Help with turbo intake choice

Joey7508 · Mar 7, 2010

I have been going back and forth on which upper intake to run on my new motor and turbo combo. Here is what I have
302 ci boss302 9:1
gt40x heads
f303 w/1.6 rr
turbo is single 62mm hellion kit
I have two intakes to chose from, because I alredy have them I am limiting myself to these two.
I have a 96 explorer intake that I can run i it or I have a Downs box upper I can run on the explorer lower.
I do not plan on running over 9# of boost any time soon. I bought the Downs box in hopes of moving the peak torque up a little in the rpms. I had runa TFS intake with the turbo and f303 before and made peak torque at 4000 rpm ish. And peak hp at around 5000. But now I am afraid that the box will be too much intake for my set up and if I don't spin it to like 6500+ I will be leaving some power on the table. On the other hand I don't know how the explorer will do. It might make peak torque at like 3200rpm? Im not sure what the useful rpm range of an explorer intake is either? Is the box to much for only 9#s?
Any thoughts would be helpful.

84Ttop · Mar 7, 2010

Downs box all the way. You will lose a little low end torque but will more than make up for it on the top end. Where do you plan on shifting?

Joey7508 · Mar 7, 2010

Not sure where I'll shift? The f303 says it good to 6500? I ran it before and shifted at 5500rpm but since the motor is all balanced my inital thought was I would ring its neck, but I am worried about valve float. I have been reading about the high ramp rates of the letter cams and don't know about the valve springs that came on these heads/crate motor. They said good for any letter cam, but don't know if its lift, rpm, or both. Shift it when its stops pullling....thats what I was told.

clement · Mar 7, 2010

with a downs box on a ported gt40 lower and stock gt40 irons, with a turbo technology street kit and a turbonetics 60-1 mine put down 560rwtq at 3000 rpm. that was with a jacked off tune and it was running way to rich because i had the stock computer. this was in 1998, so i didnt have a lot of options.

you will have way more torque than you can hook up, even if the tune is off. with this f-ed up tune mine made 505rwhp at 5800rpm. this was with about 12lbs of boost on a stock shortblock and cam.

Joey7508 · Mar 7, 2010

Pretty good and that was on stock short end correct 302ci? I had tfs heads,intake, and f303 on a stock 302 and with a good tune it made 500hp/560ft# at the wheels with only 7# of boost. But that was short lived with a bad regulator. I don't think this combo will make that much, but I am o.k. with that. I couldn't use all of it on my last set up and wound up driving it around on 5# of boost most of the time, and still dusting off the tires. So that was another vote for the Downs I take it?

Joey7508 · Mar 7, 2010

And it was a stock cam? What rr 1.6 or 1.7? I have concidered swapping the cam to a stock and running the explorer intake. Be a real sleeper then. The car is a 100% stock exterior 86gt.

Tanus · Mar 7, 2010

I vote for the downs also, on a NA motor you'd need to be spinning some serious rpm's to benafit from a box upper but with boost the box is a way WAY better choice than the explorer/cobra intake.

clement · Mar 7, 2010

yes, it was the 40K mile original 302 that the factory installed. the thing i dont like about the stock cam is that with boost it builds a lot of dynamic cylinder pressure. id stick with the f cam. i had 1.7 cobra bolt down rockers. with the heads, rockers and lower intake is was basically a 93 cobra longblock with an HO cam instead of the t bird cam.

hell, my buddies bone stock 93 cobra engine (stock from TB to pan) with an s trim made 440rwhp for 8 years at 12lbs of boost and made 493rwhp at 16lbs of boost. that lasted about a month before the block split. the stock hyperutectic pistons were perfect, but the block split from the mains through the lifter valley.

Joey7508 · Mar 7, 2010

I have read about how the cams affect dynamic cylinder pressure, but I was not sure how much better the f303 would be over stock. I plan on staying with the f303 at the moment, but the f303 has no overlap, so I was under the impression that it couldn't bleed off boost either?

clement · Mar 7, 2010

the f cam has a hell of a lot more valve overlap than the stock cam.

Joey7508 · Mar 7, 2010

Yes you are right my mistake. f303 is 60.00 degrees. the stock is only 39.00 degrees. Don't know why I thought it was the other way.

Help with turbo intake choice

Joey7508

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84Ttop

They make new pistons every day, so why worry?

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Help with turbo intake choice

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They make new pistons every day, so why worry?

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