Anyone ever experience this with their Roller Cam?

[QKRNYRS]

Or any cam for that matter....

I have been chasing this stutter/miss for a little while and it has baffled me.

At anywhere from 15 psi to 22 psi my car will run 115 mph. in the 1/4 with the Speedpro showing only 1 to 3 % correction. But usually when I hit 2nd gear with higher boost or at the top of second gear with lower boost the car starts to miss erratically. Not like a secondary ignition miss but like cylinders are dropping out.

I've tried to check fuel pressure, and it doesn't seem to be dropping off. Yet if it starts to stutter and I let out and get back into it the miss is gone for a second or two and then returns. In those couple of seconds the car will pull harder than it was.

Now for the other bit of info..... Today, I left work and got the car up to temp (5 mins of driving) and then blasted off and recorded the run. It pulled harder and faster than it did at the track Friday at only 15 psi. Then I went ahead and tried it a couple of more times tonight, recording each, and the miss/stutter came back the hotter the car and the longer I ran the car.

Could this be Valve Float? What does Valve float feel like? What about fuel related? I got the cam from The GSCA as a kit with valvesprings cam chain and pushrods a couple of years ago. This is the first time I've had everything "right" and able to take it to the track.

I can send some of the LOG files to anyone if they think that it'll help. Thanks!!

Pat

 

[Nick Micale]

First thing I would look at is fuel delivery. Local car with similar build/similar problem turned out to be that. From your description, sounds like it is running out of gas for a very short time. Any spikes in the A/F log? Full tank of gas?

Not sure what your entire fuel delivery system is from your sig. Any in-tank pump? -8 to the fuel rail?

 

[QKRNYRS]

fuel system

Walbro 340m intank Bosche external (NOS pump) and -8 all the waw to the rail.

 

[REDS HOT AIR]

try some ngk ur5 plugs gapped at .030 first ...thats a cheap try.

 

[Whitettype86]

Try what Red said gap your plugs to .032 and go from there.
I had the same problem and was going threw coil packs and modules and wires. Went threw 3 set of spark plugs and decided to re-gap to .032 from .035. And solved all the problems.

 

[QKRNYRS]

Are the NGK UR5's for stock heads or the Champion's?

I thought that I had TR5's in my heads now..... could be wrong.

They are gapped at .035" though.

Thanks

 

[Whitettype86]

Ngk TR5's are for Aluminium Heads and ngk ur5 plugs are for stock heads. Try gaping them .032 and run 18lbs see if there is any difference.

 

[1badTTA]

And just to let you know from experience, floating valves feels like a rev limiter. Mine started floating around 4500rpm and it would not exceed 4800rpm. Fell flat on its face and would not even shift. HTH

 

[REDS HOT AIR]

oops missed the alum head part..

i just run them at .030 and dont worry about them... no missfire at all even with a cruddy wells module and coilpack..

 

[Chyke]

The one thing you mentioned that got my attention was that the hotter the car gets the worse the miss becomes. Do not rule out an electrical problem. Usually the hotter an electrical part becomes the worse the problem. Couple that with trying to fire a plug under boost and bingo. Maybe coil pack or other directly related ignition part. Just a thought.

 

[JeffG]

Wow, I have a VERY simmilar problem with my roller cammed 3.8. i never figured it to be cam related though. Here are the things I have tried, but still have had no luck. Anything over the 19-20psi mark and it starts to miss.

New Coil pack. no change
New Module. no change
New MSD wires. no change
Tried different plug brands at different gaps as low as .020. Currently running NGK UR5 @ .032
Swapped out the 120lbs at the seat v-springs for 135lbs on the seat springs (325ish on the nose).
Swapped out hot wired 307 pump for a 340.
Tried Cam sensor seating from 26* down to about 20*.
Checked for exhaust leaks.
Checked voltage are various ground points.....pretty consistent.
Added a couple additional ground straps.
Output voltage at Alt. is 14+ volts full throttle.
I have tried race gas with and without the alky. Still missed.
Removed the ribbon cable for the Direct Scan. No difference.
Tried base fuel pressures from 38 to 60. Two different gauges to make sure they read the same......they do.
Made sure the FP regulator is working correctly.
Compression is 160-165 in all holes.
The Mass Air sensor reads up to 255.
All of the plug look fairly consistent. None of them are pig rich, or super lean. Never melted an electrode or anything crazy like that.
No detonation.
With and without RJC power plate. (I know, wishful thinking)
Can't find any vacuum leaks.
Hamonic balancer/crank trigger ring is tight, and the crank sensor is working properly.
Pressure tested the Intercooler. No leaks.
Made sure all of the ground wires on the back of the motor are attached well.
Interupter ring is tight on cam sensor.
Ran with the cam sensor unplugged. No change.
TPS voltage is fine...4.8v.
Changed from a PT51 to a 53 (unrealated problem)
I have cussed at it several times and that didn't seem to help either. Made me feel better though.
There are probably other things I have tried and just can't think of right now.

 

[Russ Merritt]

More timing??? That happened to me, any fuel over 108 octane and cool temps and it would miss, +20# boost. Jack cotton said MORE TIMING, the chip needs more timing. Something to try, you sound like your running out of options.

 

[JeffG]

I can try that. For what it's worth though, usually I am running pump gas and EGT's in the 1450-1500 range. Pretty normal combo that didn't use to miss with the old motor. No two combo's are alike though.
Thx,

 

[KWIKR 1]

I recently had a simular problem on a new rebuild with a Crane 212/206 Roller . Everthing on the car was new (coil , wires , all sensors , O2, Alt, EGR) . It felt like something turned the "off" switch to my car when I was hitting high boost (18-19 psi) . It would recover when I took my foot off of the gas . It was something that never happened all the time . I was never able to figured it out .I'm in the middle of doing a new rebuild .

 

[Russ Merritt]

It sounds like ignition. I know you've tried everything but if it runs fine up until HUGE boost it's blowing the flame out!! Are you running super cold plugs? Lots of people have good luck with the stock ignition, but it might need MSD DIS-4 HO to get the job done. Good luck, Kick some GN A$$

 

[meanmachine]

jeffg a friend of mine had the same problem as you , we tried evevery thing . then we changed the est sensor and that fixed it . something to do with the timing..

 

[steve hughes]

JEFFG I had a problem like yours. Can ran good up to 17#'s .Anything over that and it would miss. The more boost i put to it the worse the miss got and the slower it ran. Turned out to be the comp. 212-206 i put in it.

 

[QKRNYRS]

I'll try gapping them at .030" and see what she does. If not then I think that I'll go valve springs. But I'll try the plugs tomorrow. Thanks for the help

Pat

 

[JeffG]

meanmachine,
EST sensor and timing? You mean ESC sensor?

Steve,
Did your Comp do it right from the start? My car seemed to run good for about the first 500 miles of it's life. Burn offs from a 50+ mph roll were not a problem. They are a thing of the past now. I'm running a Comp 210/210 for what it's worth.

Thanks,

 

[steve hughes]

Jeff mine did it from the start. Freshened up the motor and changed the cam.winter before last. I was trying a max effort chip at the same time. At first i thought i just wasn't getting the tune right with the ME. After chasing the problem all last year and replacing numerous head gaskets And going to a dfi last winter AND replacing every sensor on the car earlier this year i put the old 208- 208 in it before norwalk life is good again. Funny thing was it had no driveablity problems. I was also glad to see it wasn't a problem with the ME.