I found a set of 350 vortec heads off of a 97, 200$ for both, didn't think that was a bad deal, so.... I've looked into it and I'm getting frustrated, I need an exact answer, WHAT INTAKE, will work best??? 1992 rs 305tbi, I have egr and yada yada!! Any help???

 

You can not just slap on a set of stock 350 vortecs the 305 and expect it to performe better.

Milled 350 vortec heads with the LT1/LT4 cam (not hot), on your 305 with complete exhaust upgrade and a tune should make some decent power.

You can use the search function to find out how much to mill the 350 heads you have, to get a resonable CR (compression ratio) on top of a 305 bore.

Here is a wery practical CR calculator http://www.kb-silvolite.com/calc.php?action=comp

Here you find information on how to use a production LT4 cam with the 350 vortec heads, without machining work https://www.thirdgen.org/forums/tbi/...i-buildup.html
It also describes how to retain EGR.

Some 350 injectors with increased fuel pressure and a VRFPR (vauum referenced fuel pressure regulator) should handlle the new fuel demand.

Tu tune the beast, best, quickest and easiest is EBL flash http://dynamicefi.com/

Some general information about 305 and heads options https://www.thirdgen.org/forums/tbi/...check-out.html

 

None of that had anything to do with building a 305, but was interesting info. I have read on this forum people putting 350 vortec heads on their 305 with no tune, and no issues!! All I wanna do, and eventually will mill, is put the intake, heads, an lt1/lt4 cam, and headers. If I have to mod the tbi, then I will eventually, but h,c,I, and headers should be no more than 600$ with the prices here and just bout double my power, right? I don't think that's too bad, and then swap my rear to 3.42 gears to wake it up a bit! What say you on that combo?

 

It has basically ewerything to do with upgrading a 305 TBI.
All information, to do what you plan is there.

A complete exhaust upgrade is about all the stock tune will handle decently.

If the purpose of the head swap is a repair, to keep your car bringing you from A to B, then the stock 350 vortecs should work.
But with around 8 CR and no way to add fuel in the higher RPM's and tune in general, the 305 may loose some owerall power, vs stock.

Milled 350 vortec heads with the LT1/LT4 cam (not hot), on your 305 with complete exhaust upgrade, adequate fueling and EBL flash tune should make some decent power. Probably around 300fwhp.

Not sure all that fits in the 600$ budget, probably close if you find some really good deals in the classifieds.

 

300 is about what I wanted, that's awesome. The ebl tune throws the 600$ budget out the window bc it's like 350$ but everything else I found for about $490-590

 

That sucks.

Maybe you could start with the LT1/LT4 cam, exhaust, fueling and EBL to tune, should make around 250fwhp. (was one of the first mods I dit)

https://www.thirdgen.org/forums/tbi/...-ultimate.html

As for the EBL, I highly recomend you to send your ECM to have it istalled, except if you'r equipped and used to do such work.

 

If you don't have the money to mill the heads, buy a vortec intake manifold (with adapter plate), and tune the combo, than leave your motor as is. Just throwing those heads on now, which will require a different intake manifold, will likely make less power than your current set-up does now. The stock Lo3 heads are not #1 when it comes to bottlenecks on these motors.

Exhaust
Tuning
Air Inlet
Cam
Intake Manifold
Heads
And much much more tuning.

 

So your stock heads will work with a vortec intake?

 

No.

The vortec heads have a different bolt pattern which require a specific manifold. Likewise for your stock heads. They require an 1986 or later intake. GMPP sells a vortec TBI intake manifold but it is expensive. The prefered way is to use a vortec carb intake with an adapter plate for your TBI. There isn't any benefit of using these heads unless you perform the supporting mods to make them work.

 

I guess I misunderstood your last post, you're meaning get the carb vortec, adapter, and with the vortec heads tune that set up? Then move onto other mods? Or am I misunderstanding again?

 

You are on the right track now. However, if your car is stock, you should not do a heads and cam swap first. The exhaust is the first thing that needs to be upgrade. From the headers to the tailpipe. Then some form of air induction. From there you will want to become skilled at chip tuning (search for EBL and get ready to read and read and read). A head swap without tuning will just really upset you. Your car will eat gas, stumble around all RPM's, and likely make less power than stock.

Order of mods that these cars need to make the most out of them.

Exhaust
Air Intake (not manifold but air cleaner assembly)
Tuning
Cam
Heads
Tuning

A head swap can be expensive. You will need new intake gaskets, head gaskets, timing gun, RTV, head bolts. You have at least another $100+ in additional parts. I would set those heads aside for right now and do some reading on this site.

 

Well I'm looking for a header/ y pipe combo bc the car came with the cat gutted and a full flowmaster cat-back assembly. Air intake system is full edelbrock and k and n combo. But other than that nothing has been done. I was planning on starting with a 3.42 rearend anyways til I get everything I wanna do to the motor, tuning chips are nothing in my knowledge, lol, I will need help there.

 

Gears and headers are a great first place to start. Do plenty of reading and you will spend less money and have a better set-up in the end. Just keep those heads for a rainy day.

 

All of the above comments are a must for a decent upgrade to a L03. For my 305, 906 heads were milled for a 9.2:1 compression. LT1 cam will go in with an ultimate TBI mod and 55lb injectors. You'll also need new springs in the heads plus 1.6 rockers. 1.5s are okay, but for me the extra lift is good with the new sprins.If you do the cam swap, don't forget the new timing chain. Hoping to get 300hp. With the new TBI set up, don't forget to bump up the fuel pressure with a new 18lb spring. Also will need a new fuel pump since the stock probably won't handle the increased power and will blah out at WOT.

 

BTW.....yes the GMPP TBI vortec is expensive, but you'll be able to keep you EGR.

 

Do you happen to know how much the heads were milled and what the final cc 's where?

Did u mill the deck of block and what gasket did u use? stock pistons?

 

Milled to 61ccs. stock pistons. 1094 fel-pro gaskets

 

With 61cc, it shows just under 9 CR on a stock LO3 short block http://www.kb-silvolite.com/calc.php?action=comp

Still would have been interesting to know how much the 906 was milled to get 61cc.

 

I have a similar build planned. Here is what I have already but may go to a 350 instead at one point so I'll wait to mill the heads until the end.

062 Vortec Heads w/ 7k miles - from 330 crate motor
GMPP Vortec Intake from Fastburn 385 Crate motor - like new
LT1 Camshaft from 94 Z28 - Not going to use now that I got a deal on the Isky...
Isky 209/217 @50 Camshaft, 0.465 in / 0.485 ex lift, 112 lsa
GMPP Self Aligning 1.5 roller rockers

I planned to have them milled 0.030 and use felpro 1094 shim gasket if I keep the 305. I would like to shoot for close to 10:1. Still need to calculate that.

I still need Timing set, all gaskets, springs & retainers, head bolts, larger TBI unit, EBL, etc.

Already have Hooker 2055's, and full 3" exhaust, injector spacer, ADS superchip, open element w/K&N & Walbro 255 fuel pump.

There are people on here who have used straight vortec heads without milling them and had good results even with the loss of compression.

 

I was told by the machine shop that the compression would be 9.2:1. Can you send me the values you used?
You don't need a new TBI. The stock unit is good with the ultimate TBI mods and 55lb injectors.

 

I doubt it all came from the heads. What I mean, an LO3 with LT1 cam, full exhaust, air, fuel, tune and 3.23 gears is quite a good result too.




I recall reading a tread somewere on tgo, mentioning how much would need to be milled off a 350 head to get around 58cc, wich would result around stock 9.3 CR on a LO3 short block.

 

, and then swap my rear to 3.42 gears to wake it up a bit! What say you on that combo?[/QUOTE]

fyi.a lot of[most?]v6 camaros came with 3.42 rear gears in the same 7.5 rearends as the v8s.i put one in my rs.bolted right in.how do the vortec heads affect gas mileage?if i throw them on milled on my 305 with the gm intake how much will my mileage drop?seems if they are a better design they may give more hp without a mileage drop.

 

It has been reported by tgo experts that the only advantage of the vortec heads, is to make more power @4000rpm up, then swirlport heads.

 

Yes, but the overall difference can be quite substantial which is why so many people do it. A full exhaust L03 makes around 200HP at its peak and with the Vortec heads and LT1 cam you can push that to around 280 - 300HP. Really it just stretches the torque curve out giving you a much better powerband.

 

I do believe I need another TBI with larger bores in the future due to the Camshaft I have. This is because I don't think I could get to the full power potential without flowing more air. It is my understanding that you cannot get much past 300HP with the stock unit.

 

I'll see if I can find that thread. I think he already had headers. There was someone who only swapped the heads without milling and kept the L03 camshaft even and claimed to get some power gains. There is also Fast355 who made close to 300FWHP using a set of Vortec heads and the stock L03 Camshaft with a full exhaust and good tuning.

 

Yes and a modded "LO3" as I described around 200-220rwhp.

Basically you are saying exact the same thing as I am.

My impression is, that slapping a pair of stock 350 vortecs on a LO3 is not the first mod to do and is a compromise later on still.

Though if anyone proofs that it is really worth to slap a set of stock 350 vortecs on a LO3, that would change ewerything.

The better flow and bigger valves should help the top end for sure.

My impression here is that the overal power band is an important factor, these cars are heawy.

Again, not saiyn, do not use 350 vortecs on a 305, I just pointing out that a lot more then the head swap is involved if performance is the goal.

I have read fast's great tread's a coupple of times too.

Not sure if you are refering to this one https://www.thirdgen.org/forums/post...638-post1.html 305 vortec heads, back-cut valves, milled .025", 9.75 CR, full exhaust, fuel, air, 1.6 roller rockers and for sure a wery good coustom tune.

 

sounds like the vortec heads would be fine with a turbo on the 305 .

 

Mine were 059 casting 305 Vortec heads with 56-58cc chambers stock, but those were milled a little, it had 12cc dished pistons in it for 9.75:1 compression, but latter swapped for flat-tops, and a rubber embossed steel waffer head gasket that is only .016" thick compressed. That was over 10:1 compression. I had the peanut cam, but I also had 1.6:1 full roller rockers and an adjustable timing set on the 4* retard setting. I switched the same engine from the peanut cam to a production LT4 cam and swapped a TPI onto it. At that time I also ported the 059s even more and put 1.94/1.60 valves into them. It was a BEAST.

 

couldn't help but post on this old thread. I happened across it here.

350 Vortecs that will be used on a 305 should be milled .045", then use a .015" head gasket, and it'll be at 10.1:1 compression, and the engine will run fine on 88 octane.

I'm in "excited" mode here, since I am finished with my LT1 head and cam swap. Soon, my car will be on the road.

 

nm

 

I was just going to reply to you. It's a 350.