Big Red Z28

iTrader: (4)

I currently have the TEA trick flow heads milled to 60cc with aftermarket cam using the morrell lifters.
I had the comp cams 7.4 length pushrod but always had the sewing machine sound so is switched to 7.425 rods, the sound reduced but after a short drive I'am getting a random or multiple missfire code.
I did the swap myself, I unbolted the yella terra rocker arms one intake one exhaust at a time since they are shaft connected took out the pushrods, replaced and bolted the rockers back in doing the same step one cylinder at a time. What the hell did I do wrong?

Bramlok

iTrader: (7)

I've always had the code PO300 random misfire deleted and removed when getting a tune. If you have a cammed car, it will sometimes trigger this code.

Not sure if it's related to your pushrod swap, but you can try clearing the code and see if it comes back. Does it still run the same or does it feel like a misfire? If you have a misfire, there's no mistaking how it feels when driving.

Big Red Z28

iTrader: (4)

I don't feel a misfire, I know exactly what you are saying. My dyno guy deleted the misfire back over a year ago when installing the heads and cam ran fine for a year or two, put in a built auto ran good for a couple months with no code switched pushrods and here I'am.
The dyno guy did a swap from some one elses car that had an auto to mine.

Bramlok

iTrader: (7)

Your tuner should have removed the code completely not just deleted it. It needs to be removed from the PCM the same way as removing rear o2 sensors or air pump / egr codes.

salemetro

iTrader: (5)

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Did you measure for preload, or just guess?

RonSSNova

iTrader: (3)

If you can't feel it, reset the PCM and see if it comes back.
Changing the pushrods should not affect this.
The real question is, did the noise go away?
Ron

Big Red Z28

iTrader: (4)

The valve train is not as loud as before.

ZeeOSix

With all your mods, it seems you would have needed shorter than 7.400 pushrods to start with - unless the new cam's base circle was more than 0.060" less in radius. And then you increased the pushrod lenght by another 0.025" on top of that ... just wondering what the real lifter pre-laod is now.

Big Red Z28

iTrader: (4)

From what I know the trick flow 215 heads require a 7.5 pushrod, If milled to 60cc that that would require a 7.485 if using morrell lifters that =7.435, other than custom made I could not find this so think I played it safe with the 7.425.
Thanks to everyone so far. Please help or correct if I am wrong on anything.

Darkman

iTrader: (2)

For what it is worth, I am running Trick Flow 215s milled to 61.5 cc, with Morel lifters, a EPS cam (that required 7.425 push rods in conjunction with stock 243s), and Jesel Sportsman shaft rockers. The push rod length to establish a 0.050" preload on the Morels is 7.367" overall length which equates to 7.350 gauge length.

oddwraith

iTrader: (1)

Is it in fact a random po300? What are the counts and cylinders affected? A little sewing machine sound doesn't seem like enough to change up pushrods.

PREDATOR-Z

You are wrong on the way you put it all together. You'll need to measure for correct preload. Don't you have adjustable rockers?

ZeeOSix

From: http://www.compcams.com/v002/Pages/4...-tech-faq.aspx

Setting Hydraulic Lifter Pre-load (Adjustable Valve Train)

"When installing a hydraulic cam, lifters or rocker arms, establishing the correct lifter pre-load improves both performance and engine life. Insufficient pre-load will create excessive valve train noise and wear. Excessive pre-load will cause rough idling and low manifold vacuum, and can even lead to severe engine damage."