Problem over 4000rpm
05-25-2007, 01:16 AM
#1
1st Gear Member
Thread Starter
Join Date: Apr 2007
Posts: 112
Problem over 4000rpm
I have a 1995 Gt with a kenne bell, edelbrock performer heads, green top injectors, and some other stuff. I'm not sure what you need to know to help me out but I'm having a problem with my car it pulls hard (really hard) up to about 4000rpm then at 4000rpm it starts to die off and by 4500 it just won't rev any higher, I can hear something differnt in the exhaust but I don't know how to describe it, its not pinging but almost a tapping sound. I have good fuel pressure from an electric and mechanical gauge. I'm trying to get the car ready for the track and today was the first time I was able to get it over 4k rpm. Oh and I bought the car modified so I really have no way of telling what the tune is, all I can say is I know its tuned to some extent since it idles perfect even with the cam, it revs over 4k in park, and it dosn't have any other problem it dosn't even have idle surge. Any thing to try to figure out or at least narrow down what it could be, I don't have a check engine light on either. Thanks
05-25-2007, 01:23 AM
#3
1st Gear Member
Thread Starter
Join Date: Apr 2007
Posts: 112
RE: Problem over 4000rpm
Both, and i'm assuming both are accurate since they both read the same in the driveway, I have a mechanical under the hood and an electric inside the car but I have no way to test the electric on the inside really, I was also thinking lack of fuel since it revs great up until that point and then falls flat on its face so tomorrow i'm going to look into that more.
05-25-2007, 12:16 PM
#7
2nd Gear Member
Join Date: Apr 2006
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Posts: 291
RE: Problem over 4000rpm
Thats odd, check your fuel pump and make sure your getting good pressure and not running lean in the top end. I just sold my 347 kenne bell and that car didn't run out of power till about 5,500. At 4,500 that thing would scream like a bat out of hell going down the road. I know that if you tried running my car past 5,500(on the dyno), my car would lean and slud down. With a twin screw, from like 2,500rpm+5,500 should feel like a rocket 
05-25-2007, 05:00 PM
#9
6th Gear Member
Join Date: May 2004
Location: las vegas, nv
Posts: 9,092
RE: Problem over 4000rpm
what type of plugs and at what gap? the plugs should be at about .32-.35 did the guy put new plugs in just before he sold it to you? he may have put in platnum plugs thinking they would make more hp. platnum plugs dont work with boost, the spark is easily blown out. this usually happens around 4000rpms, exactly where your having problems. if the fuel pressure is fine all they way up to 4000 and the problem still is happening, i would check the plugs next.
05-25-2007, 05:03 PM
#10
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
RE: Problem over 4000rpm
ORIGINAL: skielk
I have a 1995 Gt with a kenne bell, edelbrock performer heads, green top injectors, and some other stuff. I'm not sure what you need to know to help me out but I'm having a problem with my car it pulls hard (really hard) up to about 4000rpm then at 4000rpm it starts to die off and by 4500 it just won't rev any higher, I can hear something differnt in the exhaust but I don't know how to describe it, its not pinging but almost a tapping sound. I have good fuel pressure from an electric and mechanical gauge. I'm trying to get the car ready for the track and today was the first time I was able to get it over 4k rpm. Oh and I bought the car modified so I really have no way of telling what the tune is, all I can say is I know its tuned to some extent since it idles perfect even with the cam, it revs over 4k in park, and it dosn't have any other problem it dosn't even have idle surge. Any thing to try to figure out or at least narrow down what it could be, I don't have a check engine light on either. Thanks
I have a 1995 Gt with a kenne bell, edelbrock performer heads, green top injectors, and some other stuff. I'm not sure what you need to know to help me out but I'm having a problem with my car it pulls hard (really hard) up to about 4000rpm then at 4000rpm it starts to die off and by 4500 it just won't rev any higher, I can hear something differnt in the exhaust but I don't know how to describe it, its not pinging but almost a tapping sound. I have good fuel pressure from an electric and mechanical gauge. I'm trying to get the car ready for the track and today was the first time I was able to get it over 4k rpm. Oh and I bought the car modified so I really have no way of telling what the tune is, all I can say is I know its tuned to some extent since it idles perfect even with the cam, it revs over 4k in park, and it dosn't have any other problem it dosn't even have idle surge. Any thing to try to figure out or at least narrow down what it could be, I don't have a check engine light on either. Thanks
A little more info would be helpful otherwise you will be chasing your tail.