Nice intake manifold... - The ITB thread
It is a pretty common problem for cars with ITBs to have that problem, though 1700 sounds a bit high.
Your ECU is functioning properly and trying to slow the motor down via closing the IAC all the way (Whcih should stall a stock motor/TB). Hoewever because no machine is perfect, there are flaws, however minute they may be. So it could be that even though the blades are all of the way closed, they are still leaking enough air to idle really high. And when you increase your overall plate circumfrance as much as you did, these flaws become much more apparent. That's my guess.
Your ECU is functioning properly and trying to slow the motor down via closing the IAC all the way (Whcih should stall a stock motor/TB). Hoewever because no machine is perfect, there are flaws, however minute they may be. So it could be that even though the blades are all of the way closed, they are still leaking enough air to idle really high. And when you increase your overall plate circumfrance as much as you did, these flaws become much more apparent. That's my guess.
TECH Enthusiast
Joined: Nov 2002
Posts: 550
Likes: 0
From: Michigan, auburn HIlls
Use a unison to measure the cylinder to cylinder airflow at idle. Then adjust to get same flow in all cylinders. This should allow for a lower idle because all the butterflys will be in the same position meaning it will be the stop that holds them open and not the butterflies on the intake walls of certain cylinders and not others. Kinsler.com sells them. Another way is to use feeler gauges between the butterfly and its wall. I think a good start is like .002-.005.
I have their manifold on my car and it idles to whatever I want it to.
http://i12.photobucket.com/albums/a2...lt_Racer_1.jpg
I have their manifold on my car and it idles to whatever I want it to.
http://i12.photobucket.com/albums/a2...lt_Racer_1.jpg
Last edited by Argon Z; Dec 13, 2006 at 12:48 PM.
On The Tree
Joined: Nov 2004
Posts: 143
Likes: 0
From: Macomb Township, MI
Well I've got it idling at 500 RPM LOL I cant believe that.. a 408 idling at 500 RPM.. unreal! We will of course up it to 750 for streetability but man this thing is finally starting to come together 
This one tried to idle at 500 at first also. But it was because it was lean and trying to die. After giving it some fuel and getting the idle fuel trims close to zero, I can't get it to idle below 1000 once warm. I did pull the intake back off to check the head bolt clearance issue you talked about. We had no such problem with the AFR 225's.
On The Tree
Joined: Nov 2004
Posts: 143
Likes: 0
From: Macomb Township, MI
We've got it idling below 1000 warm with the idle commanded at about 750, the throttle blades and horns are dissimilar metals so they obviously expand at different rates. The horns grow faster than the blades so you end up letting quite a bit of air around the blades after it's warmed up. You should be able to get a happy medium roughing in the base idle mechanically and then adjusting the tune.
FWIW... at least on the LT1 cars, the base of the windshield is a high pressure zone. I've done yarn testing and the yarn at the back of the hood actually sucked back under the hood from speeds of 65mph plus. There was also some very substantial high pressure from about 24 inches behind my WS6 scoop. I would imagine this would change a bit with the different body style... but I can't see a huge difference. Vents in the back half of the hood should suck air instead of pushing it out. Just another data point to consider.
Staging Lane
Joined: Jun 2005
Posts: 67
Likes: 0
30thTA,
Do you have any problems with the blades sticking? Once the car cools down overnight the blades are sticking and we actually have to tap them to get them to open up. We could adjust them, but then they aren't all the way closed and the idle goes up. Argh, this intake is getting more frustrating all the time. Just when you think you have it ready to go its something new.
Do you have any problems with the blades sticking? Once the car cools down overnight the blades are sticking and we actually have to tap them to get them to open up. We could adjust them, but then they aren't all the way closed and the idle goes up. Argh, this intake is getting more frustrating all the time. Just when you think you have it ready to go its something new.
I'm wondering myself. I had mentioned that the cam seemed to be to big to me, but he didn't seem to think it would be a problem. Hopefully his dedication to the project will pay off and he can help us all out. Again, many thanks to 30thTA.
The cam has been proven to be an excellent pick as it's made mid 5 hundred rwhp with the FAST 90/90 through a Moser 12 bolt, 3500 PE Yank converter, Beefed up 4L60E, Danny's steel nitrous ready drive shaft and CCW 19 inch rims. At this point in time we have not put a final stamp of approval or disapproval on the Harrop, as there are bugs still to be worked out. I'm hoping after the bugs are gone, the final results will produce some sold 600ish rwhp numbers. Time will tell.............
Originally Posted by Cliff
The cam has been proven to be an excellent pick as it's made mid 5 hundred rwhp with the FAST 90/90 .
Originally Posted by topperge
30thTA,
Do you have any problems with the blades sticking? Once the car cools down overnight the blades are sticking and we actually have to tap them to get them to open up. We could adjust them, but then they aren't all the way closed and the idle goes up. Argh, this intake is getting more frustrating all the time. Just when you think you have it ready to go its something new.
Do you have any problems with the blades sticking? Once the car cools down overnight the blades are sticking and we actually have to tap them to get them to open up. We could adjust them, but then they aren't all the way closed and the idle goes up. Argh, this intake is getting more frustrating all the time. Just when you think you have it ready to go its something new.
Have you driven yours yet? This one feels like it has a miss just off of idle. After that it feels fine.
Last edited by 30thta436; Dec 16, 2006 at 11:09 AM.
Originally Posted by Cliff
30thTA spent all last night from 4pm to 7am trying to get the car ready to hit the track in Houston today but no such luck. It's idling consistent at 950rpm's. 
The street tune is done and running fine but the power on the dyno is not were it should be. 
More research and time. This intake is a major pain and I think at this point in time it's not worth the extra work and hassle. It is not user friendly and simply not an item anyone can plug and play. 30thTA is determined to find out if this intake will produce another 70 hp over the FAST. 30thTA is brilliant with computers and mechanical issues. He loves the challenge and is extremely dedicated when it comes to solving problems. Personally I would throw the towel in and go back to the FAST 90/90 set up. but he's on a mission to work out the bugs and save someone else a lot of time and money.
The street tune is done and running fine but the power on the dyno is not were it should be. More research and time. This intake is a major pain and I think at this point in time it's not worth the extra work and hassle. It is not user friendly and simply not an item anyone can plug and play. 30thTA is determined to find out if this intake will produce another 70 hp over the FAST. 30thTA is brilliant with computers and mechanical issues. He loves the challenge and is extremely dedicated when it comes to solving problems. Personally I would throw the towel in and go back to the FAST 90/90 set up. but he's on a mission to work out the bugs and save someone else a lot of time and money.Thank you for the compliments. You making me tear up.
I won't give up.