So according to the sticky threads, my 241 heads on my 02 trans am have 230 intake cfm...
so, installing a fast 92mm intake and throttle body (with 275 intake cfm) will not give me a hp/torque increase on my stock heads, since my heads only have the 230 cfm?

& I would need heads with 275 intake cfm to reach a higher power level?

( https://ls1tech.com/forums/generatio...heads-cam.html )

^^ just reading the intake chapter of Patricks great thread ^^ Thanks

 

No you can't look at it like that. You'll gain about 15 hp regardless

 

I figured my ls6 intake was more than enough for the head flow, what am I doing wrong here lol
how will I gain any power if the stock heads are that low cfm?

 

Just because something flows a certain number doesn't mean it's still totally "efficient" before that number. Follow?

 

right. I figured it wasn't spot on.
but with an increase in a rpms will definently range it out, so a 90 fast tb/intake, with my .525 lift hotcam would work pretty well then. I was thinking it would be a waste, after paying for tb, intake, and new MAF I suppose

 

Yep, and it really boils down to is the hp gain worth the cost, and only you can decide if that's right for you

 

Originally Posted by absolute

Listed below is the corrected flow numbers off my superflow at 28 inches of water depression
lift- int - ex
200-153-117 stg2 5.3l 3.9 test bore
300-207-171 1-3/4 ex test pipe
400-257-204
450-278-214
500-291-222
550-304-224
600-311-229

best of all the numbers through an ls6 intake
200-153
300-204
400-247
450-261
500-272
550-279
600-283

According to the chart here, my intake lift being .525, I should be looking for cfm of 275 or higher to make more power. According to the sticky, about 2 hp for every cfm. with the fast 90, id be spot on supposedly? I feel like I'm thinking too far into it lol

**Patrick G**
(((First, an LS6 intake will start to lop off airflow above 265cfm. A stock FAST 90mm intake seems to lop it off around 275cfm and a ported FAST 90 seems to lop off flow above 280cfm. You get around 2.2 hp for every cfm of flow increase. That extra 5-7 cfm may not look like much, but it's additional flow going into the head. If your heads will flow the number, that extra 5-7 cfm will give you 10-15 rwhp more power. ))))

 

The intake and head have to be flowed together as you did. If you did that with the 241s/LS6 vs the 241/FAST combo you'd see a flow delta.

While the FAST might flow in the 275-285 realm, it does so without the benefit of a head behind it. The head improves flow... even a 230cfm head. And vice versa. What you see on the bench is not the system working together.

 

You have to remember that most of the air is being brought in at less than max lift. That's only a fraction of the open valve time. What the head does at partial lift is very important. It's spending about twice as much time (on open and close event) at say 500 than it is at peak lift

 

Pretty much what these guys said lol. You cant look at those flow numbers you have to see how it works in a system. A part of it also comes down to runner design rather than just straight airflow. An ls6 is choked on a cam only motor despite what you may see on a flow bench with the 2 pieces separated. The fast is just better designed in the runners in addtion to flowing more air, however at a certain point you reach diminishing returns. When you put a fast on, again despite what you may think on paper the restriction becomes the stock heads.

A fast 102 wont pick up 15 over a 92 on a cam only engine because the flow delta is much smaller/non existant than it was from a ls6-fast 92 and the runner design is less effective. And on a stock ls1 you wont see really anything from an ls6 to a FAST again because the engine simply doesnt need the air that a fast provides.

 

Thanks for info, all of you.
(Set the head flow aside for a sec)
So, a FAST intake/tb will actually give me more useable power because of the extra intake lift from cam? But only as much as the heads will let me, correct?

 

Exactly the lift of the cam will draw in more air at its highest lift because it opens the valve more. It also keeps the valve open (duration) longer, again increasing the amount of air drawn in. The ls6 intake cant keep up with all these demands, the fast has better flowing runners and can do so. However at a certain point the intake flow is more than the heads can flow in a given moment thus shifting the restriction to the head ports.

The better the heads or larger the cam the more air the engine needs and the large choke point the intake becomes. But on a stock engine the air demands and air supply from an ls6 intake are pretty equal thus little to no gain by going to a FAST when you still have the stock cam, runner design helps but at the end of the day if the engine doesnt need the air it wont do much unless the runner design changes drastically.

You can get much more specific with bernoulli's principle and fluid mechanics through a pipe but thats it in a nutshell lol

 

Thanks for the description redbird, appreciate it.

I'll get better heads soon, after more research of course, but stock 241s (just for my knowledge) are capable of reaching 400rwhp with a healthy cam, fast intake & headers?

 

Absolutely, you just put in a hot cam iirc? That with a FAST and some good headers, 1 7/8 if you dont have headers yet, should get you to there or petty close with an M6. With a larger cam it would do it no problem.

With the hot cam I would turn up compression with the heads. If you wanted to keep cost down sending your 241's to AI and have them do their "high compression" job on them. The cam isnt a world beater with lift or duration but has a good amount of room for PTV clearance. Up the compression to 11:1 or a tad more, get a good quench and it will make for a fun combo.

 

That can be done with an ls6 intake as well!

 

It's going to depend on the dyno but almost all cam only cars that make over 400 rwhp are running a Fast intake. Most I've personally seen was 420 rwhp and that was with a trex cam, ported fast 92, and a 4 inch cutout

 

This is true. I'm almost there now. If I port my fast 92 and switch to true dual exhaust I'd hit 420+ with stock 241s. Add in lighter wheels,light weight flywheel, electric water pump ect. And it would be more.

 

My 228 cam only car made 380whp on a Mustang dyno so a big cam only ls1 can easily hit 400

 

Awesome news to know the 241s are capable of that. I know the hotcam isn't the biggest baddest cam, but it works for me. I'll be adding fast intake/tb, with a nice set of headers/y pipe, and hope to reach my goal of 400. Maybe even switch the cam and stronger valvetrain components as well. thanks guys

 

I would do the fast and headers at the same time to save on tuning costs. Go with 1-7/8 headers. They will always gain over 1.75 and lose nothing down low. Dont believe everything you read by people on here.