90CamaroTBI

Ok guys I hope this aint too off topic, but this is getting into a heated rivalry. My friend has a 1987 IROC-Z with a 4bbl 305 700R4 with the following mods:

-600 cfm carb (probably Edelbrock)
-world products iron heads
-1.6 roller rockers
-Edelbrock shorty headers
-3 inch flowmaster catback with gutted cat (stock 2.25 y-pipe)
-Edelbrock performer intake
-Open element air cleaner
-8.8mm Accel wires
-Accel Hei distributor cap
-Smog stuff gone
-All A/C gone except compressor just for a pulley

He has a B&M shift kit waiting to go on if he needs it.

The SRT-4 is bone stock.

What do we possibly need that is cheap to take this SRT-4 in the 1/4 mile?

DuronClocker

iTrader: (1)

A cam kit and possibly better heads (without knowing how those flow).

Or strap on a 75shot and you should be golden. SRT-4s are usually low 14sec cars from a dig (or worse depending on driver), but from a roll they can seem like mid 13sec cars based on their trap speeds. They're just hard to launch apparently.

90CamaroTBI

I believe they are world products torquer heads ( I think thats the name). Also how much will a cam wake up this combo?

DuronClocker

iTrader: (1)

A lot. The '87 LG4 cam sucked. Get something like a 210/220 cam or 218/224 or something around there, and that combo will really wake up.

IROCThe5.7L

Make sure they race from a stop.

90CamaroTBI

We already raced and the Camaro lost, but we changed the old fuel filter and gained incredible power. We just dont want to race and lose twice.

phoenix305

what kind of gears, if they are 2.73 that would be the next thing i would do. also that cam will help out alot and if you can a higher stall converter, also that y pipe is killing him why even put on a 3 inch exhaust if your going to keep the 2.25 inch y.

90CamaroTBI

Good question man, but it has 2.73's by the way.

Street Lethal

iTrader: (16)

I don't feel the stock Y-Pipe is going to hurt you, it's only a 305... and can only exhale so much. I would have to agree with some of the other's; Cam, Stall & Gears.

... if this second race is going to happen in the coming week or two, I'd say three angle valve job, while port matching the heads and intake. IMO, toss that Edelbrock carb, and throw on a Quadrajet. I used to love how the quad's secondaries made my ole semi-worked 305 feel like a very healthy 350.

vortecfcar

A Summit cam kit will work wonders. And for 70 bucks you cant beat it.

If the carb works, save your money.

you will see the biggest drop in E.T. with a converter or nitrous.

fly89gta

iTrader: (1)

So a stock cam and 2.73's?

Say goodnight. See the post by IROCThe5.7L

superGMman

Yeah, those are hurting you horrrrribly. Don't race until you get those two problems fixed.With the 2.73's you won't even be able to take advantage of your torque, especially with a 305. Do the gears first.

Ray87Z

Assuming you're running the stock LG4 "peanut cam" you will literally pick up 30 plus HP with a decent cam.

Even with the stock crappy cam you would also benefit a fair bit by upgrading the intake to a Performer RPM instead of the plain performer. Car Craft or CHP did a LG4 bolt on test article a few years ago and gained 15 hp with the stock crappy cam still going to the RPM over the regular Performer... They got up to around 230hp with just headers, intake, and carb tweaking with the stock cam. With a 218/224 cam they made 269hp.

Do the mild cam and intake swap at the same time, get one of the generic Summit cam grinds and maybe pickup the intake on Ebay or something and you can get this done for under $200. Summit has a 214/224 cam w/ lifters for under $100 that would probably work pretty well... The 204/214 cam wouldn't be bad with the 1.6 rockers he already has either. I would want to make sure w/ a larger cam with more lift that he doesn't go beyond the capabilities of the heads/valve springs. Not sure what World runs on the S/Rs... Should be a damn great gain with even the 204/214 cam... If the race was close before and you guys don't blow the launch with the newfound power you'll work the SRT-4 over...

Gears would be a good idea but since that will usually run a decent bit of money with the gear purchase, install kit/bearings, and labor price for the install if you don't know how to do it yourself, I'd concentrate on the cam and intake swap first. That really is darn cheap for the huge power gain compared to the stock LG4 cam...

You sure he doesn't already have a hotter cam though? Seems pretty stupid to do a head swap, even to stock replacment heads like the World S/R Torquers, without doing a cam swap to something that doesn't suck as bad as the peanut... Find out if he is running a decent cam, and post up the specs if so.

If he already has a decent cam you're down to gaining a little power with an intake swap, and then looking at gears.



I'd really want a significant power gain to solidify the win though. How close was the race before/how did it go down exactly?

{EDIT} Whoops, I forgot 87 would have a roller cam, at least I assume the 87 LG4 was upgraded to a roller cam setup from the factory along w/ the TPI engines that year. That will mean more money for a replacement unfortunately. However you might be able to score a used LT1 cam or something for fairly cheap, with 1.6 rockers that wouldn't be too bad...

90CamaroTBI

I would say he had no more than a car and a half on us, what does this convert to in seconds? After we changed that fuel filter though, we found power that we didnt know the car had.

ShiftyCapone

iTrader: (7)

The exhaust is the worst part on an LG4 car. The cam is small but you should not swap cams until you change to a full 3" exhaust. The stock piping is horridly restrictive and is choking that motor. You will pick up an incredibale amount of power from that alone. A cam swap with the stock exhaust components is a lost cause until you upgrade the exhaust. A full exhaust changes the VE on a 305 up to 10%. That is HUGE. Those who say exhaust on a stock 305 car is pointless are just speaking hearsay. Some people have dropped off over .95 seconds by going with a full exhaust.

Beating an SRT4 takes some serious mods. I watched one put down 210at the wheels bone stock and then he bested that with a 240hp run after he unplugged some vacuum line. In a 3k lbs car that is some serious motor.

You will need to run mid to low 14's to hang/beat him. That will require a cam swap, full exhaust, suspension upgrades, and gears (posi at the least).

Street Lethal

iTrader: (16)

Telling someone that it's merely "hearsay", while backing it up with mere speculation, doesn't prove you're side of the arguement though....

Please don't throw "so and so gained this", and "so and so gained that" (on the dyno), because it proves nothing to me. What would solidify it for me, would be to say, "so and so ran a best of 13.15 with his worked 305, running a 2 1/2 inch exhaust, but then swapped to a 3 inch exhaust, and is now running consistent 13.0x's (with video, to prove it)...

... I never seen (only heard) of such a benefit of a three inch exhaust for the anemic 305 small block chevy. An engine with more cubes though, yes, I see a full three inch exhaust working wonders.

With a 305? Now "that" sounds more like hearsay, to me.

vwdave

That vacumn line is for the wastegate. You unplug the line and the wastegate stays shut, making maximum possible boost.

And I think he's going to need all that, PLUS spray.

ShiftyCapone

iTrader: (7)

I don't speculate . I was forced to change many of my previous misnomers about 305 motors because of facts that were presented to me. No hearsay here, I promise.


Why does dyno data prove nothing to you? It takes away all ambiguous parameters that you see at the track? The track only confirms it with some additional error based on conditions and driver skill.

None the less I can respect that.

Dewey316 dropped a full second off of his ET by adding a full 3" exhaust (from stock 2.25") and dialing it in with chip work. He has the slips and datalogs to show you. He has posted on TGO the dyno runs that confirm the gains he saw at the track. The last of the LG4 cars ('87 LG4 170hp and 250tq) basically made the same power as an LO3 with the same size exhaust. It is not unreasonable to compair the two for this discussion and for the sake of the origonal poster.

Board member 84L69TA also has time slips that he can provide that show the gains he saw at the track with with a full exhaust.

Quote found here

All of the following board members can provide dyno runs, track data, and data log screen shots on command to show you the increase in VE along with the numerous improvements that it made to their 305 car. Video data won't prove what motor is acutally in the car or to the extent of its tuning. The data logs will prove the displacment of the motor, induction, and engine parameters (both before and after).

Fast355
JPrevost
Dewey316
Dimented24x7
kdrolt

A quick PM to any of these guys or a few searches under their names will uncover this supportive evidence. Much of it is already provided on the TGO archives in the TBI and exhaust board.

I agree with you that the exhaust upgrade goes farther on a larger displacement motor. No one will argue that. The stock exhaust on 305 cars is just terrible and in some spots is less than 2" in diameter.

The full exhaust on my LO3 made a huge difference on the butt dyno. I cannot qauntify that because I did not do back to back track or dyno runs. I only have the evidence that others above have provided for me.

You may also want to search under redraif. Their 3.4 V6 makes about the same power as an LO3 and they have all kinds of posted dyno data that shows the increase in power (in all areas of the curve) that a 3" system made.

Because of guys above and the data they have provided me I have also been forced to change my stance on swirl port heads.

stu

People put single 3" exhaust on turbo 4 cylinders that aren't overkill, I don't see how it would be on a 305. Does it hadrly breath or something? I don't think I've ever heard anyone suggest that 3" pipes on a 302 are overkill. *shrug*

vwdave

Turbos need as little backpressure as possible. So its not 100% the same thing.

IROCThe5.7L

Yea, that catback is really killing his performance.

DuronClocker

iTrader: (1)

My cousin had a 485awhp Talon that was breathing through a 3 1/4" exhaust. Sounded amazing too

Backpressure isn't good for any car in race terms. Stock tunes are designed to work with the stock exhaust's backpressure, but if you are doing any chip tuning, the less backpressure the better. Even on a stock tune, a 3" cat-back on a V8 thirdgen will only gain power, never hurt.

stu

Good point, sometimes I forget.

Street Lethal

iTrader: (16)

I agree with this perspective, but, we're talking about a 305 with it's puny stock bore, stroke and heads. You can put a 4" Muffex set-up on the original poster's car, and it won't make it any faster than what a 2 1/2" exhaust would.

...hell, let the above car run in the quarter mile. See what it runs, then run it again with completely open headers. I'm willing to bet that the quarter mile performance stays exactly the same (save for the SOP feeling).

Again, I agree that backpressure can be a performance car nightmare... but we're talking about a 305 here, and if anyone considers a stock bored and stroked 305 "performance oriented" (even with a bigger cam), well....

Stroke that 305 to 335, throw in a more aggressive cam, better heads.... than I agree, a 3" exhaust just might be the right choice.

I'd like to add to this though; "Even on a stock tune, a 3" cat-back on a V8 thirdgen will either gain power, remain exactly the same (having no effect), but never hurt....

Street Lethal

iTrader: (16)

3.736 inch bore, 3.48 stroke.

Different engine. Ford's 302 bores are much larger, and it's valves aren't shrouded.

ShiftyCapone

iTrader: (7)

The bore to stroke issue has nothing to do with it. The bores on a 305 are shrouded which cause its limitations. You know this because you just mentioned it but didn't realize the connection you were making


There are many motors that have a smaller bore than a 305 yet have a greater potential to make power. Valvetrain layout is what limits the 305 and other motors alike. If you could add a different head design to a Gen I 305 it would have just as much potential as any other motor configuration with that total displacement (ford 302, GM 307, 301 ect ect). The power curves and RPM ranges will be different but you could get the same power out of them. The actual numbers for bore and stroke are irrelevant. The 305 has limits because of the 23° head layout with small valves that are not properly placed in the combustion chamber. A larger bore just decreases the inefficiency of that head/valve layout. It just so happens that ford and GM shared a 4.00" bore that made the best use of that design. The 305 was a compromise to increase fuel efficiency yet keeping the tooling and manufacturing basically the same.

Street Lethal

iTrader: (16)

I disagree. The bore, stroke, valve size, porting, all dictate how much flow is really needed. Careful inspection of all of my posts will embellish that a larger exhaust (in this case, three inches) is very beneficial, but for bigger cubed engines.

I'm well aware that power can be made with a 305, I have posted so many different posts in reference to Preston Smith, and his "street legal" 10 second, blown 305 (which now runs 9's, with a turbo). Preston however needs a three inch exhaust....

I didn't realize the connection I was making? My goodness, you're very full of yourself, aren't you. Yes, I'm very well aware as to why the 305 is limited....

Careful inspection of my initial post will show that I was referring to the Y-Pipe, and that it wouldn't be that much of a burden. I mean realistically, exacly how much horsepower do you think the above referenced engine is making?

I appreciate the rest of you're post, but it's simply smoke and mirrors to me. Getting back to the original topic, he'll need a cam, stall speed and gears. The stock bore and stroke starts losing power at 4500-RPM and up. The cam and heads will help him of course, but how much fuel can the anemic 305 burn for Christ's sake.

... and let's remember here, we're talking about a;

-600 cfm carb (probably Edelbrock)
-world products iron heads
-1.6 roller rockers
-Edelbrock shorty headers
-3 inch flowmaster catback with gutted cat (stock 2.25 y-pipe)
-Edelbrock performer intake
-Open element air cleaner

Exactly how much "power" do you think this combo will be making? Better yet, to counter my original response, why would the stock Y-Pipe be "that" restrictive? When I responded, I already took into consideration that he'd be running a three inch exhaust from the Y-back.

My arguement with you here, is that a 305 does not need a three inch exhaust. Two and a half will be more than adequate (and will not knock off almost one full second, as opposed to the stock 2.25, unless mucho work is done along with it). However, unless you're spinning close to 800 horsepower, like Preston Smith.

ShiftyCapone

iTrader: (7)

I agree with you here. A mandrel bent 2.5" system is a dramatic increase over the crimped 2"-2.25" stock system. However, you should still see/maintain the same results/benefits with a 3" system. If you have no other plans for power than by all means stay with a 2.5" system. The differences would be small by going larger and I agree completely with you. Sure it may not be needed now but a 3" gives you more potenatial for future mods or motors down the road without any of the negative affects of going too big.

I am not full of myself and I don't know your background. I have no idea what you know and what you don't know. I was giving you the benefit of the doubt since I agreed with you on that particular aspect. I feel that is unfair judgment on your part to think otherwise. I just have lots of evidence that shows the benefits of a 3" exhaust on a 305 and none of the contrary that tells me otherwise. Until I see dyno sheets and track data that show how a 3" was not the best choice and that a 2.5" was a better choice (or sufficient/equal enough compared to a 3”) I will stick to the multitude of data that others have proved on this site that show the beneficiary gains one can see with said system.

Here is a pic of the stock LO3/late LG4 y-pipe. Many parts of this y-pipe are crimped to less than 2". It has an abrupt t-connection that follows along through more crimps. The y-pipe and exhaust manifolds are the most restrictive parts on these cars. If anything these items should go first. My stock crap 140hp cavalier has the same size exhaust as the y-pipe connection (to cat) does on the LG4/LO3 cars.

If I had to guess I would say that with his mods he should be making around 210hp which is not enough to beat an SRT4. That is unless he has a cam and didn't add it to his list of parts. It strikes me as odd that he would have world heads with the stock cam. Which World heads do you have? The SR torquers with a cam could be a 250hp car or the 76cc chambered worlds with the stock cam could be a low compression, low velocity, under-cammed slug.

90CamaroTBI

They are torquer heads, and as far as anyone can trace, the cam is supposed to be stock. By the way its a 650cfm carb.

vwdave

NA cars need backpressure. I am sure one of the kind gentlemen on this forum would be glad to elaborate as to why. Cause honestly, I am not 100% as to how it works.

I know on turbos, basically the faster and more exhaust gases get out, the quicker the turbo can spool up and the longer it can hold boost.

ShiftyCapone

iTrader: (7)

You never really want back pressure for a performance engine. Some cars do require it to maintain proper EGR function. Severe reductions in backpressue can keep EGR valves from opening. This is easily overcome and only applicable to EGR equipt set-ups. The important thing to focus on is scavaging. A "tuned" exhaust manifold will have a locally lower pressure (reduction in backpressure) when the exhaust valve is open, increasing the exhaust flow.

DuronClocker

iTrader: (1)

Thanks for elaborating on what I said. I gave the short version because I posted about the exact same type of comment in another thread in this forum not more than 2 days ago. Exhaust scavenging is what is important; backpressure is bad.