecm generally ran the truck pretty lean but it really enjoyed the extra fuel and exhaust flow. I could blow away 12" wide 305/50r20s at 1/2 throttle.

 

I upgraded to a 1.6 ratio rocker on my Vortecs however the heads had been upgraded with a bee-hive springs and guide plates. Because of the guide plates, I had to have the pushrod holes enlarged to eliminate any binding between the plates and the head.

Exactly this. I had been running a flat tappet cam with a 1.5 ratio lift of .454". Making the switch to a 1.6 rr increased that lift to .484". Testing at the track yielded a modest couple of tenths however such a small change could have been attributed to the weather as much as it could be to the new cam profile.

 

My understanding, as you've stated here, is that the collector has more effect on the tune than whatever changes you might be able to make in the primaries (unless you've got a miserable set of short headers with a restricted y-pipe and your engine might really want 1 3/4" LT headers). Considering that the primaries are fixed in most cases (yes, I'm aware that certain headers have extensions for the primaries) the collector is the last place to make any sort of change.
Earlier, Gary had touched upon exhaust scavenging. The collector length, and as a result, the timing of the reflected exhaust pulse is the critical element in achieving an exhaust induced induction. That's why when experimenting with lengths and the car has more trap speed (as opposed to ET but that's affected also), you've hit the sweet spot. Have no illusions though, as was posted earlier, there's more to it than just headers.

 

Skinny,
That fact different collector lengths effect trap speeds is confirming headers effect is in a higher rpm range.Deductive logic works like this.Hp happens in a higher rpm range and HP is = to mph which effect trap speeds.

 

Not necessarily all the mph gains are from top-end hp. My Titan had the perfect example of this. It had a throttle restriction in the software that prevented the throttle from fully opening between 0 and 35 mph and again between 45 and 55 mph. Both of these areas and in the low-midrange torque area of the power curve in 1st and 2nd gear. I gained 3 tenths and nearly 2 mph with no change in horsepower on the dyno.

 

I agree with you 100% that increased trap speed is generally a result of an increase in power prpoduction. Just as an quicker 60' time (that's not raction limited) is generally a result of more torque.
Don't forget that horsepower is a product of torque and rpm (HP=T x 5252). Unless you raise the point at which maximum power is produced (by reving higher), you have to have an increase in torque production to make more hp. Naturally, that torque is produced lower in the rev range. On a mild street build, without the accompanying extras that we've discussed (like heads and cam), you won't be raising the peak torque or horsepower rpm value any significant amount. Despite this, the engine will inevitable produce more horsepower. Provided of course, the increased engine efficiency doesn't result in an overly lean condition and hurt output.

 

Fast.Don't know how many hrs I put into dyno rm work because at the time we where working 12 hr days 13 straight one day off for a very long time.

Also we have been building tailor made curves for our Super Gas 9.90 cars for yrs as well. Certainly we have won our fair share and a national.Some go their whole career never winning a national.

So the factors of hp and mph is well established.

 

Gonna cut this talk about headers short in respect of the O/P and the header discussion being off topic.