Well it seems that I have been having an issue now for coming close to 2 months after I had installed some full roller rockers.

Finally the car was running amazingly and had kicked off all the small quircks and kinks that it had needed worked out. Car was running terrific and was surprising our local 4.6 and LS crowd. I had purchased some these full rollers to install them and tried them 1 weekend to see if they would clear the valve covers, unfortunately they did not (needed just a hair more room) so i took them off and went back to the stock 1.5s and took the car out and raced it that night, ran like a champ.

Next weekend i had my taller covers in so again stripped it down and put them on. I tweaked and tweaked with them all day trying to get them set exactly properly, the car was gutless. Called a favor from a guy my dad is friends with who builds race engines on the side, he came over and set the valves with these rockers....i was gone at work so the car never left the driveway. That night i came home and took it for a drive, it sounded amazing but the car was gutless (he set them with the car running) to the point i couldn't break the tires loose without having to do a 3k clutch dump and even then it was only for 4-5 feet and it would fall on its face.

So we tried setting them again a few more times with another mechanic helping and still the same symptom. So we decided to try the stock ones again cause it ran fine originally with them on. Put it back to stock, and still the same symptom. Car starts, sounds alright, but cannot break the tires loose and is extremely doggish(perspective, Im pretty sure my friends 90s cavalier would walk me). I have ran out of ideas on potential problems cause by my ear the car sounds like it always has, it just doesn't run like it always has. No codes, no nothing. I have replaced the coil and checked the pickup coil in the distributor as well.

I don't know if its related or not, but for some reason during the time period the tach stopped reading. It picks up from its resting position when i turn the key to the on position but it just doesn't read for some odd reason once the car is started.

Any and all insight would be much appreciated and helpful cause I have ran out of ideas and anybody i know of that knows anything about cars in general, so now its time to pick the brains of my fellow Camaro owners as I do not trust local shops around me enough to let them touch my cars. The car in question is my Z28 in my signature.

 

have you checked your fuel pressure?

 

Sounds like an ignition timing or coil problem. changing rockers won't affect what advance curve the engine likes, and the dizzy shouldn't've been moved. So I'd start with the coil, and the wires connected to it. All of them.

 

Exactly what my thoughts were was something in the ignition after we had first had the problem. But I couldn't think of any possible reasons for why it wouldn't be advancing properly. I replaced the coil already in thinking along those lines when it first was acting like this. Is there anything else in particular that would keep the Dizzy from advancing accordingly?

 

Lets assume the old guy knew what he was doing, and the valves were completely seating. Then if the lift was too much, and you were either getting coil bind, or the retainers hitting the guides, you would've either pulled press-in studs, or bent pushrods, or damaged lifters.
Most likely of those is pushrods, which would explain alot. But so would the valves not fully seating. But that would be audible, pushrods much less so.
Pull all the pushrods out, roll them along a flat pane of glass. Not glass from before 1940, but modern, truly flat glass.
This is a sure way to catch pushrods that aren't straight enough.

 

I'll check the pushrods as well then this evening and chase all the ignition wiring down and report back with what I find/results. Didn't know one could be bent enough to keep it from seating all the way without there being some audible noise (had 1 on the Ls and you couldn't miss it). Coil bind shouldn't be occurring cause the springs are for .600 lift.

 

I think we got out of synch. A bent pushrod won't keep the valves from closing, it'll hurt effective lift and effective duration. If you get 8 bent pushrods, you really can lose huge percentages of your power, and it gets worse the higher you rev it.

 

If your pushrods are good, check the tach wire & distributor conections.
IDK how your tach is wired-- my 1st one had the tach wire passing thru
the firewall without a grommet, stripping enough coating to allow bare wire
to contact the firewall when the gas pedal was used. Idled fine, sputtered when goosed.
Just a thought..

 

Did some checking, chased down all wiring for the dizzy & coil. All checks out good, all is hooked up like always. Pulled out all the pushrods and ran them across the glass tabletop and all checked out good except for 1 that had a minor bend to it & 1 questionable 1. So that could be a small piece of the puzzle, however no shops can get me any pushrods until monday at the earliest so i'll be dismantling an old motor tthat ran decent to nab a couple good ones to put in their place.

 

Sometimes the smallest most obvious things are the real problem. Did you perhaps forget to plug the advance wire back in, that should have been disconnected when you set the initial timing?

 

What timespy said. Also, can you connect a scanner and read data? Watch advance and look for knock retard. Ive had trouble with knock retard when running big cams and roller rockers. You may have to disable the knock sensor.

 

Well the timing hasn't been set since September when the the guy dyno tuned it for me. So that lil wire hasn't been played with ( i also checked it for any potential breaks etc). And would TunerPro work to watch the timing advance etc as I have all the hardware to do that just have to put the program on the laptop ( What can I say, I have zero trust in the shops around me that can run diagnostics. Especially our GM dealers)

edit: I have a full set of Pro Comp pushrods that a shop expedited the shipping of them for me to be here tomorrow morning so we'll see if that fixes my issues. Ten if not i'll try the Tuner approach.

 

Update---

Installed the new pushrods alongside the roller rockers. Still lacking in the power department. Still feels like its the low-end grunt that is missing. I didn't get a chance to hook the computer up to it yet but thats what i'll be hopefully doing this afternoon.

Talked to a local IMCA racer and he "believes" its possible that a valve kissed a piston and the valve lost since a pushrod was bent, might be a possibility so i'll be doing a compression test. My answer however I believe is still in the dizzy, primarily in the advance (or lack there of potentially) as for some odd reason yesterday i could not for the life of me get a consistent timing out of it (and for that matter it seemed extraordinarily high for base and advanced timing)

 

Im not familiar with tuner pro but I would imagine that it would read data. Also connect a timing light and verify that actual timing mirrors data. Btw, what tall valve covers are you using? I might want some.

 

I cannot remember what kind they are right now, but I like them. Soon as I find the receipt i'll say for sure (its in the file somewhere, with about billion others) but I wanna say they are Moroso.

 

I hadn't had a chance to play with the car for a few days as it had become busy and was working too much. Finally got around to playing with it a bit and checked the timing as well as having done a compression test.

Compression is still amazingly well off and the most difference I had was 5 psi from the highest to the lowest. So that made me feel better on that front as i was slightly worried.

Played with the timing light and am pretty confident i hit my timing on the head (timing has always been my pita, hence my new love in Ls engines ) and I am running 8 base, and when at 2500 rpm I have only advanced to 12 degrees, which I know it should be significantly higher then that by that rpm.

 

http://www.asashop.org

Advance is way too low. I think you may have the issue I mentioned before with your roller rockers and big cam producing noise and causing knock retard.

Connect a scanner and watch datastream. Look at spark advance and knock retard. Spark advance should respond to changes in RPM and load. Knock retard should be 0.

The test sequence for the EST circuit is way too long and involved for me to spell out in this post. Try the above link for some helpful info. You can also find a reasonably good test description on Mitchell On Demand at your local library. Or just google "GM Electronic Spark Timing". Youll find some helpful sites.