sleeper101

Well I got a 5.3 bored to 5.7 76mm turbo 20psi. I have a holley dp 650cfm carb. I've been 6.21@118mph 1/8th on bone stock 862 heads dual plane intake. I've recently had 862 heads ported polished w bigger 2.0 int ss valves installed. went from a dual plane to single plane intake and went from pump gas 93 to 115 race gas. I have went 6.18@119mph@best. motor does not seem to pull over 6k rpms no matter either setup. the only thing I have not changed is carb. Have I reached the 650 limit? or am I missing something?

chiaj144

iTrader: (4)

What turbo? What's your AFR? A properly built 650 will support a ton of power if built properly. You may be out of turbo, valvespring etc. What exhaust? Have you checked back pressure? If your not going lean look somewhere else. Give as many details as you can on your setup.

sleeper101

On3 turbo..96a/r exhaust .80a/r cold. a/f is 12.2-12.4, 321 stainless 3" exhaust. How do you check back pressure? I have approx 3ft of exhaust pipe from turbo.I've got plenty of valvespring says my machinest. I done leak down test on motor sat. has 10-15% on every cyl. so its good internally.

chiaj144

iTrader: (4)

What does your car weigh? I'd take a guess and say you have that turbo maxed out. To check backpressure you need to get a pressure reading before the turbo. Take that reading and compare it to your manifold pressure and that's your back pressure ratio.

sleeper101

3212 with me in it. what is the max of the 650? I really don't feel the turbo is maxed. I could be wrong. but I really don't think I'm any were near the 800hp rating of the turbo.

chiaj144

iTrader: (4)

Depends how your 650 is set up. Single/Dual power valve are the boost referenced, what size PVCR's etc etc. Do you have vent tube extensions on it? I still say your turbo is done. It takes every bit of 800fwhp to go low 6's like you are at that weight. I never came close to maxing my old 650 so I can't really tell you how much they will support. Go to the blow through section on the turbo forums you may find more info there.

midevil1

iTrader: (17)

I would be running a Boost gauge on the manifold side of the turbo anyway. Really simple and can save you alot of damage later on. What are your EGT's? Your temps will help you figure out if your turbo is the restriction.

sleeper101

I have a single power valve. 3.0 non boost reference. rear pv is blocked off. I don't have vent tube extensions. I've seen guys at the track put fittings in from and rear fuel bowls as a balance tube. I thought about trying that. I don't have no way of monitoring egts.

midevil1

iTrader: (17)

Get you a pyrometer gauge setup. Autometer sells them. You can put in your downpipe. After turbo temps are usually 200 to 400* cooler than before turbo. You can mount a boost gauge in your exhaust flange with cooper tubing and it won't melt.

boostdoctor

I've made 911rwhp on a 650, so i doubt thats your problem.

19trans_am98

iTrader: (3)

sounds like the turbo i had the 0n3 turbo and it was pretty much maxed out at about a 6.40 on my car...changed turbo and fixed the problem

sleeper101

Thanks for the tips guys. I got a guys c&s carb were going to throw on and see if it makes any changes. if not I will look into the turbo. The class I run has a 76mm turbo max limit and a cap of 5.70 I really need another 3tenths to really be good. I won the last race but if I don't get faster I won't be in the money. I got some strong competition coming soon. I wanna be ready. Will any 76mm turbo be capable of 5.70's?

sleeper101

Any tips on the carb setup? I would like to make mine better. I know its missing a few small tweaks that would make it a lot better. it runs strong now. but there is always room for improvement.

WR450SM

iTrader: (3)

What did you change to run the 5.74 @ 120 in your sig?

sleeper101

Changed out 22yr old bushings front and rear. adj traction rods. toe rods and lower control arms. got the whole tire planted now so I can launch harder. motor is still lacking something. it just doesn't pull up top like it should.

NemeSS

iTrader: (127)

Who built carb?

sleeper101

I built the carb. only thing I don't have compared to some others is the balance hose from front bowl to rear bowl. how critical is that?

NemeSS

iTrader: (127)

I've only built one to date. With the tm/tf sticky. From a old 650dp. Never been all that involved or built an all out. Just the basics. And car still runs good. A stock 5.3 with bout 8-10psi.
I want use a 650 for my 4.8.
I think that will be enuff for 500-600rw thru built a3/ 12bolt

sleeper101

U can make that all day long. I use to have a 60mm turbo on it. which was way too small. but it made490whp on a dyno jet. pump gas and 12psi.