Knock at 5psi?

[short_dustin]

Ok, I bought this car about a week ago and since then I've put a scanmaster and a new boost gauge in the car along with new line to the boost gauge.

First question: I don't think there's a leak on the new boost gauge because it's showing 20in of vacuum so if there was a leak the vacuum would be reading less than 20in right?

Second question: I'm getting between 5-9 degrees knock at 3/4 to WOT. This is all with the boost gauge reading 5psi of boost. And I've had a couple of these cars and this one is pretty damn fast at 5psi. The tires are getting pretty slick but if I'm cruising at 50mph and go WOT it spins the tires quite a bit.

As for the car and mods,

'87 T-type the seller had the car for 15 years and claims the heads and intake were done by Weber, Lunati 200/200 cam, Red Armstrong Volt booster, Red XP fuel pump, forged pistons, TE-44 turbo, 3in DP and Red 93 chip.

The car has had 93 octane in it since October and I'm trying to run it all out so I can fill it up with fresh gas.

I don't think I've missed anything, any help is greatly appreciated guys thanks!

 

[ZNix]

Does it down shift when you see the knock? Could be false. Is the DP close to anything?

Nix

 

[short_dustin]

The knock is after the car shifts, and the tires quit spinning. And I'm pretty sure the DP isn't hitting anything

 

[ZNix]

If it occurs near/after the shift, it might be false. Get on the road in drive(not overdrive), accelerate to about 55 MPH I think, then step on it. It shouldn't downshift. If it does, go a little faster till it doesn't downshift. If you see knock, then there is an issue. If not, its false.

 

[short_dustin]

I got it out and drove it and it's getting knock in drive at 60 at WOT no shifts, I also saw today that it's getting 2-5 degrees KR at half throttle when it just starts to build boost. The only thing I can think is the motor mount on the drivers side looks kinda crappy. I don't really know what to do, the brand new auto meter boost gauge is reading 18-20in of vacuum and only 5psi of boost! If there was a leak and it wasn't reading the boost correctly doesn't that also mean the vacuum would read less too? Any help would be appreciated!

 

[BIGPSI]

if the motor mount is bad and the motor is flopping around,that will get knock. whatever it is you need to find it before you romp on it any more. you should not be getting knock at 5psi. verify good fuel pressure and get some fresh gas

 

[short_dustin]

The car has fresh gas, as far as motor mounts go, I'm not going to race the car at the track it's just a weekend driver. Should I get stock mounts or aftermarket? The price isn't a big deal either way I just want to use what I need.

Could the motor mounts be causing false knock? I've got an engine strap could I hook it on the alternator bolt and tighten it down to eliminate motor mounts as a problem?

 

[BIGPSI]

the strap can help ,whether its a street car or race car you shouldn't get on it till you solve the problem! you need to check fuel pressure,that is simple and a good start. wouldn't hurt to pull a spark plug and read it, and a scanmaster at minimum is a must! if you decide it needs motor mounts,buy the H&R drivers side that is all you really need

 

[blackgn1]

How's the fuel pressure at WOT? Are you sure it is only 5psi?

 

[short_dustin]

the strap can help ,whether its a street car or race car you shouldn't get on it till you solve the problem! you need to check fuel pressure,that is simple and a good start. wouldn't hurt to pull a spark plug and read it, and a scanmaster at minimum is a must! if you decide it needs motor mounts,buy the H&R drivers side that is all you really need

I know I shouldn't get on it, when I was saying the car isn't raced I was just meaning as far as which motor mounts I would need stock or HR? I have a scanmaster and a kenne bell fuel pressure gauge. The car is new to me and I've never had a car with a Red 93 chip before, the idle fuel pressure is 39psi and I'm pretty sure it's getting up around 70 at WOT.

blackgn1- I'm pretty sure it's 5 psi, I took an airgun and a regulator today and set it at 15psi and put it on the end of the line going to the gauge and it holds 15psi. It's really hard for me to believe the car is only running 5psi because it runs REALLY good! I don't really know what else to check as far as the boost pressure...

Sorry, I should have mentioned I have a scanmaster. Now that you guys know that I should also mention that at WOT it runs between 760-790 and the knock can be anywhere between 3-10 degrees. Are there any other numbers I should be paying attention to on the scanmaster?

I know I'm asking a lot of questions but I don't know that much about these cars...I'm still learning and I really do appreciate everyone's help

 

[short_dustin]

The list of mods I have are in the first post, I have Accel 44lb injectors, are they too small?

Another thing I noticed today is my bat on the SM reads between 11.7-13.1 should I get the alternator rebuilt?

 

[blackgn1]

With that amount of knock you will have a headgasket failure if you haven't already. I personally like the HR motor mounts after continuous stock type mount failures. What chip do you have? You need to add fuel and do it now. Until things are sorted out. PLEASE don't let this become a "I lost a headgasket" thread. It happens fast.

 

[short_dustin]

With that amount of knock you will have a headgasket failure if you haven't already. I personally like the HR motor mounts after continuous stock type mount failures. What chip do you have? You need to add fuel and do it now. Until things are sorted out. PLEASE don't let this become a "I lost a headgasket" thread. It happens fast.

I really don't want that to be an issue! I have a Red Armstrong 93 chip, how do I add fuel? Do you mean bigger injectors or what?

 

[blackgn1]

You have enough injector right now. With a TurboTweak chip it is done through the chip. Not sure on the Reds Chip. You can use some race fuel to raise the octane. Just take it easy till you find the issue. The boost is too high or your not getting fuel. I lost my headgasket years ago when I first got my car. Really wasn't much fun having a new toy and then breaking it in 2 months. Scanmaster showed 10 degrees knock for a second then game over.

 

[short_dustin]

Unfortunately Eric can't burn a chip for me with my current injectors because he said he doesn't have the data on them, I don't know anything about that. Yeah I definitely don't want to tear it up with summer right around the corner. I just don't understand how it's getting knock at 5 psi? I think for now I'm going to order some 65lb injectors so I can get a TT chip.

 

[Drewster]

vacuum can hold a hose closed as where pressure will push it open. you may have a hose leak near where your boost gauge Ts is. hopefully it is not the same hose going to the fuel pressure regulator.
Turn the wastegate/boost down. if the knock goes a way then you can rule out false knock. keep it down till you find the leak. or what ever is causing it.
Andrew

 

[Brad T]

If you are getting 70 psi on the fuel pressure and the pressure is 42 with the vac line off of the reg the car is making 28 pound of boost not 5 .That would be alot of boost on 93 in the cool air .What do you have for boost control ?

 

[larrym]

What does the stock boost gauge show compared to the after-market 1?

 

[short_dustin]

Stock boost gauge doesn't work

 

[jasjamz]

Can you post a picture of your turbo and wastegate combo?