Aaron's 3.4 DOHC 88GT Build Thread

Fastback86 · Post by **Fastback86** » Tue May 02, 2006 5:07 pm

Sure, I get that, but my point was that your displacement is a constant, your engine is only going to pull so much air. At some point, it won't matter how much the heads can flow because they'll outflow the engine. Unless you're running forced induction, of course.

product1620 · Post by **product1620** » Tue May 02, 2006 5:10 pm

Fastback86 wrote:Sure, I get that, but my point was that your displacement is a constant, your engine is only going to pull so much air. At some point, it won't matter how much the heads can flow because they'll outflow the engine. Unless you're running forced induction, of course.

What? :scratch:

Fastback86 · Post by **Fastback86** » Tue May 02, 2006 5:15 pm

product1620 wrote:
Fastback86 wrote:Sure, I get that, but my point was that your displacement is a constant, your engine is only going to pull so much air. At some point, it won't matter how much the heads can flow because they'll outflow the engine. Unless you're running forced induction, of course.
What? :scratch:

I'm saying the amount of air that the cylinder can physically move doesn't change. A 3.4l engine is only capable of moving a certain amount of air naturally aspirated. Each cylinder is only capable of moving a certain amount of air. You're going to get to a point where your valves are open far enough and long enough for the pistons to pull in as much air as they possibly can. There's no reason to spend lots of money to make your heads flow more air than the cylinders can move, you're not getting any more power out of it. Unless, you have a turbo or SC and can force more air into the chambers than they would otherwise pull in by themselves.

The Dark Side of Will · Tue May 02, 2006 5:32 pm

product1620 wrote:
Fastback86 wrote:Sure, I get that, but my point was that your displacement is a constant, your engine is only going to pull so much air. At some point, it won't matter how much the heads can flow because they'll outflow the engine. Unless you're running forced induction, of course.
What? :scratch:

If the ports are bigger than ideal, he'll lose velocity and low RPM torque, without commensurate high RPM gains.

The Dark Side of Will · Tue May 02, 2006 5:34 pm

Fastback86 wrote:I think the more pertinant question is why, when you have 4 valve heads, do you need such huge lift? If it were a 2v motor, ok I see it.

Why would you not want as much lift as you can get on a 4 valve engine? The higher you lift the valve, the more air you can get in. Four valve heads tend to flow better at low and mid lift than 2 valve heads, but that doesn't mean that you don't want as much lift as you can get.

Fastback86 · Post by **Fastback86** » Tue May 02, 2006 5:48 pm

Right, I'm just saying there is a point of diminishing returns. Sure, you can keep throwing money at it until the heads cannot physically flow anymore air, but you'll likely be long past the point where its useful to the engine. Plus you have to start thinking about shrouding and what not at huge lift.

The Dark Side of Will · Tue May 02, 2006 6:27 pm

got to think about shrouding at low lift as well...

Shaun41178(2) · Post by **Shaun41178(2)** » Tue May 02, 2006 7:52 pm

Aaron wrote:Well of course I don't "need" it. But if I have the intake manifold to take advanatge of it, why not?

YOu are going to have an intake manifold that is designed to take advantage of a .5 lift cam in a dohc?? WTF are you talking about? You can't even get the stock cams to that lift. So my whole point of this was, why is your guy flowing your heads to .5 when your cams dont' even have that much lift? Damn dude get a clue.

The Dark Side of Will · Tue May 02, 2006 10:03 pm

Probably for bragging rights.

Aaron · Post by **Aaron** » Tue May 02, 2006 11:22 pm

Shaun41178(2) wrote:
Aaron wrote:Well of course I don't "need" it. But if I have the intake manifold to take advanatge of it, why not?

YOu are going to have an intake manifold that is designed to take advantage of a .5 lift cam in a dohc?? WTF are you talking about? You can't even get the stock cams to that lift. So my whole point of this was, why is your guy flowing your heads to .5 when your cams dont' even have that much lift? Damn dude get a clue.

You can't get the stock cams past the lift they are at now. But who said I was going to use stock cams?

My cams will have that much lift. He gave me the numbers at .5 because it is pretty standard, he wasn't trying to show me exactly what he did, just an idea of how much he improved. As I said before, I'll have the full charts in a couple weeks.

For the sake of porting I told him they will be going on a 3.35l V6, running to a max of 8,000rpm, making approximately 120hp/l. It will be a while before I hit any of these, but I wanted the ehads done to fit these requirements so that I didn't have to pull them off later. And it isn't like they'll go stale, they may need a valve job after 60k, but I won't need to drop another couple grand on porting.

product1620 · Post by **product1620** » Tue May 02, 2006 11:31 pm

Are you going to go ahead and put the independent throttle bodies on, or are you continuing with the 96 intake swap?

Aaron · Post by **Aaron** » Tue May 02, 2006 11:42 pm

product1620 wrote:Are you going to go ahead and put the independent throttle bodies on, or are you continuing with the 96 intake swap?

This is actually something that is bugging me right now. I don't want to put the ITBs on if I can't add cams/headers to go with them, but with the extra time that the maroon car has boughten me, I'm at a point where I need to make a decision. I think I might fix up the maroon car, make it look and drive nice, and put the black car on the back burner while I build the motor. This will allow me to save up money so I don't have to shortcut ANYTHING, and get some of my ideas rolling.

But if I do this, the 96 intake parts are useless. Luckily I didn't spend too much on them, and I don't even have every piece yet.

Approximate cost now for black car's engine:
Independent throttle bodies: $100 for new aluminum laser cut flanges, $100 for mandrel bent aluminum tubing, injectors, and some sort of filtration setup.

Cams: $400 for regrind, $100 for lifter shims

Headers: $40 for laser cut flanges, $300 for mandrel bent tubing

And that doesn't even include a new EFI system, hardware, gaskets, time, other misc items, etc. But Oh God will it be worth it, until my connecting rods find their way outside of their big iron prison at least...

product1620 · Post by **product1620** » Tue May 02, 2006 11:49 pm

But if I do this, the 96 intake parts are useless. Luckily I didn't spend too much on them, and I don't even have every peice yet.

Why don't you put the 96 intake swap parts on the maroon car? Or does it already have a 96 motor?

Aaron · Post by **Aaron** » Wed May 03, 2006 12:07 am

It's going to be a daily driver, and I'd like to keep its drivability aspects to a maximum. And with the way the 96 parts fuck with tuning, I'll leave it be. It'll have plenty of power as it is, and I really like the idea of having an engine that's got nearly 100hp on the 2.8, runs SOOOO much smoother, gets better mileage, is more reliable, doesn't reek of exhaust, doesn't smoke, starts easily, and when needed to, can physically peg the speedometer.

I was so impressed with my red car's stock 3.4l, that I want one in a Fiero. I never knew a 3.4 could run so good. Maybe it was the fact that it was new, or maybe it was because every other 3.4 I've had I've fucked with. And sure they pulled hard, but drivability took a big hit.

Aaron · Post by **Aaron** » Mon May 22, 2006 8:43 pm

Small Update:

I bought a Dynojet Wideband Commander system for the car. It is a wideband O2 sensor that can be used as the factory O2 if the ECU operates on either a 1v or 5v system. It comes with the sensor, the datalogging system, the software for a laptop, and a white faced gauge.

I've heard nothing but good things about them, and plan to use it on a few of my cars.

My heads are also finished, and my friend picked them up. I should have them in a week or 2.

SappySE107 · Post by **SappySE107** » Mon May 22, 2006 9:45 pm

I can show you flow sheets with more flow up top and nothing down low, and I can show you flow sheets with a lot more low/mid and practically nothing past .400. You cannot assume a damn thing from .500 lift. .650 lift is the milzymotorsports standard apparently as he likes to use that for his flow claims. I prefer the whole sheet myself but the .500 lift is one I remember because so many people use it for reference (like it matters or something to know 1 point of lift).

.500 lift on the DOHC would allow you to use less duration/higher ramp up rate and get the valve opened all the way at the beginning the peak cylinder vacuum and close the valves sooner. Other than that, .500 lift is retarded for the 3.4 DOHC. Shrouding isn't much of an issue at higher lifts because the valves lift towards the middle the cylinder, not towards the edge.

Do you know what max lift is without modifying anything to go higher lift?

Aaron · Post by **Aaron** » Mon May 22, 2006 10:19 pm

Well I will have the full chart in a week or two.

And I agree the whole chart is better, and that a redneck in his garage with a dremel can really fuck things up. But for a shop that professionally does 4 valve heads, and is known across the West Coast for this work, I think I can accurately guess that there will be flow gains across the board. But he didn't bother reading me off these, he just gave me one number for reference, that being the .5 lift that even you agree is pretty universial. So we will see in a few weeks.

I can honestly say this shop is not much like Milzy's, thank god. If there was one thing I would buy from Milzy, it would be his brain. Would be fun to swap that into a Monkey and see how stupid it got.

SappySE107 · Post by **SappySE107** » Mon May 22, 2006 10:35 pm

Since you didnt answer my question on max lift, ill just tell you. .488 is the magic number for hte heads. For the cam side, 35mm lifters are good for about .475 lift. There are 37mm lifters out there but they may all be solid for all I know.

Kohburn · Post by **Kohburn** » Tue May 23, 2006 8:14 am

Aaron wrote:Small Update:

I bought a Dynojet Wideband Commander system for the car. It is a wideband O2 sensor that can be used as the factory O2 if the ECU operates on either a 1v or 5v system. It comes with the sensor, the datalogging system, the software for a laptop, and a white faced gauge.

I've heard nothing but good things about them, and plan to use it on a few of my cars.

My heads are also finished, and my friend picked them up. I should have them in a week or 2.

I've got the innovate setup and am real happy with it - 2 programable analog outputs.. I am contemplating using one to run the ECM.. right now i have one running a narrowband gauge - and I picked up one of these to give me a more accurate display form it
-- its not a narrowband display.. its linear like the wideband - 1V = 10:1, 2V= 20:1

the narrow band is for quick refference to catch any indication of a problem since its easy to see a sweeping needle out of the corner of my eye

Aaron · Post by **Aaron** » Fri Sep 22, 2006 4:05 pm

Now that I got my maroon car out here, running and driving reliably, I figure it is time to start gathering parts again for this car.

So today I ordered Rodney's poly engine and trans mounts. This is how my current DOHC is mounted, and I was pretty happy with it. $203 later and they'll be on my doorstep in a week.