'87 IROC VERT

iTrader: (4)

I posted this question in the regional/southern california forum, but then thought maybe I should post it here as well...

I've searched a bit, but can't seem to find the right answer to this question: how can I get, say, 300hp or more from my 305?

I am happy with my car, and TPI, and the auto - I like my a/c, and I don't want to use NOS. Well, okay, not just yet...

All I've done so far is install two K&N filters.

I'm told these TPI engines can't breathe in stock form. So, what should I do, and in what order? Money is available, although I don't want to go too nuts.

Because I'm told the 5 speed version of my car came with 25hp more just because it has a different cam, I thought maybe getting a good cam could add that much, maybe more. Which brand, which one, and what about the part I don't really understand (life, duration, etc).

I also thought a set of performance heads would help, but again, which ones? I don't want to spend $1500 on a set to find out that for $500 I could have gotten the same hp from a different set...but I would spend it if that was the way to go.

What about roller rockers, and solid vs. hydraulic lifters?

Lastly, and one reason I don't want to run NOS - my car has 89k miles on it, and the motor runs well and is quiet. I really don't want to pull the engine and rebuild it now, since it doesn't need it. Can I do heads and a cam with my motor as is? Can I get 100hp or more from these mods?

Thanks, guys. Sorry if these questions are the same old thing, but I know you guys know you're stuff and I hope to benefit from your experience and do this right!

JesasaurusRex

iTrader: (3)

vortec heads, lt4 hot cam, performer rpm w/ a 650 double pumper and you should reach ur 300 mark

'87 IROC VERT

iTrader: (4)

JesasaurusRex, what combo would allow me to keep my TPI setup? Looking stock but going fast would be ultra cool..

1991CamaroRslow

iTrader: (3)

Get the stock heads ported, keep the cam under 210 degrees duration @.50 and under .450 lift with a 112 degree lobe seperation, get the stock plenum ported and get an adjustable fuel pressure regulator set to around 48psi. Nitrous won't hurt your engine when set up right, you should be able to spray a 100 shot to the 305 with no problems. It's actually a tad better to have a motor with some miles on it than a brand new one when spraying. The head porting costs about 450 in IN here that includes new valves, the cam should run around 200, and the fuel pressure regulator will be somewhere around 80. This isn't going to net you 100 hp but will make a pretty big difference. The nitrous kit on the other hand will cost around 500 and 35 or so to fill the bottle and will put you right at your 100 hp goal.

'87 IROC VERT

iTrader: (4)

That sounds interesting - what do you think those mods will make for power before the NOS?

JesasaurusRex

iTrader: (3)

Those 305 heads are f*ckin garbage, dont listen to that guy. Go to www.sdpc2000.com, they have a vortec head top end package, comes with vortec heads (get teh upgraded springs) and a tpi set up thatll bolt onto vortec heads, only downfall is if you ever change heads that tpi wont bolt onto any standard small block head only the vortec/edelbrock e-tec or somethin like that pattern. However im not 100 percent but im pretty sure their TPI is much better than the stock one. Then you could just choose a cam (id get teh lt4 hot cam should net you 300 and very streetable, also easy to find on ebay and decently priced).

85z28guy

cough cough 350

JesasaurusRex

iTrader: (3)

guess ur the first to say it

85z28guy

I guess I just don't understand why someone would spend the same amount on a 305 as they would a 350 and be happy with less hp per mod? I'm not saying 305's can't be built to be fast, but no matter what a 350 will be faster with those same mods.

Stekman

Do you have emissions?

84z28350

The 350 will also appear stock because the blocks are identice from the outside.

JesasaurusRex

iTrader: (3)

Thing is he wont spend the same amount, he keeps the entire bottom end, now if he can pick up a 350 short block for next to nothing hell ya do it. I'm just tryin 2 help the guy out thats all. Might as well getta 400 then if he wants to change the bottom end. He asked how he could get 300 horses outa his 305, i told him. Thats it.

Nate86

The 081(?) TPI heads can actually be made to flow as well as stock vortecs with a pocket port and polish job and slightly larger valves. 300HP from a 305 shouldn't be too hard to obtain (as long as we're talking about flywheel HP, not rear wheel).

Vortecs are nice, but I wouldn't invest in them for a 305 when there are cheaper options out there that would provide just as much power.

Theoretically speaking, the only major things that keep a stock LB9 from 300 HP are the heads, cam and tune. Make the heads flow better and add in a slightly hotter cam, along with a good dyno tune and 300 HP should be a peice of cake. Then the problems becomes how to get that power to the ground, and how fast/efficiently you can get it there. Start looking at a better tq. convertor and some decent rear end gears at that point.

JesasaurusRex

iTrader: (3)

the combustion chamber design is no where near as nice as the vortec heads, id like to see some mid lift #s outa a set of 305 heads that match the vortecs. I don't think theyre worth the trouble when vortec heads can be had so cheaply.

'87 IROC VERT

iTrader: (4)

I don't want to pull the motor if I don't need to - heads, cam, etc. can be done with the motor in the car, and then the car has trhe correct motor. I know when I was looking for a car, I stayed away from the ones that were advertised as 'was a 305, now a 350 from a 1978 Vandura, no wait, it was cousin's Nova, I think..'

I have the original motor running well, so, seems like doing the top and and cam seems like a good idea. It's not really an issue of money, I've alreadry dropped more cash into switches, plastic, console, rotors, powder coat/polish, etc. than I would spend on a 350 block. I just don't want to.

I've only been posting about wanting to build my 305, and with all the various opinons and some people telling me to do a 350, for some reason I'm now dead set on building my 305 just to see if it can be done and how well...

Okay, so because I'm not as well versed in this as some of you guys, what heads and cam should I get? Is there a set of heads I can buy already ported, etc and ready to bolt on? And cam?

Will heads, cam and exhaust get me to 300hp or close to it?

1991CamaroRslow

iTrader: (3)

Those Vortec heads have to be milled to get them to work with a 305 plus the price of the new intake, it's not worth it. Are you in Cali? If you are then you have emmisions like nobodies buisness so your safest bet will be to port the stock heads, a carb legal cam and a nitrous kit, all of this will keep you legal and I'm not sure how much horsepower the heads and cam would make, maybe not 300 but close, and you'd make a TON more torque, that's what it's really all about. Also if you do all of this to your 305, then drive it till it goes bad on you, you can port it directly over to a 350 roller block, change the tune in the prom and have good equipment plus a the 45 extra cubes, ditching the 305 for a 350 right off the bat is very un-economical, especially when you have the tuned port on your 305. If you don't mind taking the heads off of your car you can port the heads, intake, plenum and install the cam all at once; if you don't want to rip into the motor at all you can have a nitrous kit installed in a few hours and you will turn that car into a monster, trust me I've done it.

Stekman

Vortec heads have an external EGR. I think that alone would fail a visual (I think). I would just find a used set of 081 heads (305 TPI heads) or similar castings and work with them.

Run a mild cam swap, LT1 cam would be a good choice. Keep in mind, anything you do will require tuning to get it to run correctly.

dimented24x7

iTrader: (2)

With the MAF and the above mentioned cam, you can probably scoot around the tuning issue if the fueling is based strictly off of registered airflow with your ECM, which it usually is. Unlike speed density, the fueling with a MAF is based on the airflow, and not the engine itself. The potential for a new prom comes up with new injectors, as youll have to change the injector constant in the ecm to match the injectors.

Ideally, though, you should tune it even if it has MAF. The calculated load value with the new combo will differ from the old motor and that will skew the timing and any other terms based off of the load value. Might be fine with the new combo, but with a 383 or a 400 this would definatly be an issue. Thats one of the weak points of the MAF only systems.

RestoRoc89

How come no one's mentioned some of the more reputable cylinder head manufacturers (i.e. Airflow Research, Trickflow, Brodix, etc...). Firstly, '87 IROC VERT has mentioned he wants something that will flow well out of the box...AFR Competition CNC ported heads anyone? I get the idea that this isn't a budget buildup at all. Also, if anyone's noticed a previous thread about how '87 IROC VERT just got a new polished TPI intake, he probably doesn't want to go replacing that right away (that I would look into porting if it's a keeper). However, I'm not at all familiar with California emissions inspections. Would a nice set of AFR heads be an issue? A lot could be gained from an upgraded valvetrain as well. Everyone keeps saying that building a 305 is pointless...but has anyone every tried to build a 305 without huge budget limitations? I agree that theres likely more potential in a larger displacement engine, but sticking with the 305 keeps car closer to the often desired 'numbers matching' ideal.

As for NOS, who wants to hit a button every time they want to go fast? Any sort of power adder should really bring considerations of forged internals anyhow fro reliability.

'87 IROC VERT

iTrader: (4)

I am BESIDE myself. I just spent 10 minutes writing a response thanking some of you guys for your thoughts, and talking about some choices, then my retarded laptop somehow clicked IE back, and I lost my changes becsue this stupid form refreshed when you go forward or back. I'm really annoyed. I can't do it all again...

RestoRoc89 - thanks, you hit the nail on the head. This is not a budget build, it's a mission - to make my 305 go go go, and retain my polished TPI setup. And I'm not knocking NOS, it's fine, just not what I'm looking for. 85% of my driving in the IROC is done with my 5 year old little girl next to me, so zero to 45mph is where it's at for me. That's why I'm okay with changing gears next weekend to 3:73's.. (also posi/disc, which I already had).

You guys had some great suggestions, including Brodix heads, which I saw on the Speed channel tonight.

I know I can do this, and it will be cool when it's done. And will hopefully look really nice as well.

Any other specific head/cam combo suggestions? Thanks, guys...

Vader

Are you shooting for 300HP at the wheels, on a treadmill, or at the crank? 300 BHP at the crank is very easy. Getting it to the wheels is a different story.

You're fortunate to have a roller cam setup. That broadens your cam options. You can get some serious lifts and still maintain a short overlap. Keep in mind that a TPI intake is going to tend to make more power below 4,500 RPM, then fall off. Unless you heavily modify it, that's about what you're stuck with. With some modification, you can extend that torque into a higher RPM, but you'll still have limitations. With heavy modification of the TPI you can support power at 5,588-5,800 RPM.

Programming will be imperitive if you intend to make that level of power at the road. Dump the stock MAF tables, and plan on higher fuel pressure or larger injectors to support the power at higher RPM. Program accordingly.

The cam has to go. You can safely go to 108° LSA with a MAF, and even lower with the correct programming. Don't let that limit your choices, but remember that long durations don't really like to make lower RPM power, where your TPI works best.

Keep poking around through the forums, You'll get plenty of ideas.

dimented24x7

iTrader: (2)

Theres also the issue of the fact that the MAF pegs at 255 gms/sec. With a mild setup this wont be an issue, but with a hot high HP setup you can peg the MAF. Id probably consider using a SD setup with an aftermarket intake if you intend on closing in on 400 HP or more.

'87 IROC VERT

iTrader: (4)

You guys have shown me hope - below 4500 rpm is fine, that's where my street driving will happen. Again, it's not going to be a track/strip car - ever.

My car has a roller cam? Cool. I had no idea. I was planning to have someone work with me to get a chip mapped out and burned, and then dyno tst and tune it to get it right.

I feel like at least I'm moving forward on this. Thanks!

dimented24x7

iTrader: (2)

Given that you wont be straying too far from stock probably the limit of what youll do will be changing the injector constant if different injectors are used and tweaking the timing table a bit. There may be other minor things to tweak as well.

JesasaurusRex

iTrader: (3)

The reason nobody mentioned a decent aftermarket head is because most of them use a larger intake and exhaust valve which are too big to fit on a 305 with out notching the cylinder walls which by itself is too much trouble in my eyes when you could get something with larger displacement. Now since this guy mentioned this is definetly not a $ issue then imma have to agree...toss that POS 305.

'87 IROC VERT

iTrader: (4)

You guys are killing me. Are you trying to tell me that with some money and effort, I can't come close to 300rwhp?

50 cubic inches - can't make THAT much difference. I just need to find the right heads and cam, I know I can make this work.

Anyone can buy a 5.7 - I want to build my 5 liter...

JesasaurusRex

iTrader: (3)

why?

'87 IROC VERT

iTrader: (4)

I don't need that much power. 300rwhp would be great.

My car runs (well) and the motor is in there. I should (at least in theory) only have my car down for a couple of days to do heads and a cam, etc...

If I can keep my motor, and still accomplish my goal, there is no need to go to a 350, buy it, rebuild it, transport it, and so on.

JesasaurusRex

iTrader: (3)

you can not get any real good heads thatll fit over a 305 because of how small the bore is...unless you want to notch the cylinder walls which im guessing you wouldnt wanna do urself meaning youd have to take the motor out strip it down and bring it to a machine shop to do. Meaning you might as well build a 4" or bigger bore motor to start out with. So yes it can be done, but no it wont be easy and wont be economical to do. That being said, 300 horses to the crank are as simple as vortec heads (milled down to 58cc chambers), lt4 hot cam, and what ever intake it is ur going to go with. Throw the bottle on and ull have 300 to the wheels. If you wanna do it all on motor good luck have fun it can be done but I wouldnt. That's my last post cuz this is rediculous now.

'87 IROC VERT

iTrader: (4)

I don't think it's rediculous to want to try to do something a little different, but you are entitled to your opinion.

I will do what I can, and get as much power as I can. 3:73's should help a little bit.

I will still pass on the NOS for now. Down the road, sure, a 350 will be the ticket. Just not now. Thanks for the advice!

genob4c

Here's the formula I'm using on my 86 Iroc and its anemic LG4 305.....

GMPP ZZ4 intake
Edelbrock 1901 Q-jet
MSD Digital E distributor (I’m ditching the ECM)
Comp Cam/Lifters Hydraulic flat tappet 0.462 int./0.477 exh. Lift - 218 int./224 exh. Duration
Trick Flow 175cc 23 degfree alum heads – 1.94 intake/1.50 exhaust
SLP Headerss/Firehawk exhaust
Emmisions in the dumpster
Summit 1.6 ratio Roller Rockers

I'm not sure what the HP will be, but I'll let you know in a month or so. I do not see it getting to 3 hunna HP. Two Fitty maybe.

88_Import_Slaye

*** damn it, has any one of you 305 owners seen the links i've posted?

http://www.goingfaster.com/spo/modthel03.html

read that page and follow the links at the bottom for 325-400hp 305 builds.

I thought I was the biggest supporter of doing it different. I built my 305 in spite of the "Get a 350" crowd, but now i'm starting to get the urge to say the same thing. It's like 305 owners dont have brains, they ask the same questions over and over.

To go fast, get better parts! Big heads, Big cam, Big carb, toss everything except the motor, 4.10 posi and 4000 stall converter. There, now you will go fast. Geeze.

Be sure to get a water cooled wallet, cuz that **** will be smokin when your done.

Fast355

iTrader: (2)

272 HP at the rear wheels through the mufflers and restrictive 2 1/4" dual exhaust and 300 RWHP through open cut-outs, but from TBI rather than TPI. With the right mods to the TPI system, I could see you making more mid-range torque with roughly the same HP. Think ported base, ported plenum, oversize or siamesed runners, etc.

305sbc

iTrader: (3)

Ported 305 heads will support 350rwhp if done by a competent porter.
https://www.thirdgen.org/techbb2/sho...hreadid=335850

85z28guy

I would say fine go ahead and build the 305 if all you were to do is bolt ons. Your taking about a complete performance rebuild. Your going to have it down to a block with pistons sitting in your car. At that point, you might as well pull 2 more bolts, and slap a 350 is there. Its not being different, its common sense. And yes, 50 cubic inches will make a difference. Your a complete and utter lost soul if you can't get 300hp from a 350. You also say that down the road you may go to a 350. That makes no sense because most of the parts you buy (especially the heads) will be a porr choice for 50 extra cubes. A 300hp 350 will be more reliable then a 300ho 305 too. Numbers matching really is not gonna mean much. Your talking about modifying it from original anyways. You could always just store the 305 block in some oil.

Fast355

iTrader: (2)

A 300HP 305 is just as reliable as a 300 HP 350, IF you keep the RPMs the same. The rotating assembly is the same and the 305 blocks are usually a little thicker. You might argue that a 350 has 4 bolt mains, some do, some 305s do too. For under 450 HP that is not an issue anyway! The power in the 305 is in the heads, just like a 350.

'87 IROC VERT

iTrader: (4)

I am going to do it. I don't want to take the motor out of my car, I would rather do heads and a cam and see if I get get 300hp.

After all I've read here, and with some competant help, I know I can get this project started. I'll let you guys know how it comes out. And if it comes anywhere close to 300hp, I will be very happy with my 305!

(Hey - LOOK - 305 POSTS!!!! IT MUST BE A SIGN!!!!!)

Now I'm afraid it's bad luck to post anything.

And now, I KNOW I'M GONNA GET FLAMED WHEN I HIT 350 POSTS!
And 327, and 383....this is never gonna end...

mnorton

Sounds like we are in pretty much the same boat. My car is an 87 vert as well, but with a T-5 manual transmission.

I think that getting 300 HP at the wheels while still passing CA smog may be more than you should really be shooting for, 300 HP at the flywheel is an easier target to hit. An automatic transmission looses about 20+% so you'd need to get about 360 HP at the fly wheel in order to get 300 HP at the rear wheels....

Here's the deal:
You need a better torsional strength suspension via sub frame connectors (maybe Alston SFC's), a higher lift longer duration cam (maybe a Crane Powermax 2032 452/465 214/220 112 deg. P/N 104224 -OR- Competition Cams Xtreme Energy 488/495 212/218 112 deg. P/N 08-501-8), better flowing heads with new ~ 100# valve springs, screw in rocker studs to support the higher lift cam, and better valve spring clearance that will support the higher lift cam (maybe world Products S/R 305's WRL-042750-2 -OR- you can just get your stock heads REALLY worked over), better flowing exhaust (maybe SLP headers w/AIR injectors, a 3" exhasut pipe, and a new CAT), an adjustable fuel pressure regulator (maybe a Holly P/N 512-501), and more fuel delivery into the stock intake system.


Your stock TPI intake flows enough air for a 305 at 300 FWHP already. The stock 19# injectors will support up to 300 FWHP, but only if you run them at about 54 psi WOT. That much fuel pressure is a pretty big strain on a stock fuel pump. TPI stock fuel pressure at the rail is about 43.5 psi.

If you decide to go with 22# injectors (maybe Bosch 0280150561 D9B-22lb), you will need to get a new PROM that at least tells the computer that the fuel injector constant is now 22# instead of the old stock 19#, otherwise, even with a lower fuel pressure, you will be probably be running a little too rich. You can lower the fuel pressure to about 38 to 40 psi just to get it running, but to get it to run well you will really need to get a custom PROM to go with all these mods.

Do not go past 221 duration on the cam, and a lift between .455 to .510 is plenty for these heads.

To get all these parts parts will cost you about $2300. Figure on at least another $200 for other misc. stuff along the way. The labor to install it all is extra of course!

It's a pretty big job to do all this work by yourself for the very first time, I know.... My engine should be running again in about three more weeks!

88_Import_Slaye

Thats about right. Of course I got my stuff all for around $1800 (including new tranny, converter, and all machine work on the block), but spent $500 in misc parts Damn misc parts. Spent $75 alone in fittings for fuel system, another $40 just for bolts.

Thats correct, taken me 2 years. Gonna put in the torque converter this weekend and speedogears so I can drive after having it sit for SOOOOO long! Luckily, I had TGO and my friends from work.

'87 IROC VERT

iTrader: (4)

Will a set of vortec heads and a cam be a good start?

I found a set of heads for $250 -
Chevy 305 Vortec Cylinder Heads (1990 matched pair). Magnafluxed - Professionally rebuilt - 3 angle valve job - resurfaced - casting number 14101081

If these work, what cam should I use?

Fast355

iTrader: (2)

You already have a pair. You need the Vortecs that end in 062.

'87 IROC VERT

iTrader: (4)

See, that's exactly why I post these questions - okay, I'll look around for the 'cool' ones - thanks!

Zero

An aluminum flywheel and other lightweight drivetrain parts will increase engine life and horsepower!

Nate86

I thought I might mention that 300 peak HP is not going to do much good for you if the rest of your powerband is making way less power than that. Make sure you match your parts appropriately.

Fast355

iTrader: (2)

Good point.

Another thing is make sure the resonance tuning of the TPI is working for you not against you. The peak torque RPM is more or less permanant, meaning you can shift the higher RPM torque off but the low speed will drop. Its like a see-saw. You trade one end for the other. Then things like oversize runners, ported heads, exhaust, more compression, etc, will raise power everywhere. Stay with successful TPI cams.

VincentZ28

iTrader: (2)

The best thing you can do for now is change the exhaust system. Headers, dual cats and 3in cat-back system. Get in touch with Jerrywho(on this board) he has SLP runners for sale and maybe an intake manifold. You can buy my BBK 52mm throttle body. It fits your year. Modify the trans an install 2400 converter. 3.27-3.45 gears. This where you need to start. Your $1500 is gone.

Now! the rest of your money should be save up for a 350 short block and after market heads and cam. The reason is that it's not worth the money to put in a 305 and make less hp than a 350. But if you want to do it anyway,

here's the link for World Products 305 Heads. These are the only heads that are 58cc. This will help keep the compression up around 9.5 to 1. The other heads are 64cc and it will drop ithe compression down to 8.8 to 1 to 9.1 to 1 depending on the head gasket.


This is Summit price.....
502-8 Competition Cams Xtreme Energy Camshafts
Camshaft, Hydraulic Roller Tappet, Advertised Duration 269/ 276, Lift .495/ .503, Chevy Small Block, Each
Tomorrow $245.88

LUN-54755 Lunati Hydraulic Roller Tappet Camshafts
Camshaft, Hydraulic Roller Tappet, Advertised Duration 268/ 276, Lift .489/ .503, Chevy Small Block, Ea.
12/27/05 $279.69

You can have your stock manifold Extrude Honed for $300 and add Arizona Speed & Marine Runners with this combo and you will be over 300rwhp.

Lunati Cams

Comp Cams

World Products 305 S/R Torquer Heads

mnorton

I suspect that on a stock piston and cam 305 engine, (without decking the block) that the compression ratio using world 305 sr torquers is going to be closer to 9.1:1 (with the recommended felpro #1003 head gasket @ .041 compressed).

I think that you would need to use a much thinner gasket (like the stock one) to keep the stock 9.3:1 compression ratio. The problem is that then you would really increase your risk of getting a leak....

The stock 305 steel head gasket is I believe .021, and the felpro #1003 is actually a gasket made for a 350, not a 305, so I bet that there's some loss of compression ratio due to the bigger bore size gasket as well.

I don't believe that a streetable 305 needs a bigger than stock throttle body. It has enough air coming into it already.

'87 IROC VERT

iTrader: (4)

Vincent,

Nice post - I made a deal on a 3:73 posi rear end (mine is making some odd noises) to replace my 3:23 or whatever I have now.
Doing the exhaust this weekend (Christmas present to myself!), and will get to work on ordering the rest of the goodies shortly...

Still got to call Kevin's Dad (Dyno Don) and talk with him, hopefully can do that in the next day or two...

Do I need to modify the trans and change the converter? What should I do exactly, and why do you suggest it? Just curious.

I think I'm finally getting this worked out.

Thanks for the really nice links, too...

VincentZ28

iTrader: (2)

That is a must to modify the trans when making more power.
My susgestion will work because I had done it back in 89 and was beating the 5.7 IROC's by 4 cars with no chip tuning on an 85 TPI Z28.

'87 IROC VERT

iTrader: (4)

So, I simply buy and add a 2400rpm stall converter, or do I need to do additional mods? How will that affect street driving? I'm not actually going to race the car....ever.... but if I can get the power and keep the car driveable, then that would be great.