Can anyone tell me what the recommened pre load is for the Lt4 roller rockers? I have installed them in an Lt1 and am having trouble getting them set. The Lt1 fact. man. sets the standard ones at one turn after removing the slack, and that ain't working. Thanks, Tom
What isnt working about it?Are you sure both valves are fully closed when your taking out the slack?And its normally a 1/4 to 1/2 turn(90 to 180 degrees) after slack is removed.If that doesn't work,and you dont mind getting messy,try to find some rocker clips that will work on your rocker arms.And do it while running(one side at a time)Back them off one at a time,till it clacks,take it down till it stops,then another 1/4 to 1/2 turn.It helps if you have an extra old valve cover with the top cut out to access the rockers(this keeps the oil mess down).With the center bolt valve covers, you would have to rig something up to pull them down tight enough to seal to the head.Hope this helps.Let us know.
I set the preload first by doing each cyl. at a time. I did this twice, then did it with engine running, using 1/2 turn. Same result. It will run strong and smooth for a few minutes, then begin to stumble and quit pulling. I am begining to think that my timing is being retarded and then advanced by the anti knock sensors. I tried a lt4 module and it improved, but still a bad problem. I'm open to suggestions. I believe the pre load is correct, but something else is happening that is getting by me. This is my first computor equiped vette, and I'm learning as I go. Thanks for the reply. Tom
Sounds like a seperate problem.You say it runs smooth when you fire it up,but then starts running rough a few minutes later?I wouldnt think just a rocker ratio change would be enough to throw off the computer,but maybe it is.Have you tried unhooking the battery for 5 minutes,to see if the computer will "reset" and compensate the new change?Just throwing out ideas.
Yes, I tried the battery unhook. No change. I'm going to play with it this weekend and see if I can find anything. I don't think that the rocker change should have been radical enough to have required a change to the computor either. I think that I must be doing something wrong. I welcome any suggestions. Thanks, Tom
If you followed the firing order when you adjusted, starting with #1 cylinder on the compression stroke, adjusting both the intake and exhaust,than you are ok.
You need to buy a computer scan tool ASAP,or at least find someone who has one you can use/rent.The PCM should illuminate the MIL if its receiving incorrect data from a sensor or if your fuel trims are out of limits.Unless things are really out of whack,it takes at least one full "drive cycle" to throw a code,usually three.(intermittent problems)I'm thinking,if that hasnt happened yet,then you should be looking for "non-input"(not sensors) components,(vacuum leaks etc.)Without a scanner,its back to old school troubleshooting,problem is,there isn't much left to check that is "old school checkable.See what your fuel pressure is doing,check for cold cylinders,and read your spark plugs.Let us know what you have eliminated and what you are leaning towards.Sorry I couldn't help more.:confused Shannon
Shannon, I ordered a codescanner last Thursday. It should be here by next Wednesday. I hope that it will tell me where the problem is. If not, you are exactly right about chasing down the problem. I have looked for vac. leaks, and am about to change the fuel filter. The odd problem is that it isn't always there. When I changed the anti-knock sensor module the car ran perfect for about five minutes, pulling smoothly and strong thru 5000 rpm's. When I shut it off, thinking I had solved the problem, and restarted it, I thought that it wasn't going to make it the five miles home. At times you can feel the car pick up and begin to run smooth for a ways, then when you give it any gas, it begins to stumble. Still looking. Thanks, Tom
You dont smell a little whisp of coolant sometimes do you?(i.e.optispark issues)But I am a little suspect of a fuel problem,from what your saying.If it was bogging out and dying,I would say fuel pump,but....:confused
No, no coolant smell, and it looks dry everywhere I can see. The change from rough to smooth is so fast that I don't think it is fuel related, but it won't hurt to change the filter anyway. I can be driving at 25 mph, with the car bucking slightly, like it was lugging, then you can feel it smooth out, and speed up slightly, running very smooth. If I give it gas, it again begins to run rough.
When the code scanner gets here, I will look at it again. Right now I'm giving up before I get mad at it.
I found my problem. Most of it was me. When I put it back together, I swapped the plug wires on 2 and 4. It took me two days to find this, as you can't see the routing. I hooked them up right, and replaced the two plugs as they were badly fouled. It still ran bad, so I kept thinking that I had not got the valves set right. When I got the code scanner, it told me that both the o2 sensors on the right bank were not working. When I took them out, both were black with fouling. I replaced them, and the car runs great.
My guess is that they got fouled with the plug wire swap,and stayed that way even after I corrected the problem.
Thanks for the advice from everyone. (The code scanner is the greatest thing you can have for this car!)
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