Problem after installing 1.6 roller rockers. Need ideas
Racer
Joined: Dec 2003
Posts: 277
Likes: 3
Originally Posted by etteroc27
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
Melting Slicks
Joined: Apr 2003
Posts: 3,281
Likes: 3
From: Wood Dale Il.
Originally Posted by JAKE
Let me answer that this way:
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.
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.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by srsjuju
The part number that you have listed is that the GM number or a different brand?
Jake
Burning Brakes
Joined: Nov 2002
Posts: 1,239
Likes: 1
From: Las Vegas NV
Originally Posted by etteroc27
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
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by etteroc27
I'm ordering the lt4 sensor module. I think that could be my problem.
I suspect it's the procedure you used in setting the preload. Bring the #1 to TDC on the compression stroke, etc., isn't one of the ways to do it. I'm always amazed at all the different ways used to try to set lifter preload correctly.
The real trick in correctly setting lifter preload is to make absolutely sure tht the lifter is riding on the base circle (sometimes referred to as the "heel") of the cam lobe when zero lash is found and the preload set. There are a couple of recommended ways to set preload, but the procedure you listed isn't one of them.
The EO/IC method is the most commonly recommended way to set lifter preload. It's the procedure found in most camshaft catalogs, TPIS booklet, etc. I repeatedly advise against using the procedure shown in the shop manuals NOT because it won't work (it will) but simply because it's too easy to make a mistake using it.
The EO/IC method involves simply turning the engine over while watching the exhaust pushrod. As soon as it begins to rise (opening the exhaust valve) you stop turning. You then find zero lash and then set the intake lifter preload. Then watch the intake pushrod and when it has travelled about half way down (closing the intake valve) stop turning the engine, find zero and set the exhaust lifter preload. Stopping at the "half way down" position isn't too critical; about any position on the closing ramp will work.
I'd try resetting the lifter preload before spending money on a part I may not need. I always advise against throwing parts at a problem in the hope curing it. I believe in testing and diagnosing first, then buying parts, if needed, second.
Just my thoughts.
Jake
Last edited by JAKE; Apr 29, 2005 at 06:31 AM.
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Burning Brakes
Joined: Nov 2002
Posts: 1,239
Likes: 1
From: Las Vegas NV
Originally Posted by richy rich
You may not like my idea but,I would remove the spring's & 1.6's.If it runs clean try installing just the 1.6's,although it may not rev clean it will go past 3 grand-I think your problem may be fuel slosh-Filler up!!
Melting Slicks
Joined: Mar 2003
Posts: 2,472
Likes: 0
From: Toronto ONTARIO
i had the Exact same problem when i did the EXACT same mods back when my car was a stocker. i decided to go with new springs and pushrods and 1.6 rrs. i ALso decided to put on a throttle body. now this may not be your proble,.. but remove the intake tube that connects to the filter housing. have someone press the gas pedal down to wot.. and make sure ur throttle blades are open 100%.
Problem i had was the throttle cable wasnt adjusted and at wot.. the throttle blades were only 65% of the way. at idle it would feel like it revved so clean. under load it seemed to run out of air.. kinda like it just lost torque above 4k rpms.
check ur cable..
Problem i had was the throttle cable wasnt adjusted and at wot.. the throttle blades were only 65% of the way. at idle it would feel like it revved so clean. under load it seemed to run out of air.. kinda like it just lost torque above 4k rpms.
check ur cable..
Le Mans Master
Joined: Feb 1999
Posts: 6,172
Likes: 11
From: somers, ny
Was the car doing this before you did the rockers or did it start after the installation? If it's the later i think you can safely assume it's got something to do with the valve train. Are you sure you have the right springs and the install heights are correct. Do you know anyone with a spring pressure tester?
Thread Starter
Racer
Joined: Sep 2003
Posts: 275
Likes: 0
From: West Monroe La.
The springs are a new set of Crane's, made specificly for the change to 1.6 rollers on an LT1. I checked height on only three when I was installing, and it was correct for each, I think that the rest are alright.
The car was smooth before I changed rockers, so I am pretty sure it is a result of something I've done.
Yesterday I reset them doing the ex open in closed method, and got no change. I did notice that some of the pushrods could be shoved down into the lifters easily and some could not. Now I'm wondering about the lifters. Maybe I over tightened and got the lifter springs? No bent pushrods though. I followed Crane's method on their web page, letting the pressure off the lifters for a couple of minutes before setting them.
Still not right..... I don't know what I have done.
The car was smooth before I changed rockers, so I am pretty sure it is a result of something I've done.
Yesterday I reset them doing the ex open in closed method, and got no change. I did notice that some of the pushrods could be shoved down into the lifters easily and some could not. Now I'm wondering about the lifters. Maybe I over tightened and got the lifter springs? No bent pushrods though. I followed Crane's method on their web page, letting the pressure off the lifters for a couple of minutes before setting them.
Still not right..... I don't know what I have done.
