Problem after installing 1.6 roller rockers. Need ideas
Thread Starter
Racer
Joined: Sep 2003
Posts: 275
Likes: 0
From: West Monroe La.
Problem after installing 1.6 roller rockers. Need ideas
I have a 95 lt1 with 6-speed trans. When I bought it it had a set of hooker short headers, a thru the front license plate cold air induction system, and a Edelbrock/BBK throttle body. The exhaust has been modified. I don't know what stock looked like, but this one has two cats running into larger pipes going to the mufflers. There is no connection , Y or X between the two sides. I don't know what else might have been done.
I put a set of Crane 1.6 full rollers, and their replacement springs. It starts and runs fine until you get on it, and then at about 3000 rpm's it feels like it is shutting down. It feels strong and smooth up until this point. If I ease it up it pulls more smoothly, but still begins to feel like the valves are floating. I can rev it sitting in neutral, and it pulls strong up to 5000 rpms +. With a load it won't.
Any ideas on where to look would be helpful. Thanks, Tom
I put a set of Crane 1.6 full rollers, and their replacement springs. It starts and runs fine until you get on it, and then at about 3000 rpm's it feels like it is shutting down. It feels strong and smooth up until this point. If I ease it up it pulls more smoothly, but still begins to feel like the valves are floating. I can rev it sitting in neutral, and it pulls strong up to 5000 rpms +. With a load it won't.
Any ideas on where to look would be helpful. Thanks, Tom
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Team Owner
Joined: Sep 2003
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From: I'm the walkin dude I can see all of the world...
St. Jude Donor '03
Probably ought to ditch that BBK throttle body too. Without a stroker or ported heads, its just making tuning even harder for your motor.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
It would help us dismiss the lifter preload issue as the possible cause if you would post the exact, step by step procedure you used in setting the lifter preload.
If I had a dollar for every time some one posted that they had set their lifter preload correctly, only to find out later they hadn't, I could retire. Oh, I forgot, I'm already retired. LOL
Give us the details, this one doesn't sound too complicated.
Jake
If I had a dollar for every time some one posted that they had set their lifter preload correctly, only to find out later they hadn't, I could retire. Oh, I forgot, I'm already retired. LOL
Give us the details, this one doesn't sound too complicated.
Jake
Thread Starter
Racer
Joined: Sep 2003
Posts: 275
Likes: 0
From: West Monroe La.
I first set the preload by moving #1 cyl. to tdc on the firing stroke, setting the clearance by tighting down the rocker until I could just rotate the pushrod, and then giving it 3/4 of a turn. The fact. man. says a full turn, but I have had better luck with 1/2, so I split the difference. I then followed the fact. man. setting each rocker in it's order. The engine started right up and idled smoothly. When I took it out to try it out, it would not run right, missing and pulling something less than smooth. I figured that the rocker pre load was too tight, so I pulled the valve covers off and started it up. I backed off each nut until the rocker clicked, pulled it back down until the click went away, and locked it in with 1/2 turn. Still no luck, so I did it again, giving each a 1/4 turn and locking it down.
It pulls up to about 3000 rpm's and falls on it's face. Starts and idles smooth as glass.
I have built several small block hyd lifter engines for my early vette with no trouble. The only difference was they weren't roller lifters or full roller rockers. I thought maybe there was something I didn't know about them( it's beginning to look like there's something I don't know!)
I'm am open to any of you guys suggestions. Tom
It pulls up to about 3000 rpm's and falls on it's face. Starts and idles smooth as glass.
I have built several small block hyd lifter engines for my early vette with no trouble. The only difference was they weren't roller lifters or full roller rockers. I thought maybe there was something I didn't know about them( it's beginning to look like there's something I don't know!)
I'm am open to any of you guys suggestions. Tom
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
I would say it sounds like 2 problems.
1. you need an LT4 knock sensor,mine would not run with out it.Knock counts above 30,000.GM dirrect $39.95
2. I would install a Worlboro 20000169 fuel pump.
or you could readjust the valves.
http://corvetteactioncenter.com/foru...ad.php?t=45701
1. you need an LT4 knock sensor,mine would not run with out it.Knock counts above 30,000.GM dirrect $39.95
2. I would install a Worlboro 20000169 fuel pump.
or you could readjust the valves.
http://corvetteactioncenter.com/foru...ad.php?t=45701
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by srsjuju
I am having the same problem in my dads 85, can you run with out the knock sensor?
The ECM runs a test on the knock sensor circuit each time the engine is started. It sends enough timing to cause the sensor to respond and when the sensor does, the ECM knows the circuit is okay.
If no response is received, the ECM causes the SES dash light to illuminate and it remains on until the engine is shut down and restarted.
You can installed a 1/4 watt resistor into one of the ESC module wires. this resistor simulates the signal the ECM is looking for and assumes everything is okay with the circuit.
The resistor does, however, effectively disable the knock sensor. So if ACTUAL knock occurs, the ECM cannot retard the ignition timing and engine damage could occur. It's one of those "last resort" mods.
Hope this helps.
Jake
A couple of years ago, I installed such a resistor to the ESC module on my 86 and it works. I've since removed it and installed a different ECM module, 16038331, which is less sensitive to false knock signals.
Thread Starter
Racer
Joined: Sep 2003
Posts: 275
Likes: 0
From: West Monroe La.
Where is the knock sensor located? This sounds like an easy thing to replace, and I would guess that it can't hurt. I'm pretty sure the valves are set right, and I might try this first before looking at fuel pressure.
If I have to increase fuel pressure, what's the best way?
If I have to increase fuel pressure, what's the best way?
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by etteroc27
Where is the knock sensor located? This sounds like an easy thing to replace, and I would guess that it can't hurt. I'm pretty sure the valves are set right, and I might try this first before looking at fuel pressure.
If I have to increase fuel pressure, what's the best way?
If I have to increase fuel pressure, what's the best way?
It'll be loaded with information you will now and in the future. It'll even have step by step trouble shooting procedures for many of the most common problems.
On my 86 the knock sensor is located screwed into the passenger side of the block, down low between about cylinders 6 and 8 (or is it 4 and 6) anyway, it's round, slightly larger than a silver dollar.
To adjust the fuel pressure, the best way is to buy an adjustable fuel pressure regulator and a fuel pressue gauge. They're listed in all of the catalogs, like JEGS, Summit, PAW, etc. There are a couple of other ways to adjust the fuel pressure, but an AFPR is the best way to go.
Jake